TheTimeTraveller

OneMan’sMissiontoMakeTimeTravelaReality

RONALDMALLETTWITHBRUCEHENDERSON

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AbouttheAuthor

RonaldMallettwasborninPennsylvaniain1945andgrewupintheBronx.In 1973 he was one of the first African-Americans to receive a PhD intheoretical physics and is now a professor of physics at the University ofConnecticut.Hehaspublishedmanypapersontheoreticalphysics,andhistimetravel research has been featured in the TV special The World’s First TimeMachine as well as in publications as diverse asWall Street Journal, RollingStoneandNewScientist.

Bruce Henderson is the author and co-author of numerous bestsellingbooks, includingAndtheSeaWillTelland,most recently,TrueNorth:Peary,Cookand theRace to thePole.He teacheswritingatStanfordUniversity,andlivesinMenloPark,California.

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PraiseforTheTimeTraveller

‘Thepowerfulstoryofason’sloveforhisfather...providesdeepinsightsintotheinfluences,bothpositiveandnegative,thatimpactanindividualwishingto go into science, and the interplay between family, emotions, race, andambition’

RonaldE.Mickens, Ph.D. distinguishedFuller E.Callaway professor ofphysicsatClarkAtlantaUniversityandtheauthorofMathematicsandScienceandMathematicalMethodsfortheNaturalandEngineeringSciences

‘Mallett’spoignantandpowerful text correctlypaints the scientist as firstandforemostahumanbeinginawayfewotherscientificautobiographieshavemanaged.ThescienceenthusiastwhocomestothisworkfascinatedbyMallett’sground-breaking research into time travelwill come awaywith an unexpectedunderstandingofhisstrugglesagainstprejudice,bothsocietalandscientific’

KristineLarsen,professorofphysicsandastronomyatCentralConnecticutStateUniversityandauthorofStephenHawking:ABiography

‘Mallett is suchagreat teacher that the complex ideas that shapemodernphysics aren’t so scary under the professor’s easy guidance ... strange,interestingandultimatelytouchingmemoir’

BruceLieberman,SanDiegoUnionTribune

‘Mallett never comes off as a puffy-chested smarty-pants.His delivery ishumble, his voice enthusiastic, his optimism contagious. For anyone, butespecially for the aspiring scientist, The Time Traveller is a worthwhile andsurprisinglyentertainingread’

JulieMayeda,SanFranciscoChronicle

‘Whileatheoryfortimetravelisinitselfextraordinary,Mallett’sownstoryofhowhebecameoneofthefirstAfrican-AmericanPh.D.sisjustasremarkable...Therehavebeenanumberoftimetravelbookspublishedoflate,but this is

one of the more accomplished. His theory is the first serious and practicalattemptatmakingtheimpossiblepossible.TheTimeTravellerisaboutfarmorethan theory, however, and will undoubtedly serve as inspiration to buddingscientistsandthegeneralreaderalike’ScienceBookReviews

“Flight by machines heavier than air is impractical ... if not utterlyimpossible,” statedoneof thegreat scientists of thenineteenth century, JohnsHopkinsprofessorofastronomySimonNewcomb(1835–1909),whospentmuchof his career producing improved orbital tables for the moon and planets.Newcombwas convinced that a newmetal or unknown force of naturewouldhavetobediscoveredbeforemancouldconsidertakingtotheskies.Evenshoulda “power-machine” be invented that could lift a man off the ground, hepredicteditwouldfall“adeadmass”tothegroundandkillanyoneaboard.

Simon Newcomb’s comments about the impossibility of manned flightwerepublishedin1902.

Ayearlater,OrvilleandWilburWrightprovedtheexpertwrong.

Prologue

June25,2002

Washington,D.C.

Itwasyet anotherhot andhumid summerday in thenation’s capital as Ientered a large lecture hall on the sprawling urban campus of HowardUniversity. Inside theair-conditionedhall, rowsof seats roseupward from thepodium, creating a theater-like setting that seemed apropos, as Iwas about todeliverthemostimportantpresentationofmylife.

Since theageofeleven, Ihad toldonlya fewconfidantsaboutmysecretdream.Longfearingprofessionalsuicide,Ihaduntilrecentlyheldoffrevealingto colleagues at the University of Connecticut, where I am a professor ofphysics,myhopeofturningoneofman’sfavoritescience-fictionfantasiesintoascientificreality.HadIspokenofitearlier,Iwouldnothavereceivedtenure.

The timehad arrived.Before fifty or soof theworld’s leadingphysicistsassembledherefortheInternationalAssociationforRelativisticDynamicsThirdBiennialConference,Iwasabouttorevealindetailmyplanforfinallyrealizingmylifelonggoal.Itwouldnotbeenoughformetotellthemmybeliefthatthiscenturywillbe thecenturyof time travel justas the twentiethcenturywas thecenturyofairandspacetravel.No,thisaudiencewouldwantthenutsandbolts.

Myworkhadbeenoutedinthepastyear,whichwasnodoubtthereasonIhadbeeninvitedtodeliverapaperbeforethisprestigiousbody,whosemissionwas“tofacilitatetheacquisitionanddisseminationofknowledgeaboutresearchprogramsinclassicalandquantumrelativisticdynamicsofparticlesandfields.”Yet,thefactthatmyresearchhadbeenfeaturedinpublicationsasvariedasNewScientist,theVillageVoice,theBostonGlobe,theWallStreetJournal,RollingStone magazine, and even Pravda (Moscow) would mean little at this augustscientificgathering,andmightevenraiseaneyebrowortwo.

Sittingintheseatsandpeeringdownatmewouldbesomeoftheheaviesthittersinmyfieldofrelativityphysics:BryceDeWitt,directoroftheCenterforRelativity at theUniversity of Texas atAustin and one of the founders of anearly form of a quantum theory of gravity; Georgia Institute of Technology’sDavid Finkelstein,who hadmade several important contributions, including a

novelwayoflookingatblackholes,andL.P.Horwitz,aninfluentialTelAvivUniversityprofessorwhohadhostedthelastconferenceandhadmadeanumberofsignificantcontributionstorelativisticquantummechanics.

Although my work is based squarely on Einstein’s general theory ofrelativity—a solid foundation for any physicist to stand upon—I would bepresenting some controversial results. This audience would expect to see theequations and solutions that led me to believe I had made a theoreticalbreakthroughthatcouldleadtothedesignofthefirstworkingtimemachine.

Forafewweeks,Ihadspenttwelvetofifteenhoursadayworkingonmycalculationsinordertobeready.Ihadtransferreddatatotransparencies,whichIintended toprojectduringmytalk. If Ididn’tgetmymathright, theseexpertswouldletmeknow,andwouldbenonetootactfulaboutitintheprocess.ShouldImake amistake in a calculation and veer off course, Iwould be interruptedmid-speechandsubjectedtoin-your-facecritiques—“Professor,yourequationsare wrong”—rather than any gentle, instructive words of advice. That is theworldofphysics;weare,afterall,scientists,notpsychotherapists.

Iwasscheduledtodelivermytalkat10:00AMthatmorning.Muchtomychagrin, I sawon theschedule thatBryceDeWittwouldbegoing rightbeforeme,presentinghispaperon“TheEverettInterpretationofQuantumMechanics,”aboutthemany-worldsorparallel-worldstheoryoftheuniverse.ThatIwouldbefollowing such awell-known star to the podiummademe appreciate how theguywhocameuptobatafterBabeRuthmusthavefelt.

IknewIwasintroublerightawaywhenDeWittstartedoffbysayingthataspeaker needed only six transparencies to discuss his ideas, which, of course,wastheexactnumberhehadbroughtalong.Ilookeddownwithdismayatmybulgingfolder,crammedwithtwenty-sixtransparencies.DeWittwentontosaythathe always toldhisgraduate students that theyneednot tell their audienceeverythingtheyknewaboutasubject.Itoldmyselftokeepbreathing.

DeWitt, a legendary andpioneering theoreticalphysicist, receivedhisPh.D. from Harvard in 1950. Tall, lean, and energetic, DeWitt had hiked in theHimalayasandAfrica.DuringWorldWarIIheservedasanaviatorandafterthewarconductedresearchatthefamedInstituteforAdvancedStudyatPrinceton,whichwasatthattimealsoEinstein’sacademichome.

Elegant is an adjective often used byDeWitt’s colleagues to describe hisuseofmathematicsinphysics,anditiscertainlyacompliment.Theeleganceinhisworkshowed in thenatural flowofhisphysicalarguments,and thebeautywas to be found in the pleasing symmetry of his equations. As a graduate

student, I had learned that elegance and beauty in physics were nearly asimportantaswhetheranideawascorrect.DeWitt’spresentationaboutoneofthestrangest consequences of quantum mechanics—the possible existence ofparalleluniverses—couldplayanimportantroleinthepossibilityoftimetravel,sohehadmyraptattention.

Quantummechanicsisthemechanicsofsuddenenergychange.Inquantummechanics, energy cannot be gained or lost continuously, but only in fits andstarts. In 1913, the Danish physicist Niels Bohr,1 often called “the father ofquantum mechanics,” showed that the electron orbiting the proton in thehydrogen atom can change its orbit only by either gaining or losing a certaindefinite amount of energy—nomore and no less. These definite, or discrete,amountsofenergyarecalledquantaofenergy.

In1957,physicistHughEverett III,2 thena recentgraduateofPrinceton,first applied quantum mechanics to the entire universe, which resulted in hismany-worlds,orparallel-worlds,interpretationofquantummechanics.

Quantummechanics, in short, is a world of probability. In the ordinary,everyday world, when a pitcher throws a baseball, it is possible to describeexactly where the ball is and how it’s moving. In the world of quantummechanics,wecanonlysaywhatwillprobablyhappennext,aswecan’tknowexactlywhatanobjectisgoingtodo.

Inapplyingquantummechanics to thewholeuniverse,Everett found thatwheneverthereisthepossibilityofmorethanoneoutcomeforanevent,thereisa potential split in the universe. For example, suppose that at lunch you aretrying to decide between a cheeseburger and a tuna sandwich.At themomentyoumake thedecision,according toEverett, theuniversesplits into twoparts.Thereisauniverseinwhichyouhavechosenthecheeseburger,andthereisalsoanequallyrealuniverseinwhichyouhavechosenthetunasandwich.Thesenewuniverses are parallel and separate. The you in the universe with thecheeseburger is not aware of the you in the separate universe with the tunasandwich. Although this idea of a parallel universe seems incredible, it iscompletelyconsistentwiththeproventheoryofquantummechanics.

Like everyone in the audience, I was familiar with Everett’s parallel-universetheory.Ihadusedthecheeseburger-tunasandwichexamplemanytimestoexplainthetheorytogeneralaudiences.Andyet,IwasenthralledbyDeWitt’smasterful though highly-technical discussions of concepts like the “wavefunctionoftheuniverse.”WhenDeWittfinished,Iwenttothepodium.Havingnot forgotten his pronouncement that a speaker needed no more than six

transparenciesanddidnothavetotelltheaudienceeverythingthespeakerknewaboutasubject,Idecidedtofacethesituationstraightup.“Justtoletyouknow—I have nomore than sixty transparencies.When I found out that ProfessorDeWittwasintheaudience,IfeltasifIwasbackingraduateschool,andthatI’dwanttoshowhimeverythingIknowaboutthesubject.”

DeWittandtheaudiencelaughed,andIcaughtmyfirstdeepbreath.I began by reviewing the tenets of Einstein’s general relativity theory,

whichinthiscrowdofrelativisticphysicistswasakintopreachingtothechoir.Forthwith, I began to outline my own theories based on Einstein’s work,projectingonascreenmytransparencieswithillustrations,equations,andfinalsolutions,which I said showed that space and time could bemanipulated in awholenewwaythatwouldleadtothepossibilityoftimetravelintothepast.

Asatisfyingthoughthitme—mydreamandIhadcomealongway.Then,Irealizedthatpencilsandpenshadbeenputtopaperinthoserowsof

seatsabovemeandthatmyesteemedcolleagueswerebusyscribblingawayastheybeganworkingthroughmycalculations.

One

ADeathintheBeginning

TimestoppedformeinthemiddleofthenightonMay22,1955.Myparents,BoydandDorothy,hadhoursearliercelebratedtheireleventh

wedding anniversary.Momwas theprettiest of all themothers, and I idolizedmysmartdad.Theylookedhappythatevening,anditwascleartheywereverymuchinlove.

MytwobrothersandIknewwewereloved,too.Myearliestmemoryisofahappyfamilyoutingtoaneighborhoodpark.

Thatnight,aSaturday,myparentshadinvitedadozenfriendsovertoourapartment in anewcomplexofprojects at1455HarrodAvenue in theBronx.Thehousewas filledwithmusic and laughter, andmymother hadprepared aturkeydinnerwithall the trimmings.Theadultsmixedbourboncocktails, toldstories,cracked jokes,andsmokedcigarettes.Myfather,a renownedpranksterandelectronicswhiz,hadwiredspeakersallaroundthehouse—includinganewinstallationinthebathroom,whichdispensedmusicwheneverthetoiletseatwaslifted.As it grew late, the kidswere shooed away. Snuggled up inmy bed, Imusthavefallenasleepfeelinghappyandsecure.

Myfatherhadbigplans,andourfutureseemedbright.WeweretorelocateinafewmonthstoLongIsland,whereheplannedtoopenaTVrepairshop.Ahard worker, Dad had been holding down two jobs—working for SigmaElectronics by day and repairing TV sets on nights and weekends. He wasskilled, it seemed, at everything he attempted. He had helped wire the newUnitedNationsbuildinginManhattan,andmadeTVrepaircallsonthelikesofJackieCooperandWalterMatthau,bothofwhom,inappreciationofhiswork,gavehimasignedphotograph.MyfatherbuiltourfirstTVset,completewithamagnifyingscreenthatmadethepicturelarger.Notlongafterthat,hedeliveredtomymaternalgrandparentsinPennsylvaniaoneoftheirtown’sfirsttelevisionsets.Mygrandfather’s favorite pastime soonbecamewatchingwomen’s rollerderby,andhehowledindelightwheneveracollisionsentskatersflyingoffthetrack.

Myfatherwasahandsome,robustmanwithasoftbaritonevoice.Hehadanaturalwarmthwithpeople,andpossessedagentlemannerandkeencuriosity.

Althoughheput in longhours,hewasnever too tired toanswermyquestionsabout how thingsworked.When hewas twelve, he had lost his father, at ageforty-three,tosilicosis,alungdiseasebroughtonfrombreathingsilicadustthatresultsfromthemanufactureofbricks,ajobmygrandfatherhaddoneformostofhisadult life.Iwouldcometorecognizethatmyfatherwasdeeplyaffectedby his boyhood loss. Driven by a determination to rise above a menial laborexistenceforhimselfandhischildren,healsoseemedtroubledbythepossibilityofhisownearlydeath.

MomandDadgrewupandwent to school together inClaysburg, a ruralhamlet in central Pennsylvania. Claysburg’s black population residedpredominatelyintownonShantyRow,whereDad’swidowedmotherlivedinacompanyhousenexttorailroadtracks,andinanoutlyingareacalledTheField,where Mom’s family had a small farm with chickens. My two sets ofgrandparents—Ira and EttaMallett andWilliam and PinkyKimbrough—grewupinMississippiandtogetherventurednorthin1917toescaperacialinjusticeandfindabetterlife;theyendedupinClaysburg,wheremygrandfatherswenttoworkmakingbricksatthe“Brickyard,”asdidmostofthelocalmen.

Somehow,giventheclosenessofthefamilies,itseemedrighttoeveryonewhenmy parents fell in love.Married just beforemy fatherwent towar,mymotherwaspregnantbythetimeheshippedoverseas.DadservedasabattlefieldmedicwithaunitthattookpartinthefirstcrossingoftheRhinebyU.S.troopsinearly1945.Later,Momrevealedthathewasattimeshauntedbythememoryofthesufferinganddeathhehadseenincombat,althoughitwasnotsomethingIheardhimdiscuss.AfewweeksaftercrossingtheRhine,hebecameafatherwhenIwasborninRoaringSprings,Pennsylvania,onMarch30,1945.

After thewarmy father enrolled at aNewYork electronics schoolunderthe GI Bill, and worked as maintenance superintendent for our building inexchangeforfreerent.Afterlearninghistradehealwayshadagoodjob,whichallowedMomtostayhomewithourgrowingfamily.MybrotherJasonwasbornayearafterme,followedthreeyearslaterbyKeith,andthenEve,eightyearsmyjunior.

Dad preached the importance of an education, and would withhold mytwenty-five-centweeklyallowanceuntilIpassedhisquizzes,suchastestingmymemory of the multiplication tables. Once, frustrated by too many wronganswers,hetookmeovertothelivingroomwindow.Belowwasanewhighwayconstructionproject,andIcouldclearlyseeateamofditchdiggersbendingtheirbackstothearduouslabor.“Isthatwhatyouwanttodo?”Dadasked.Itoldhim

no.“Thenyoubettertakemultiplicationandschoolmoreseriously.”Onedayhebroughthomeacrystalradiosetwithearphonesandhelpedme

setitupinmyroom.ByadjustingasmallcoilIcouldhearAMstations.Iwasintrigued with how the device could snatch signals out of the air from somedistance away. Although we had a big console radio in the living room, mycrystalsetseemedmoreamazingbecauseIhadbuiltitwithmyownhandsanditwassosmall.Anothermemorablegift frommyfatherwasagyroscopewithametalrotarywheel,andastringattachedtoaspindle.WhenIpulledthestring,itspun the wheel, which in turn danced atop a little pedestal until the rotationstopped.AsIwatched,itwasclearthattherotationkeptthewheelfromfalling,butwhy?Dad talkedabout theenergyof thespinand theaxisof the rotation,explainingtermsIhadneverbeforeheardbutwhichmadesensetomegivenhiseasy-to-understandexamples.

At this junctureof their lives,myparentshadmuch to look forward to—fourhealthychildren,myfather’snewbusiness,lifeinthesuburbs.OurpreviousChristmashadbeenjoyful.Dadtookonaddedworktohaveextramoney,asheenjoyedseeingstacksofpresentsunderthetree.ItwasimportanttohimforustobelieveinSantaClaus,butbythenIbegantofigurethatthejollybeardedwhiteguyhadsomehelpfromDad.Encirclingthetreewasatraintrack,andaLionelelectrictrainriggedtostopandgoonvoicecommands.

My father was not always the life of the party. He would sometimes sitalone inneardarkness, readingpoems intohis tape recorderwithoperamusicplaying in the background. At these times he seemed very sad, and I didn’tunderstand why. Only in later years would I begin to piece together somepossibilitiesastowhatmayhavebeentroublinghimatthosetimes.

ThatSaturdaynight,aftertheanniversarypartyguestsdeparted,Momtoldmelater,shesuggestedcleaningupinthemorningbecausetheywerebothtired.Withchurchinthemorning,Dadsaidhewouldratherdoitbeforebedandgotstarted.As theyworkedsidebyside, theydiscussedourupcomingvacation toClaysburg;MomwantedtotakethetrainorbusandDadfavoreddriving.Theyhadrecentlyboughttheirfirstcar,andwehadbeenenjoyingSundayrides.

I always looked forward to going to Claysburg and visiting my threesurvivinggrandparents.Wespentmostofoursummersthere,withDadjoiningus for his two-week vacation from work. My brothers and I ran through thefields and hills with our cousins, reveling in the open spaces.My father andmaternal grandfather, Grandpap, got along well and enjoyed one another’scompany.Irecallafamiliarsceneofmyfatherrelaxinginalawnchairreading

anelectronicsmagazine.Inmymemory,Claysburgisalwayssunny,andinthemiddleofoneofthoselazysummers.

Myparentscarriedtheirdiscussionthatnightintothebedroom.WhenMomturned off the bedside light, she heard Dad sigh deeply. Thinking he wasexasperated with her insistence about not driving, she said, “Okay, let’s talkabout it tomorrow.”Shenudgedhimplayfully,andhisheadfelloff thepillowlikeasackofflour.

Awakeningtomymother’ssoftcrying,Igotuptoinvestigate.When I stepped into the hallway, I heard her whimpering. “Oh, Boyd.

Boyd.”Shewas in thekitchenwith the lightson. Ihearda strangevoice, andsawthatapolicemanwaswithher.Downthehallintheotherdirectionwasmyparents’bedroom.IfIturnedleft,I’dgotothekitchen;right,totheirbedroom.

Iwentright,openedtheirdoor,andsteppedintothedarkroom.Myfatherwasunder thecovers.Hewasn’tmoving,buthe lookedfine to

me.Washeasleep?Iwentaroundthebed.Mybrothershadsilentlyfollowedmeintotheroom.BeforeIcouldtouchDad,apolicemanappearedandorderedusout.HetookusintothekitchenwhereMom,dabbingherreddenedeyeswithawaddedtissue,satatthetableshakingherheadsadly.

Wethreeboyslinedupinfrontofher.Shetookadeepbreathandlookedupatus.AlthoughIcannotrememberherexactwords,shetoldusthatDadwasdead. I remember feeling as if I was stuck in some kind of a bad dream Icouldn’t get out of.Everything after that, in fact, becameverydreamlike, andmymemoryisfilledwithfleetingimpressions—somedreadful,othersabitodd.

For some reason, Dad’s body remained in the house until Monday.Apparentlytherewasadelayinfindingthedoctor,whowasrequiredtosignthedeath certificate; Mom also remembers something about a citywide workslowdownbyundertakers.SoDadstayedinhisdeathbed.Asifinslumber,helaytherewiththecoversundisturbed.Inthehallwayoutsidethebedroomstoodauniformedofficerintentonkeepingoutvisitors.Mother,however,insistedongoinginanumberoftimes,andtheguardalwaysrelented.

ThenextthingIrecallaremyauntsandunclesatthehousewithplatesoffood,andbeingtakenasidebyoneuncleandtoldhowIwasnowthemanofthehouse.Iwastenyearsold,twoyearsyoungerthanDadhadbeenwhenhehadlosthisownfather.

AtthefuneralhomeafewdayslaterIstoodatmyfather’sopencasket,stillfeelingasifeverythingwasunreal.MomhadDaddressedinhisbluesuit,andhelookedhandsome.Heseemedtohavefallenasleepwithoutanypainoragony

registeringonhisface.Heseemedsoalive—asifIcouldnudgehimawakeandsay,“Hi,Dad.It’sgoodtohaveyouback.”

Since thenightmy fatherdied, I hadbeen in shock, andnumb—at timesfeelingthiswasnothappening.Iexperiencedthesamedisconnectatthefuneralhome.Thenwetookthelong,slowridetotheveteran’scemetery,wherehewasgivenamilitary funeral,withabuglerblowing tapsandsevenramrodsoldiersfiring their guns into the air three times each, loud reports that causedme tojump.Mom,dressedinblack,satholdingthefoldedU.S.flagfromthecasket.

As I stood lookingdown into thathorribleholeacoldnesscameovermethat Iwouldnot soonshake.As ifawakeningsuddenly,everythingaroundmetookonachillingclarity.Emotionallyconfrontingmyfather’sdeathforthefirsttime,IbegantocomprehendthatIwouldneverseeortalktohimagain.

Dad’sfinalrestingplacewasinLongIsland—theonlyoneofuswhomadeitthere—endingupindeath,ironically,wherewehadplannedtomoveandstartanewlifetogether,andwherehewasgoingtoopenhisnewbusiness.

Ibegancryingaquiet,sorrowfulweepingthatcamefromdeepwithin.WhenIsawmyfatherintohisgrave,hewasthirty-threeyearsold.

Two

MySecretMission

After we buried Dad, Mom went to work at a Manhattan restaurant onForty-second Street making salads and sandwiches to be sold in vendingmachines. She had regular hours, and everymorning on herway towork shewould takemy sister,Eve, to the freedaycare center located in theprojects. IwasresponsibleformakingsurethatmybrothersandIreachedtheschoolbusontime,andforhousekeepingchoreslikefoldinglaundry,dusting,andmoppingfloors. Sometimes I helpedwith dinner—peeling potatoes to have readywhenMom arrived, or cooking hamburgers and creamed corn for my brothers andmyself.

Oneofmyjobswastotakeacartandwaitinlineonceamonthatadepotintheprojectswherefreefoodwashandedoutbyagovernmentagency.Iwouldreturnwith our family allotment of flour, sugar, cheese, and other basics.Mymother’s employer regularly sent her homewith restaurant leftovers. Lookingback,I’mnotsurehowshemanaged,keepingushealthy,fed,andclothedwhiledealingwith theemotionalweightofmyfather’sdeath.Lateatnight, Iwouldhearhercryinginherroom,orcomeuponheratthekitchentablesippingmilkandwhiskeyandlisteningtosadmusic.Mom’slosswasmine,andheranxietywas contagious. Like her, I had no idea howwewouldmanage, let alone behappyagain,withoutDad.

AsIwentaboutmynewroutine,Iwasawarethatsomethinghadhappenedinsideofme.ItwasifIhadshutdown,andwasjustgoingthroughthemotions.Once a naturally exuberant child with a gregarious personality, I becamewithdrawn and sullen.My father’s absence left a void inmy life that nothingseemed to fill.Thehow-and-whyquestions Ihadalwaysput tohimnowwentunasked.Schoolworklostitsmeaning,asIknewtherewouldbenomoreweeklyquizzes thatIneededtobesharpfor.Justhearing theclassicalmusiche lovedcouldbringmetotears.ItwasunbearabletothinkIwouldneverbeabletomeethimattheendofthedayathissubwaystop.Iwasalwayssooverjoyedtobeinhispresence,and thrilledwhenhe letmecarryhis toolbox the restof thewayhome.With his sudden and unexpected departure frommy life,my childhoodended,andhappinesswasnolongermynaturalstate.Inarealway,apartofme

waslostforever.Mombegandating,andevenatmyyoungageIunderstooditwasbecause

shewas terribly lonely.Amongaseriesofmenwasa truckdriverwithwhomshewould get into terrible arguments. I recall us driving one night through adarktunnelsomewhere,andMomandthisguyarguingviolently.Hedrovefastanderratically,andIcoweredinthebackseat,fearinganimminentcrash.Iwasgladwhenhe stopped coming around. IwantedMomnot to be so lonely andunhappy,butnoneofthemenshedatedwereanythinglikemyfather.

TwosummersaftermyfatherdiedwemovedtoPennsylvania.Muchlater,Momtoldmewedidsobecausemymaternalgrandfatherhadinsistedshereturnhome.Concernedaboutherbehaviorwithmen,aswellas thestressof raisingfouryoungchildrenonherown,Grandpapwantedus all underhis roof sohecouldkeepaneyeonherandsoGrandmacouldhelpwithchildcare.By then,Grandpaphad retired from theBrickyard and theyhad leftClaysburg—forcedoutwhenastatehighwaywasbuilt through theirproperty—andmovedfifteenmilesuptheroadtoAltoona,wheremymother’sbrotherlivedwithhisfamily.ComparedtotinyClaysburg,Altoona—population100,000—wasametropolis.However, I never felt as comfortable there as I did in the Bronx or visitingsleepyClaysburg.

Mom went to work as a cleaning lady at a dress shop, and left everymorning looking as if she would be taking over the front office any day.Cleaning lady or not, she had her pride, and when Mom dressed up it wasimpossiblenottonoticeher.Customersbegantoaskheradviceaboutablouseoradress, andshewas soonpromoted,becomingoneofAltoona’s firstblacksalesclerks. It was a lesson not lost on me. I observed that when onecommunicatedaninnerpride,itwasoftenreturnedintheformofrespectfromothers.While Iwas fortunate tohavehadasmartandambitious father for thedecadeIdid,Iamstillblessedtohaveaproudandstrongmother.

The year after wemoved in, Grandpap took ill with the sameBrickyardmalady that had killed my Dad’s father: silicosis, the dreaded “white lungdisease.”IknewGrandpapwasreallysickwhenthetelevisedrollerderbyheldnointerestforhim.MomandGrandmatookcareofhimroundtheclock,andintheendherequiredanoxygentent.Afterhisdeathatseventy-eight,Momfeltitwastimeforustohaveourownplace.UsingDad’sGIhomeloan,shewasableto buy amodest house in an all-white neighborhood, andGrandmamoved inwith us. It turned out the house was affordable because it was located at thebottomofahillrightnexttotherailroadtracksthatranthroughAltoona,which

served as a hub of rail traffic between Pittsburgh and New York. The entirehousewouldshakeonitsfoundationwheneveraspeedingtrainpassed.

The move to Pennsylvania brought about something more drastic thansimply a change in scenery. To that point in my life, being “colored”—thedescriptionofAfrican-Americanspopularatthattime—didnothaveanegativemeaningtome.IntheBronx,welivedinapredominatelyJewishneighborhood,and Ihadnever facedanyhostility.As theonlyblackmemberofawhiteandlargely JewishBoyScout troop, I hadneverbeen treated anydifferently.AndeverysummerwhenwewentonvacationtoClaysburg,mybrothersandIplayedwithourcousinsandtheirwhitefriendswithoutincident.IhadeveryreasontobelievethatthingswouldbenodifferentinAltoona.

Oncesettledinournewneighborhood,mybrothersandIwentexploringtomeet some of the local kids.We spotted a group of four white boys playingnearby, and ran up to say hello. They looked at us, and one of them spat,“Niggers.”Iwasstunned.Ihadneverbeencalledthathorriblename—notintheBronxor inClaysburg.Not anywhere.Something snapped insideme.Leapingforth without regard for the fact that I was outnumbered, I pounded the boyfuriouslywithmyfistsuntilhesaidhewassorry.Noneoftheotherwhiteboysmadeamove,andmybrothersremainedfrozenlikestatues.

ThatuglywelcometoAltoonamademeconsciousofmyraceinanewandnegativeway,andbecauseofmyalreadyprecariousemotionalstate,itmadememoredepressed.Ihadastrongsenseofbeinganoutsider,andlongedmorethaneverformypastlife—whenmyfatherwasaliveandwewerehappy.

After thedeathofGrandpap,mygrandmotherwent rapidlydownhill.Shebegan wandering aimlessly around town, and once took a train to Chicago“looking for my children,” believing that Grandpap and their children werewaiting there for her. When she became unmanageable, Mom was given nochoice but to have her committed to the state hospital, as there were noaffordablecarefacilitiesforpatientswithadvancedsenility—whatwouldlikelybediagnosedtodayasAlzheimer’s.IwentwithmymotheronSundaystovisitGrandma at the hospitalwhere shewas to live out her final years.Once in awhileIcouldglimpseinhervacanteyesthelovingwomanIhadknown,butforthemostpartGrandmaleftuswellbeforeherdeath.

AbjectunhappinessismyoverridingmemoryofmyAltoonayears.Losinginterestinschool,Ibegannotshowingupthere.Sneakingbackhomeaftermymotherleftforwork,Iwouldclimbthroughthebasementwindowandspendthedayaloneinmyroom.Momfoundoutonlywhenatruantofficercametoour

door.ThoughIwasthreatenedwithrestrictions,IcaredlittlesinceIdidn’thaveany friends or activities anyway, so my truancy habit continued through theseventh and eighth grades. Still mourning the loss of my father, I becameincreasingly isolated and embittered. Not interested in games, sports, orsocializingwithmypeers, Iescapedintomagazines,books,andmovies,manyof them fantasy and science fiction,which succeeded in takingmeaway frommyreality.Iindulgedinendlessdaydreamsaboutfaraway,make-believeplacescomplete with good-versus-evil battles and noble heroes—worlds far moreenchantingthanmyown.

IhadbeencaptivatedwiththeKnightsoftheRoundTablesinceDadtookustothe1954moviePrinceValiant.Ihadsinceidentifiedevenmorewiththegallantknightsandtheirnoblecause,wishingIcouldrightaterriblewrong(myfather’s death) and protect a damsel in distress (my mother). Before long, IwouldevenfindmyownHolyGrail,whichwouldleadmeonalongquest.

My life-altering discovery came from an unlikely source. ClassicsIllustrated,publishedby theGilbertonCompany, reprinted167 titles incomic-bookformat(Iprobablyreadallbutadozenorso),summarizingandillustratingforyoung readers theplots of classicbooks.They cost fifteen cents, a sizableexpenditure in light of my twenty-five-cent weekly allowance. I had startedreadingthemwhilestillintheBronx,andbythetimewemovedtoPennsylvaniamycollectionincludedKnightsoftheRoundTable,basedonThomasMalory’sclassic, TheDeath ofArthur; SirWalter Scott’s Ivanhoe;CharlesDickens’ATaleofTwoCities;RobertLouisStevenson’sDr. Jekyll andMr.Hyde;MaryShelley’s Frankenstein; Jules Verne’s 20,000 Leagues Under the Sea; HenryWadsworth Longfellow’s The Song of Hiawatha; Homer’s Iliad; andShakespeare’sJuliusCaesar,Hamlet,andMacbeth.

IvividlyrecallthemomentwhenIspottedClassicsIllustratedNo.133ondisplay in themagazine rackofadrugstorenot far fromourhouse.Thecoverillustrationstruckmelikeaboltof lightning.Asolemn-facedman,surroundedby a futuristic scene, sat atop a strange machine that looked to be a crossbetween a motorcycle and a one-man spaceship. The machine had varioushoops,tubes,andwiresprojectingfromit,andthemanwasgraspingtwoleversthatappearedtocontrolthemachine.Thetitleatthetopread:

THETIMEMACHINE

H.G.WELLS

Entranced, I opened themagazine. On the first page was the sameman,picturedsmokingapipewhileintentlyworkingonthemachineinaroomwithgreenhouse windows. Tools laid out on a wooden platform includedscrewdrivers,wrenches,smalltorch,oilcan,screws,bolts,electricalcords.Themanwastighteningastripofwhitetapearoundsomepartofthemachine.

Printedinthetextboxatthebottomofthatfirstpagewasthefollowing:Scientificpeopleknowverywellthattimeisonlyakindofspace.Wecan

moveforwardandbackwardintimejustaswecanmoveforwardandbackwardin space.Toprove this theory, I inventedamachine to travel through time. Ifyoupressedone lever, themachinewentback into thepast. Ifyoupressed theotherlever,themachineglidedforwardintothefuture.Withthismachine,Isetouttoexploretime.

Iwasdumbfounded.“Wecanmoveforwardandbackwardintimejustaswe can move forward and backward in space. ...” The most incredible andwonderful thing I had ever heard, these words filled my wounded heart withhope. “Scientific peopleknowverywell that time is only akindof space. ...”Expertsknewthis?Didthismean—coulditreallymean—Imightbeabletogobackintimeandwarnmyfathertogotothedoctor,slowdown,takebettercareof himself? Things to prevent that frightful night from happening. Could Ichangehisfate?Andmine?CouldIbringhimback?Idroppedthreenickelsonthecounterandracedforhome.

Aloneinmyroom,Isatonmybedandbeganreading:One summer evening toward the end of the nineteenth century, some

friendsofmineweregatheredinmyhomeinRichmond,England,asIentered.“Goodheavens,man!Whathappenedtoyou?”“Wereyouinawreck?”“I have just traveled through time. I don’t mind telling you the story,

thoughmostofitwillsoundfalsetoyou.Butit’strue,everywordofit....”The time traveler told of having made the last adjustments on his time

machine.“Igaveitalasttap,triedallthescrewsagain,andputinafinaldropofoil.Iclimbedup,satinthesaddle,andtookthestartingleverinmyhand.”Hepushedtheleverforwardslightly,andwithinsecondsnoticedthattheclockonthewallhadmovedaheadfivehours.Hetookadeepbreath,grippedtheleverwithbothhands,“andwentoffintotime.”Whilehismachinestayedinthesameplace, the time around him quickly advanced, and he went through rapidly-

flashingscenesofwhatthefuturewouldhold.He eventually stopped to see the future for himself. The surface beneath

him suddenly became uneven, and themachine reeled over, flinging the timetraveler onto the ground. He found himself in the midst of a forest during arainstorm.Righting hismachine and checking the instruments, he saw that hehadtraveled800,000yearsintothefuture.Hewalkedaroundintherain,cominguponahuge,forbiddingstructurewithnowindowsordoors.

Decidingtoreturntohisowntime,hetookhispositioninthemachineandpreparedtopullbackthecontrolleverwhenheheardvoices.Peoplespeakinga“very sweet and musical language” approached him. He soon knew he hadnothingtofearfromthese“simpleandchildlike”people,whocalledthemselvesEloi, and joined them for ameal.When he returned towhere he had left hismachine,itwasmissing.Hefoundtrackssuggestingthathismachinehadbeendraggedintothenearbystructureandsoliddoorsclosedbehindit.

Soon thereafter, the time traveler saved anEloi fromdrowning in a lake.HernamewasWeena,andshewasbeautiful.Inthanks,shegavehimflowersofa variety he had never before seen. He placed two of them in his pocket toexaminelater.Inthedaysthatfollowed,thetimetravelerandWeenafoughtofftheMorlocks, strange creatures that resembled human spiders, in a nighttimebattle inaburning forest.Finding thedoors to the structureopenandhis timemachinea fewfeet inside,hestarted todrag itoutsidewhen thedoorsclosed.SurroundedbyMorlocks,hequicklyactivatedthemachineandpulledbackonthecontrollever.Heendedupbackinhistimeattheoppositeendoftheroom—thesamedirectionanddistancethattheMorlockshaddraggedthemachine.Thetime traveler then walked into his parlor where his friends had gathered.“Incredible?Yes,” he admitted to his friends. “Take it as a lie, if youwish. Ihardlybelieveitmyself.Andyet...”

Andyet,hehadthosetwoflowersfromWeenastillinhispocket.Beforeleavingmybedroom,Ireadthestoryseveralmoretimes.ThenIwentintothebasementandshutthedoorbehindme.Iknewexactly

whatIwaslookingfor:myfather’stools,lastusedbyhimandbroughtwithusinourmovefromtheBronx.Iopenedthefirstboxwithcompetingdegreesofexuberanceand reverence.Carefully, I laid themoutbeforeme.Screwdrivers,wrenchesofvarioussizes,screws,bolts,nuts,electricalwires.Ifoundinotherboxespiecesofradioreceivers, televisiontubes,anoilcan,solderingiron,androllsofelectricaltape.

AlthoughitwouldtakedaysformetogathertheothermaterialsIneeded,

myplanhadcome together that firstday. Ihadasecretmission thatmademeeagertowakeupinthemorning,andIdidsowithrenewedpurpose.

I tried to build themachine exactly as I saw it on the cover of ClassicsIllustrated, using television tubes, discarded pipes, and other junk. Fromwatching my father work, I knew something about electronics, and he hadalwaysbeenpatientaboutexplainingwhathewasdoing.Ispenthoursdowninthebasementeachday,puttingtogethertheoldtubes,wires,electricparts,andattachingsomeoldcartiresforlandinggear.Finally,itseemedIhadsomething.Ipluggeditinandpulledonsomelevers,butnothinghappened.

I was disappointed but not discouraged. The time-travel story hadmentioned “scientific people,” and I concluded that I needed to learn science.That would allow me to put things together correctly, and build a workingmachine.Butfirst,IwantedtoreadmoreaboutthetimetravelerandWeena.Iwent to the public library and took out Wells’ original book. I needed adictionary for even the first sentence: “The time traveler was expounding areconditematter tous.” Ihad to lookup“expounding”and“recondite” just toget to thesecondsentence.But Idid so,and finished thebook,along thewaylearning that the time traveler’s machine had taken him back before his owntime, too. That scenario gave me renewed hope that my dream was indeedpossible,asIdidnotwishtogointothefutureandmeetthegentleEloianddobattlewiththedreadedMorlocks.No,Iwantedtogointheoppositedirection.

MyquestfromthenonwastopreparemyselfsothatonedayIcoulddesignamachinethatwouldtakemebackintimetobeforeMay22,1955.

Iwantedtoseemyfatheragain.

Three

EinsteinandMe

After my discovery of H. G.Wells’ The TimeMachine, my hunger fortime-travelstoriesturnedinsatiable.

In the summer of 1957, I discovered a comics series, Weird ScienceFantasy. Issue #25 was entitled “A Sound of Thunder,” adapted from a 1952storyofthesamenamebysciencefictionwriterRayBradbury.Ifoundthestory—nowconsideredatime-travelclassic—trulycaptivating.ThoughIhadnowayof knowing it at the time, the inventive plot began to prepare me for futureconsiderationabouttheperplexingparadoxesoftimetravel.

The Bradbury tale involves a private company, Time Safari, Inc., whichspecializes in sending hunters backmillions of years to shoot a dinosaur. Topreventtamperingwiththepast,theycarefullytracethelifespanofaparticularanimal and find out how and when it is to die naturally, such as an agingtriceratops becoming hopelessly stuck in a pit of tar. They then take a hunterback in time justprior to thatevent,andhe isallowed toslay theanimalabitprematurely.After thenaturalcourseofevents takesplace,which thedinosaurwouldnothavesurvivedinanycase,thehuntersarecarefultoremovealltheirbulletsandleavenothingelsebehind.

Oneday,awealthybusinessmannamedEckleswalksintotheTimeSafariofficewith a check for $10,000, the fee for a dinosaur hunt. Eckleswants todown a tyrannosaurus rex, the largest carnivorous dinosaur. He meets theexperienced guide, Travis, and the two men idly discuss the previous day’selectioninwhichaliberalpresidentialcandidatenamedKeithdefeatedanarchconservative, Lyman, whom they agree would have led the country into the“worstkindofdictatorship.”Ecklesisbriefedonthestrictrulesofthehunt—nosteppingoffthepath,havingcontactwithanyfloraorfauna,alteringthedestinyofothercreatures,orotherwise“touchingthisworldofthepast.”Thereason:“Atimemachineisafinickybusiness.Notknowingit,wemightkillanimportantanimal, a small bird, a roach, a flower, thus destroying an important link in agrowingspecies.”Ecklesagreestotherules,andTravisleadsthehuntingpartytoametalmachinethatresemblesaflyingsaucer,“asnakingandhummingofwiresandsteelboxes...[with]anaurorathatflickerednoworange,nowsilver,

nowblue.”With“themerest touchofahand,” theyare soon transportedbackmorethansixtymillionyearsbeforetheelectionofPresidentKeith.

Landing in theCretaceousperiod,whendinosaurs roamed the earth, theytrack a particular tyrannosaurus rex. When they come face-to-face with themassive creature, Eckles panics and runs away.Other hunters bring down thedinosaurwithseveralshots,andsoonthereafteramassivetreelimbfallsatopthecreature,whichhadbeenintendedasitsnaturalcauseofdeath.Thebulletsarecutoutofthecarcass,andthepartydeparts.Ecklesiswaitingforthembackatthe timemachine. Transported back to their time, they find that many thingshavechanged, including the resultsof theelection,withPresidentLymannowset to pursue his “anti-Christ, anti-human, anti-intellectual” agenda. As anexhaustedEcklessitsdown,cakedmudfallsfromthesolesofhisshoes.There,stuck in themud is the smashed remains of a golden butterfly, stepped on byEckleswhen,infullflight,heveeredoffthepathintothejungle.Allthehuntersrealize,withhorror,whattheyhavewrought.“Asmallthing,”Bradburywrote,“thatcouldupsetbalancesandknockdownalineoftinydominoes,andthenbigdominoes,andthengiganticdominoes,alldowntheyearsacrosstime.”

At the library I locatedBradbury’s original story, read it, and ruminated.Forthefirsttime,Ibegantoconsiderthedelicaciesoftimetravel,andrealizedtherecouldbemajorundesiredeffectsonthepresentasaresultofsomethingatime traveler inadvertentlydid in thepast.Bychangingsomethingasminorasthelifespanofabutterfly,theworld’sfuturehadbeenaltered.

Asreadingbecamebothanescapeandapassion,Iwasspendingsomuchtimeat thepubliclibrarythatall thelibrariansknewmebyname.Theyletmecheck out more books than the rules allowed, even titles not in generalcirculation.IwasalsomakingregulartripstotheSalvationArmy,whereIcouldbuyusedpaperbacksfortencents.Withnohesitationaboutspendingmyschoollunchmoneyforbooks,Ibecamesothinthatmymothertookmetothedoctor.As a result of my poor diet, I had developed secondary anemia. The doctorprescribedironsupplement,andtoldMomtoservemeliveratleastonceaweek.WhenMom realizedhow I hadbeen reallocatingmy lunchmoney, shebegansendingmeofftoschoolwithabaglunch.Beforelong,Ifoundanafter-schooljobatalocalbarbershop—shiningshoesandsweepingfloors—toearnmoneytofeedmybookhabit.

Not longaftermy failedattempt tobuilda timemachine,AlbertEinsteinenteredmylife.Notinperson,ashehaddiedinApril,1955,ironically,onlyafewweeksbeforemyfather’sdeath.IrememberseeingtheheadlineintheNew

YorkTimes,andgatheringatthetimethathehadbeenagreatman.Itwas in the SalvationArmy one fall afternoon in 1957 that I happened

upon a thin paperback published in 1948: The Universe and Dr. Einstein, byLincolnBarnett.IrecognizedthenameandimageofEinstein,standingbesidealife-sizehourglass thathad thesunandtheearth in the topandthestarsat thebottom.Iboughtthebook,anditprovedtobeanunderstandableaccountofthestructureoftheuniverseaswellasofEinstein’swork.Hisbreakthrough,Iread,was to treat time as a fourth dimension. He said that the universe had fourdimensions—three of space and one of time—which linked together to formspace-time.IwaselatedtodiscoverthatEinsteinhadstudiedtime,andIknewIwouldwanttolearnmoreabouthisworkinordertoachievemygoal.

TheUniverse andDr.Einsteinwas tobecome the secondmost importantbook of my childhood. At that formative age, I saw little difference betweenscienceandsciencefiction.WhatIreadinthelattergenreseemedforthemostpartasplausibleaswhatIreadintheformer.Infact,learningaboutEinstein’sworkmademeevenmoreappreciativeofH.G.Wells.In1895,whenTheTimeMachine was published, a full decade before Einstein described a fourdimensional universe, the English novelist wrote about time as a fourthdimension.HowcouldWellshaveguessed?3

DivingintotheEinsteinbookwithgreatenthusiasm,Ireadaboutafamousexperiment done by two American physicists, A. A. Michelson and E. W.Morley,in1887.FromwhatIcouldunderstand,theywantedtofindouthowthespeedoflight,whichIreadwas186,000milespersecond,waschangedbythemotionoftheearth.ThatspeedmeantlittletomeuntilIreaditwasfastenoughtocircletheearth10timesinonesecond.Nowthatwasfast!Ididn’tgraspthedetailsof theexperimentat thetime,but itseemedthatMichelsonandMorleywanted toshowthatasyoumoved towarda lightbeam, thespeedof the lightbeam should be different from the speed that youmeasure as you’re movingawayfromthebeam.Tome,thisseemedtomakesense.IfIwasrunningtowardsomeonewhowasrunningtowardme,theywouldbecomingatmealotfasterthanifIwasrunningawayfromthem.ButtothesurpriseofMichelson,Morley,and seeminglyeveryoneelse in the scientific community, theyproved that thespeedof lightdidn’tchangenomatterhowfastyouweremoving toward itorawayfromit.Howcouldthatbe?Iwondered.

Curiousandexcited,Ireadon.Theanswer,Ilearned,camein1905fromayoungpatentclerknamedAlbertEinstein.Einsteinsaidthatlightisspecial,andthat,unlikeeverythingelseintheworld, lighthasthesamespeedwhetheryou

runtowarditorawayfromit.Theproblem,hepointedout,waswiththeclocksthatweuse tomeasure the speedof light.According toEinstein, the speedoflight doesn’t change because the clocks that we use tomeasure it change. Inotherwords,lightisnotaffectedbymotion,butclocksare.

Onpage59ofTheUniverseandDr.EinsteinIcameacrosstheformulathatshowedhowtimewasaffectedbymotion:

The formula was called the Lorentz transformation, developed by DutchphysicistHendrikLorentz.4Thisequationwasexpressedinelementaryalgebra,but might as well have been ancient hieroglyphics. Nonetheless, the Lorentztransformationbecameasortofmantratome.WhileIdidn’tunderstandmuchof its meaning, I did feel its power. I would often repeat to myself and idlyscribble thisequation for timeas though itwassomeholyscript,all thewhilenot really knowing what was being said in the equation. Still, I did graspsomethingessential:Lorentzsaidtime,representedbythelettertinhisequation,couldbeaffectedbymotion.Too, the fact that timecouldbe representedbyasymbolmade it somehow lessmysterious tome.Timewas, in fact, aphysicalobject thatcouldbeworkedwithandchanged.Furthermore,Einstein’s specialtheory of relativity, utilizing the Lorentz transformation, said that time slowsdownthefasteryoumove.Inotherwords,timeslowsdownforamovingclock.

Ididnotfullycomprehendallthearticulationsaboutthemovingclockandthespeedoflightbeingtheoneconstantintheuniverse,butIdidkeepcomingback to time. Tomy eager twelve-year-oldmind, Einstein’s theory of specialrelativityservedasan inspirationbecause it seemed tosuggest that time travelwaspossible,whichI tooktomeanthata timemachinewasalsoapossibility.Now,IjustneededtobetterunderstandwhatEinsteinwassaying.

Turning into an avid collector of information and trivia about Einsteinwherever I could find it, I soon learned that his interest in nature had beensparkedasaboybyacompasshisengineer fatherhadgivenhim.Withwarmmemoriesofthecrystalradiosetandgyroscopegiventomebymyfather,Ifeltmyfirstrealconnectionwiththefamousgenius.IfeltanotherbondwhenIreadthis inspiringEinstein quote: “Imagination ismore important than knowledge.Knowledgeislimited.Imaginationencirclestheworld.”

IwassurprisedtoreadthatEinstein,asayoungman,hadtofindatutorandstudy hard to learn the sophisticated language of mathematics he would laterneedtopresenthisrevolutionarytheoriesabouttime.IcameacrossastatementEinsteinhadmadethatcausedmetosmile:“Donotworryaboutyourproblemswithmathematics.Iassureyouminearefargreater.”Andthis:“It’snotthatI’msosmart,it’sjustthatIstaywithproblemslonger.”

Intruth,allthistalkaboutmathematicsgavemepause.Although I had an idea that—like Einstein—I would eventually need to

learnanewlanguageofmathematicstoattainmygoal,Ihatedarithmetic.

Four

InMyFather’sFootsteps

Understanding Einstein and the still mysterious Lorentz transformationseemednecessaryifIwasevergoingtobuildatimemachine.ButIfeltwhollyinadequate, andnodoubtwithgood reason. Iwasan inquisitive teenagerwholovedreadingevendifficultbooks,yetEinstein’sworkmademyheadhurtfromtryingtounderstandit.

A classic science-fiction film, Forbidden Planet, suggested a plausiblemethodformetoincreasemybrainpower.Inthemovie,atwenty-third-centuryspace traveler visits a planet called Altair Four to find out why its colony ofinhabitants had died offmysteriously. It turns out that the colonists had beendestroyedbycreaturesformedbytheir“unconsciousid.”ThiswasthefirsttimeIhadseenthewordid,andIlookeditupatthelibrary,findingoutitwaspartofthe human psyche that is the source of our psychic energy. Learning that theconceptwasdevelopedbypsychoanalystSigmundFreud,Iwentintothestacksto find his book, The Ego and the Id. Reading it, I became excited about thepossibilityofincreasingthepowerofmybrainsoIcouldbetterunderstandtheworkofEinsteinandotherimportantscientists.Takingbabystepsatfirst,whichinvolvedreadingmoreandmorechallengingbooks,Ieventuallybecameafirmbeliever that people can build intellectual power just like physical musclesthroughexercise;themoreone’sintellectisstimulated,thestrongeritbecomes.

My mental powers were also expanded by two high school courses thatcaughteveryounceofmyimagination:electronicsandalgebra.

Motivatedbymyfather’sbackgroundasanelectronictechnician,Isignedup for an electronics class inmy junior year.A practical course designed forfuture electricians, it covered basic electrical circuitry theory and hands-onwiring. With recollections of my father showing me the inner workings oftelevisions,Inowwonderedifhehadbeenpreparingmetoworkinhisbusiness.Ipictured the sign thatwouldneverbe: “Mallett&SonTVRepair.”Myplanwastotakemyfather’sleadandbecomeanelectricalengineer,whichseemedanidealwaytoacquiretheskillsnecessarytobuildatimemachine.

InthatfirstelectronicsclassIlearnedaboutOhm’slaw,andthemanbehindit. While teaching mathematics in high school in Germany, physicist Georg

SimonOhmdiscoveredthatataconstanttemperaturetheflowofelectriccurrent(I) through a conductor is directly proportional to the potential difference, orvoltage (V), and inversely proportional to the resistance (R). The equation hecameupwithisI=V/R.Althoughhistheorywasatfirstrejected,itsooncametoberecognizedasthebasiclawofelectricity,andthephysicalunitmeasuringelectricalresistancewassubsequentlynamedforOhm.5

I learned that an electric current in a wire is essentially the flow of tinyparticlescalledelectrons.Electronscanbeforcedtomovethroughthewirebyconnecting the wire to a battery, which is a chemical source of energy. Theenergy of a battery is measured by its voltage—named after the eighteenth-centuryItalianphysicistCountAllessandroVolta(1745–1827),whoseinventionoftheelectricbatteryin1800providedthefirstcontinuousflowofcurrent.

A9-volt batteryhasmore stored chemical energy than a 1.5-volt battery.Thehigherthestoredenergyofthebattery,thegreateritspotentialformovingelectronsbetweendifferentpointsofthewire.Hence,thevoltageofabatteryisalso known as its potential difference. The greater the voltage, the larger theflowofelectrons.Ifsomethingischangedinthewire,suchasaddingapieceofwiremadefromadifferentmaterial,thenaresistancetotheflowoftheelectronsoccurs. This resistance is a friction that causes the addedmaterial—such as afilament—to heat up and glow. This is what happens when a light bulb isconnectedtoawirethatisattachedtoabattery.

My electronics teacher, John Bathgate, was a skilled and dedicatedinstructor.HerequiredustomemorizeallthepermutationsofthebasicequationforOhm’slaw.Fromtheequationthatdescribedelectriccurrentflowingfromabatteryintoalightbulb,IcouldseethatifIputalargerbattery(V)inthecircuitthere would be more electric current in the circuit (I), and if I increased theresistance(R)ofthelightbulb—suchasbyusingonewithalongerfilament—itwoulddecreasethecurrent(I)inthecircuit.

These equations were a revelation to me. I grasped how the symbolsrepresentedtheelementsinanelectricalcircuit.Withthisknowledgecamemyfirstinsightintohowmathematicsconnectstothephysicalworld.Mathwould,fromthistimeforward,neveragainseemabstract.

After going over the basics of house wiring, we moved further intoelectronics,learninghowelectronsarecontrolledtoproduceradiowaves.Whenelectrons are forced to move rapidly (oscillate) back and forth along a wire(antenna), radio waves are generated that move through empty space and arepicked up by a receiver. The radio waves caused electrons in the receiver to

oscillate.Thoseoscillationsareconvertedintothevibrationsofthediaphragmofaspeaker.Thesoundwehearfromtheradioisduetothevibrationoftheairbythediaphragmofthespeaker.

My cousin, Jones Kimbrough, was inmy electronics class. A year olderthanme, Jones was also fascinated by electronics.We shared the notion thatthroughelectricity theworld couldbe changed.Wehad to lookonlyas far asradioandtelevision,andwonderwhatothermodernmiraclescouldbeshapedbyelectronics.Inthiscontext,Itoldhimaboutmyplanstobuildatimemachine;infact,hewasthefirstpersontowhomIrevealedmysecretproject.Jonesdidnotlaugh,andhetoldmehedidn’tthinkitwasbeyondtherealmofpossibility.Heagreedthatknowingelectronicscouldbekeytomysuccess.

Attheendofthecourse,wewererequiredtopresentMr.Bathgatewithabinderofneatlywrittennotescoveringtheentirecurriculum.Istayedupseveralnightswithoutsleep,rewritingmychaoticlecturenotes.ItwasthehardestIhadeverworked in school. I relishednotonly the learningexperiencebutalso thementaldiscipline.TheworkwedidintheclasswithequationsmademerealizeIneeded togetovermymathphobiaandsignup foralgebra,which Ihadbeenavoiding.

Itookalgebramysenioryear,andtomyshockfoundthatitcamenaturallytome. I loveddoing theequations,andwouldworkand reworkproblemsdayandnight forentertainment.Algebraseemedmagical tome;numberscouldberepresented by letters, and then you could do anything with those symbols. Ireceived nearly perfect grades and went to the top of the class. During onesession, the teacher,EthelynFurrer,whohadawayofmakingnumbers comealive, talked about a formof highermathematics that she saidwas evenmoreinteresting thanalgebra.Right then Idecided that Iwouldoneday learnmoreaboutthisintriguingsubjectcalledcalculus.

AsjazzedasIwasaboutalgebra,Ihadtheoppositeexperiencethatyearinphysics, taught by aworn-out general science teacherwho spent a lot of timereadingaloudfromthetextbook.Writingonthechalkboardanequationsuchasthe trajectoryofaballwhen it is tossed,hewouldshowus theresultswithoutexplaining the process, leaving out important details like what forces the ballwentthroughfromthetimeitwasthrownuntilitlanded.AlthoughIpassedthecourse, physics struck me as boring and somewhat incomprehensible. Thisdisappointed me because Einstein was a physicist, and I continued to becaptivated by anything I read about his life and work. For some years, thisdisconnectexistedformebetweenthegreatmanandphysics,thesamefieldthat

infutureyearswouldbecomeformeaworldofexplorationandadventure,andinwhichIwouldfindmyownacademicandscientifichome.

Myvastlydifferentexperiences inalgebraandphysicsprove thevalueofinspiring teaching, and the positive impact on an impressionable student, asopposedtoalackadaisicalteacheruninterestedinlightinganyfires.WhenIlaterbecameaclassroomteachermyself,Itriednottoforgetthatlesson.

With my new found skill in algebra, I discovered that I could begin tocomprehendtheLorenztransformation.ReturningtothebookTheUniverseandDr.Einstein I could now see that, prior to theLorenz transformation, time onsomeoneelse’sclock(t')andtimeonmyownclock(t)wasalwaysthesamenomatter how fastwemovedwith relation to eachother.According to classical,pre-Einstein physics, time was an absolute, and regardless of our differentspeeds, the equation was always t' = t. This equation states that time is notchangedbymotion,and,therefore,timetravelisnotpossible.ButaccordingtotheexcitingrelativityphysicsofEinstein,ifI’mmovingveryfastandsomeoneelse is standing still (or vice versa), then t' does not equal t. Because I ammoving, theother person’s time is not equal tomy time. In relativity physics,timeischangedbymotion—andtimetravelispossible.

AsIaccumulatedthecombinedknowledgeofelectronicsandalgebra,IwasthrilledtobegintoactuallyunderstandEinstein’swork.

Thingschangedathomeaftermymotherremarriedin1960.HisnamewasJuliusOscarWilliams,andwecalledhimBill.Hewasadecentmanandgoodprovider, which greatly improved our financial situation.Mom didn’t have toworkasmanyhoursandwasabletospendmoretimeathomewiththeyoungerkids.Andsoon,therewasanewonetocarefor:mybabysister,Anita.

Although at fifteen I was old enough to give Bill credit for taking on awidowwith four children,we did not grow close.A high school dropout andnonreader,hehadnointerestinanythingintellectual.Infact,heoftenbadgeredmewheneverhesawmynoseburiedinabook.“Whatareyoudoing?”hewouldaskasifIwascommittinganindecentact.“Reading,”Iwouldanswerwithoutlookingup.Hebelievedthatteenageboysshouldbeinterestedincars,girls,andhunting, thelatterbeinghisownpassion.“There’ssomethingwrongwithyouroldestson,”hewouldcomplaintomymother.“Allhedoesisreadandgotothelibrary.”Momdeclinedtogetinthemiddle,andIkeptdoingwhatIlikedbest.Intruth,somethingelsecamebetweenBillandme.Ihadelevatedmyfathertosuchmythicproportions that Ihadnoroominmylife forastepfather,whoinanyscenariowouldnodoubtproveaninferiorsubstitute.

The fire inside me that kept the memory of my father alive was furtherstokedbyachanceencounter.ItturnedoutthatmymotherkeptallofDad’sreelaudiotapes in the basement of our house. Discovering them one afternoon, Ibroughtseveralofthemupstairs.ThefirstoneIplayedwaslabeledRubaiyatofOmar Khayyam. At first there was opera music, then I heard the deep, richsoundofmyfather’svoicethatIhadnearlyforgotten.

Awake!FormorninginthebowlofnightHasflungthestonethatputsthestarstoflight:Andlo!ThehunteroftheeasthascaughtThesultan’sturretinanooseoflight.

Iwasstunned.ThiswasoneofthepoemsIrememberedmyfatherreadingin the living room of our Bronx apartment, when he had seemed so sad andlonely.

Lo!Someweloved,theloveliestandthebestThattimeandfateofalltheirvintageprest,Havedrunktheircuparoundortwobefore,Andonebyonecreptsilentlytorest.

A sorrowful longing came from somewhere deep insideme. Iwanted somuchtoseemyfather’skindfaceagain.Then,asIlistened,herecitedthestanzathatmademeunderstandwhat this poemmayhavemeant to him, andwhy itmadehimsosad.

Ah,makethemostofwhatweyetmayspend,Beforewetoointothedustdescend;Dustintodust,andunderdust,tolie,Sanswine,sanssong,sanssinger,and—sansend!

OnceIlookedupthedefinitionofsans,themeaningofthisstanzahitme.Iremembered the preacher atmy grandfather’s funeral saying, “Ashes to ashesanddusttodust.”Iknewthispoemhadtobeabouttheshortnessoflife.Iwasconvincedthatmyfatherwasreadingthispoembecauseheknewhewasgoingto die soon. I listened to the tape over and over, unwilling to let go of thisaudibleproofthatIoncehadafatherandknewhappiness.

As I look back, I believe that this taped message from my dead fathercausedmetobecomeobsessedwithdeath—otherpeople’saswellasmyown.IstartedtoreadthepoemsofEdgarAllanPoe,andcouldrecite“TheRaven”inits entirety at age fifteen. Death seemed a close companion at an age that Ishouldhavebeenfeelingyouthfulimmortality.

Afterreading,moviesweremynextfavoriteformofentertainment,andinthat regard 1960 represented a special year with the release of The TimeMachine,starringRodTayloras thetimetraveler.Thefilmplayedat theStateTheater in downtownAltoona for twoweeks, and I saw it five times, settlingeachtimeinthefifthrowcenter,withaboxofbutteredpopcorn,alargeCoke,and eyes riveted to the big screen. Iwas astounded by the time-travel specialeffects.Againthisvividstorygaveflighttomyimagination,andmadememoredeterminedthanevertoonedaybuildmyowntimemachineandseemyfatheragain.Thepromiseofdoingsoseemedalmostrealenoughtotouch.

That same year a new TV show debuted that won my undying loyalty.Twilight Zone aired on Friday nights, and I always made a point of rushinghome from the library, where I oftenwent after dinner, stopping only to buychocolatemilkanddonutstosnackonduringtheshow.Itwasimportantnottomiss the introductionbyRodSerling,whospokeoverspine-tinglingmusicsetagainst a defused sky representing themysteries of the universe, with imageslikeatickingclockandEinstein’sE=MC2equationfloatingacrossit:“You’retraveling through another dimension, a dimensionnot only of sight and soundbut of mind; a journey into a wondrous land whose boundaries are that ofimagination.That’sthesignpostupahead—yournextstop,theTwilightZone!”Pourthemilkandpassthedonuts.Mynextstop...

AsignificantnumberofTwilightZonestoriesinvolvedtimetravel,whichofcourseheldmespellbound. Inoneclassicepisode,“The7thIsMadeUpofPhantoms,” a trio of National Guardsmen conducting war exercises in a tankneartheLittleBighornencountersevidencethatanotherbattleisgoingon—thehistoriconethatoccurredin1876.Theirdilemmabecomeswhethertorolltheirpowerful tank into the battle to save Custer and his men, and thereby alterhistory, or leave well enough alone and allow the massacre to happen.Compromising,theyabandonthetankandenterthebattleonfoot,disappearinginto the fray. Time lapse to present: their National Guard comrades find thedeserted tankbutnosignof the threemen—until theycheck thenamesof thedeadlistedattheCusterBattlefieldNationalMemorialnotfaraway.Ithoughtitinterestingthatthethreetimetravelershaddecidedtojointhebattleandbecome

participantsinhistorywhilenotattemptingtochangehistory,asthedeploymentofamodern-daytankatLittleBighorncertainlycouldhavedone.

From the world of science fiction, I developed an interest in computers,which were then primarily mainframes the size of a large room. They wouldsoon start to shrink in size while computing power increased as a result oftransistors replacing vacuum tubes. Compact computers were required for theU.S. space program, gearing up after the launch of the Soviet Union’s firstSputnik satellite in 1957.Given all the space travel stories I devoured, I fullyexpectedmanwould get into space, so the launch of Sputnik and the suddeninaugurationoftheSpaceAgedidnotcomeasasurprise.Idorecallhowupsetpeople inAltoonawere that theSovietsmade it into space first and that theirsatellite could at times be seen streaking overhead, glinting against a starrybackdrop.

Convinced that computers would be increasingly important in the yearsahead, and hopeful that as artificial brains they might one day be an aid inbuilding my time machine, I decided on the topic “The Role of ElectronicComputers inOurFuture” formy seniororation inEnglish. Ididnotmentionanythingaboutmytimemachineplansforfearofbeingridiculed,butIdidopenwith a kind of Twilight Zone scenario. I askedmy classmates to imaginewewere in the twenty-second century and that we had already landed on all theplanets andwere starting to reach out to the stars—all thanks to computers. Iwentonfromtherewithsomefactsmixedinwithafewfancifulpredictions,atleastsomeofwhichwouldcometrueinthedecadesahead.MyEnglishteacher,Mrs.Rhodes,whohadpassedalongtomeandmanyofherstudentsherloveofShakespeare,was kind enough to tellme that itwas one of themost originalseniororationsshehadeverheard.

Although I was coming into my own academically and feeling moreconfident,collegewasoutofthequestionforfinancialreasons.IknewtheonlywayIwouldeverbeabletocontinuemyeducationwouldbeifIwentintothemilitaryand then,when Igotout,used theGIBill togo toschool, justasmyfatherhaddonetoacquirehiselectronicstraining.

I tookanairforceaptitudetestandscoredin theeightiethpercentile.Therecruiter said that my score combined with the fact that I had taken twoelectronicscourses (the secondone inmysenioryear involved radio receiversand repairingelectroniccircuits)wouldguaranteemyentry into theair force’selectronics school. Then he said something else—that the Strategic AirCommand(SAC)wassettingupanewsystemofcomputersnationwidefor its

command-and-control systems, and electronic computer technicians wereneeded.Isignedonthedottedline.

The recruiter said he assumed that, like most boys just graduating highschool,Iwouldwanttospendthesummerathomeandhaveagoodtimewithmyfriends.HecouldarrangeformetostartbasictraininginSeptember.

“HowsooncanIleave?”Iasked.Helaughed,thinkingIwasjoking.Butofcourse,Iwasnot.“Sir,Iwanttoleaveassoonasyoucanschedulemetogetoutofhere.”TwoweekslaterIwasonatrainleavingAltoona.FromawindowseatIwatchedaswesnakedthroughsteepridgescutinto

themajesticAlleghenyMountains.Icouldnotknowwhatthefutureheldforme,butIwaseagerforittostart.

Five

AProjectUnderDevelopment

WithinminutesofsteppingoffamilitarybusatLacklandAirForceBasenearSanAntonio,Texas,Iwasinagroupofotherrecruitsbeingyelledatbyahard-nosed, ill-tempered training instructor nicknamed the Gray Fox. Hepronounced us the worst bunch of “rainbows”—slang for recruits due to ourmulticoloredcivilianattire—hehadeverseen.Hesaidevenourmotherscouldnotsaveusnow,andannouncedthatourlivesandassortedbodypartsbelongedtohimandtheUnitedStatesAirForce.

IbegantothinkIhadmadeabigmistake.We ran everywhere anddrilled incessantly in a stifling heat.A season in

hellcouldnothavebeenmuchhotterthanthatTexassummer.Whenitreached120degreesaredflagwasraised,signalingtherewastobenomorerunningthatdayandeveryonewastostayindoors.Noflagwentupwhenitwas110or115,andoverheatedrecruitspassingoutbecameadailyoccurrence.

Standardbasictraininglastedeightweeks,butbecauseIwasgoingontoatechnicalschoolIwasletoutaftersixweeks,andsenttomyschoolforthefinaltwoweeksofbasicbeforestartingmyelectronicsclasses.AlthoughIwashappytobe leavingTexas, Iwondered if Iwasgoing from theproverbial fryingpanintothefireasIboardedabusforKeeslerAirForceBaseinBiloxi,Mississippi.Keeslerwassupposedtobeatopmilitaryelectronicstrainingcenter,andIwasexcited about the course work I would be doing there. On the other hand,growingupIhadheardsomeveryscarystoriesaboutMississippi.

In 1912, some five years before the familymigrated north, mymother’soldersister,Lavinia,hadbeenborninKosciusco,Mississippi.AuntLaviniawasagentlewomanwhostoodbarely five feet tall.Shewasmygodmother,and IlovedvisitingherandUncleGeorgeinClaysburgduringoursummervacations.AsIgotolder,Iwantedtoknowwhatlifehadbeenlikewhenshewasgrowingup in Mississippi. She saddened whenever she related some of the dailyhumiliations my grandparents suffered. She said that black people weren’tallowedtogointocertainstorestobuythings.AuntLaviniarememberedatimemy grandmother took her shopping for flour. Grandma worked for a certainfamily picking cotton, andAuntLavinia remembered the store clerk shouting:

“Hey, isn’t youMiss so-and-so’s nigger?Don’t youknowyou’re supposed tocome in with her to get the flour?” Black people, more often than not, werereferredtonotbytheirgivennames,AuntLaviniatoldme,butasthe“nigger”ofthepersontheyworkedfor.

Shortly after moving to Altoona in 1956, I heard from my cousins aterrifying story about a black youth from theNorthwhowasmurderedwhilevisitingrelativesinMississippisimplybecausehewhistledatawhitewoman.Ihave since found thatvirtually everyblackmalewhogrewup in the ’50sand’60s heard this same story, and all were as terrified and angered by it asmycousins and Iwere.6Partof the loreof theAfrican-Americancommunity, thechilling story served as a kind of coming-of-age for myself and many otheryoungblackmales.“WebeststayoutofMississippi,”myNortherncousinsandIhadallagreed.

Andhere Iwas sixyears lateronabusheading thatway.Aswecrossedinto Mississippi, passing thickets of strange, flowered trees that someoneidentified as magnolias, I ruminated about the stories told by my aunt andcousins. Iwas returning to the very placemygrandparents had fled to escaperacial injustice.Were timesdifferentnow? Iwondered.Had thingschanged inMississippi?

Biloxi isasmall town locatednear thesoutheastcornerofMississippionthe Gulf Coast. The daywas hot whenwe arrived at the base, and I felt myclothessticking tomeassoonasIsteppedoff thebus.Thingsgothectic rightaway,andforawhileIhadlittletimetothinkaboutthoseoldstories.

WhenIreceivedmyfirstdaypasstoleavethebase,IwentintoBiloxiwithsomeclassmates.The first thing I noticedwere the signs, the likesofwhich Ihadneverbeforeseen.“WhitesOnly.”“NoColored.”Thentherewerethecoldstaresof the locals as Ipassedbywithwhite servicemen.Thiswasbefore theCivilRightsBillandduringMartinLutherKing,Jr.’sactiveyears;insomanyways, I realized, it was still the JimCrow South ofmy grandparents’ days. IunderstoodveryquicklywhytheyhadgoneNorthinanefforttoimprovetheirlives, andwhyGrandpap had not permittedmymother to visitmy father at amilitarybaseinMississippibeforeheshippedoverseas.

Hushedstorieswere toldbyair forcepersonnelaboutblacksdisappearingwhen they happened into thewrong sections ofBiloxi.On base,we could goanywhereandbetreatedasequalsduetofederallaw.Butoffbasewecouldn’tgo through the front door of a hamburger joint—“colored” were shooed to aback door or service window. I was terrified and angry at the threatening

meannessofitall,ofbeingjudgedoutwardlybythecolorofmyskinandnotformyvalueasahumanbeing.ThebigotrythatIhadlashedoutatshortlyafterwemovedtoAltoonanowsurroundedme.

WhenIreturnedfrommyfirsttripintotown,myragewaspalpable.HereIwasintheuniformofmycountry,beingaskedtopossiblydieunderOldGlory,while not being allowed to live in this country equally with other citizens. Imadeavow,atthatpoint,toremainonbaseforthedurationofmytraining—sixmonthsofbasicelectronicsandthreemonthsofadvancedtraining.Iresolvedtospendmyfreetimestudying,readingorwatchingmovies.WiththeexceptionofgoinghomeforChristmas,Ikeptmypromisetoremainonbase.

The rigorouselectronics traininghelpedme tochannel someofmyangerand other emotions. The trainingwas divided into twenty units called blocks.Thirteen blocks were devoted to basic electronics training and the remainingseven blocks consisted of an intensive study of electronic computerfundamentals.Frommyhighschoolcourses, Iwasalreadyfamiliarwithmuchof the basic electronics. The computer training, however, was fascinating andnew tome.Wewere required to learnaspecialmathematical techniquecalledBoolean algebra. This algebra aided our understanding of how computersprocesseddata.Booleanalgebramakesuseofabinarycodethat isusedbyallcomputers.Inbinarycode,onlyonesandzeroesareusedtorepresenttheusualnumbering system. For example, the usual sequence (0,1,2,3,4) would berepresentedbythebinarysequence(0,1,10,11,100).Computercircuitsarequitesimple devices that are either on (1) or off (0).Because of this simple circuitbehavior,binarycodesareacompletelynaturalwayforcomputerstodealwithnumbers.

InOctober1962,mysenseofpersonal isolationwas temporarilydwarfedbythethreatofall-outwar.AfewmonthsafterIarrivedatKeesler,thenationwas thrust into the nuclear face-off with the Soviet Union during the CubanMissileCrisis.Aswe hadn’t finished technical school yet,we speculated thattheywouldgiveus rifles and sendusdown toFlorida to protect the coastlinebecauseweweren’tworthmuchelse to theair force. Itwasakindofgallowshumortorelievethetension,aswewerecertainthatnuclearwarwasimminentand that mushroom clouds would soon materialize on the horizon. After theworldavoidedanuclearholocaust,IwentbacktotryingtosurviveMississippi.

Toeasemyloneliness,Ispentmostofmywakinghoursinthebaselibrarywhennotintheclassroom.Mylongtimeinterest inEinstein’sworkhadturnedinto a hunger to learn more about the man behind the famous theories and

equations.Browsing the stacks, I foundEinstein:Profile of theMan, byPeterMichelmore.Settlinginawell-litquietcornerofthelibrary,IopenedthebookandbecameimmediatelyabsorbedinEinstein’spersonallife.

ThefirstthingaboutEinsteinthatsurprisedmewasthathehadchildren.Inthe author’s note, Michelmore discussed having conducted an interview withEinstein’s oldest son, Hans Albert. There had been no mention of EinsteinhavingafamilyinanythingIhadpreviouslyread.Thefactthatthegreatgeniushadbeenafathermadehimseemallthatmorerealtome.

AlbertEinsteinwasbornonMarch14,1879,inthetownofUlm,Germany,to a well-to-do Jewish family, and grew up in Munich. His engineer father,Hermann,movedthefamilytoMilan,Italy,leavingAlbertbehindtofinishhighschool inGermany.Albertwasunhappyat theabandonment,andmade lifesounpleasantforhisteachersthathewasallowedtodropout.AlbertimmediatelyjoinedthefamilyinItaly.Sincehewantedtobecomeascienceteacher,hewentbacktoschoolinAarau,Switzerland,andattainedhishighschooldiploma.Atseventeen he began studying at the esteemed Zurich Polytechnical School.Although his father urged him to learn a trade, such as electrical engineering,Albertwasdeterminedtostudytheworldofscience,anddecidedtospecializeinmathematicsandphysics.Aftergraduatingfromcollege,hemarriedaclassmate,Mileva Maric, a trained mathematician. Unable to find a teaching jobimmediately, he went to work at the Swiss patent office in 1902 in Bern,Switzerland,whileattendingtheUniversityofZurich,wherehewouldearnhisPh.D.fouryearslater.

IrespondedtoEinstein’sfiercedeterminationtotakehisownpathinlife.Duringtryingtimes,heheartenedhimselfwithEmerson’sline:“Ifamanplantshimselfindomitablyonhisinstincts,theworldwillcomeroundtohim.”Einsteinwasdescribedasa“pleasantandconventionalgood-lookingyoungmanwithacarefullytrimmedblackmustacheandneatlybrusheddarkhair,”whichIhadahardtimeassociatingwiththepicturesIhadseenoftheelderlymanwithwild,funny-looking white hair. “Only the eyes dispelled an impression of thecommonplace; theeyeswerebothbroodingandbrisk,restlesswithenergyandintense in quick perception.” The year before he received his doctorate inphysics—1905—is known as Einstein’s miracle year. He won his firstinternational recognition that year with five published papers: the first on thephotoelectric effect, inwhich he demonstrated the particle nature of light; thesecond on determining the size of molecules; the third on Brownian motion,demonstrating the existence of molecules; the fourth on his special theory of

relativity;andthefifthpaperasupplementthatincludedhissoon-to-be-famousmass and energy equation, E =MC2. By the age of twenty-six, hewas fullylaunched,withprofessorshipsandresearchpositionsfromwhichtochoose.

Einstein’searlypersonallifewasalsoeventful.In1904,hisfirstson,HansAlbert,wasborn.In1910,whileEinsteinwasaprofessoratZurichUniversity,asecondson,Eduard,wasborn.Einstein’sreturntoGermanyin1914tobecomeaprofessor atBerlinUniversity seemed to cause problems between himself andMileva. In 1919,Mileva andEinsteinwere divorced, and he soonmarried hiscousin, Elsa. Einstein had a full life, which included playing the violin andsailing.Ilearnedthathesometimesdidhismostimportantthinkingwhilesailinghis small boat on a lake. Even with everything that was happening in hispersonallife,Einsteinwasabletofocusonhiswork.Ilearnedthatheconsideredhisgreatest triumphtobehisgeneral theoryofrelativity,sometimescalledhis“theoryofgravity,”whichhepublishedin1916.

Michelmorementioned a book of essayswritten by Einstein called IdeasandOpinions.Findingthebookinthelibrary,IwasamazedbyallthesubjectsinwhichEinsteinwas interested besides science. I could hardly believe it buttherewasanessayentitled,“Minorities.”AsIreadwhatEinsteinhadwritten,Iwasdeeplymoved that heunderstood theproblems that blackpeople faced inthiscountry.Hewroteeloquentlyaboutthe“tragedy”and“unfairtreatment”ofthe“AmericanNegro.”ThismademefeelallthemorethatEinsteinwastrulyagreathumanbeingaswellasagreatscientist.

“The power of our imagination,” Einstein once said, “is greater than thepowerofourintellect.”Ofallthepeopleintheworldtohavesaidthosewordstheycamefromperhapsthegreatestintellectofthetwentiethcentury.WhatdidthatsayaboutEinstein’spowerofimagination?And,Iwondered,whatmighthethink of where my imagination was taking me?Would Einstein consider mydreamtobuildatimemachinewildandcrazy—orimaginativeandpossible?

Afterninemonths, I finished theelectronicsandcomputer training. IwasexcitedaboutwhatwasgoingtohappennextandespeciallyaboutgettingoutoftheSouth.AspromisedshouldIfinishinthetoptenpercentofmyclass—whichIdid—upongraduationIwasallowedtoselectaStrategicAirCommand(SAC)base for assignment. I requested a location thatwas closest toPennsylvania—andatthesametimethefarthestNorth.

I soon settled into my duties at Lockbourne Air Force Base outside ofColumbus,Ohio.MyjobwastohelpmaintainthecomputersystemforSAC’srefueling wing. I was responsible for a room-size, solid-state mainframe that

monitoredthedistributionof theair tankersaswellas theB-52bombers toberefueledin-flight.Shouldthecomputerbreakdown,whichwasseldom,Iwouldbringonlineabackupsystem, then repair anyhardwareproblemor send forasoftware specialist. It was easy duty, sitting at a desk watching the blinkinggreen lights thatmeanteverythingwasfine,andreactingon therareoccasionswhenaredlightflashed.Ivolunteeredforthegraveyardshift—midnightto8:00AM—therewere fewsupervisorsaroundbecause theypreferredworkingdays.Enough ofmy fellow techniciansweremarried andwanted to spend nights athomethatIwasabletoworkgraveyardforthenexttwoyears.Isataloneinthecontrolroomthroughtheweehours,freetoreadandstudytomyheart’scontentas long as those green lights stayed on. The graveyard shift was great forcatchinguponmyacademicstudies.Theair forceencouraged itspersonnel totake correspondence courses, and I signed up eagerly for different subjects.SinceIhadnosociallife,Ihadplentyoftimetohitthebooks.Whenitwastimetotakeatest,IreportedtoanofficewhereIwasgivenatimedexaminationwithaproctorpresent.Theanswersheetsweremailed in,andI received theresultsbackinthemailshowinganyquestionsIhadgottenwrong.

Although it could be difficult taking advancedmath as a correspondencecourse without a teacher present to explain equations, I enjoyed working andreworkingtheequationsandwasusuallyabletofigurethemout.Inthisway,ItookalgebraIIandgeometryandalsoanalgebra-basedcoursecalledsolid-statedevices—required by the air force as part of the continuing education forcomputertechnicians—thatdescribedtheelementaryphysicsofsemiconductorsandtransistors.IhadreceivedsometrainingatKeeslerintheareaofsolid-statedevices such as transistors (the new SAC computers were all solid state,replacingoldermodelswithvacuumtubes),butthisadvancedcoursewentintomoredetail about thebehaviorof theelectron, the lightest electrically-chargedsubatomicparticle.7Ilearnedinthiscoursethatanelectronbehaveslikeawaveratherthanlikeaparticle.Noneofmyearliertechnicaltraininghadpreparedmeforthisrevelation.Sincehighschoolelectronics,Ihadthoughtofanelectronasalittlebilliardballrollingmerrilyalongthroughavacuumtubecreatingsparks.

Theauthorsof thecorrespondencecoursewenton tosay thatanAustrianphysicistnamedErwinSchrödinger (1887–1961)hadbeen the first toproduceanequationtodescribethewavelikebehavioroftheelectron,whichcouldpassthrough barriers and do all kinds ofmagical things.They pointed out that themathematical training needed to understand the equation went far beyond thecourse,butthattheywoulddisplaytheequationsoitcouldbeappreciatedlikea

beautifulworkofart,eventhoughonemightnotunderstandwhatwentintoitscreation:

Theauthorswerecorrect:Iunderstoodnothingabouttheequation,butwasmovedbyitssymmetricalbeauty.Iwrotetheequationdowninmyownhandasifitwouldmakemoresensecomingfrommypencil.Ilovedthewavylines,andtherepetitivenessofthesymbols.Inasmuchasthecharacteristicsofanelectronwereresponsibleforthisregal-lookingstatement,Iwasdeterminedtodevotemyefforts to learning more about electrons in the hope that one day I wouldunderstandeachsymbolofSchrödinger’sequation,forwhichhesharedthe1933NobelPrizeforPhysics(withEnglishphysicistPaulDirac)for“thediscoveryofnewproductiveformsofatomictheory.”

It was about then that I began to view myself as a project underdevelopment; I sensed thatmy intellectualwingswerebeginning tounfold. Inpreparingmyselftobeaknowledgeable,scientificperson,Ireadconstantly.

We had the option to eat our meals on base or receive a monthly foodallotmentandfendforourselves(wecouldstilldineinthemesshallbutwouldbechargedformeals).Ioptedfortheallotment,andreturnedtomyoldwaysofusing food money to buy books. As I ran low on funds near the end of themonth,mydietbecamesomewhatlimited:chocolatemilkandpotatochips.

I looked forward to my regular forays into town, which I dubbed my“ColumbusBookRaids.”Oneusedbookstorebecameafavorite; it specializedintechnicaltitlesatlowprices.There,Iunearthedsomeremarkablebooks.

The Strange Story of the Quantum, by Banesh Hoffman, wasnonmathematical, yet it was billed as being faithful to the basic concepts ofquantum mechanics, which were described as the branch of mathematicalphysicsthatdealswithatomicandsubatomicsystems.“Themagnificentriseofthe quantum to a dominant position in modern science and philosophy,”Hoffman wrote, “is a story of drama and high adventure often well-nighincredible.”ThebookdidreadlikeanArcticadventure,andIwasmesmerized.AsIreadHoffman’sbook,Irealizedthatthepeople—Schrödingerandothers—who wrote the mathematical equations to explain a world that had mecompletelycaptivatedwere theoreticalphysicists.For the first time I seriouslybegantowonderwhetherphysics,ratherthanengineering,mightbeabetterroadformetofollowtogaintheskillsnecessarytobuildatimemachine.

Quantum Physics of Electronics, by Sumner N. Levine, was a

comprehensive textbook for first-year graduate students. Although I was lostwhenIfirstcrackeditonthegraveyardshift,Iwasdeterminedtokeepatituntilthingsbecameclearer.Itwouldtakeawhile.Theprefacerecommendedthatthereader be familiar with vector calculus, elementary matrix algebra, and basicphysicsinordertofullyunderstandthematerialcoveredinthebook.

Unhappily,thereweretimeswhenmynocturnalstudieswerecutshortandmy comfortable routine was interrupted. This happened on the infrequentoccasions that I had towork either the dayor swing shift.At these times, theugly face of prejudice sometimesmade its appearance.Oneof the technicianswas constantly preening himself. Someonemust have told him he looked likeElvisPresley,andhe thoughthewashotstuff.OneafternoonElvisstoppedatmydeskandsaid,“Mallett,youlookjustlikeSammyDavis,Jr.”Ihadastrongsense from the way his words came out that it wasn’t complimentary.Admittedly,Ihadlostweightonmymeagerdiet,andcouldcorrectlybecalledskinny. I smiled, and said, “Yeah, and have you seen Sammy’swife?” I wasreferring, of course, to the blonde Swedish actress, May Britt. Elvis’s eyesnarrowed,andheemitteda forced laughashemovedaway. It feltgood that Ihadgottentohim.

Ironically, I had recently read Sammy Davis, Jr.’s autobiography, Yes ICan, which had been a revelation of sorts. Here was a black man, highlysuccessful,who lived life on his own terms. I identifiedwith SammyDavis’sstruggleagainstprejudice.WhenDaviswasinthearmyduringWorldWarII,agroupofsouthernrecruitsgangeduponhimandcoveredhimwithwhitepaintbecausehehadbeenseentalkingtoawhitefemaleofficer.Inshortorder,Davishadusedhis talentasaperformer tobe transferred intospecialservices.Fromthatpointon,herealizedthat“mytalentwastheonlythingthatmademealittledifferentfromeverybodyelse,anditwasallthatIcouldhopewouldshieldmebecause Iwas different.”ThroughDavis’s story, I began to understand that I,too,mightfindprotectionfromprejudicebyutilizingmyskillsandtalentsinaway thatwouldmake it difficult for bigots to get tome. Thiswas a definingmoment forme in termsofhow todealwithprejudice.Davis’s life storywasalso,Imustadmit,thebeginningofarebelliousinterestinwhitewomen.IbegantodevelopelaboratefantasiesaboutthetypeofwomanthatImightonedayletin my life. (I had still never been kissed and wasn’t dating.) Being able tocommunicatewithherwouldbeimportant,andalsorespectingoneanother.

Around that time I visited a cousin, EstherReynolds,whowas anX-raytechnicianinNewYorkCity.Ialwayslovedthestoriesshetoldaboutmyfather,

whomshehadadored.Onthisparticularvisit,Iconfidedinhermyloneliness,and admitted how shy I was aroundwomen. I bemoaned that I wasn’t sure Iwouldeverfindagirlfriend.Esthertoldmenottoworry,thatwhenIgotoutoftheairforceandwenttocollege,thingswouldgetbetterinthatdepartment.ShesaidthattheproblemformewouldprobablybethatIwouldn’tbeinterestedinawoman unless she was “as brilliant as Einstein and as beautiful as MarilynMonroe.” That instantly struckme as the perfect combination, indeed. Estherknew ofmy long interest in Einstein, but her innocent remark aboutMarilynMonroewasthebeginningofwhatwouldturnintoanotherfixationforme.(Tothis day, the only photographs on thewall ofmy study at home are ofAlbertEinsteinandMarilynMonroe,whichtogetherneverfailtoraisetheeyebrowsofvisitors. One is perfectly expected of a theoretical physicist; the other mostcertainlyisnot.)

IknewthatMarilynwasconsideredthemostbeautifulwomanintheworld,andtheobjectofmostmen’sdesires.IdecidedrightthenthatIwantedtoknowmore about her, and started reading everything I could find about her life andcareer.IlearnedthatNormaJeanBakerhadcomefromnothingtomakeherselfsomething,andIadmiredherdriveanddetermination.TherebellioussideofmeembracedthepossibilitythatonedayImighthaveabeautifulwhitewomanlikeMarilyn Monroe or May Britt in my life. I found myself taking pleasure inwondering:WhatwouldthecrackersinMississippithinkthen?

Midway throughmy enlistment,mydrive to get aheadwas stronger thanever.IfIwasgoingtogettocollege,dowellinmystudies,changemylifeinameaningful way, and achievemy goals, I knew I had to stay focused onmyprivatestudiesofquantumtheoryandrelativityduringthoselongnightshifts.

One title I liberated fromadusty shelfduringaColumbusbook raidwasSelected Papers on Quantum Electrodynamics, edited by Julian Schwinger(1918–1994). I was fascinated by Schwinger’s definition of quantumelectrodynamicsinthepreface:“thetheoryofthequantumdynamicalsystemininteractionwithchargedparticles.”Ihadonlyavagueideawhatthisstatementmeant,butIwouldkeepthisbooknexttomeonvariousnightstandsthroughtheyears,and itpresently residesona shelf inmystudy.Fora time Igaugedmygrowing knowledge of quantummechanics by howwell Iwas able to absorbSchwinger’spreface.Thebookcontainedoriginalpapersbyanumberofwell-known scientists, including “The Theory of the Positrons” by Americanphysicist Richard Feynman (1918–1988). Unlike Schwinger, Feynman had averyaccessiblewritingstyle.Heexplainedhis theory thatapositron,which is

theantiparticleoftheelectron,isactuallyanelectronthatistravelingbackwardintime.Iwasexcitedwiththetalkoftravelingbackintimeasascientificgiven.Due to the paper’s easy-to-understand “Feynman diagrams”—a new graphicalmethodhedevelopedtorepresenttheinteractionsofelementaryparticles—Iwasable tograsp thegeneralitiesofhis theory rightaway,withoutcomprehendingall the mathematical calculations that he had no doubt used to reach hisconclusions.8

Awell-worn1924DoverpaperbackeditionofPrincipleofRelativityhadEinsteinonthecover,sonaturallyIboughtit.AcollectionoflecturesandpapersbyEinsteinandotherrenownedphysicists,it tracedtheevolutionofthetheoryofrelativity.Thisbookbecameakindofholyscriptureforme,andservedasaguidelineforwhereIwantedtogowithmyfuturestudiesinphysics.IwantedtoseeifEinstein’sfundamentalpaperongeneralrelativitywouldshedsomelightontimetravel.At the time,Ididn’tgraspmuchof the theorybecause itwasahighly technical paper and involved a type of mathematics that wasincomprehensibletome.

IshowedEinstein’spapertomybestfriendintheairforce,PaulShattuck,whowasalsoanenlistedcomputertechnician.PaulwasseveralyearsolderthanI,acollegegraduate,andthefirsttrueintellectualIhadknown.Hehadreadallthe classics, and was at ease discussing them, introducing me to notablephilosopherssuchasDescartesandKant.Hehadsigneduptobeanofficer,butduring flight training had become a born-again Christian and decided againstbeingafighterpilot.Hewasnowservingtherestofhisenlistmentwithaplantoentertheministrywhenhegotout.

“Paul,onedayI’mgoingtobeabletoreadthispaperaseasilyasacomicbook,”Itoldhiminallseriousness.

Helaughed.Themathwasoutofhisleague,too.“Well,goodluck.”(Unfortunately,IhavelosttrackofPaulovertheyears.ShouldIeveragain

meetupwithmyairforcebuddy,thefirstthingIwouldsaytohimis,“Ididit,Paul.Icanreaditthateasilynow.”)

ModernScienceandTechnology,editedbyRobertColborn,wasabigbookthatcostnearlyaweek’sworthoffoodmoney.Containingsomeeightyarticleson various areas of science and technology, it included the article “TheDynamics of Spacetime,” by John A. Wheeler and Seymour Tilson. Theydescribedinanontechnicalwayhowspaceandtimearewarpedbymatter,andalso thatspaceand timewere flexible,whichwasanotherexcitingconcept formymind to absorb.Where gravitation in the long-accepted theory byEnglish

physicistandmathematicianIsaacNewton(1642–1727)wasa“forcedependingon matter for its existence, Einstein’s giant step forward liberated gravitationfrom matter by describing it geometrically instead—as a curvature of space-time.”

IftherewasanymissinglinkinthereadingIwasdoingintheairforce,itcametomewhenI locatedausedcopyofa1949editionofabookpublishedupon the occasion of Einstein’s seventieth birthday. Albert Einstein:Philosopher-Scientist,editedbyPaulArthurSchilpp,containedanessaywrittenthatyearbyanAustrianmathematicianandlogician,KurtGödel(1906–1978),who in 1931 had made one of the most important discoveries of twentieth-century mathematics. Gödel’s theorem states the impossibility of defining acomplete system of mathematical rules that is also consistent, and as aconsequence,mathcanneverbeplacedonanentirelyrigorousbasis(i.e.,therewill always be some uncertainties). I read how Gödel was a close friend ofEinstein’swhentheybothwereattheInstituteforAdvancedStudyatPrinceton,and this connection ledGödel into the field of general relativity theory.Also,Gödel had used general relativity to study cosmology, which I surmised hadsomething todowith theuniverse.Then I cameacross this nugget inGödel’sessay: “[I]t is possible in these worlds to travel into any region of the past,present,and future,andbackagain,exactlyas it ispossible inotherworlds totraveltodistantpartsofspace.”Thrilledtoreadthisstatement,IunderlinedthepassageandrereadituntilIcouldreciteitfrommemory.

In the same book was this reaffirming comment from Einstein: “KurtGödel’s essay constitutes, in my opinion, an important contribution to thegeneraltheoryofrelativity,especiallytotheanalysisoftheconceptoftime.”

AlthoughEinstein’sgeneraltheoryofrelativitywouldnotbecomecleartome until my later studies in college, I knew at that point it had to be key tounlocking themysteries of time travel into the past. In themeantime, generalrelativityasdescribedbyGödelandotherswas likeasymphony tomyears; IenjoyedthemusiceventhoughIcouldn’treadandunderstandthenotesof thescoreorhowthesymphonywascomposed.

When Iwasn’t reading,mymain sourcesof entertainment atLockbourneweremoviesandTV.SinceIstillwasn’tdating,Iwenttothemoviesaloneand,asIhaddonesinceIwasayoungster,satupclosewithmypopcornandCoke.As I didn’t report for work until midnight, I was also able to watch the TVprogramsthatwereshowneveryeveninginthecommonroominthebarracks.

In1964,Ibecameengrossedinanewscience-fictiontelevisionseriesthat

capturedmyimaginationasmuchasTwilightZonehaddonewhenIwasinhighschool.ThenewserieswasTheOuterLimits.Myattentionwasrivetedthefirsttime I heard the opening narration—reminiscent of Rod Serling’s eerieintroduction—spokenbythemonotone“ControlVoice”beforeeachepisode:

There isnothingwrongwithyour television set.Donot attempt toadjustthepicture.Weare controlling transmission. Ifwewish tomake it louder,wewill bring up the volume. If we wish to make it softer, we will tune it to awhisper.Wewillcontrolthehorizontal.Wewillcontrolthevertical.Wecanrolltheimage,makeitflutter.Wecanchangethefocustoasoftblurorsharpenittocrystalclarity.Forthenexthoursitquietlyandwewillcontrolallthatyouseeandhear.We repeat: there is nothingwrongwith your television set.You areabout toparticipate in agreat adventure.Youare about to experience the aweandmysterywhichreachesfromtheinnermindto...TheOuterLimits.

Inmanyrespects,TheOuterLimitswastheshowthatpeoplelikeme,whohadgrownupwatchingtheoriginal—andsincecancelled—TwilightZone,hadbeenwaiting for ever since that cancellation. The new showhadmany of thesamemoralityissuesandtwistsoffateandfaithfullystayedwithintheboundsofsciencefiction.

Oneevening,Isawatime-travelepisodethathauntedme.“TheManWhoWasNeverBorn”wasoneof thebestofTheOuterLimits time-travel stories.The episode starts off with an astronaut who has gone through a strangedisturbance in space. He lands on a planet that is desolate, and encounters agrotesquecreaturethatlivesontheplanet.Thecreature’snameisAndro,playedbyMartinLandau.Androtellstheastronautthathehassomehowcomethroughatimewarpandhaslandedontheearthinthedistantfuture.Androexplainsthatintheastronaut’stimetherewasabiologistwhohaddevelopedwhathethoughtwasanimportantcurefordisease.Itturnedoutthattheso-calledcurewasanewplague.Thehuman racewasdecimatedby theplagueand thosewho survivedevolved into grotesque creatures likeAndro. The astronaut suggests toAndrothat,sincehehascomethroughatimewarp,perhapshecouldbringAndrobackto his time, and together they could convince the scientist to stop hisexperiments. Andro agrees.When they go back through the time barrier, theastronaut is not able tomake the transition and vanishes. Andro lands on theearth alone. Wandering around, he encounters a young woman. He’s able tohypnoticallysuggesttoherthathelooksnormal.Talkingwithherheishorrifiedtofindoutthathehasarrivedtoosoon.Itturnsoutthattheyoungwomanisthefuturemotherofthebiologistwhodevelopstheplague.Inthestory,Androtries

tochange thedestinyof theyoungwomanbywooingher fromher fiancé.Heconvinces her to go back with him to the future. Unfortunately, Andro hassacrificed himself, because by changing her destiny he has changed his futureand he is never born.AsAndro and the youngwoman pass through the timebarrierintothefuture,hedisappears.Endofstory.“TheManWhoWasNeverBorn”hadapowerfuleffectonme.Itmademethinkaboutwaysthatgoingbackintomypastcouldaltermylifeforever.

Myfinalyearintheairforcebroughtmebackdowntoearth.Transferredtoadministration, Iworked as a clerk for sixmonths. Justwhen I thought Iwasdoing themostboringworkpossible, they turnedmeintoa telephoneoperatorsitting all day at a main switchboard. When it came time for a recruiter tointerviewmeaboutreenlisting,Ilethimknowthatideawassolongdeadithadalreadyturnedtoashes.Thankyou,andgood-bye.

Separatedfromtheservicein1966,IwenthometoAltoona.My stepfather,Bill, had lined up a full-time job forme that he thought I

wouldbepleasedwith.Hehadpulledsomestringsandarrangedformetobethemanager of a gas station in town. I must have looked at him like I had thatrecruiteraboutreenlistment.Thanks,butnothanks.

IhadalreadybeenacceptedintothephysicsprogramatPennState.

Six

TheEducationofaPhysicist

In Fall 1966, I started my new life as a college student at the AltoonacampusofPennsylvaniaStateUniversity,situatedontheoutskirtsoftowninaheavily forested area. Like other branch campuses of Penn State, Altoonaofferedatwo-yearcurriculum;uponcompletion,studentstransferredtothemaincampuslocatedinthetownofStateCollegetocompletetheirfour-yeardegrees.Although I wasn’t crazy about the idea of returning to Altoona and living athomeafterbeingawayfouryearsintheairforce,thesituationwouldenablemetosavemoney,withtheGIBillcoveringmytuition,books,andotherexpenses.

IhaddreamedofthemomentthatIwouldstepontoacollegecampusasafull-timestudent.Iwaseagertostudyeverything,evenphilosophy,which,frommy independent studies in the service, I knew might answer some of mynontechnicalandunendingquestionsaboutthenatureoftime.

My philosophy course was taught by a young, eager instructor namedCharlesWatkins.Duringclassdiscussions, the twoofuswould frequentlygetinto intense and lengthy debates about the meaning of the philosophy ofDescartesandKant.WhatIreallywantedtodowasgetintoadiscussionaboutthenatureoftime,butIhadn’tfoundmanyopportunitiestodoso.Onedayafterclass,theinstructortookmeasideandsaidhefeltthatIhadstudiedbeyondtheleveloftheclass,andhadsuchunderstandingofthecoursematerialthathewaswilling togivemeanA.Hesuggested that rather thanattendingclass, Icouldhave weekly meetings with him in his office to discuss those philosophicalissues that interestedmethemostbutwhichwerenotpartof thecurriculum.Ithinkhewantedmeoutof theclassroomsohecouldmovethroughthecoursematerialwith fewer interruptions. Inanycase, Iwas thrilledat theprospectofhavingone-on-onesessionswiththeinstructor.Inshortorder,afterIdescribedmy interest in time, the instructor suggested I look upTheConfessions of St.Augustineatthelibrary.

Going to the Altoona library felt like a real homecoming; some of thelibrarians recognizedmeandwelcomedmeback tomyoldhaunt. I found thebookrecommendedbymyinstructor,andlearnedthatAugustine(354–430)wasabishopof theearlyChristianchurch inNorthAfrica.Confessions isactually

comprised of thirteen separate books, each one a different meditation. Thesection thatmost interestedmewasentitled “TimeandEternity.”Onechapter—“What Is Time?”—seemed as though it was written especially for me.Augustineasked,“What,then,istime?Ifnooneasksme,Iknow:ifIwanttoexplain it to someonewhodoes askme, I do not know.”At firstAugustine’sanswerdisappointedme,althoughI,too,feltIknewwhattimewasuntilIhadtodefine it in a preciseway.As I read on, I found that Augustine continued towrestle with the question of the “beginning of time.” What exactly did thebeginning of time mean—when the universe was formed or even earlier? IhappilyponderedthisandothermeditationsbyAugustineonthenatureoftime.Rather thanbe suppliedwith a bevyof answers, however, I found I had evenmorequestions.

Although school was going well, I was having problems with living athome, as old patterns of behavior emerged.My stepfather, still clueless as towhatIwastryingtodowithmyself,keptaftermetoquitschoolandgetajob.Thisonlyputmoredistancebetweenus.Italsomademeacheallthemoreforthepresenceofmyfather,whoIknewwouldhaveunderstoodandencouragedmyinsatiablethirstforlearning.Tomakemattersworse,Iwaslonelyandhadnosociallife.Theseunhappydistractionssoonbegantoaffectmystudies.

My smart and savvy German teacher, Ida Ficker, must have sensedsomethingwaswrong.Shecame tomy rescue, insisting that I takepart in theactivitiesoftheGermanclub.Ms.Ficker,whoregularlyhadstudentsovertoherhomefordinnerandsocializing,alsointroducedmetoapetitebrunettenamedMarjorieGey,whohadgraduatedfromPennStateayearearlierasaphilosophymajorandwhohadquithersocialworkerjobinPhiladelphiaandreturnedhometohelpcareforhermother,whohadterminalcancer.Ms.FickeraskedMarjorietogivemearidehome(Ihadneverbotheredtogetadriver’slicense)followingaGermanclubevent.Marjoriewasbeautiful aswell asbrilliant, andoncewewereinthecarshedivedrightintothetechnicalaspectsofthepresentationwehad heard that night from theGerman-American physicist ErwinMueller, theinventorofthefieldionmicroscope.9

Marjoriewasinterestedinphysicsaswellasphilosophy.Inherfreetime,shehadbeenstudyingthehighlyabstruseworkBeingandTime,bytheGermanphilosopherMartinHeidegger(1889–1976).ItoldherIwouldliketoknowwhatHeideggerhad to say about thenatureof time.Marjorie struck abargainwithme.ShewouldbriefmeonHeidegger’s theoriesabout timeif IwouldexplaintheuncertaintyprincipleofGermanphysicistWernerHeisenberg(1901–1976),

one of the founders of quantum mechanics. She had never completelyunderstoodtheuncertaintyprincipleinspiteofhavingtakenphysicsincollege.Wehadourselvesadeal,andwebeganmeetingafterclassforcoffee.

I told Marjorie about my first reading of Heisenberg’s theory in TheStrangeStoryoftheQuantumwhileintheairforce.Quantummechanicsruledtheworldofmatter and energy, I explained, and theuncertaintyprinciple is afundamentalaspectofquantummechanics.

I recalled that in his book The Feynman Lectures on Physics RichardFeynmanhadgivenaclassicexampleofwhyweneedtheuncertaintyprincipleto explain certain phenomena. I decided to use Feynman’s characteristicallyunderstandableexplanationoftheuncertaintyprincipleinquantummechanics.

IaskedMarjorie toconsiderasimplehydrogenatom,whichconsistsofanucleus with one positively charged proton that is orbited by a negativelychargedelectron.Theoppositechargesof theprotonandelectron result in theattractive electrical force between them. Common sense dictates that as theelectron orbits the proton it should lose energy and fall into the nucleus.Thisshouldhappenso fast thatall thematter in theuniverseshouldhavecollapsedlongago.Clearly,thisdidnothappen.Thereasonwhy,ItoldMarjorie,iswherequantummechanicsandtheuncertaintyprinciplecomeintoplay.

AccordingtoHeisenberg’suncertaintyprinciple,itisnotpossibletoknowexactlyboththepositionandmotionofanyatomicparticle.Thismeansevenifyouknowtheexact locationyoucannotknowhowit’smoving.Conversely, ifyouknowhowit’smoving,youcannotknowexactlywhereitis.

I askedMarjorie to consider the situationof the electron in the hydrogenatom.As the electron tries to get close to the proton, the protonwould knowexactlywheretheelectronislocated.But,accordingtoHeisenberg’suncertaintyprinciple,theprotoncan’talsoknowhowtheelectronismoving.

The electron gets a little energy kick from the proton that moves theelectron away from the proton.As the electron tries to get close again it getsanotherkickfromtheproton.Ifweaveragethedistancetheelectronstaysawayfrom the proton due to the uncertainty principle, we find that the distance isexactly the size of the hydrogen atom. “In other words,” I said, “without theuncertaintyprinciple,theelectronwouldcrashintotheprotonandthehydrogenatom would collapse. So, you see, matter is stable because of quantummechanicsandtheuncertaintyprinciple.”

MarjorielikedtheFeynmanexample.Now,itwasmyturntolistentoher.

SheexplainedthatHeideggerwasconcernedwithaconceptcalledDasein,whichisessentiallyanothernameforexistence.InBeingandTime,shewenton,Heidegger addressed the problemof howwe exist in time.The commonsenseview of time is linear, and we think of time as a stream that flows past us.Yesterday is downstream and past us,while tomorrow is upstream and yet toreachus.AccordingtoHeidegger,timeisnotlinear;theessenceofourexistenceencountersalloftimeinonefellswoop.Hisconceptoftimetakesintoaccountallthemultiplepossibilitiesthatpotentiallyexistinthefuture.

My ongoing intellectual conversations withMarjorie helped me to focusagainonmystudies.Aswecontinuedtoenjoyeachother’scompany,shesooninvitedmehomefordinnerandtomeetherparents.

Although itwas not somethingMarjorie and I discussed, I knew the factthat she was white and I was black could cause possible problems for herparents.Iwantedtobelievethatasacollegephysicsmajor,anairforceveteran,andayoungmanstrivingtobetterhimself,IwouldbeacceptedforwhoIwas.Marjorie’s mother was friendly and I liked her immediately. But whenMarjorie’sfathercamehome,thetemperatureintheroomsuddenlydroppedtobelowfreezing.Marjorietoldmelaterthatherfathersaidshewasnevertobringmetothehouseagain.Thatwasfinebyme.

Ironically, this incident brought us closer together.Wecontinued tomeetalmostdaily,andoftentalkedforhours.Onespringafternoonweweretakingaride to the neighboring town of Hollidayburg. Suddenly, somewhere on theoutskirts ofAltoona,Marjoriemade a sharp turnonto adirt road.Surprised, Iaskedwherewewereheading.Smiling,shesaidcryptically,“You’llsee.”

Theroadgotsteadilysteeperforaboutahalfmile.Wepulledupinfrontofa sign that read “Chimney Rocks Park.” On foot, I followed her up a roughhiking trail. As we approached a clearing, I could see an enormous rockformation that looked like a gigantic thumb jutting up out of the ground. Therockformationwasneartheedgeofacliffandaswegotnearerabreathtakingviewoftheentirevalleybelowopenedupbeforeus.Marjoriesaidthiswasherfavorite spot in the world. The day was sunny, with a blue crystalline skyoverhead.Wesatnexttoeachother,bothspellboundbythebeautifulsetting.

Finally,Iaskedherwhatshewantedtodowithherlife.“Iwanttolearnmorephilosophy,”shesaid.Shethenaskedmethesamequestion.“I’mgoingtofindawaytobuildatimemachine,”Iheardmyselfsay,even

thoughIhadtoldonlyoneotherperson—mycousinbackinhighschool—about

myobsessionwithtimetraveltothepast.Iwentontotellheraboutmyfather,andhowI longed toseehimoncemore.Marjoriecommiseratedwithmyloss,then asked a series of technical questions about time travel, some of which Icouldnotanswerbutonlytouchontheoreticalsuppositions.Clearlythiswasonesmartwoman.

MarjorieandIseemedtoshare,at that timeofourlives,a tragicsenseoftime and fate—as well as an unshakeable belief in the other person doingsomethingimportant.Althoughwewerenevertobecomelovers,philosophyandphysicsbecameforusakindofintellectualmarriage.

After Marjorie’s mother died, her father made it clear that she was nolonger needed in Altoona. Not long after our visit to Chimney Rocks Park,MarjoriemovedawaytoChicago.Iwasheartbroken.

Iretreatedintomyselfandlostinterestinmystudies.AsinthepastwhenIneeded to go to a different place to escape reality, I found solace in sciencefiction.ThefallthatIstartedattheAltoonacampusmarkedthebeginningofaphenomenoninthehistoryofsciencefiction.ItwastheyearthattheTVseriesStar Trek first aired, and I quickly became immersed in the travels andadventures of Captain Kirk, Spock, and the rest of the crew of the starshipEnterprise.Anepisodethatairedneartheendofthefirstseasonin1967hadaparticularresonanceformebecauseitinvolvedboththethemeoftimetravelandlost love.Thisclassicepisode,“TheCityontheEdgeofForever,”becamemyfavoriteoftheStarTrekseries.ThecrewoftheEnterpriseencountersdistortionsin time that are emanating from the surface of a planet.As they travel to theplanet, the ship’s doctor, McCoy, is accidentally injected with a drug thatinducesdelusionalbehavior.McCoybeamsdowntotheplanet.Whenthecrewarrives at the surfaceof theplanet they find that the timedistortions theyhadexperienced in space were coming from a time portal built by some ancientcivilization. A derangedMcCoy runs through the portal. All of a sudden thecrewfindsthatthestarshipEnterprisenolongerexists.TheyrealizethatMcCoyhas changed something in the past that has changed their present. Kirk andSpock followMcCoy to the time portal and arrive in anAmerican city in the1930s.InsearchingforMcCoy,KirkmeetsandfallsinlovewithasocialworkernamedEdithKeeler, played by JoanCollins.As it turns out, Spock is able todetermine thatMcCoy saved the life of EdithKeeler, who eventually leads amovementthatdelaysAmerica’sinvolvementinWorldWarII.HitlerisabletodevelopanatomicbombandwintheSecondWorldWar.Inasadandpoignantscene,KirkpreventsMcCoyfromsavingEdithKeelerfrombeinghitbyacar.

Keelerdiesandthecrewreturnstotheirpresent,wherethestarshipEnterpriseisnowinexistenceagain.Thestorybroughthometomeonceagainthepotentialintricacies of time travel, as well as the many unanswered questions thatsurroundedthesubject.

Unabletoconcentrateonmystudies,Ileftschoolafterthefallsemesterof1967andmovedtoNewYorkCitywithawomanIhadmetatPennStatewhowasfleeinganunhappymarriage.DorothyFry,whohadplanstobea teacher,was nine years my senior. With dark brown hair, brown eyes, and olivecomplexion she looked Italian but came from German-Irish stock. Her moststrikingfeaturewasherradiantsmile,whicheveryonenoticedrightaway.

DorothywasthenextpersonItoldaboutwantingtobuildatimemachine,andwhy.WeweresittinginthehallofanAltoonacampusbuilding,twoorthreemonths after we met, as I related my story. Dorothy listened attentively as Iexplainedwith some emotionhow I haddreamed since Iwas a youngboyofgoingbacktoseemyfatherandsomehowpreventinghisfatalheartattack.“Allof this emphasison schooling,” I said, “is about thatdream.And it’swhymyeducation is centered on learning physics and mathematics.” When I wasfinished,shelookedatmewithherexpressiveeyes,andsaidshehadnodoubtthat I would one day succeed in building a timemachine. At that moment, Ileanedoverandkissedherforthefirsttime.

Atfirst,DorothyandIbothweremainlyinterestedintheother’sfriendshipandhavingsomeoneintelligenttotalkto.Soon,itgrewintomuchmore.Ifoundhereasytobewith,andalwaysfeltasenseofcalminherpresence.Shemademefeelsafe.

Anorganization that assistedveterans helpedme find a job as a researchlaboratory technician at the Markite Corporation, a Greenwich Village firmdoing revolutionaryworkwith a patented plastic that carried electrical current(plastics are normally insulators). I fabricated and tested potentiometers—voltageregulators—fortheSaturn5rocket.ItwasaninterestingjobuntilIgotto know the process,which never varied and soon became rote.During lunchbreaks,thetechnicianswouldgatherinthelunchroomandplaydominoes.Ireadinstead.

Oneday in spring1968,Dr.ScottBonis, a research scientistwhose lab Ihadbeenassignedto,satdownwithmeandaskedwhatIwasreading.Ishowedhimmybookonmodernphysics.Heaskedaboutmybackground.ItoldhimIhadbeenaphysicsmajoratPennStateandaboutmy interest in thenatureoftimeandEinstein’stheoryofrelativity.IexplainedthatIhaddecidedtotakea

breakfromschool.“That’samistake,”hesaid.FromthenonDr.Bonisinsisted,almostdaily,

thatIshouldreturntoschooltofinishmyeducationandbecomeaprofessionalphysicist.Beforelong,hedecidedtoleavethecompany,andonhislastdayhetookmetoonesideandmademepromisethatIwouldreturntocollegesoonerratherthanlater.

That evening when I returned to the Brooklyn apartment Dorothy and Ishared I told her about my promise tomy departing supervisor. Dorothy hadfoundajobintheactuarialdepartmentofaManhattaninsurancecompany.Shelovedherwork,andthevibrancyofNewYorkCity.Butshesaidshehadsensedmyrestlessness,andwouldsupportmydecisiontoreturntoschool.WetalkeditoveranddecidedwewouldreturntoPennsylvaniacomesummer.

We were living in an upstairs one-bedroom apartment in Brooklyn. Thebuilding was a brownstone owned by a good-natured Jamaican woman wholived downstairs. On the evening of April 4 we heard her crying. Alarmed,DorothyandIrushedtoseewhatwaswrong.

“TheykilledDr.King,”shesobbed.“Dr.Kingisgone.”The shock, anger, and frustration came pouring in. I vividly recalled the

firsttimeIheardMartinLutherKing,Jr.Itwassummer,1963—Iwasstillintheair force—and the occasion was his soon-to-be-famous “I Have a Dream”speech in Washington, D.C. I immediately loved the deep resonance of hisvoice,andthewayheusedhiswordstotouchandinspire.AsIhadsorecentlyspenttimeinMississippi,thesadtruthsofhismessageaboutwhatlifewaslikeinpartsofAmericaacenturyafteremancipationhithome.“Onehundredyearslater,”hepassionatelyintoned,“thelifeoftheNegroisstillsadlycrippledbythemanacles of segregation and the chains of discrimination.” Somehow, hedispensedhope;withmenlikehimintheforefrontofthecivilrightsmovement,it somehow seemed possible that our country might yet make good on thepromise inherent in theDeclaration of Independence that “allmen are createdequal.”Thathopewasrewardedon the joyousoccasionwhen theCivilRightsAct of 1964was passed and signed into law.Not a first step—theFourteenthAmendmenttotheConstitutionshouldhavebeenthat—butamightybigone.

Andnowthemanwhoengenderedsuchhopewasgone.ThatKing’sassassinationwasfollowedtwomonthslaterbythemurderof

RobertF.KennedyrobbedmeofwhateverlingeringhopeIharboredasablackAmericanthatwewereonthevergeofracialequality.Inthosetwotragedies,Ifeltthatsomethingfundamentalhadbeenlostinthesoulofourcountry.

*

In the summerof1968 Ibeganclassesat themaincampusofPennStateUniversityinthetownofStateCollege,forty-fivemilesnortheastofAltoonainthegeographiccenterofPennsylvania.

AtthefootofpicturesqueMountNittany,StateCollegeisaquiettownofsome38,000permanent residents,mostofwhomareemployedbyPennState.For its size, State College is a refreshingly cosmopolitan community with adowntownatmospherereminiscentofGreenwichVillage.Iwasdelightedtobethere,andbackinschool.

Afterworkingforawhileinadepartmentstore,Dorothylandedajobintheuniversity’s undergraduate admissions office and eventually was promoted toexecutivesecretaryfortheheadofthedepartment.Shelikedthework,andwasdelightedtobeabletoenrollattheuniversitypart-timeatreducedtuition.

I returned tomy studieswith a renewed commitment. Iwas now able totakeadvancedphysicscoursesandreceiveinstructioninthephysicsofrelativityandquantummechanics taught by someof the finest professors at the school.Enthused bymy studies, Imade the dean’s list for the first time that summerterm.

Ialsomadesomeoneelse’slist,asIsoonreceivedavisitfromtheFBI.TheWattsRiotshadhappenedwhileIwasstillintheairforce,workingthe

nightshiftandwrappedupinmyownworldofreadingandstudying.Ofcourse,Iwasawarethat thecountryseemedtobeteeteringontheedgeofaracewar.Status,power,andwealthwere regularlydeniedmanypeopleofcolor;havingexperiencedracismmyself,Icouldempathize.Andyet,asalaw-abidingcitizenandmemberofthemilitary,Ididnotcondonethestreetviolenceandloitering.Itseemed tome therewere a lot betterways to express frustration than burningdown one’s own neighborhood. Like Dr. King, I believed the majority ofNegroes still supported nonviolent resistance to laws and practices thatwouldkeepusseparateandunequal.

TheFBIagentsstartedoffwithsayingtheyknewhow“patriotic”Iwasduetomy fouryears in theair forceandmyhonorabledischarge.They said therewasawayIcouldstillservemycountry.

“How’sthat?”Iasked,suspiciousfromtheget-go.“Wewouldlikeyoutoinfiltratetheblackstudentmovementoncampus,”

oneoftheagentsexplained.“Makementalnotesaboutwhatisgoingonduringthemeetingsandwhoattendsthem.Reporttousonaregularbasis.”

Shock must have registered on my face, because the agent immediatelybegansoft-pedalingtheirrequestformetobeanFBIcampusspy.

“We aren’t really concerned about themovement per se,” the agentwenton.“Wearebasicallylookingoutfortheinterestsofallthestudents.”

Iwas seething at their suggestion that I should spy on fellow students—blackandwhite—andreporttheiractivities.Itoldtheagentstoforgetit.

“Thinkaboutitforafewdaysandwe’lltalkagain.”When they returned, I told the agents I hadn’t changed my mind. The

answerwasstillno.Oneofthemthenmadethischillingstatement:“Okay,youcancontinueonyourcareer.”Theveiled threatwasclear.Theywantedme tobelievethattheFBIcould,anytimeitwanted,derailmyacademiccareer.

This would-be recruiting incident made me even more interested in theblackpowermovement.ItooktimeoutfrommystudiestoreadTheFireNextTime,writtenbyJamesBaldwin twoyearsbeforeWatts.Thebookstokedmyangeratthegovernment’streatmentoftheblackcommunity,andIfoundmyselfmoredeterminedthanevertosucceedinbecomingaphysicist.

Oneof the first courses I tookon themain campuswasmodern physics,whereIlearnedmoreofthedetailsofEinstein’sspecialtheoryofrelativity.Atlast I began to fully understand why time slows down for a moving clock, aconceptIfirstreadaboutatagetwelveinTheUniverseandDr.Einstein.

The explanationgiven in the coursewas basedon a device called a lightclock,whichconsistsofaverticaltransparenttubewithamirroratoppositeendsanda lightbeamthatbouncesbackandforthbetweenthemirrors.Onetickofthe clock occurswhen the light beam goes from the bottommirror to the topmirrorandreturns.Iftheclockismovedtotheleftorright,thelightbeamfromthebottommirrorhastotravelalongerdistancetohittheuppermirror.Astheclockcontinuestomove,thelightbeamhastofollowalongerpathtoreturntothebottommirror.Sincethelightbeamis takingalonger timetogetfromthebottommirrortothetopmirrorandbackagain,ittakeslongerforonetickofthemovingclocktooccur.So,timeforthemovingclockislongerthantimeforaclockthatisstandingstill.

The proof that time slows down for a moving clock comes fromexperiments with cosmic rays. These rays are highly energetic elementaryparticlesthatconstantlybombardtheearthfromalldirectionsofspace.Someoftheparticlesincosmicraysliveonlyforanextremelyshortperiodbeforetheydisintegrate. One of the short-lived particles is called a muon. A muon is aheaviercousinof theelectron,about200timesmoremassive thananelectron.

Asfarasweknow,electronsneverdisintegrate.Ontheotherhand,amuononlylivesforaboutonemillionthofasecondbeforeitdisintegrates.

Physicistswere facedwithaproblemwhen it came tomuons.Muonsarecreated in theearth’supperatmosphere.Since themuons live for sucha shortperiod of time, they should disintegrate in the upper atmosphere and none ofthemshouldbeseenattheearth’ssurface.Butwhatphysicistsfindisthatweareshoweredatsealevelwiththousandsofthesemuons.Howdotheylivesolong?

WithoutEinstein’sspecialtheoryofrelativityitisimpossibletounderstandwhatishappening.Themuonsintheupperatmospherearetravelingclosetothespeedoflight.Becauseofthishighrateofspeed,theinternalclockofthemuonslowsdown.CalculationsusingEinstein’sspecialtheoryshowthatitispossibleforamuontravelingclosetothespeedoflighttoliveeighttimeslongerthanitwouldnormally.Sincethemuonislivinglonger,ithastimetoreachthesurfaceof theearthbefore itdisintegrates,whichexplainswhyweareable toobservemuonsatsealevel.Timefortherapidlymovingmuonhassloweddown.

This“timedilationeffect”alsoleadstoarelatedpredictionassociatedwiththetheoryofspecialrelativity.Thisprediction,called“thetwinparadox,”wasafavoriteofEinstein’sandhadcaughtmyattentionearly inmyreadingsonhiswork.Thetwinparadoxgoeslikethis:considertwenty-five-year-oldtwins,Fredand Jim, in the year 2035. Suppose that Jim is the more adventurous of thebrothersandhe takesa journeyona rocket that isgoingclose to thespeedoflight.Hejourneystoastarthatistwenty-fivelightyearsaway—thatistosay,ittakestwenty-fiveyearsforlightleavingthestartoreachtheearth.AsforFred,whohasstayedbehindonearth,heseesatimedilationeffectforhistwin.Thismeans that as Jim’s rocket approaches the speed of light everything thatmeasures timeonJim’s rocket slowsdown.This slowingdown includesJim’smetabolism and heart rate. On the other hand, onboard the rocket nothingunusualisoccurringforJim.Infact,timepassesforJimatitsnormalrate,andhe finds that the journey to the star takes only about five years. From Fred’spointofview, ithas takenJimfiftyyears tomake theround-trip to thedistantstar and back. Fred is now seventy-five years old when Jim arrives home in2085.However,fromJim’sstandpointtheround-tripjourneyhastakenonlytenyears,andhe’sonlythirty-fiveyearsold.ThismeansthatJim’srockethasactedasatimemachine,inthatithastakenJimonlytenyearstotravelfiftyyearsintotheearth’sfuture.

Scientistshavelongknownwithcertaintythatthistypeoftimetraveltothefuture will occur, because we have already seen it in connection with real

experiments involving subatomic particles like the muon. Someday whentechnological advances have led to propulsion systems capable of attainingvelocities near the speed of light, effects such as the twin paradox will be anormaloccurrence.

We will by then, I hope, have taken into account the sociologicalimplications associatedwith an astronaut leaving home and traveling near thespeedoflightandreturningtofindthatheisyoungerthanhisgrandchildren.

This typeof time travel associatedwith the timedilationeffect in specialrelativityisaone-waytrip.Forexample,whenJimarrivesontheearthin2085hecannevergetbackto2035.So,Einstein’sspecialrelativityallowstimetravelto theearth’s futurebutnot intoourpast—thedirection inwhich, formyownverypersonalreasons,Iwasinterestedingoing.

Ialsolearnedinthemodernphysicscoursewhynothingintheuniversecanexceedthespeedoflight.Asthespeedofanobjectincreases,itsmassincreases.The reason for this can be found in the most famous equation of Einstein’sspecialtheoryofrelativity:E=MC2,whereEistheenergy,misthemass,andc2isthespeedoflightmultipliedbyitself.Thisequationsaysthatifyouapplyenergytospeedupanobject,someofthatenergygoesintobecomingapartofthemass of the object.As the object getsmoremassive it becomes harder tospeed it up. Eventually, it would takemore energy than there is in the entireuniversetogettheobjecttogoatthespeedoflight,whichmeanswecanneverspeedupanobjecttoreachthespeedoflight.Wecangetclosetothespeedoflight,butwecannever reachorexceed it.Thespeedof light is theuniverse’smaximumspeedlimit.

ThecoursediscussedEinstein’sgeneraltheoryofrelativityaswell,whichis also considered Einstein’s theory of gravity. I learned that Einstein had toinvent the general theory of relativity because of a problem with Newton’stheoryofgravitydevelopedintheseventeenthcentury.InNewton’stheory,thegravitationalforceofattractionbetweentwoobjects,likethesunandtheearth,becomestrongertheclosertooneanotheryoubringthetwoobjects,andweakerthe farther you move them away from each other. But something strangehappenswhenyoucomparethegravitationalforcewiththespeedoflight.

The earth is 93,000,000 miles from the sun. It takes light, traveling at186,000milespersecond,afulleightminutestogetfromthesuntotheearth.Shouldsomecosmiccatastropheoccur thatdestroys the sun,hereon theearthwe would still see the sun for eight minutes before it disappeared. However,according toNewton’s theory, the gravitational force shuts down immediately

andtheearthwouldnolongerfeeltheattractionfromthegravityofthesun.Thiswould mean that even though we could still see the sun in the sky for eightminutes, the gravitational forcewould go away immediately. Sans gravity,wecouldfindourselveshurtlingintospaceeventhoughwecouldstillseethesun.Einstein said this cannot happenbecause it implies that the gravitational forcecantravelfasterthanthespeedoflight.TheonlywaythatEinsteincouldsolvethisproblemwastodevelopawholenewtheoryofgravity.

Einstein’s new theoryof gravity canbeunderstoodby a simple example.Consider a rubber sheet stretched on a wooden frame—something like atrampoline—with the rubber sheet representing empty interstellar space. If abowlingballisplacedontherubbersheetitwillcurvethesheet.Ifwethenplacealittlemarbleontherubbersheetatsomedistanceawayfromthebowlingball,themarblewillrollalongthecurvedrubbersheetuntilhittingthebowlingball.Now,imaginethattherubbersheetistransparentandwecanseeonlythemarbleand thebowlingball.Thesituationwillnow look tousas though thebowlingball is directly attracting the marble due to some force of attraction betweenthem.However, thisisanillusion.What’sreallyhappeningisthat thebowlingball is curving the rubber sheet and themarble ismovingalong that curvaturetowardthebowlingball.

Einsteinsaidthatthisisthesortofthingthat’shappeninginemptyspace.Inotherwords,amassiveobjectlikethesunisbendingtheemptyspacearoundit,andtheearthismovingalongthecurvedemptyspacecreatedbythesun.Iftheearthdidn’thave its sidewaysmotion itwouldplunge into thesun just theway the marble plunges toward the bowling ball. But because of it sidewaysmotion, the earth ismoving constantly around the sun like one of those rollerderbyskatersGrandpaplikedtowatchgoroundandroundtherink.

Einstein’s theoryofgeneral relativity states that thegravitational forceofattraction is really the bending of empty space by amassive object.With thisnewviewofgravityasthebendingofspace,Einsteinwasabletoreconcilethespeed of light with the gravitational force. In his theory of gravity, thedestructionofthesunbysomecosmiccatastrophewouldchangethebendingofspace, but it would take the change in the bending of space eightminutes toreachtheearth.Aslongaswecanseethesun,wewouldfeelthegravitationalforcedue to the sun.Gravity is thebendingof space, and thatbendingcannottravelfasterthanthespeedoflight.10

OneofthemostimportantexperimentaltestsofEinstein’sgeneraltheoryofrelativitytestedapredictionthatEinsteinmadeaboutwhathappenstoarayof

lightwhenitcomesclosetothegravitationalfieldofthesun.Einsteinpredictedthebehaviorofastarthatislocatedbehindthesun.Ifthestarisdirectlybehindthe sun,we can’t see it because the light from the star is blocked by the sun.However, Einstein said that, because the sun is bending space, a ray of lightfrom the star passing near enough to the sunwill get deflected by the curvedspace around the sun.We would be able to see the deflected ray of light. Itwouldappearasthoughthestarisnotbehindthesunbutislocatedattheedgeofthesun.

Einstein’spredictionofthedeflectionofstarlightbythesunwasverifiedin1919 in one of the most famous observational experiments in the history ofphysics. The observation was performed by Englishman Arthur Eddington(1882–1944),oneofthemostprominentastrophysicistsofhistimeandamongthe first scientists toappreciate the importanceofEinstein’s relativity theories.Inthenightsky,Eddingtonlocatedstarsthatwouldnormallybeblockedbytheposition of the sun. Then, during a total eclipse of the sun, he measured thepositionsof the same stars near the edgeof the sun.Eddington found that theapparentpositionsofthestarshadshiftedfromtheiractualpositionsbyjusttheamountpredictedbyEinstein.AtameetingoftheRoyalSocietyinEnglandin1919,EddingtonannouncedthatEinsteinhadcorrectlypredictedthedeflectionofstarlightduetothegravitationalfieldofthesun.

The news of Eddington’s successful observation of Einstein’s predictioncausedaninternationalsensationandwasthebeginningofEinstein’sworldwidepopularcelebrity.ThiswasdueinpartnotonlytoEinstein’sstrangenewtheoryof curved space, but also to the hope that people found in the scientificcollaborationoftwonations—EnglandandGermany—thathadsorecentlybeenenemiesinoneofthemosthorrificwarstheworldhadeverseen.

ThePennStatemodernphysicscoursehadnotgone into theequationsofgeneral relativity, which had so baffled me when I first saw them in thepaperback edition of Principle ofRelativity. To understand the equations, oneneeded to follow in Einstein’s footsteps and learn a whole newmathematicaltechniquecalledtensorcalculus.

After completing his special theory of relativity, Einstein turned to theproblem of gravity, but soon realized that themathematical tools that he hadbeen using were not adequate for the task. The mathematics he had used inspecialrelativitywasbasedonordinarycalculus,whichcanbethoughtofasthemathematicsofmotioninflatspace.Newtonhaddevelopedcalculusasameansof calculating themotion of planets. In using ordinary calculus, it is assumed

thatspaceisflatandunchanging.11Incontrast,tensorcalculusisthemathematicsofmotionincurvedspace.It

worksandlooksthesameonanykindofcurvedspace.Anintegralsegmentoftensorcalculusisitsuseofvectors,definedasdirectedlinesegments.Avectorisrepresentedbydrawinganarrowasastraightline.Thedirectionofthearrowis the direction of the vector, rather like a straight arrow drawn on a mapbetweentwocities.Atensorisageneralizationofavector,takingintoaccountthe possibility of representing a quantity that is pointing in more than onedirectionatthesametime.

Anexampleofatensorwouldbethestressesonatennisballthatisbeingsqueezed by a mechanical vice. The different parts of the tennis ball areexperiencingdifferentstresses.Asinglequantity likeavectorcannotrepresentthe stresses on the ball coming from multiple directions; only a tensor canrepresentsuchforces.

In Einstein’s general theory of relativity,matter causes stresses in space,whichresultinacurvatureofspace,whichwecommonlycallgravity.Forthisreason, Einstein needed to use tensors for this new theory of gravity. (WhiletensorswereexploredbeforeEinstein,theacceptanceandsuccessofhisgeneraltheory of relativity led to their widespread exploration and use bymathematiciansandphysicists.)

To learn tensor calculus, Einstein sought the aid of his longtime friend,MarcelGrossman,whowasaprofessorofmathematicsinZürich,Switzerland.It took Einstein ten years, from 1905 to 1915, to learn tensor calculus andcomplete his revolutionary theory of general relativity. In tensor calculus,Einstein’sfamousequationofthegravitationalfieldofgeneralrelativityhasthefollowingform:

Theleft-handsideofthisequationshowsthecurvatureofspace;theright-handsiderepresentsthestressesofmatter.Theequalsignintheequationmeansthatthestressesofmattercausethecurvatureofspace.

Fortunately, since Einstein’s day, courses in tensor calculus have beendevelopedthathavetaughtfuturegenerationsofmathematiciansandphysicists.Givenmyinterestinpursuinggeneralrelativity,IdecidedthatIshouldtakethetensorcalculuscoursethatwasofferedbythemathematicsdepartmentatPennState.AlreadyIhadbeentakingsomanycoursesinmathematics,alongwithmyphysicscourses, thatsomemembersofthephysicsdepartmentthoughtIwasamathmajor.Ifoundtensorcalculusaneasylanguagetolearn,whichputmeon

tracktonexttacklethetechnicalaspectsofgeneralrelativity.Itwas in themodernphysics course that I finally learned themeaningof

Schrödinger’s equation, which had somovedme with its symmetrical beautywhen I first came across it in a correspondence coursewhile Iwas in the airforce. My determination to one day understand Schrödinger’s equation hadsurely led me in the direction of studying physics, and even to my eventualcareerpath.

InSchrödinger’sequation,thereistheGreeksymbolpsi:ψ.Thissymboliscalledthewavefunctionanddoesnotdescribewhereanelectronactuallyisbutonly where it might possibly be. At the core of quantum mechanics is theuncertainty in the behavior of the electron represented by the wave function.Under anygiven circumstance,we cannot predict exactlywhat the locationofthe electron will be; we can only predict the probability of it being at thatlocation.ThisinterpretationofSchrödinger’swavefunctionwasfirstintroducedin 1926 by the German physicist Max Born (1882–1970). When the wavefunctionismultipliedtimesitselfinaspecialwaythatlookslikeψ*ψ,wecanthendeterminetheprobabilityoftheelectron’slocation.Thelargerthenumberthatwegetfromψ*ψataparticularlocation,themorelikelytheelectronwillbefoundatthatspecificlocation.

As I thought about this feature of quantummechanics, it seemed strangebecause it implied that the electronhas someprobabilityofbeinganywhere. Isoon discovered that this sense of strangenesswas shared by none other thanEinstein.WhilereadingRonaldClark’scomprehensivebiographyEinstein:TheLifeandTimes,justafewyearsafterItookthemodernphysicscourse,Ilearnedthat Einstein had been strongly opposed to the probabilistic interpretation ofquantum mechanics. Einstein fundamentally disagreed with the developers ofquantummechanics,suchasNielsBohr,WernerHeisenberg,andMaxBorn.ForEinstein, the world was deterministic—that is, in any given situation one canexactlydeterminethebehaviorofanindividualelectron.

AccordingtoEinstein,statisticscanandshouldbeappliedtosituations inwhich one is dealingwith a large number of particles. For example, only theaverage behavior of themillions ofmolecules in a gas can be determined. Infact, the average energy of the motion of gas molecules is what we calltemperature.Einsteinwasamasterofusingstatisticstodeterminethebehaviorof physical systems. In his famous explanation known asBrownianmotion—namedafterEnglishbotanistRobertBrown(1773–1858),whoin1827observedthat pollen grains suspended in water jiggled about under the lens of his

microscope in a zigzag path—Einstein showed that the seemingly randommotion of the pollen grain suspended in a liquid was due to the grain beingbombardedbymillionsofwatermolecules.Prior toEinstein’sdefinitivework,physicists had been skeptical about the existence of molecules, the smallestparticleofapurechemicalsubstance thatstill retains itschemicalcompositionandproperties.12

AlthoughEinstein’sworkonthephotoelectriceffect—whichshowedhowelectronsareejectedfrommetalbybeingbombardedbyparticlesoflightcalledphotons—was one of his early great contributions to quantum theory,when itcame to quantum mechanics he was a reluctant revolutionary. He could notbelievethatstatisticswereneededtoexplaintheactionofanindividualelectron.Einstein’s famous quote regarding the myriad probability factors involved inquantummechanicsstates:“Goddoesnotplaydicewiththeworld.”

Withmyacademiccareerbackontrack,DorothyandIdecidedtomarryin1969.SinceourreturntoPennsylvania,shehadfinalizedherdivorce.Ourcivilwedding ceremony was not attended by anyone from either of our families.Dorothy’sfather,KenFry,whowasdispleasedabouthermarryingablackman,announced that he did not wish to see her again. Fortunately, he eventuallyrelented,andheandIdevelopedagoodrelationship.KenhadwantedtobecomeanengineerbutafterreturningfromWorldWarIIhadgonetoworkrunningaboiler at apapermill to supporthisyoung family andwasunable to return toschool.Hereadengineeringjournals,andenjoyeddiscussingtechnicaltheorieswithme.Itwasavaluablelessonformeinhowprejudicecanbeovercomebygetting past racial generalizations and connecting as individuals. Ken and Iendeduprespectingandevenlikingoneanother.Still,Ineverfeltcomfortabletellinghimaboutmy interest in time travel. In retrospect, I imagine that, as athwarted,would-beengineer,hewouldhavebeenenthralledwith the technicalchallengesofmydreamproject.

DorothyandIjoinedtheUniversityBaptistChurch,andDorothybecameamemberofthechoir.ThechurchbecamealargepartofoursociallifeinStateCollege. None of us there had muchmoney, and the parties at the homes offriendswere always casual and simple. Once amonthwewould get togetherwithfriendsandgooutforpizzaandbeer,andthatwassomethingspecial.Asfar as how other people viewedDorothy andme as an interracial couple, wedidn’tnoticeanythingnegative.Wehadourfriends,families,andeachother.

To help make ends meet, I took a part-time night job as a computerprogrammer for a trucking company, which eventually offered to pay for my

schoolingifIwouldswitchmymajor tocomputersandworkfor themat leastone year after graduation. It was a generous offer, but I could not fathomabandoningmystudiesinphysics.IstillreceivedtheGIBill,whichcoveredmytuition and books, and I occasionally taught as a substitute at the local highschool, an experience that made me realize that one day I wanted to teachphysicsincollegeinadditiontoconductingmyownoriginalresearch.

Igraduatedwithmybachelor’sofsciencedegreeinphysicsinthewinterof1969,andwentstraightintoamaster’sprograminphysics,whichIcompletedinDecember1970.AsIwasfinishingmymaster’sworkIbegantolookaroundatthePh.D.programsofotherinstitutions.(Onaverage,aPh.D.takesfouryearsof full-time work, although, depending on the student’s desire, aptitude andability to work independently, it can take much longer.) It was then that theassociatedeanofPennState’sCollegeofScienceaskedtospeaktome.Hesaidthat because of my academic record during the time I had been on the maincampus,hewasnominatingmeforaNationalScienceFoundationTraineeship.IfIreceivedtheNSFappointment,itwouldmeanthatIwouldreceivefinancialsupportduringmyPh.D.programandbeabletodevoteallmytimetoresearchwithouthaving toworryabout theusualdutiesassociatedwithapaid teachingassistantshiporhavingtofindotherworktosupplementmyincome.However,the traineeship was nontransferable; by accepting, I would have to remain atPenn State, which I ended up doing not only for financial reasons but alsobecausetheuniversityandthephysicsdepartmenthadtreatedmewell.

IknewjustthefacultymemberIwantedtoworkwithonmyPh.D.thesis:the brilliant, iconoclastic, and charismaticProfessorGordonFleming. Fleminghadatop-flightreputationasbothateacherandaresearcher.Hewasafreespiritwithmovie-stargoodlooksandadeepbaritonevoice,andhewaspopularwithstudents and staff alike. At one point, Fleming had the largest number ofgraduate students of any of the physics faculty doing theoretical research.Heenjoyed cigars and riding his motorcycle. A true renaissanceman, he was asmuchathomeinthephilosophydepartmentashewasamongphysicists.Ihadheard of Gordon Fleming long before I met him. It was rumored that hisnickname FlashGordon came about because of the speed that he couldwriteequationsontheblackboard.

In the courseofworkingonmymaster’s, I hadgivena lecture about theEinstein-Infeld-Hoffman(EIH)problemataphysicsseminarheldatPennState.TheEIHproblemisatechnicalonethatgoestotherootsofthegeneralrelativitytheory.Generalrelativitynormallyrequiredthatonesetofequationsbeusedto

determinethegeometryofcurvedspacecreatedbyamassivebodylikethesun,andaseparatesetofequationstodeterminethemotionofabodyliketheearthinthecurvedspacecreatedbythesun.In1938,Einsteinandhiscollaborators,LeopoldInfeldandBaneshHoffman,wereabletoshowthatonlyasinglesetofequationswasrequiredtodeterminethegeometryofcurvedspacecreatedbythesun.Thissinglesetofequationscanbeusedtodirectlydeterminehowabodylike the earthmoves around in the geometry created by the sun, replacing theneed for twoseparate setsofequations—oneset for thegeometryandanothersetforthemotion.

Bythistimeinmyeducation,IhaddiscoveredthatIcouldrememberandreproduce long mathematical derivations. The type of memory I have seemsmoretemporalthanspatial;thatis,Irememberequationsandderivationslikeamusical theme rather than visualizing a whole equation as if it were aphotograph.So, formy seminarpresentation, I decided toderive andwrite alltheequationsfortheEIHproblemontheblackboardfrommemory.IknewthatProfessorFlemingwouldbeintheaudience,andImustadmitIdidsopartlytoimpresshimwithmyquicknessandagilitywithequations.Duringthequestionand answer period, a facultymember askedme if I had given any thought towhom I would like to work with onmy Ph. D. thesis. “Dr. Fleming,” I saidwithouthesitation.InoticedthatFlemingsmiledratherproudly.

Iwas also interested inworkingwithFlemingbecauseof a paper hehadwrittenentitled“TimelikeReflection:TheCouplingbetweenTimeReversalandthe Poincaré Group.”When I saw the term “time reversal” in the title of thepaper,IwantedtoknowmoreaboutFleming’sresearch.

Theearlierworkthathehaddoneinvolvedlookingatwhathappenstothemotion of a particle when you reverse the sign of time from t to –t, whichamounts to putting themotion of the particle in reverse. That is to say, if theparticle ismoving from the left side of a room to the right side, changing thesignfortimefromtto-twouldcausetheparticletomovebackintheoppositedirection.Inthiscase,timereversalamountstomotionreversal.WhatFlemingwastryingtoachievewasawaytolookatthistimereversalfromthestandpointofEinstein’sspecialtheoryofrelativity.InEinstein’sspecialtheoryonetriestowriteequationsinawaythateveryonecanagreeonnomatterhowfastparticlesaremovingwithrespecttoeachother.Todothis,physicistsfoundthattheyhadto make use of a four-dimensional point of view that was developed by theGermanmathematicianHermanMinkowski(1864–1909).

In1908,threeyearsafterEinsteindevelopedthespecialtheoryofrelativity,

Minkowski, Einstein’s former math professor, realized that if you combinedspace and time into a new fourth dimensional entity called spacetime, theequations of physics could be rewritten in a simple way. “From henceforth,”Minkowskiwrote, “space by itself, and time by itself, have vanished into themerestshadowsandonlyakindofblendofthetwoexistsinitsownright.”Thisnewwayofwritingtheequationsofphysicslookedthesamenomatterhowfastnumerous bodies were moving with respect to each other, all of which takesplace in the flat spacetime of special relativity. This perfectly clear, four-dimensionalwayofwritingequationsiscalled“manifestcovariance.”

Thenotionofmanifestcovariancewasmyfirstofficialintroductiontotheideaofeleganceinphysics.Iwastolearnthat,foratrainedphysicist,elegancemeantsimplicityintheformoftheequations;atthesametimethatthephysicalcontentoftheequationsisclearlyconveyed,thereisalsoacertainartisticbeautyintheformoftheequationsthemselves.

Fleming,whofeltthatelegancethroughmanifestcovariancewassomethingthat one should try to achieve as well as correctness in physical theory, hadsuccessfully foundaway towrite themathematicaloperationof time reversal,going from t to –t, in a way that everyone could agree on no matter whatconstantspeedbodiesweremovingrelativetoeachother.Inotherwords,hehadfound a clear—and yes, elegant—way of describing time/motion reversal inEinstein’s special theory of relativity. Fleming did this by usingMinkowski’sfour-dimensionalwayoflookingatthings.

Iwasmore interested than ever inEinstein’s general theory of relativity,andwantedtoknowhowgravitymightaffecttheoperationoftimereversal.Ashort timeaftermyseminarpresentation, I approachedFlemingandasked if IcoulddoaPh.D.thesiswithhimonthetopicoflookingattheeffectofgravityon time reversal.He said he thought the topicwouldmake for a good thesis;however,hecautioned that trying to tackle thegeneralproblemofgravityandtimereversalwastoobroad.Hesuggestedthatwenarrowtheproblemdowntoaparticular curved space that was of interest to cosmologists. The space wedecided onwas deSitter space.The curved space of deSitter had a long andinterestinghistoryincosmology.

In1917,Einsteinpublishedapaper,“CosmologicalConsiderationson theGeneralTheoryofRelativity,”inwhichhelaidouthisfirstattempttoapplyhisgeneraltheoryofrelativitytotheuniverseasawhole.Heunveiledatheorythatthe universe we see is static. To ensure that his equations would lead to thatunderlyingassumption,Einsteinwentonto introducea termintohisequations

that kept the universe unchanging. This concept he called the “cosmologicalconstant,” a genie he would regret letting out of the bottle following thegroundbreakingworkofAmericanastronomerEdwinHubble(1898–1953).

Hubble, who earned a degree in mathematics and astronomy at theUniversity of Chicago, observed in the early 1920s at the Mount WilsonObservatory in Pasadena, California, that the galaxies surrounding our MilkyWayaremovingawayfromusinsuchawaythatthegreaterthedistancefromus,thefastertheyaremoving.Thismotionoccurs,Hubblerecognized,ineverydirectionaroundourgalaxy.Hisconclusionwasthat theuniverse isconstantlyexpanding—a bold contradiction to Einstein’s static-universe theory. Einsteinsoon confessed towhat he called his “greatest blunder.” In an effort to agreewithHubble’sastronomicalfindings,Einsteinquicklydroppedhistheoryofthecosmologicalconstant,showing,ifnothingelse,thatgreatmindsremainnimble.

Dutch astronomer Wilhelm de Sitter eventually solved the gravitationalfieldequationsofEinstein’sgeneraltheoryofrelativity.DeSitterpostulatedthateven with the cosmological constant the universe could still be shown to beexpanding. It turnedoutEinsteinwaswrongnotonlyabout theuniversebeingstatic,butalsoabouthisconcernthatthecosmologicalconstantwasaproblemforhisgeneraltheoryofrelativity.ThesolutionofEinstein’sgravitationalfieldequations leading to an expanding universe with the cosmological constant isnowknownasthe“deSittersolution,”andtheuniverseitrepresentsiseither“deSitterspace”orthe“deSitteruniverse.”

IsoonlearnedthatthereisasimplewayofimaginingtheexpansionofdeSitter space. Take a black balloon and paint white spots on it—the balloonrepresents empty space and the white spots represent the galaxies in theuniverse.Asoneblowsuptheballoon,thewhitespotsstartmovingawayfromeachother.Nomatterwhat spot theeye focuseson,allweseeareother spotsmoving away from that spot. The expansion of the balloon represents theexpansionoftheuniverse.Likeaballoon,theuniverseisallsurface.(Alsolikeaballoon, theuniversehas a finite size.There is an equation for the sizeof theuniverse;itsradiusisbelievedtobesomefifteenbillionlightyears.)Themotionoftheballoon’sspotsawayfromeachotherrepresentsthemotionofthegalaxiesawayfromeachother.Andthespotsaremovingawaybecausetheyareonthesurface of the balloon. In just the same way as the spots on the balloon, thegalaxiesaremovingawayfromeachotherbecausetheyareembeddedinspace.Itisspacethatisexpanding(liketheballoon),andthegalaxiesarealongfortheride (like thestarson theballoon).This is theexpandinguniverse thatHubble

firstobservedwithhistelescope.MythesiswastofindawaytodescribetimereversalindeSitterspace.It

turned out that stating the thesiswas far simpler than solving the problem. Infact, Ispentmonthswithapproaches that led todeadends.Afternearlyayearandahalf,Ibegantodespairofeverfindingthesolutiontotheproblem.Then,one afternoon I came back to my apartment exhausted and lay down on thecouch.As I dropped off to sleep, I had this dreamlike vision ofmathematicalsymbols putting themselves together in differentways until it seemed that thesymbols for four dimensions combined with an extra symbol to make a fifthdimension. I awoke with a start and realized that the four dimensions of flatMinkowskispaceofspecialrelativitywerenotenough.WhatIhadtodowastogotofivedimensions.Ihadtousethefourdimensionsofspacetimeinanextradimension that represented the curvature of de Sitter space in a fictitioushyperspace.Iknewatoncethatthisfive-dimensionalpointofviewwascorrect.

Excitedly, Iwrote upmy results and took them to Fleming.He said thisapproachlooked“promising,”buthewantedtostudyit.Isaidthatifhefeltmyresultswere correct,whichwould be amajor breakthrough to completingmythesis, I would very much like to have them appear in the Journal ofMathematicalPhysics,arespectedandrefereedprofessionaljournal.

PublicationwasnotarequirementofthePennStatephysicsdepartmentforPh.D.students,andFlemingcautionedmethatmypapercouldberejected.HeaskedhowIwould feel if thathappened.Notgood,obviously.Nevertheless, ItoldhimIwaswillingtotakethatchance.

Ihadacoupleofreasonsforthisrequest.ThefirstwasduetoanincidentthathappenedwhileDorothyandIwerelivinginBrooklyn.Oneafternoonwewent to the Brooklyn Public Library, and as I browsed through the physicsjournalsIpickedupanissueoftheJournalofMathematicalPhysics,publishedinabeautiful,redvelvet-likecover.Atthatpoint,Icouldn’tunderstandanyofthe technical papers in the journal, but I told Dorothy that one day I wouldunderstandwhatthesescientificpapersmeantandhavemyownpaperpublishedinthishandsome-lookingjournal.

The other reason was more complex. I wanted proof outside of mydepartmentthatIwasaprofessionalphysicistbyhavingthepaperbasedonmythesispublishedinarefereedjournal,meaningthataleadingscientistinthefieldwoulddecideitsoriginalityandworthiness.ThatwaytherecouldbenoquestionthatmythesiswasoriginalandworthyofaPh.D.

Ididn’thear anything fromFleming for anumberofweeks.Then, at the

physicsdepartmentpicnic,FlemingsaunteredovertomeandashegnawedonabarbecuedchickenlegsaidthateverythinglookedgoodandhehadgoneaheadandsubmittedthepaperforpublicationasIhadrequested.ThenhewalkedawayascasuallyasifonaspringtimestrollthroughCentralPark.Speechless,IturnedtoDorothy,whorewardedmewithhergorgeoussmile,accompaniedbyaflowofhappytears.Wehuggedliketeenagers.

Mythrillsoonpassedintoastateofanxiety.Waitingforthereportfromtherefereemade the summerof1972oneof the longestofmy life.Finally,wordcame that the referee considered thepaperoriginal and interesting, andwith afew minor changes it was recommended for publication. My first academicpaper, “PositionOperators in a (3+ 1) deSitterSpace,”was published in theJournalofMathematicalPhysicsinJanuary1973.

I brought home a copy of the published paper and autographed it toDorothy,thankingherforherloveandsupport.“ThisisjustlikewinningagoldmedalattheOlympics,”Igushed.Afewdayslater,Dorothypresentedmewithashinygoldmedallionatourownprivateawardsceremony.

As I would ultimately discover about myself, my personal happiness isgreatlytiedtowhateverishappeninginmywork.Ingraduateschool,withmythesisresearchgoingwell,Iwasontopoftheworld.Foroursummervacation,Dorothyand I tooka road trip toColumbus,Ohio, tovisit a sciencemuseum.Webothlovedanyreasontotravel,andIalwaystookphysicsbookswithme.IrecallfeelingsuchasenseofjoyasIworkedcalculationswhileDorothydroveacrosslongstretchesofinterstatehighway.Ialwaysmadeapointofexplainingmylatestworktoherinelementarywayswithanalogiesthatsomeonewithoutabackgroundinadvancedscienceandmathematicscouldgrasp,andsheseemedtoappreciatetheexplanations.Inarealsense,Ithinkthisinteractionbetweenushelpedpreparemeformyfutureroleasaclassroomteacher.Onourdrives,welistened toPeter,Paul,andMary tapesandsometimessangalong.Thesewereveryhappytimes.

Ispentthenextacademicyearcompletingmythesis.Thesecondpapertocomeoutofmythesisshowedhowtowritetheoperationoftimereversal inawaythateveryoneintheexpandingdeSitteruniversecouldagreeon.Thepaperwasentitled“CouplingbetweenTimeReversalandtheSpaceTimeSymmetriesofthedeSitterUniverse.”ThispaperwasmygeneralizationofFleming’sworkapplied to time reversal in a curved space,whichwas eventually published inanotherprofessionaljournal,PhysicalReview.

Aftertwoandahalfyearsofstudy,Ireceivedmydoctorateinphysicsfrom

Penn State in 1973. At the time, I was one of only seventy-nine African-AmericanPh.D.s inphysics—outofapproximately20,000Ph.D.physicists intheUnitedStates. (Asof2006, thereareapproximately250African-AmericanPh.D.physicistsintheUnitedStatesoutofatotalof25,000.NoblackscientisthasyetwonaNobelPrizeinanyfield.)

Mycareerinphysics,andthenextstageofmypursuitoftimetravel,wasabouttostartinearnest.

Seven

MyIntroductiontoLasers

NowthatIhadmyPh.D.itwastimetofindajob.Evenbefore I finishedmy thesis I had started searching for a position in

physics. I hoped to continuemy research in general relativity and explore thenew avenues thatmight open up regarding time travel to the past. In order toaccomplishthis,Ineededtofindanacademicpositionatacollegeoruniversitythat would allowme to conduct research as well as teach. Unfortunately, thecountrywasinarecession,andtherewasdecreasedfundingforthesciences.

I searched the classified sectionof theAmericanPhysicalSociety’s tradejournal,PhysicsToday,butthepickingswereslim.Previously,Ihadseenissueswith several pages of physics openings, but nowwith the economy in troublethere was only one side of one page. It was not encouraging. Nevertheless, IwenttothePennStatecareercentertolookupaddressesandappliedtonearlyahundredcollegesandaboutadozencorporations.Ineverheardfromanyofthecolleges,buttomysurpriseIreceivedsixresponsesfromindustryrequestinganinterview.

Becoming an industrial scientist was not what I had ever envisioned.However, the advantage to being a trained physicist is that one developsanalyticalproblem-solvingskillsthatcanbeappliedtootherareasofscienceandevenengineering,asphysics isat therootofallof theengineeringdisciplines.With this in mind, I felt equipped to apply my knowledge in an industrialenvironment, although my hope was to continue to search for a way intoacademia while working in industry. I took heart in remembering that evenEinstein had been unable to find a teaching job upon graduating from collegeandhadbeenrequiredtotakeapositioninthepatentofficetopaythebills.

My first interviewwas atGeneral Electric in Schenectady,NewYork. Itwasthemiddleofthewinterandthesnowwasknee-deepinsomeplaces.Thepeople at theG.E. laboratorywere cordial, but Iwasn’t thrilled aboutwintershere.Mynext interviewwas at theG.E. think tank,Tempo, inSantaBarbara,California.IlikedtheareaandthepeopleImet,andtheofficeswerelocatedjusta coupleblocks from thebeautifulPacificOcean,but I couldn’tget a readonhowtheinterviewhadgone.WhenIreturnedhomeabitdiscouraged,Ilearned

thatUnitedTechnologies(atthetime,UnitedAircraftResearchLaboratories)inEastHartford,Connecticut,wantedtointerviewme.

UnitedTechnologiesconsistsofseveraldivisions,thelargestbeingPratt&WhitneyAircraft,whichproducesenginesforcommercialandmilitaryaircraft.TheResearchCenterisaseparatedivision(modeledafterBellLaboratories)thatis engaged in scientific research aimed at industrial application.My interviewwas with Dr. Gerald Peterson, principal research scientist in charge of theTheoreticalPhysicsGroup. I liked JerryPeterson right away.A tall, leanmanwithanopenengagingmannerandaquick,eclecticmind,hehadreceivedhisPh.D. in theoreticalsolid-statephysics fromCornellUniversity.Themembersof the group he headed were first-rate scientific problem solvers who werecontractedoutasneededtotheotherdivisionsofUnitedTechnologies.

Iwasalittleself-consciousandprobablylookedlikeagenuinenerd.Ievenhadastripofwhitetapeholdingmyhorn-rimmedglassestogetheruntilIcouldaffordnewones.Petersonputmeat easeandasked insightfulquestionsaboutmy thesis research and scientific interests. He then asked if I felt I could doindustrialscientificresearch.

“Mythesisadvisersaidthatagoodtheoreticalphysicistcoulddoanything,”Ireplied,notrealizinghowarrogantthatmayhavesounded.

Wehadlunchinthecafeteria,andJerryintroducedmetosomeoftheothermembersofhisscientificgroup.Overall,Ifeltthattheinterviewwentwell,andI told Peterson that I liked the environment of the Research Center. I alsomentioned that inacoupleofdaysIwouldbeflyingback toCalifornia foraninterviewatTRWinRedondoBeach.

I returned to Pennsylvania that evening. The phone rang before I hadfinishedunpackingmybag.ItwasJerryPetersoncallingtooffermearesearchscientistpositioninhisTheoreticalPhysicsGroup.Yearslater,Jerrywouldtellmehedecided tohiremewhen Idescribedhow Ihadmade thebreakthroughregardingmy thesis—the afternoon I had gone home and taken a nap on thecouchanddreamedof a solution.He figured that anyonewhocouldworkoutphysicssolutionsintheirdreamswassomeonehewantedonstaff.

DorothyandIbothlikedtheideaofConnecticutanditsclosenesstoNewYorkCity.Iacceptedatonce,andwepackedupourbelongingsandmovedinthesummerof1973.Wesettledintoanapartmentcomplexrecommendedtousby United Technologies, where other new employees and their families wereliving.Dorothystayedhometherestofthesummer,reading,workingonatan,andwatchingtheneighbors.Shesharedwithmeonefunnyscenethatshesaid

tookplaceatprecisely5:00PMeverydayattheapartmentpatiodirectlyacrossfrom us. The neighbor came out, opened the barbecue, took off the grill andplaceditontheground,thenlitthecharcoal.Shethenwentinsideandherdogwentover and licked thegrill clean.When the firewas ready, the ladywouldcomeout,putthegrillbackonthebarbecue,andplacetheeveningmealatopit.WhenDorothyshowedmethesceneunfoldexactlyasshehaddescribedit,mycommentwasaquiet,“Yuk!”Ittookusawhilebeforewewerereadytobuyabarbecue.

MyfirstassignmentwasacontractwithPratt&Whitney.Atthetime,Pratt&Whitneywasinvestigatingthepossibilityofusinghigh-poweredlaserstodrillholesintheturbinebladesoftheirjetaircraftengines.Theyhadbeenperformingexperimentsandneededtheoreticalsupport.AsthetheoreticalresultsofmyPh.D. thesishadbeenvery remote fromexperimentation, thiswas the first time Ihad been in a situation where the theory I would be developing could beimmediatelytestedbyexperiment.Thatprospectwasabitdaunting.

Myassignmentwastodevelopamathematicalmodelforthelaserdrillingof metals and alloys of interest to Pratt & Whitney. At this point, I hadpracticallynoknowledgeoflasers.However,asaPh.D.researcherIhadbeentrainedtodocreativeproblemsolving,andJerrysaidIwouldbegiventhetimeto learn the necessary background. So I spent weeks in the company libraryreadingaboutlasers,whichatthetimewasarelativelynewlightsource.

Theworld’sfirstoperationallaserwasbuiltin1960attheHughesResearchLaboratories in Malibu, California. Lasers, however, would never have beenpossiblewithout thedevelopmentofquantumtheory,socreditmust firstgo totheGermantheoreticalphysicist,MaxPlanck(1858–1947),whoatthedawnofthetwentiethcenturydevelopedthequantumtheory,forwhichhereceivedthe1918NobelPrizeinPhysics.

In 1900, Planck introduced a radical explanation of how energy isexchangedfromtheheatradiationinanoventothewallsoftheoven.Hesaidthattheenergydoesnotflowcontinuouslyfromtheheatradiationintothewallsbut is given to thewalls only in definite amounts, or quanta. Prior to Planck,physicists thought that the exchange of energy from heat radiation was likepouring water into a glass, although this did not agree with what had beenobserved experimentally. Planck proposed that the energy exchangewasmorelikeputtingcoins ina slotmachine,witheachcoinbeinga separatequantum.Planck’stheoreticalmodelwassoonverifiedthroughexperimentation.Becauseenergywasexchanged inquantaamounts, thenew theorywascalledquantum

theory. Itwas thebeginningofa revolution thatwas tohavean impactonourentireunderstandingofmatterandenergy,andleadtoatechnologicalrevolutionthatisstilldevelopingtoday.

InEinstein’smiracleyearof1905,whenhepublishedhisspecialtheoryofrelativity, he also made a major contribution to quantum theory. Einsteinsuggested that not only is the energy exchanged in definite quanta but theradiation itself inside the oven is alsomade up of individual particles of lightcalled photons.Einstein used his theory to explain the phenomenon known asthe photoelectric effect. The German experimental physicist Philipp Lenard(1862–1947)observedthatshininglightonametalsurfacecausedelectrons tobeejectedfromthesurfaceofthemetal.Einsteinwasabletoexplainthisresultby saying that the light shining on the metal surface consisted of photonsbombardingthesurface.Itwasthesephotonsthatcausedelectronstobeejectedfromthemetal.Itisforthiswork,andnotrelativity,thatEinsteinwonthe1921Nobel Prize in Physics. Today, the photoelectric effect is important foreverythingfromautomaticdooropenerstotelevisioncameratubes.13

Einstein’swork led to thenext importantdevelopment inquantum theoryandprovidedanotherpieceof the laser story,when, in1913,DanishphysicistNielsBohr used Planck’s quantum theory andEinstein’s theory of photons toexplain the behavior of the hydrogen atom. As it happens, prior to quantumtheoryphysicists couldnot understandwhy thehydrogen atomdidn’t collapseon itself.Ahydrogen atomconsists of a positive protonorbitedby a negativeelectron.Astheelectronrevolvesaroundtheprotonitshouldcontinuouslyloseenergyandeventuallycollapse into theproton.Since this isnotwhathappens,somethingelsehadtobegoingon.Bohrsuggestedthatthekeytotheproblemwasquantumtheory.Inquantumtheory,theenergycannotbelostcontinuously,asenergyisnotcontinuous.Thismeansthat theelectronhastostayinafixedorbit,calleditsenergylevel,becauseitcannotloseenergycontinuously.

There’sonefinalingredientinthetheorybehindthelaser.OnceagainthiswasprovidedbyEinstein,whoin1916publishedapaperentitled“EmissionandAbsorption of Radiation According to the Quantum Theory,” in which hecombined the ideas of Planck, Bohr, and his own earlier work. Using thiscombinationof ideas,Einstein investigated the three fundamentalprocessesbywhich atoms emit and absorb light. The first process is called inducedabsorption. In this process, a photon coming into the atom is absorbed by anelectron in a low energy level. The incoming photon induces the electron tojump to a higher energy level. The second process is called spontaneous

emission.Once the electron is in the higher energy level it can spontaneouslyjumptoa lowerenergy levelbyemittingaphoton.Thisspontaneousemissionprocessoccursrandomly.Thefinalprocess iscalledstimulatedemission; ifanincomingphotonfindsthattheelectronisalreadyatahigherenergylevel,thenthephotoncankick theelectronoutof that level. In theprocess, the incomingphotondoesn’tgetabsorbedandkeepsmovingon.However,whentheelectronfallstothelowerenergylevelitemitsitsownphoton.Sothenetresultisthatasinglephotoncomingintoanatomcanresultintwophotonscomingout.Oneoftheoutgoingphotonsistheoriginalphotonandtheotheroutgoingphotonisthestimulatedphoton.Thisleadstoanamplificationofthelightcomingoutoftheatom,anotherkeyingredienttounderstandingthelaser.

The word laser itself reveals how they work. Laser is an acronym thatstands for Light Amplification by the Stimulated Emission of Radiation. Thefirstoperationallaserwasdesignedin1960byanAmericanphysicistandjunioremployee at Hughes Aircraft, Theodore Maiman. He used a synthetic rubycrystal shaped into a cylinder. The trickwas to get all of the electrons in theatomsofthecrystalintoahigherenergylevelatthesametime,aprocesscalledpopulation inversion. This is done by wrapping the ruby crystal with a flashtube. Light from the flash tube puts all of the electrons into a higher energylevel.Twomirrorsareplacedattheoppositeendsoftherubycrystal.Oneofthemirrors is completely reflecting and the othermirror is partially reflecting. Aspontaneouslyemittedphoton fromoneof theatomsgets thingsmoving.Thatphotonwillstimulate theemissionofanotherphoton inadifferentatom.Thenthose two photonswill hit twomore atoms and stimulate those atoms to emitphotons.Nowtherearefourphotonswhichstimulatefourotheratomstoemit,andsoon.Thiswillresult inachainreactionofphotonsthatbouncebackandforthbetween the twomirrorsof the rubycrystal.Because eachphoton in thelaserisinstepwithalltheotherphotonsthatwerestimulatedbythem,thebeamthey form is said to be coherent. There is an essential difference between thecoherent photons of a laser source and photons from an ordinary light sourcesuch as a standard light bulb. The photons from a light bulb tend to clumptogetherorbunchup.Bycontrast, thephotonsofa lasersourcearedistributedlike drops in a steady rainfall. The coherent state of a laser source was firstdescribedindetailbyRoyGlauber.14Itisthecoherenceofthelaseroutputthatallows a very narrow beam to be formed. Eventually the photonswill streamthroughthepartiallyreflectingmirror,resultinginanintense,incrediblynarrow,purelaserbeamoflight.Whenarubycrystalisused,thecolorofthelaserlight

isred.A distinctive characteristic of the laser is that the coherent narrow light

beam can result in an intensity ofmillions ofwatts per square centimeter.Atthese levels of intensity, a laser beam on a metal surface will cause thetemperatureofthemetaltorisetoapointofvaporization.Thiswouldgivethelasertheability,atleasttheoretically,todrillholesthroughsolidmetalblocks.

Withmynewunderstandingofhowalaserworkedandwhatitcoulddo,Iwas now ready to develop a mathematical model that would predict howeffectivealaserbeamwouldbeindrillingholes.Itturnedoutthattodeveloparealisticmodel itwasnecessary to calculate the energy transfer from the laserbeam to the metal’s surface, and then calculate heat conduction in the metalwhile thesurface ismoving.This iscalledamoving-boundaryproblem,and itcan be notoriously difficult to solve. In fact, Pratt &Whitney had a team ofengineersusingelaboratecomputercodestotrytosolvetheproblem.Iplannedtoconsultwith them,but I foundout ratherquickly that informationexchangewithin the company was not encouraged. This was quite different from theacademicenvironmentIhadbeenaccustomedto.Inauniversityresearchsettinggenerousinformationsharingwasthenorm,butIfoundthatwasnotthecaseinprivateindustry.Infact,Pratt&WhitneyprovidedmewithanearlyversionofadesktopcomputersothatIwouldnothavetousethemainframecomputerandinadvertentlyletotherpeopleknowwhatIwasdoing.

While browsing through the Research Center’s library, I had hit upon atechniquethatallowedmetodevelopamathematicalmodelthatwouldpredictwhat would happen when a laser beam is drilling through metal. Using themodelIdeveloped,Iwasabletocalculateaccuratelytheexactdepthoftheholethat would be produced in a particular metal or alloy for any given laserintensity. The results of my calculations were soon observed experimentallyduring laser hole-drilling in theResearchCenter laboratory.At that point,myjobwasdone.

Whileeveryoneseemedhappywithmyworkonmyfirstassignment,Ihadnotgivenuphopeoffindingawayintoacademia.Inthemeantime,Icontinuedmyownstudies.Intheevenings,Iwouldcomehome,havedinnerwithDorothy,whoafterher summerof relaxationhad founda jobwithaHartford insurancecompany,andspendafewhoursstudyinggeneralrelativityandthenewtheoriesthatwerebeingdevelopedtounderstandthebasicforcesofnature.

Physicists believe that there are four basic forces in the universe. Thestrongestoftheseforcesiscalledthestrongnuclearforce.Thisistheforcethat

holdsprotonstogetherwithneutronsinthenucleusofatoms.Thesecondforce,in order of strength, is the electromagnetic force. Besides gravity, theelectromagneticforceistheonethatwemostcommonlycomeincontactwithinourdailylives.Themagneticfieldof theearth,whichdeterminesthedirectionofacompassneedle,ispartoftheelectromagneticforce.Thisforcealsoleadstotheelectricalattractionbetweenprotonsandorbitingelectronsinanatom.Radioandtelevisionsignalsaretheresultofchangingelectromagneticfields.Thenextforce is the so-calledweak nuclear force. This is the force behind radioactivedecay. Surprisingly, the weakest of the four forces is the gravitational force,which holds the planets in orbit around the sun and keeps us attached to thesurfaceoftheearth.Itseemsoddthatgravityissoweak,butitdependsentirelyonthegravitationalattractionbetweenmassiveobjects.Theelectricalattractionbetweentheprotonandelectronisfargreater.

Einstein spent the last years of his life trying to combine theelectromagneticforcewithgravitationalforceinwhathecalleda“unifiedfieldtheory.” Later, I learned Einstein’s striving for a unification of theelectromagneticandgravitationalfieldswasstronglymotivatedbyhisdesiretoexorcize the demon of probability in quantum mechanics. In addition tobelieving that God was not a dice-throwing gambler, Einstein made anotherfamousdeclaration regardingquantummechanics, stating, “Subtle is theLord,but malicious he is not.” In any case, Einstein failed in his efforts to find adeterministicunifiedfieldtheorythatmadesensetohim.

Einstein’seffortataunificationofgravityandelectromagneticforceswasnottheonlyattempttodoso.Ibecameinterestedinseparateattemptstounifygravity and electromagnetism by German-born mathematician and physicistTheodorKaluza(1885–1954)andSwedishphysicistOskarKlein(1894–1977).Like Einstein, I had reasons for my interest in unified field theories: I wasmotivatedbythepossibilityofusingsuchatheoryfortimetravel.

In1921Kaluzawasabletoshowthatbygoingtofivedimensionsameanscouldbefoundforcombiningthegravitationalandelectromagneticforces.Thefifth dimensionwas conceived byKaluza as an extra dimension of space, butunliketheotherthreedimensionsofspace(length,width,andheight)thisextradimension of space could not be directly measured. Kaluza was trying tocombine the electromagnetic force with the gravitational force of Einstein’sgeneral theory of relativity. In Einstein’s theory, the gravitational force is thebendingofthethreeordinarydimensionsofspaceandtheslowingdownofthefourth dimension of time. Kaluza showed that, by combining his extra fifth

dimensionwiththethreedimensionsofordinaryspaceandthefourthdimensionof time, the electromagnetic course could be combined with the gravitationalforce.SinceKleinalsoindependentlydevelopedthistheory,itcametobeknownas the Kaluza-Klein theory. At one point, Einstein studied the Kaluza-Kleintheory but decided to try an approach that did not use a fifth dimension. TheKaluza-Kleintheoryisstillstudiedbyphysiciststodayasapossibleapproachtoaunifiedfieldtheory.

Theideaofunificationgoesbacktotheveryfoundationofphysics.Infact,the first unified field theorywas developed by the nineteenth-century Scottishnatural philosopher (as theoretical physicists were then called) James ClerkMaxwell(1831–1879).Maxwell’stheoryunifiedwhatwaspreviouslythoughttobe separate electric andmagnetic fields.Maxwell wasmathematically able toshowthatitwaspossibletouseachangingelectricfieldtoproduceandcontrolamagnetic field. Earlier in the nineteenth century it had been shown by theEnglish chemist andphysicistMichaelFaraday that a changingmagnetic fieldcould be used to produce an electric field.15 Using Faraday’s observations,Maxwell was able to mathematically synthesize his results with Faraday’sobservations to create a unified theory of the electromagnetic field. In thistheory, the changing electric field produces a changing magnetic field. Thatchangingmagneticfieldinturnproducesachangingelectricfieldandsoon.Thechangingelectricandmagnetic fields spreadout throughspaceat the speedoflight.Maxwell deduced that lightwas actually changing electric andmagneticfields. This electromagnetic theory of light was the first unified field theory.Maxwell’sunificationof theelectromagnetic fieldhas led toanunprecedentedcontrolofthisforceofnature.Thefruitsofmoderntechnology,fromelectricalpower generation to television, are a result of unification of the electric andmagneticfields.

One of the predictions of general relativity is that a clock in a stronggravitationalfieldwillrunslowerthanaclockinaweakgravitationalfield.Forexample,supposeyouhavesynchronizedtwoidenticalatomicclocks.16Ifyouwere to take one of the clocks to the top of a high mountain where thegravitationalpullof theearthisweaker,andcompareit to theidenticalatomicclockatgroundlevelwheregravityisstronger,youwouldfindthattheclockatground level is running slower than theclockat the topof themountain.Thisconnection between time and gravity fascinated me. I thought that perhaps aunifiedfieldtheorycouldbeusedtocontrolgravityandhencetime.Idecidedtomakeaseriousstudyofthemodernunifiedfieldtheories.

Oneofthemajorachievementsofmodernphysicshasbeentheunificationoftheelectromagneticforcewiththeweaknuclearforce.Thisunifiedtheoryisknownasan“electroweak theory.”Theunificationwas finallyachieved in thelate1960sbyStevenWeinberg,SheldonGlashow,andAbdusSalam,forwhichthethreesharedthe1979NobelPrizeinPhysics“for theircontributionstothetheoryof theunifiedweakandelectromagnetic interactionbetweenelementaryparticles.”

The electroweak theory led to the prediction of a new particle of nature.Thisnewparticle isaheavyphoton.Anordinaryphotonhasnochargeand isessentiallyaparticleoflightwithnomass.Thenewparticle,calledaZparticle,alsohasnocharge,butitdoeshavemass.Theseparticleshavebeenseeninthehigh-energycollisionofelementaryparticles.

I read about earlier attempts that had been made to unify the strong,electromagnetic, andweak forces into agrandunified field theory.Oneof thepredictionsofthegrandunifiedtheoryisthattheproton,firstdiscoveredin1918byErnestRutherford,17whichisabasiccomponentoftheatom,doesnotliveforeverashadbeenpreviouslythought.Rather,itdisintegratesafterasufficienttime.Sincethisdisintegrationhasneverbeenseen,grandunifiedfieldtheorieshavenotbeenaccepted.

I was intrigued by the electroweak theory and decided to see if I coulddevelop a unified theory that would combine the gravitational force with theweaknuclear force. I thought I sawmathematical similaritiesbetween the twoforcesandthatthismightpointthewaytotheirunification,soIspentmydaysworking for United Technologies and my evenings studying unified fieldtheoriesthatmightbeconnectedtogravity.Ibelievedthatifacompleteunifiedfieldtheorywasfoundthatcombinedallofthefourbasicforcesthenmaybeoneoftheforcescouldbeusedtocontroltheother,andperhapsthiscouldleadtoaworkingtimemachine.

Theconstantpressureofmydayworkandmylate-nightstudiesbegan totake their toll. I yearned to be teaching and developing my ideas in generalrelativity full time. Iwas twenty-eight years old and already feeling that timewaswasting.Ihadheard itsuggested thatascientist’sbestworkisoftendoneearlier in life, by the age of thirty, and I didn’t want to miss my window ofopportunity.18

Another opportunityDorothy and I decidedwedid notwant tomisswashaving children and becoming parents, as somany of our friendswere doing.Therecamethedaywhenshethoughtshewaspregnantandwenttothedoctor.

A phone call the next day confirmedwhat we hoped for.Withinminutes webegan telling the entireWesternworld.Amonth later,Dorothyawakenedonemorningwithseverepainandprofusebleeding.Shehadlostthebaby.Wefounditdifficulttoaccept,butknewwestillhadapossibilityoftryingagain.

Aftertwoyears,Itoldmyboss,JerryPeterson,thatIintendedtoleaveandfinda teachingand researchposition in auniversity.At first he thought that Iwasnegotiatingformoremoney,andheofferedmeapayraise.WhenItoldhimthat wasn’t my intent, and how I felt more at home in academia, he wassympathetic. He also issued a warning: “You realize that in academia you’regoingtobetakinganoathofpoverty?”

WhenIassuredhimthatIrealizedpayinacademiawouldneverrivalthatofprivateindustry,hegaveupandsetouttohelp.JerryknewStevenWeinberg,then at Harvard, and he sent the future Nobel Prize winner some of theindependent research I had been doing in attempting to unify gravity and theweak nuclear interaction. Weinberg was kindly in his reply, saying that themodel had some problems but the idea was interesting. Jerry also put me intouchwiththeheadofthephysicsdepartmentattheUniversityofConnecticut,Joseph Budnik, who had been doing consulting work at United Technologiesduring the summers. Budnik has an outgoing, bigger-than-life personality; Iliked him immediately and knew it would be great to be part of his physicsdepartment. Iwas also fortunate in that Jerry’swife, Cynthia Peterson,was afaculty member in the UConn physics department. I was invited to give aphysics colloquium at UConn on my thesis research, which gave me theopportunity tomeet theheadof the elementaryparticle and fieldsgroup,KurtHaller,whogrewupinAustriaandreceivedhistraininginphysicsatColumbiaUniversity. He was friendly and encouraging, and, if I got a position in thedepartment,Iwouldbepartofhisgroup.Notlongaftermytalk,Iwasofferedaone-year provisional assistant professor position at the main campus of theUniversityofConnecticutinStorrs.Iwasbesidemyselfwithjoy,eventhoughitmeanta50percentcutinpay.Now,Icouldseriouslyreturntomystudies.

Duringmytwo-yearstintinprivateindustry,Ihadlearnedalotaboutlasersandhadadeeperappreciationfortheinterplaybetweentheoryandexperimentinphysics.Too,IwasbeholdentoJerryPetersonforassistingmeinsomanyways.Icametocomparehismanagerialbrillianceinhandlingateamofscientificfreethinkers to the cohesiveness that Robert Oppenheimer had brought to theManhattanProject.Nonetheless,at thetime,IneversaidawordtoJerryaboutmy longtime interest in time travel, as I was certain he would be skeptical.

Ironically,my research days under his tutelage atUnited TechnologieswouldforeverchangethewayIdidtheoreticalphysics,andmyworkwithlaserswouldoneday endupproviding amissing element tomydesignof an experimentaltimemachine.

At a farewell party for me at the Research Center, the staff gave me agoing-away gift: an authenticated signature of Albert Einstein. My youngestbrother, Keith, who had become a successful professional artist living in SanDiego, painted a brilliant portrait of Einstein tomountmy authentic signaturenextto.Iframedthemtogether,andhungthemonthewallofmystudy.

Underthegazeofthegrandoldrelativist,Iwasreadytofocusmyattentionon teaching, while probing further into the time-travel possibilities of generalrelativity.

Eight

FindingMyAcademicHome

Havingtraveledbackintime,IamonceagainintheBronx.ItisawarmSundayeveninginApril,1955.Enteringthebuildingat1455HarrodAvenue,Itakethelifttotheeleventh

floor.ThehallwayisnarrowerthanIremember.Iknockonthedoorof11D.Whenthedooropens,myhandsomefatherisstandingbeforeme.Iamsurprisedathowyounghelooks.Myfatheris,infact,onlythreeyears

olderthanI,andIamnowseveralinchestaller.“CanIhelpyou?”HisvoicehasadeepyetsoftqualityIremember.I am not surprised that he doesn’t recognize me. Although I have

anticipatedthismomentforalongtime,Iamspeechlesswhenitarrives.BoydMallettlookspuzzled.Ifinallyfindmyvoice.“Ihavesomethingstotellyouthatwillbedifficult

tobelieve.Butfirst,Iwanttoshowyousomephotographs.”OnebyoneIhandhimtheoldphotographsofhimwithhiswifeandyoung

children.Another image is of himworking on a TV set. I know he had seenthesepicturesbeforebecausetheyareinourfamilyalbum.

“Wheredidyougetthese?”Without answering, I show him some photos he has not seen: of his

childrengrown,andhiswife—stillbeautiful,butyearsolder.“Whatisthisallabout?”Hesoundsalarmed.IaskhimifIcancomeinforafewminutes.Heseemstobeconsideringmyrequest.Thenhestandsbackandopensthe

door fully, and leads me into the living room. I am surprised that I haverememberedthelayoutsoaccurately,althoughit feelsoddtobelookingdownontheroomfromthisheight.Wesitdown,andheagainaskswhatisgoingon.

Igazeatthismanwhoconsidersmeastranger—thismanwho,inbothlifeanddeath,gavesuchunbelievablemeaningtomyownlife.

“Look,”Ifinallysay,“youknowabouttelevision.Youknowthatbyusingelectronicsyoucangeneratesignalsandtransmitimagesacrossspace.”

Hetiltshisheadtooneside.Heisinterested.ItellhimthatIhavebuiltadevicethatcansendimagesandobjectsacross

vastperiodsoftime.Iexplainthatthisdeviceiscalledatimemachine.“Atimemachine?Isthathowyougotthosepictures?”“That’spartofthestory.”Hewantstoknowmore.Iknewmattersofelectronicsandsciencewouldpiquehisinterest.“YoushouldknowthatIbuiltitbecausemyfatherdied.”Itellhimthatmy

fatherworkedand livedhard.“Then, inMay1955,on theeveningmyparentswerecelebratingtheireleventhweddinganniversary,myfatherdiedsuddenlyofaheartattack.”

Helookspuzzled.“That’sinteresting.MywifeandIwillbecelebratingoureleventhanniversarynextmonth.”

Igoon—tellinghimthatIwastenyearsoldwhenmyfatherdied,andthatIwassolostafterhisdeaththatIdidn’tknowwhattodoforalongtime.

Heseemstosadden.Ofcourse.Heknowsaboutlosinghisfather.“Then I read this wonderful book called The Time Machine, by H. G.

Wells.ItbecamecleartomewhatIhadtodo.Itgavemehope.”His facial expression suggests that he is beginning to put the pieces

together.Helookshardatme.“You’renottryingtotellme—”“Ibuiltmyowntimemachine,yes. Ihave traveledfromthefuture tosee

you,Dad.IamyoursonRonald.”“MysonRoniswithhismotheratachurchfunction.”“LikeeverySundaynight. Iknow.That’swhy I camewhen Idid, sowe

couldbealone.I’masrealasthatlittleboyatchurchwithhismother.Iamolderandcomefromadifferenttime,butIamRonaldMallett.Pleasebelieveme.It’simportantthatyoulistentowhatIhavecometotellyou.Youareindanger.Youhaveaweakheart,Dad.Youneed togo to thedoctor rightawayoryou’llbedeadinamonth.AndforGod’ssake,stopsmoking.”

ThenItoldhimoneofthemostimportantthingsIcametosay—madesobecauseIcan’tremembertellinghimwhilehewasalive.“Iloveyou,Dad.”

This ismy fantasy.This iswhere I havegone somany times that I havememorizedthescriptcontainingthewordsofmyfatherandmyself.Iusuallygothereatnight,inthedark,withmyeyesshut,sweetlysuspendedbetweensleepand consciousness. I always return from the imagined visit wondering if hewouldreallychangehislife.Couldhe?CouldIalterhisfate?

MightIsavemyfatherfromhistragic,prematuredeath?On the morning of September 2, 1975, Dorothy kissed me goodbye and

wishedmegoodluckasIleftourtownhouseinManchester.IdrovetotheStorrs

campus of the University of Connecticut for the first day of school, and thebeginningofmynewlifeasanassistantprofessorofphysics.

StorrsissituatedinthenortheastcornerofConnecticutabouttwentymilesfrom the state capital ofHartford. The lush, tree-studded campus is a smallerscale version of the Penn State campus. To the left as I drove through theentranceweresprawlingfarmlandsand,nearby,arusticbarnandsomegrazinglivestock. Further down the way were the buildings of the College ofAgriculture.TherootsoftheUniversityofConnecticut,likethoseatPennState,arefirmlyplantedinsoilagriculture.In1881UConnwasestablishedasStorrsAgriculturalSchoolon170acresoflanddonatedtothestatebybrothersCharlesand Augustus Storrs, successful New York businessmen who were born andraisedonaConnecticutfarm.BythetimeIcametoUConnithadbecometheflagshipuniversityforthestateofConnecticut.

Followingwrittendirections,IdroveintothecenterofcampusandturnedonNorthEaglevilleRoadtowardthephysicsbuilding,amodernstructurewithalargedomeonthetopthathousedatelescope.Iparked,enteredthebuilding,andtooktheelevator.

IfeltabitanxiousasIwalkedintotheofficeofthephysicsdepartment.Atthirty, Iwasnomore than tenyearsolder than theaverageundergraduate,andonlyayearortwoolderthanmanygraduatestudents.Therewasalsotheissueof race, as I was the first and only black faculty member of the physicsdepartment.Nonetheless,Ihadaveryspecificimageofwhatacollegeprofessorshouldlooklikerightdowntothewhiteshirtwithabutton-downcollarandthetweedjacketwithelbowpatches.IfIwastobetakenseriously,IdecidedthatIwasgoingtohavetowalkthewalk.Mymother’sinfluenceandpersonalpridewere remembered—howevenwhen shewasworking as a storemaid she haddressed for success. Iwaswearing a button-down shirt and appropriate tweedjacketwithleatherpatches.

Thephysicsdepartmenthead,JoeBudnick,gavemeawarmwelcome.Hetook me around for introductions to the office staff. They were friendly andhelpedputmefurtheratease.IwasassignedtoroomP-414onthefourthfloor.Myofficewasspaciousbutwithoutmuchofaview.FrommywindowIlookeddirectly out at the Life Science Building, with a partial view of the campuscemetery, where, I would learn, a number of retired professors were buried.Aftersettlingin,Iwentaroundtovisitmyfacultycolleagues—thosewhowerestillalive,thatis.

In the physics department at the time were some thirty faculty members

engaged in all areas of modern physics. Their various fields were broadlyrepresentedbyanumberofdefinedgroups:atomicandmolecular,particlesandfields, condensedmatter, and nuclear.My area of research, Einstein’s generaltheoryofrelativity,cameundertheparticlesandfieldsgroupnominallyheadedby Professor Kurt Haller, whom I hadmet when I gave a lecture on campuswhilestillworkingforUnitedTechnologies.

IreportedtoHaller’sofficelocatedattheendofthehallonthefourthfloor.Hallerwasagenialmanof slightbuildandmediumheightwithacertainOldWorldaurabefittinghisearlyyearsinVienna.Whenhewasten,in1938,heandhis family had fled Austria after the Nazi annexation of their country. KurtreceivedhisPh.D.intheoreticalphysicsfromColumbiain1958andsixyearslater joined the UConn physics faculty. He had done some importantfundamentalwork in theoretical elementary particle physics, specifically in anareaknownasgaugetheories,whichhavetheirrootsintheordinarypracticeofmeasurement.

Togaugesomethingmeans,ofcourse,tomeasureitaccordingtosomekindofscale.Consideridenticaltwinsofthesameheight.SupposeonetwinlivesinBoston and the other in New York City. On a particular day they decide tomeasure their height. TheBoston twin has a common yardstick thatmeasuresdistance in feet and inches, while the New York twin has a meter stick thatmeasuresmeters and centimeters. TheBoston twinmeasures his height as sixfeet, and the New York twin measures his height as 1.8 meters. Themeasurements sound very different, but clearly the height of the twins hasn’tchanged.Rather,ithastodowiththescalebywhichtheyweremeasured.Inthiscase,thereisarulecalledaconversionfactorthattellsyouhowtogobackandforthbetweenmetersandfeet.Theconversionfactoris.3metersdividedbyonefoot.That is, ifyoumultiplysixfeetby .3metersperfootyouget1.8meters.This iswhatgauge theories inphysicsareallabout—thenotionbeing that theforces of nature are conversion factors needed to compensate for changes inscale.

Forexample,inquantummechanicsanelectronbehaveslikeawave.Ifwestart with two electrons we can change the scale of the wave of one of theelectronsbyshifting itswave relative to theotherelectron.Theshiftingof thewave leads to a compensating conversion factor thatwe call the electric forcebetween the electrons. In otherwords, the two electrons feel an electric forcebetweenthemtocompensateforashiftintheelectronwaves.

Kurt Haller, a leading expert in gauge theories, was interested in my

researchbecauseitwasconnectedwiththeideathatgravitywasagaugetheory.Awaytothinkaboutthisisasfollows:Supposeyouareunfortunateenoughtobeinaglasselevatorthatisfallingfreely.Surprisingasitmightseem,sinceyouare falling at the same rate at the elevator is falling, youwould find yourselfsuspended in space in the elevator. In other words, you would feel no force.However, as you lookoutside and see the floors rushingby, youwouldknowthatsomethingispullingyoutotheground.Yourchangesinscaleorgauge(i.e.,the change in the floors as you drop) lead you to conclude that there is aconversionfactorcalledgravitythatwillprobablymaketheendofyourrideanunpleasantone.Inotherwords,gravityisdetectedasadifferenceinaccelerationbetweendifferentlocations.Thisisthegaugetheoryofgravity.

From that first day I walked into his office as the department’s newestfacultymember,Kurtencouragedmetocontinuewithmyownresearch.Iwashappy to oblige, while being careful not to mention that I was interested ingravityforotherreasons—namely,thepartgravitymightplayintimetravel.

My reason for keepingmum aboutmy interest in time travelwas one ofpracticality:toadvanceuptheacademicladder,fromassistanttoassociatetofullprofessor, and in order to eventually attain tenure (meaning one cannot bedismissed without cause), it is best not to be pegged within or outside yourdepartmentasacrackpot.Whileinphysicscreativityandstrangeideasareoftenencouraged—blackholesareverystrangeandbydefinitioninvisibleobjects,butresearchonthemhaslongbeenconsideredlegitimate—timetravelwasdeemedinthe1970sastooextremeasubjectforseriousscientificinquiry.Myplanwassimple: as I progressed in my academic career toward tenure and fullprofessorship, which would provide me with both financial security andprofessional acceptance, my time-travel work would be my own business.Afterward,when Iwas a tenured full professor, Iwould feel freer to publiclyworkon,andspeakoutabout, thesubject thathadcausedmetogotocollege,studyhard,andbecomeaphysicistinthefirstplace.

AsIvisitedwithotherfaculty,Igotmoreinsightintosurvivaltechniquesinacademia.Iwas,infact,onprobation.Academicprobationforafacultymembermeantayear-by-yearappointment.Thisprobationaryperiodcontinueduntiloneachievedtenure,whichusuallytookanumberofyears.Officially,therearethreecomponents to the responsibilities of a faculty member. These are teaching,research,andservicetotheuniversitycommunity.Unofficially,onedepartmentveterantookmeasideandsaid,“Ron,inrealitythethreeaspectsofyourjobareresearch, research, and research.” I took this advice to heart, although I knew

fromotherfacultymembersthatbeingagoodteacherwasimportant,too.My teaching assignments included undergraduate and graduate courses. I

taught undergraduate general physics, an algebra-based course that coveredelectricityandmagnetism,optics,andmodernphysics.MygraduatecoursewasMethods of Theoretical Physics, covering vector analysis, matrix theory,ordinaryandpartialdifferentialequations,andgrouptheory.

Thereisatruismtotheeffectthatthebestwaytolearnasubjectistoteachit. It is not mysterious how this happens; to be a good teacher one needs toprepare, and adequate preparation requires much study and thought whenstartingfromscratchwithnocourseoutlineornotes.Ispentasmanyasfiveorsixhoursinpreparationforanhour-longlecture.Agraduateclasstooklonger—up to eight hours preparation per classroom hour. My efforts paid earlydividends: in my first year, I was surprised by a spontaneous ovation afterdeliveringalectureonelectricityandmagnetismtomygeneralphysicsclass.Iamnot sureanycompliment,beforeor since,hasmeantquiteasmuchas thatone.

Near thestartof that first term, Iwasadvisedbya seniormemberofmydepartmentthatitwouldbewiseformetopublisha“solopaper”rightaway.HeacknowledgedthatIhadpublishedtwopreviouspaperswithmythesisadvisor,butasatheoristinmyfirstfacultyposition,hesaid,itwasvitalformetodomyownpaper toprove that I couldwork independently.After that, hewenton, Ishouldworkonpublishingapaperwithagraduatestudent,whichwouldshowthatIcouldalsosupervisestudentresearchwork.

As a possible subject for my first solo paper, I ruminated more aboutgravityasagaugetheory.Ieventuallydecidedtheremightbeaninterestingandnew connection between gravity and the Einstein-Infeld-Hoffman (EIH)problem, aboutwhich I had lectured in front of Professor Fleming and otherswhile a graduate student at Penn State. I delved headlong into the subject,delightedtohavethehoursduringthedaytodoresearch,ratherthanhavingtodosoonmyowntimeafterafullday’sworkasIalwayshadbefore.

In the original EIH problem, Einstein and his collaborators were able toshowthat theequationsforgravitywereall thatwasrequired todetermine theequationsformotionofmatter.Thatis,ifyouhaveagravitationalfieldyoucandeterminetheequationsthattellyouhowmatterwillmoveinthatgravitationalfield.My calculations indicated that there was an inverse EIH problem—thatwith only the equations for motion of matter, the gravitational field can bedetermined.Byusingagaugetheoryofgravity,Icouldshowthatchangingthe

scale of the equations that determined themotion ofmatterwould lead to thecorrect equations for Newton’s laws of gravity. Amazingly, no one hadattemptedtoturntheEIHproblemaround.IwroteupmyresultsandsubmittedapapertotherespectedphysicsjournalPhysicalReview,whichhadpublishedmysecond graduate paper. My first solo paper, “Symmetry Breaking and theGravitationalField,”waspublishedinMay1976.

Withthepublicationofthatarticle,Isuccessfullysurvivedmyfirstyearinacademiaasaprobationaryfacultymember.AsIwasbeginningtofeelathomeinthephysicsdepartment,Dorothywasdoingwellherself,enjoyingherworkasan executive secretarywith Travellers Insurance Company. That summer, sheandIdrovetoAltoonaforavisit.Onesunnymorningwewalkedalongtheoldrailroadtracksthatbisectthetown.IhadcomethiswaysooftenasaboythatIbegan reflecting aloud on some of my childhood experiences, both good andbad. Suddenly, I came to an abrupt halt as something occurred to me that Ihadn’tthoughtofinyears.IturnedtoDorothyandexplainedthatonedaywhenIwasaboutfifteenyearsoldIhadtakenthisexactroutehomefromschoolandmadea“solemnpromisetomyself.”

“Whatwasthepromise?”sheasked.“Istoppedrightabouthere,andsworetomyself thatwhenIgrewupand

finishedbuildingmyworkingtimemachine,Iwouldtransportmyselfbackheretothatday—andtellmyyoungerselfthatIhadsucceeded.”

Dorothysmiled.“Itakeitthathasn’thappened.”“No,”Isaid,returninghersmile.“Notyet.”Itwasafancifulidea,granted.Yetthedream,stillhiddenfromallbutthoseclosesttome,livedon.

Nine

MyExpandingUniverse

With the calendar showing the approach of fall, I could hardly wait forclasses to resume. I was particularly enthused to be scheduled for a generalrelativity graduate course, whichwould cover tensor analysis, differential andRiemanniangeometry,and,importantly,Einstein’sgravitationalfieldequations,whichshowhowamassivebodylikethesuncausesemptyspacetocurve.Thiscurvature of space results inwhatwe call gravity. In truth, the planets of oursolar systemarenot influenced somuchbygravityas theyarepulled throughthis curved space created by the sun. It is basic, universe-building stuff that Iknewcouldbetaughtentertaininglywithexperimentsaswellaswithequations.

Theclassendedupwithonly twelvestudents,which Iwould learnwasadecent number for a high-level graduate physics course. It was an older andrather sedate group, unlike the eager-beaver undergraduates I had taught theprevious year. Nonetheless, I was excited to be leading these dedicated andfocused students through this challenging course about someof themost vitalelementsofmodernphysics,withasizabledoseofEinsteinstirredintothemix.It still felt unreal that I was actually a physics faculty member at a majoruniversity,withtheopportunitytoteach,ofallthings,generalrelativity.

During the term, I managed to slip in a lesson from Gödel’s study ofcosmology,whichIfirstreadaboutintheairforce.AlthoughtherewasmuchIhadn’t understood the first time around, I had become instantly fascinated byGödel’sworkbecauseitallowedforthepossibilityoftimetravelintothepast.

Cosmologists frequently study theoretical model universes that may besimilarordifferentfromouractualuniverse.Theystudythesemodeluniversesjust to seewhatmight be possiblewithin the laws of physics. In his rotating-universe work, Gödel allowed for closed loops in time, or closed timelines.Normaltimeisrepresentedasastraightline,thebottomofthelinerepresentingthe past, themiddle of the line the present, and the top of the line the future.Suchatimelineshowstheworldaswenormallyexperienceit;thatis,wemovefromyesterday,totoday,totomorrow.Aclosedtimelinemeansthattheendsofthelineareconnected.Thatmeant,Gödelconcluded,thattravelintothefutureorthepastisequallypossiblealongaclosedloopline.

Preparing for the general relativity course allowedme the opportunity todelve deeper into circular timelines. This came about in connection with thetheory of black holes. Previously, I had only studied black holes that did notrotate. Real stars rotate just like the earth. Black holes are formed from thegravitationalcollapseofstars.Iftherotationoftheresultingblackholeisslowenough, one can neglect the gravitational effect of the rotation. For a rapidlyrotatingblackholethesituationbecomesverycomplicated.Infact,ittooknearlyfiftyyears before a solutionofEinstein’s field equations couldbe found for arotating black hole, a solution found in 1963 byNew ZealandmathematicianRoyP.Kerr.

WantingtoknowmoreabouttheKerrsolution,asthegravitationalfieldfora rotating black hole came to be known, I found a published paper, “GlobalStructure of the Kerr Family of Gravitational Fields,” by physicist BrandonCarter (born1942).TheabstractofCarter’spaper caughtmyattentionwhen Ireadhisstatementthatarotatingblackholehas“closedtimelikelineswhicharenot removable.” Closed timelike lines are just another name for circulartimelines, and are the same timelines that appear in Gödel’s theory of therotatinguniverse.Thismeantthattherewassomeconnectionbetweentheworkof Carter and Gödel. As I studied Carter’s full paper and worked hiscalculations,Ibecameincreasinglyintrigued.Hefoundthattheclosedtimelineof a rotating black hole would allow travel into the past. In other words, arotatingblackholecouldbeused—theoretically,atleast—asakindoftransporttunnel into the past. I decided then and there that I would learn more aboutrotating black holes. Such research, and even publishing my findings, wouldallowmetostudyhowtimeisaffectedbygravitywhileprovidingcoverformyprimaryinterestinfiguringouthowtobuildatimemachine.

AsIwasgivingseriousconsiderationtotheadvicethathadbeenprofferedmyfirstdayoncampusregardingfindingagraduatestudentwithwhomIcouldworkonpublishingapaper,FredSu,aChinese-Americangraduatestudentwhowantedtoconductoriginalresearchingeneralrelativity,cameknockingonmydoorinsearchofathesisadvisor.Wekickedaroundsomepossibletopicsbeforeitdawnedonme.

“Rotating black holes are very interesting, Fred,” I said. “These are alsoknownasKerrblackholes.Theyhavesomereallystrangepropertiesandoneofthestrangest is the fact that theyaffect time.Rotatingblackholescanactuallylead to closed loops in time. That means you can go back into the past in arotatingblackhole.”

Actually,timewasn’ttheonlythingaboutblackholesthatinterestedme.Theyalso affect space, andoneof those effects is called framedragging,

whichcanbedefinedasthestirringupofspace.Ithadbeenknownfora longtimebygeneralrelativiststhatarotatingmass(suchasarotatingblackholeorplanet) drags space around in its invisiblewake. Frame dragging looks ratherlike twirling an apple (mass) round and round into a bowl of caramel sauce(space).

Whenexplainingthenatureofblackholestomystudents,Ialwaysstartbytelling themhowstarsare formed,aprocess thatcommenceswhen theheavy-hydrogen(alsocalleddeuterium)gasatoms in interstellarspacestartattractingone another gravitationally, not unlike a Friday night crowd at a singles’ bar.The nucleus, or core, of a heavy-hydrogen atom consists of a proton plus aneutron. As these heavy-hydrogen atoms collect together, they gravitationallyattractmoreatoms.When twoheavyhydrogenatomscollide, theycombine toform a helium atom, whose nucleus is composed of two protons plus twoneutrons. If themassof the twooriginalheavy-hydrogenatomswasmeasuredand compared with the mass of the resulting helium there would be adiscrepancy,with the helium atombeing something less than the two originalheavy-hydrogenatoms.ThislossofmassgetsturnedintoenergyviaE=MC2.Itisthroughthiscombustibleprocessofheavy-hydrogengascombiningtoformheliumthatanewstarisborn.

Everystar,includingoursun,existsthankstoabalancingactbetweentwoopposing forces.Thegravitationalattractionof thegasesof thestarconstantlytrytopullthestarinward,whiletheheatradiationfromtheenergygivenoffbythecollidingheavy-hydrogenatomscontinuallypushesoutward.Thispush-pullprocess goes on until the internal fuel provided by the heavy-hydrogen gas isuseduptoformhelium.Asthispoint,thereisnomorefueltofeedtheinternalheat and pressure necessary to keep the star pushing outward, and the gravitypullingthestarinwardisnolongerkeptincheck.Asaresult,thestarbeginstocollapse.Asitdoes,anumberofinterestingthingshappen.

First,thestar’selectrons(lightlychargedsubatomicparticlesthatmakeupless than one percent of an atom’s total mass) get pushed together, also bygravitational attraction. There is a law in quantummechanics called the Pauliexclusionprinciple,developedbySwissphysicistWolfgangPauli(1900–1958),which states that two electrons cannot occupy the exact same space. Thisprinciple keeps the electrons from being pushed together. The gases willeventuallysettledown,turningthemassintoawhitedwarf,astaraboutthesize

ofearththathasexhausteditsnuclearfuelandcannotproduceheattocounteracttheforceofitsowngravity.Thiswillbethefateofourfive-billion-year-oldsun,consideredamiddle-agedstar,whenitburnsoutinanotherfivebillionyears.

However, there are exceptions. If the star is significantly larger than oursun,theelectronswillgetpushedintotheprotonsbythegravitationalattractiontoformneutronsandbecomeaneutronstarwhichisadensestar(technicallyastellarcorpse)composedmainlyofneutrons.Forstarsofmassgreaterthantwoandahalf times themassofoursun there isnothing thatcankeep themfromcontinuingtocollapseinwardly.Astheydo,thegravitationalfieldcontinuestoescalate.Eventually,thefieldofgravityaroundsuchastarwillbesostrongthatanythingthattriestoleavethesurfaceofthestar,includinglight,willgetpulledback.Withnolightabletoleavethesurface,thestarbecomesanobjectthatwasfirst coined a “black hole” in the 1960s by American physicist John A.Wheeler.19

Fredwasintriguedwiththeideaofstudyingblackholes,butIknewIhadtobecautiouswhenitcametodirectinghisresearchwork.Icertainlycouldn’tassign him the task of researching time travel into the past via rotating blackholes, orwewould both pay a price.A student thesis needs to be solvable aswellasspecificandoriginal,soIsuggestedfindingathesistopicinanarenathatIhadbeenstudyinginelectromagnetismcalledtheFaradayeffect(namedaftertheEnglishphysicistandchemistMichaelFaraday),whichhastodowithwhathappens when light is sent through a transparent material (like glass) in amagneticfield.Aslightmovesforwarditoscillatesupanddownlikeawaveonastring.Theup-and-downdirectionof theoscillation iscalled thepolarizationof light. (Incidentally, polarized sunglassesmake use of this property of light.Whenlightfromthesunisreflectedoffametalsurface—likethehoodofacar—itbecomespolarized.Apolarizedlensblocksonlythepolarizedlight.)

Whenalightwaveissentthroughaglassblock,andwhenamagneticfieldis applied to the block in the direction the lightwave ismoving, the plane ofpolarization is twisted, or rotated. I had read papers suggesting that thegravitational field of a rotating body would cause a twisting of the plane ofpolarizationoflightasitpassedinthedirectionoftheaxisoftherotatingbody.Sincearotatingblackholecausesatwistingofspace,thisimpliesthatitwouldalsocausea rotationof theplaneofpolarizationof lightgoingby it, althoughthisparticulareffecthadneverbeforebeenproven.IsuggestedtoFredthathisthesistopiccouldbetolookatwhathappenstopolarizedlightwhenitgoespastarotatingblackhole.

Fredwaseagertobeginhisresearch,althoughnotbeforeinformingmethatifhesucceededinbreakingnewground,hewantedustosubmithispapertooneofthepremierrefereedjournalsforpublication.Ismiledinwardly.WherehadIheard that before? I asked if he had one in mind. He said the AstrophysicalJournal, which I knewwas one of themost difficult journals in which to getpublished.“Okay,Fred,”Isaid.“Let’sgoforit.”

The thirdofficialcomponentofmyjob—universityservice—soonrearedits head. I understood there was a role for me to play as it related to thecommunityatlarge,andwasparticularlykeenaboutgivingpubliclecturesandbeinginvolvedinminorityaffairs.AstheonlyAfrican-AmericanmemberoftheUConnphysicsdepartment,Irelishedrecruitingandadvisingminoritystudentsinterestedinstudyingthesciences,astherewasadearthofrepresentationinthebooming fields of science and engineering. But as far as any interest orinvolvementinuniversityadministrativeactivitiesorcampuspolitics,well,thatwas another matter. After a frank talk about faculty administrativeresponsibilitieswithanassistantvice-presidentofacademicaffairs,JoanGeeter,whoendedupbecomingafriend,weagreedearlyonthatshewouldtakecareoftheuniversity,andIwouldtakecareoftheuniverse.

Ten

DeeperintoBlackHoles

Theyear1979wouldusherinworldwideeventstocelebratethecentennialanniversaryofthebirthofAlbertEinstein,whowasbornonMarch14,1879,inUlm,locatedontheleftbankoftheDanubeinsouthernGermany.

Onemajorevent recognizingEinstein’spivotalworkwas to takeplace inthesummerat theInternationalCenterforTheoreticalPhysicsinTrieste,Italy.Hoping to somehow be part of the activities, I sent an application to theorganizingcommitteemorethanayearinadvance,proposingtogiveatalkonthe inverse Einstein-Infeld-Hoffman problem, about which I had, by then,publishedanumberofscientificpapers.Imadefurtherinquiries,andfoundthatintheeventIwasinvitedtogiveapaperattheconferencetheuniversitywouldprovidepartialfundsformyairlineticketandsomehotelexpenses.However,Iwouldhavetomakeupthedifferenceoutofmyownpocket.

Financial salvation came in the form of a consulting job with Pratt &Whitney Aircraft. Someone there remembered my work for UnitedTechnologies, specifically,my theoretical analysis of laser hole drilling.Now,theywantedme to conduct the same typeof researchusing electronbeams todrill holes. In addition, I was asked to teach one of the staff engineers themathematical techniques I had developed for laser hole drilling. Thismoonlightinginthesummerof1978whenschoolwasnotinsessionworkedoutwell,andIwasabletosaveenoughmoneytopayfortherestofthetrip.

MyapplicationtotheEinsteinconference,whichwastobeheldataresortneartheAdriaticSea,wasacceptedinearly1979.DorothyandI—neitherofushad been to Europe before—planned to make a vacation of it, too. A weekbeforeweweretodepart,somefriendsheldagoing-awaydinnerpartyforus.

We left the party shortly after midnight, with Dorothy driving. As weentered a turn on a rural road, the high-beam headlights of an oncoming carblindedus.Dorothysteeredovertotheshoulderasfaraspossible,comingtoastopatagrassyembankment.Asecondlater,theothercarcollidedwithus.Ihadonly minor cuts and bruises, as Dorothy’s side of the car took most of theimpact. (The other driver turned out to be drunk, and barely had a scratch.)WhenIlookedoveratDorothy,Icouldseethatthedriver’sdooranddashboard

hadherpinned.Shewaslyinglikearagdollinafrightfulposition.Firemenhadto use metal-cutting tools to get her out, and an ambulance took us to thehospital. Dorothy had a badly fractured hip and a broken leg. The orthopedicsurgeon on call was summoned, and Dorothy was wheeled into emergencysurgery.Inabizarrecoincidence,thesurgeon,DougGriswold,hadbeenourhostthat evening—along with his wife, Pat Terry, from the UConn Englishdepartment.Doug repairedDorothy’shipwithpinsandaplate, and insertedastainless-steelrodtosupportherbrokenleg.Afullrecoverywasexpected,butshewouldbeinthehospitalforthreeweeks.

Onethingwascertain:Dorothywouldnotbetravelinganytimesoon.Ourtrip to Italy would have to be cancelled. The second day I visited her in thehospital,shemadeacaseformetogotoTriestewithouther.Sheexplainedthatshewasgettinggoodcare,therewasnotmuchIcoulddoforheratpresent,andIwouldbebackbeforeshewasreleasedfromthehospital.

AfterarrangingforfriendstovisitDorothyduringmyabsence,Ireworkedmy itinerary, trimming the extra vacation days, finished packing, and flew toTriestetokeepmydatewithEinsteinathishundredthbirthdaybash.

*

Trieste is an extraordinarily beautiful city set in the isolated northeasterncornerofItalythathasattimesbeenoccupiedbyAustriaandYugoslavia.

About300physicistsfromthroughouttheworldandavarietyofdisciplineswereinattendanceattheconference.Iwasscheduledtodelivermypresentationmidwaythroughtheschedule,andIspentmosteveningsafterdinnersittingonthedeckofmyhotel roomoverlooking theazurewatersof theAdriaticgoingover my paper for the umpteenth time. About twenty people attended theeveningworkshopwhereIspoke,andafterwardtherewasalivelyquestionandanswerperiod.

The next day, relieved of my conference responsibilities, I took a late-afternoon stroll through picturesque Trieste, which was rapidly becoming themostimportantcenterforscientificresearchinItaly.Workingupanappetite,Istopped for Wiener schnitzel, and happened upon the best I had ever tasted(before or since).Raving about it the next day tomy colleagues, one of themsaidtheexcellentWienerschnitzelherewastheresultoftheAustrianinfluence.Whenitcomestoscienceandgoodfood,itseemswephysicistsknowourstuff.

I made a valued friendship in Trieste. University of Massachusetts

astrophysicistJosephTaylorisatall,thinmanwhoinpostureandphysiqueputsme in mind of the actor Jimmy Stewart. A friendly man with a quick smile,Taylor and I spent a lot of time talking about science and life, and enjoyingmeals together. In a serendipitous blend of friendship and work, Taylor’sbreakthroughresearch,forwhichhewouldeventuallywinaNobelPrize,woulddeepenmyownunderstandingoftheflexibilityofspacetime.

In 1974, Taylor, while a professor at Amherst, and his graduate student,Russell Hulse, had utilized the world’s largest single-dish radio telescope atArecibo, Puerto Rico, to discover a pulsar (a rapidly spinning neutron star)emittingradiopulsesatintervalsthatvariedinaregularpattern,decreasingandincreasingoveraneight-hourperiod.Theyconcludedfromthesesignalsthatthepulsarhadtobealternatelymovingtowardandawayfromearth.Theydeducedthatithadtobeorbitingaroundacompanionstar,whichtheybelievedwasalsoaneutronstar.

OneofthekeypredictionsofEinstein’sgeneraltheoryofrelativityisthattwo stars (binary stars) in orbit around each other will set off ripples inspacetime. Since gravity, according to Einstein, is the curvature of spacetime,then these ripplesof spacetimewouldbewavesofgravity.Gravitywaveshadnotbeendirectlydetectedbefore.

Taylor andHulse observed for several years the decay of binary pulsars,and went where others before them had not. Their breakthrough finding,reported in1978—theyear before Imet Joe in Italy—gave theworld the firstexperimentalevidencefor theexistenceofgravitationalwaves—strongsupportforEinstein’stheoryofgravity.20

AsmuchasIlikedJoefromthemomentwemet,andfoundhimtobeopenand unpretentious, I did not mention anything about wanting to build a timemachine. Not only was I still concerned about the crackpot issue and myadvancement in academia, I also had come to realize that I faced anotherproblem:itwasdifficultenoughtobeacceptedseriouslyasablackphysicist(Iwas the only one in attendance atTrieste)without being associatedwithwhatwasstillafringeareaofresearch.

BeforewedepartedTrieste, I invited Joe to give a physics colloquiumatUConnonhisgroundbreakingworkinastrophysics,whichhesubsequentlydid.

Backhome,withDorothyonthemend,Iwaseagertoreturntoschoolthatfall. During that school year (1979–80), an issue took the forefront that wasmore inevitable than surprising. I had long been bothered by the scarcity ofminority students considering scientific and engineering careers. Indeed,

attendingtheTriesteconferenceandfindingmyselftheonlyblackphysicisthadbeen a vivid reminder of the sorry state of affairs when it came to recruitingminoritiesforthesciences.Atmyownuniversity,infact,therewerenominorityphysicsmajorsandonlyahandfulofengineeringmajors.

OneofUConn’sminorityengineeringstudents,BarryWalker,wasstartingacampuschapteroftheNationalSocietyofBlackEngineers.Heapproachedmethat fall about serving as a volunteer faculty advisor for the group. I wasdelighted to do so, and served for three years (1979–1982). The group beganattracting larger numbers of minority students who had aptitude in math andsciencebuthadnotseriouslyconsideredacareerinengineering.

OneactivityIarrangedforthechapterwasavisittothesubmarinebaseatGroton,Connecticut,whichmadeforanexcitingday.Intheprocess,Ibecamefriendlywith the localnavyrecruiterswhoarranged the trip.Wediscussed thedifficulties thatminority studentshad in thenavy.As it turnedout, theofficercorpsoftheUnitedStatesNavyatthattimewasextremelyunderrepresentedbyminorityofficers,which Iwas told led to escalating tensionswithin the ranks.The navy sought to turn the situation around by developing a new programcalledCampusLiaisonOfficer.Theideawastoapproachcollegeanduniversityfaculty members who had had previous military experience. The navy wouldoffertheseindividualsacommissionintheU.S.NavyReservewiththerankoflieutenantcommanderinexchangeforhelpingthenavyincreaseitsofficercorpswithscientificallyandtechnically trainedminoritypersonnel.Forme,aftermyserviceasanenlistedmanintheairforce,theofferwasirresistible.Theprospectof receiving a reserve commission and at the same time helping minoritystudents seemed too good to be true. In a campus ceremony, a rear admiralcommissionedmewiththepresidentoftheuniversityaswellasanumberofmystudentsinattendance.

I spent six years (1979–1985) as a Campus Liaison Officer. One of myresponsibilitieswas to serve as a rolemodel forminoritymilitary recruits, aswell as students. In this capacity, Iwasaskedbyanair force recruiter tovisitLacklandAirForceBaseinSanAntonio,Texas.Lackland,ofcourse,iswhereIhadspenta“season inhell”yearsagogoing throughbasic trainingasa lowlyenlisted man. At the request of the air force recruiter, I visited the base inuniform.Wewentona tourof a trainingareawhere a training instructor (TI)was yelling at a group of hapless recruits. The TI had his back to us. Therecruiterquietlyaskedmeaquestion.AsIwasresponding,theTIsuddenlysaidinaboomingvoice,“Whoisthattalkingbehindmyback!”Hespunaround,saw

allmygoldbraid,cametoattention,andsaluted.“Excuseme,sir!”Ireturnedhissalute.“Carryon,sergeant.”AstheTIturnedhisattentiontotherecruits,IthoughtbacktothedayIhad

gottenoffthebusatLacklandandbeenyelledatmyself.IknewthattherespectIhadsodemonstrativelyreceivedfromtheTIforbeinganofficerwouldnotbelostontheminorityrecruitswhowerebeingyelledatnow.

Meanwhile, I was quite pleased with the thesis work of my graduatestudent,FredSu,whohadsucceededinshowingthatpolarizedlight(theupanddown oscillations) from a star that passes a rotating black hole would getdraggedor twisted around the rotatingblackhole. In comingupwithhis newresult,Fredsignificantlyadvancedtheunderstandingofhowrotatingblackholescan affect space. As Fred had requested when he first started his work, wesubmitted his findings for publication in theAstrophysical Journal. The paperwas accepted for publication in late 1979. In June 1980, the article appearedunderthetitle“TheEffectoftheKerrMetriconthePlaneofPolarizationofanElectromagneticWave.”Fredwasecstatic,asIwellrememberedbeingwiththepublicationofmyfirstpaperatPennState.

As for me, I had learnedmore about rotating black holes in supervisingFred’s thesis. The thesis had not dealtwith the time-travel aspects of rotatingblack holes, but it did help me better understand the phenomenon of framedragging inconnectionwith rotatingmatter.Asa result, Iwasable toask thisquestion: Is there a connection between frame dragging and closed time-likelinesoftheKerrrotatingblackhole?

If frame dragging in space did take place—as yet unproven—then theconditions for closed time loops might also exist. This meant that framedraggingmightultimatelybeconnectedwithtimetraveltothepast.Thatsuchaconnectionmightexistwas justahunchat thatpoint,and itcamewithoutoneshredofscientificevidence.Yet,Idecidedthatthisavenueofinquirywasworthfurtherinvestigation.

AsIwasthinkingmoreabouthowclosedtimeloopsmightfacilitatetravelto the past, Somewhere in Time, a beautiful and poignant movie about timetravel, was released. Based on the science-fiction novel Bid Time Return, byRichard Matheson (a frequent contributor to The Twilight Zone), the movieopens with a young playwright named Richard Collier (played by the lateChristopher Reeve) at a party celebrating the successful opening of his play.Collier is approached by an elderly woman who gives him a pocket watch.“Please come back tome,” she says before disappearing into the crowd. The

womanisacompletestrangertohim,andCollierisperplexed.Someyears later,Colliervisitsanoldgrandhotelandseesaportraitofa

beautifulyoungwoman.HelearnsfromthehotelstaffthatthepaintingisofanactressnamedEliseMcKenna (playedbyJaneSeymour),whowasconsideredone of the finest actresses in the early 1900s.Collier becomes infatuatedwithMcKenna’sportrait,andvisitsherhome.Heisastonishedtodiscoverthatsheisthe elderly woman who had given him the pocket watch. Unfortunately,McKennahassincepassedaway.AtMcKenna’shouse,ColliercomesacrossabookentitledTravelsThroughTime,writtenbyaphilosophyprofessorwhohasstudiedtimetravel.Collierfindstheprofessor,andlearnsthattimetravelmightbe possible using self-hypnosis in a suitably isolated environment linked to aprevioustime.

Collierreturnstotheoldhotelandisabletoprojecthimselfbackto1912whenMcKennawasactinginaplayatthehotel.Thetransitionisdramatic,withthesightandsoundofhorse-drawncarriagesandotherperiodtrappings.ColliermeetsMcKennaand theyfall in love.Heshowsher thepocketwatch thatshegavehim.Accidentally,acoinfallsoutofhispocketwhichhasafuturedateonit.Suddenly,Collierisunabletoremaininthepastandisreturnedtohisfuturetime.AllthatremainswithMcKennainthepastisthepocketwatch.ItisclearthatMcKennawill eventually seeCollier again in the future andgivehim thewatchback,whichwillenablehimtocomebacktoher,therebycompletingtheclosed time loop.The storylinehadmore todowithpsychology thanphysics,andyetthequestionsitposedandthepossibilitiesitsuggestedwereintriguing.

Themovieremindedmehowimportantsciencefictionhadbeeninmylife,allowingmeatayoungage,whenmyworldwasinsuchashambles,todreambig. I soon found a fellow sci-fi fan inUConnassociate deanKarlHakmiller,whowouldeventuallybecomedeanofthegraduateschool.Wegottoknoweachother while driving together to an educational conference at Harvard. As weheaded for Boston, we discovered our shared passion and started excitedlydiscussing favorite books, stories, and movies. We ended up skipping theevening session atHarvard and going toKarl’s favoriteGerman restaurant inCambridgetocontinueourlivelydiscussion,whichsoonseguedintotimetravel.

Oneshortstory,“VintageSeason,”byC.L.Moore,wasamutualfavorite.Thestoryopensataseasideinn,wheretheinnkeeperoverhearsagroupofnewandrather strangeguests talkingabouthow thiswasoneof themostbeautifultimes of this century. They seem to be talking about the present as if it hasalready happened. The innkeeper learns that these people are from the future,

andtheyknowthatthereisgoingtobeadisasterinthearea:amassivemeteorshowerisabouttohit.Thesetimetravelershavecomefromthefuturetoobservethisdisaster,somethingtheyroutinelydo.Theyobservebutdonotinterfere;inarealsense,theyaretimetourists.

Karlwassoanimatedinthesediscussions—particularlyabouttimetravel—thatovercoffeeImadeadecision.Itoldhimaboutmyfather’sdeath.BelievingIcouldtrusthim,Ithentookthefinalstepandtoldhimaboutmylifelongdreamtobuilda timemachine to travelback tomyfather’s time.“It’swhyIstudiedmathandscience,andwhyIendedupbecomingaphysicist.”

Karl was familiar with the general ideas of Einstein’s special theory ofrelativity,andwediscussedhowthesemightallowfortimetravel.Inparticular,heknewthatEinsteinhadpredicted that timeslowsdownforamovingclock.Andheknewthat this led to theso-called twinparadoxinwhich the twin thatwasmoving close to the speed of lightwould agemuch less than his stay-at-home twin. In effect, themoving twinwould have traveled into his brother’sdistantfuture.KarlunderstoodwhyatthispointinmyacademiccareerIwishedtokeepmyultimategoalunderwraps.HeseemedsomovedbymystorythatIknewmyinstinctsabouthimwereright,andovertheyearstheywouldprovetobesoagainandagain.

Karl and I endedupbecomingclose friendsaswell ascofacultyadvisorsfor theuniversity’ssciencefictionclub.Oneeveningamonth,wewouldmeetwithaboutadozenstudents ina roomat thestudentunionbuilding todiscusssci-fi storiesandbooks,andwatchmoviesononeof theearliestversionsofavideotaperecorder,whichIluggedbackandforthfromhometoschool.Insucha settingwewatchedABoy andHisDog, a post-apocalyptic story;TheManWhoFell toEarth, starringDavidBowie as an alienwhocomes to earth; andTheFinalCountdown, inwhich amodern aircraft carrier goes through a timewarpandendsupin1941justbeforetheattackonPearlHarbor,withthemoraldilemma being whether they interject their modern-day firepower to stop theJapanese attackers and thereby change history. One novel we discussed wasBringtheJubileebyWardMoore(1953),inwhichtheSouthhaswontheCivilWar.Thankfully,ahistorianisabletotravelbackintothepastandchangewhathappened at the Battle of Gettysburg to cause the future with which we arefamiliar: theNorthbeingvictorious. I say“thankfully”because the ideaof theSouth winning—andwhat, preserving slavery?—held some awfully unsettlingimplicationsforme.

Ofcourse,themostsuccessfultimetravelmovieevermade,andonewhich

spawnednumeroussequels,wasBacktotheFuture,releasedin1985.Thefactthat teenagerMartyMcFly (Michael J. Fox) is transported by his brilliant butslightlymad inventor friend,DocEmmettBrown(ChristopherLloyd),back to1955heldspecialmeaningforme.Thatwas,ofcourse,theyearmyfatherdied.McFlynearlyeraseshisownexistencebyinterferingwiththebuddingromanceof two teenagers who are destined to become his parents. The moviedramatically illustrates a potentially serious problem with any time traveling,thatofinterferingwiththepast.

Icontinuedtopublishmyownresearchpapers,whileenjoyingmyteachingassignments. My peers seemed satisfied with my research, teaching, andcommunity-based activities, and Iwas awarded tenure inMarch 1980.At thesametime,Iwaspromotedtoassociateprofessorofphysics,withonlyonemorerungremainingtoreachfullprofessor.Inordertoachievethelatter,myongoingresearchwould be reviewed and evaluated not only bymy own departmentalcolleaguesbutalsobyphysicsprofessorsatotheruniversities. Iwouldneed tokeepontrackinordertotakethatfinalprofessionalstep;manyfacultymembersneverreachtheleveloffullprofessortheirentirecareers.

While progressing inmy academic career, I hadmanaged to increasemyknowledge about relativity and thenatureof time, but Iwasnot any closer tounderstanding how to build a time machine. Then, out of the blue, anopportunitypresented itself thatmight nudgeme closer tomyultimategoal. IsawapostingonthephysicsdepartmentbulletinboardsolicitingcandidatesforaFordFoundationSeniorPostdoctoralFellowship.Thisenabledthoseselectedtostudyfulltimeforanentireyearwithanyoneintheirfield.

I would be eligible formy first sabbatical leave at the university for theschoolyear1982–83.Asabbaticalisanoldtraditioninwhichafacultymemberisgrantedleaveeveryseventhyearfortravelandresearch.Thisallowsafacultymembertovisitotherinstitutionsandcollaboratewithresearchersintheirfieldwithout the normal responsibilities of teaching and university service. AtUConn,asabbaticalleaveisgrantedforayearathalfsalary,whichcouldcausesome financial hardship. However, the Ford Fellowship would make up thedifference.

I thought aboutwho in theworld of physics Iwouldmostwant toworkwith.Itdidnottakelongformetoidentifymyfirstchoice:JohnA.Wheeler,alegend in his own time. I had admiredWheeler’s work from afar ever sincereadinghisnontechnicalarticle“TheDynamicsofSpacetime”while in theairforce.Sincethen,Ihadreadmanymoreofhisscientificpapers.

WheelerreceivedhisPh.D.fromJohnsHopkinsUniversityin1933.AsaNational Research Council fellow, he was mentored by the great quantumpioneerNielsBohr(1885–1962).Later,workingwithBohr,Wheelerhelpedtodevelop a theory of nuclear fission (1939). He went on to become a facultymember at Princeton University and a colleague of Einstein’s. (Need I saymore?)HealsoworkedwithJ.RobertOppenheimer.Inthe1940s,Wheelerandhis student, Richard Feynman, developed a formulation of electromagnetism.Thisworkultimately ledFeynman tohisNobelPrize-winningcontributions inquantum electrodynamics. By the 1950s, Wheeler had become increasinglyinterested in using Einstein’s general theory of relativity to study stellarevolution.ThisworkledtoWheeler’scoiningtheterm“blackhole”todescribetheultimatefateofadyingstar.Hehadconductedfundamentalresearchinbothquantum theory and general relativity, laying the groundwork for severalsubareasoftheoreticalphysics.Agenerouscollaboratorandmentorthroughtheyears,hehadhelped launch thecareersofmanyprominentmodern theoreticalphysicists,includingKipThorne,21inadditiontoFeynmanandothers.

At the time of my sabbatical leaveWheeler held a joint appointment asprofessor emeritus at Princeton University and director of the Center forTheoretical Physics at the University of Texas in Austin. I wroteWheeler inAustin, telling him aboutmybackground and asking if hewould agree tomyspendingayearasaFordFoundationfellowworkingwithhimatthecenter.

Aftercallingmydepartmenthead,JosephBudnick,tofindout“whatsortofperson”Iwas(Budnick,characteristicallyblunt,saidhetoldWheelerIhadmy“headscrewedonright”),WheelerofficiallyinvitedmetospendmysabbaticalasavisitingscholarattheCenterforTheoreticalPhysics.

I sent in my application for a Ford Foundation Senior PostdoctoralFellowship, explaining I had been invited toworkwith JohnWheeler and hisCenter forTheoreticalPhysics. Iwasawarded the fellowship for theacademicyear1982–1983,nodoubtlargelybecauseofWheeler’sesteemedreputation.

AtthestartofourjourneytoTexasinthesummerof1982,Wheelerandhiswife, Janette, graciously invited Dorothy and me to visit them at their HighIslandretreatnearBarHarbor,Maine.WespentalotoftimetryingtofindtheWheeler home, as it was located in an isolated, rural area. When we finallypulledupnexttothehouse,ajolly-lookingmanboundeduptothecartogreetus. Itwas the legendaryphysicisthimself.Although Iwasnervousat this firstmeeting,Wheeler’sengagingsmileandfriendlymannerquicklyputmeatease.Comparingnoteslater,DorothyandIagreedthatheremindedusoftheBritish

actorEdmundGwenn,whoplayedKrisKringleinMiracleon34thStreet.Whenwe arrived, Janettewas not home and our host invitedDorothy to

joinusinthedenforourfirstdiscussion.Wheeler’sopeningcomments,itturnedout,werenotaboutphysics,butaboutGod’sperspectiveontheuniverse.SoonJanette arrived and shewas every bit as friendly as her husband. She invitedDorothy to gowith her for awalk.Dorothy admitted tome later that she hadbeen disappointed to leave the discussion because she found Wheeler’scomments“sointerestingandnontechnical.”Indeed,IwouldcometolearnthatWheeler, at home with friends or at the university with scientific colleagues,lovedaskingbigquestionsabouttheuniverseandwhyitisconstructedasitis,questions such as “Why the quantum?” TypicalWheeler follow-up questionswouldbe:“Whydoesquantum theoryunderlie reality?”and“Could realitybebased on some other fundamental principle?” Other well-known quotes ofWheeler’s:“Withoutanobserver,therearenolawsofphysics,”and“Howdoessomething arise from nothing?” Such statements and questions are asmuch apartofphilosophyastheyareofphysics,whichgivesanaccuratemeasureofthemanwhoasksthemwithsuchexuberance.

AfterapleasantweekendDorothyandIembarkedonacross-countrytriptotheRockies,thendownintoTexas.

Austin,homeof theUniversityofTexas, is locatednear thecenterof theLone Star State in an area known as theHill Country.With its gentle rollinggreenhills, this region ismuchdifferent from themore typical flat desert andsagebrush terrain that Texas is known for. The compact campus of theUniversityofTexashad,atthattime,astudentpopulationofabout45,000.

IarrivedattheCenterforTheoreticalPhysicsjustbeforethestartofthefallsemester.WheelerwasstillinMaine,buthisadministrativeassistanthelpedmegetsettledbyprovidingmewithofficespacewithanotherpostdoctoralvisitor.My officematewasworkingwith StevenWeinberg,who hadwon hisNobelPrizethreeyearsearlierandonlyrecentlyacceptedanappointmentasafacultymemberinthephysicsdepartmentattheUniversityofTexas.

Thesonofacourtstenographer,Weinberg,borninNewYorkCityin1933,hadwon the 1979Nobel Prize in Physics (sharedwith SheldonGlashow andAbdus Salam) for contributions to the theory of the unified weak andelectromagnetic interaction between elementary particles.While I had been atUnitedTechnologies,myboss, JerryPeterson,hadsentWeinbergsomeofmyindependentresearchonunifyinggravityandtheweaknuclearinteraction.Ihadbeen thrilled with Weinberg’s reply, however guarded it might seem in

retrospect, that although there were “some problems,” my ideas were“interesting.”

Whatever fantasy I harbored now about developing any kind of friendlyrelationshipwithWeinbergwouldsoonbeputtorest.ThefirsttimeIcrossedhispathinAustin,Weinberg,atall,heavysetmanwithreddishblondhair,whiskedpast me in my shared office to remind his visiting professor about a partyWeinbergandhiswifewerehavingattheirhome.Weinbergbarelylookedatmeasheleft.Iwasalittlehurtbutpasseditoff.

Actually, itwasnot thefirst timeWeinbergsnubbedme.IhadattendedaparticlephysicsconferenceattheUniversityofPennsylvaniaaboutayearafterIstartedatUConn.WhenIsawWeinberg in thehallway, Iwentup tohimandthankedhimforthekindcommentshehadmadeaboutmyworkinhislettertoJerryPeterson.Helookedatme,saidnothing,turnedhisbackandwalkedaway.Iwasconfusedandhurtanddidn’tknowwhattothink.

OurnextencounterinAustinwasatthefacultyclub.Weinbergenteredandraised his handmyway in greeting. I happily returned the wave. Hemade apointtogesturethathewaswavinghellotothepersonnexttome.PerhapsIwasbeingtoosensitive,buttheserepeatedencountersbotheredme.HadIcomethisfar only to be treated with disrespect by a physicist whose work I greatlyadmired? I mentioned the disturbing incidents to Wheeler’s administrativeassistant,butaskedthatshenotbotherWheeleraboutthem.

Oneday,afterWheelerwasbackoncampus,heandIenteredanelevatortogether. (As casually dressed as Wheeler was in Maine, he always wore abusinesssuitattheuniversity,andlookedmorelikeasuccessfulbankpresidentthanaphysicist.)Theelevatorhadanotheroccupant:Weinberg.

“Steve,” Wheeler said, “I’d like to introduce you to my colleague, RonMallett.”

Weinbergturnedtome,andtentativelyshookmyhandasthoughthiswasthefirsttimehehadeverlaideyesonme.

Later,Wheeler’s administrative assistant admitted that she had spoken toWheeler about Weinberg’s unfriendly attitude toward me. In this and otherways,Wheeler consistently treatedmewithkindness and respect, proving thatthe biggest minds in science can have equally large hearts. Unfortunately, Icannot say that the brilliant Steven Weinberg is one of them. Somehow,WeinbergandIwereabletoavoideachotherfortheremainderofmystay.

DorothyandImovedintoacomfortablehomeintheWestlakeHillsareaofAustin, renting froma facultymemberwhowasonsabbatical in Italy.Since I

wouldbebusyoncampus,Dorothygota jobworking fora temporaryagencyand ended up doing clerical and word processing duties for the state humanresourcesdepartment.ThecommunityofAustin isvery cosmopolitan, andwefelt accepted as an interracial couplewhereverwewent.However, the rest ofTexaswasanothermatter.AssoonaswelefttheenvironsofAustinforthevastflatlands,wefeltpeopleconstantlystaringatus.Thiswasespeciallysoinsmalltowns whose names I have long since forgotten but that sounded a lot likeTumbleweedandJackRabbit.Inonesuchplace,wewalkedoutofastoreandalocal lookedatmeandDorothy, thenshowedusanuglysmile.Hecockedhishand,pointeditatmychestlikeitwasagun,andpulledthetrigger.ThissortofthingdidnotletmeforgetforlongthatIwasintheSouthonceagain.

MyworkattheCenterforTheoreticalPhysicswaseverybitasexcitingasIhad hoped. Itwas here that Iwas to first encounter in any detail thework ofStephenHawking,whichwouldleadmeintoawholenewdirectionofresearchthatwouldeventuallyhavemajorimplicationsonmytime-travelresearch.

Hawking(bornin1942)hadrapidlyemergedasoneofthemostimportantfiguresofthelatetwentiethcenturyingeneralrelativity.Heisamazingnotonlyfor his brilliant work but also for the circumstances under which hiscontributions are made. In 1963, while working on his Ph. D. at CambridgeUniversity in England, Hawking was diagnosed with a motor neuron diseasecalled amyotrophic lateral sclerosis (ALS), more commonly known as LouGehrig’sDiseaseafterthefamousYankeefirstbasemanwhodiedfromit.Thisdisease leads to progressive immobility and eventual death. Despite this,Hawking has carried on a wide-ranging research program that has led tofundamental insightsfromthecreationof theuniversetothebehaviorofblackholes.Oneofhismostimportantcontributionshasbeenthemergerofquantummechanicswiththetheoryofblackholes.

In classical or normal black hole theory, after the formation of the blackhole from stellar collapse, matter inside is forever trapped. An example of anormalblackholeisknownasCygnusX-1.Ablackholealoneinspacecannotbeseen.However,manyblackholesappearascompanionsinadoubleorbinarystarsystem,inwhichtwostarsorbiteachother.Onesuchbinarystarsystemwasfirstobserved in theconstellationCygnusanddesignatedasCygnusX-1.Thissystem is about10,000 lightyears fromearth.The two stars thatmakeup thesystemareanopticalstarthatcanbeseenfromtheearth,alongwithaninvisiblecompanioninorbitaroundtheopticalstar.Theinvisiblecompanionhasamassthat isabouteight times thatof thesun.Thegravitationalfieldof the invisible

companionissostrongthatgasesfromtheopticalstararetornfromthesurfaceofthestarandpulledintotheinvisiblecompanion.Astheinvisiblecompanionswallows up the gases from the optical star, they heat up and create a glowaroundtheinvisiblestarthatappearsasahalo.Thecenterofthehalo,wherenolightcanemerge,marksthelocationoftheblackhole.Eventually,theblackholewilldrawtheentireopticalstar(visible)intoitselfandall thatwillremainisasinglelargeblackhole.Thematterandlightoftheoriginalopticalstarcanneveremerge from the black hole.At least this is the case for a normal black hole.Then,in1974,Hawkingdroppedabombshell.

Hawkingpointedoutthatifonetakesintoaccountthatthematterinsidetheblackholeobeysthelawsofquantummechanics,thenthegamechanges.Oneoftheways of understandingwhat happens goes back tomy earliest fascinationwithquantummechanicswhenIfirstencounteredSchrödinger’sequationintheairforce.Schrödinger’sequationdescribesthewavepropertiesofmatterwithaquantitycalledthewavefunctionandisdenotedbytheGreekletterpsi,ψ.Thiswavefunctionisacentralpropertyofquantumtheoryandleadstosomestrangebehaviorformatter.Whilethewavefunctiondoesn’trevealtheexactlocationofa particle, it does tell uswhere it is probably located. This is connectedwithHeisenberg’suncertaintyprinciple,whichdoesnotallowboth the locationandmotionofaparticletobeknown.

Oneofthemostunusualphenomenaassociatedwithquantummechanicsisknownastunneling.Intheeverydayworld,ifyouthrowaballagainstawalltheballbouncesback.Intheworldofquantummechanics,asaparticleapproachesthe wall the wave that represents a particle has a probability of being on theothersideof thewall.Thismeans thatasaparticleapproaches thewall itcantunnel through the wall and appear on the other side. There are practicalelectronicdevicescalledtunneldiodesthatmakeuseofthisproperty.

WhatHawkingdidwastoapplythispropertyoftunnelingtothematterontheinsideofablackhole.Hewasabletoshowthatiftheblackholewassmallenough, then the blackhole barrierwouldbe thin enough formatter to tunnelthroughandappearoutsidetheblackhole.Inotherwords,fromthestandpointofquantummechanics,ablackholecanleakmatter.Asmatterleaks,theblackholebecomessmaller.Eventually,thisleadstotheblackholeevaporatingaway.TheprocessofmatterandenergyemergingfromtheevaporatingblackholeiscalledHawkingradiation.Theideaofanevaporatingblackholeastonishedthephysicscommunity,andcompletelyfascinatedme.

IlearnedalotduringmystayatWheeler’sCenterforTheoreticalPhysics,

mainly in theareaofacquiringadeeperunderstandingofblackholes. Ihopedthatbycontinuingmyinquiryintothisstrangephenomenonthatseemedtowarptime Imight be led, directly or indirectly, in a fruitful direction regarding thestudyof timetravel intothepast.IwasexcitedtogetbacktoConnecticutandcontinuetoexplorethestrangeworldofevaporatingblackholes.Inthespringof1983,DorothyandIpackedourbagsandheadedforhome.

In the early eighties, developments were occurring in the frontiers ofcosmologyandelementaryparticlephysicsthatweretohaveamajorimpactonmy research.Cosmologistshavebeen facedwith aproblem that theBigBangtheoryalone,whichstatesthattheuniverseemergedfromanenormouslydenseandhot state nearly 14billionyears ago, didnot seem to explain.Why is theuniverse,onthewhole,sosmooth?Whenwelookoutinspace,welookbackintime and the furtherwe look out in space the closerwe come to theway theuniverse looked in the beginning. The universe in the beginning looks prettyuniform.Whyisthatso?ItwastheworkofanMITphysicistnamedAlanGuththatfinallyshedsomelightonthisproblem.GuthsuggestedthatshortlyaftertheBig Bang the universe went through an extremely rapid expansion, which hecalledinflation.Thisinflationessentiallyerasedallthenonuniformitythatmightotherwisebeobservedintheearlyuniverse.Theinflationaryuniversebroughtanewunderstandingtohowtheuniverseevolved.

Inmyresearch,IbegantoseethatGuth’sinflationaryuniversemightaffectHawking’s evaporating black holes. Hawking had indicated that black holeevaporation would be noticed if black holes were sufficiently small. Normalblack holes are so large that the thickness of the black hole barrier wouldseverelydecrease theprobabilityofparticles tunneling through thebarrier.Ontheotherhand,Hawkingsuggestedthatsmallblackholescouldbecreatedfromthe compression ofmatter at the beginning of the universe. These small earlyuniverse black holes are called primordial black holes. Typically they couldweighaboutabilliontons(aroundthemassofasmallmountain)andbeaboutthesizeofthenucleusofanatom.

NormalblackholesarerepresentedbyasolutionofEinstein’sgravitationalfieldequationsnamedaftertheGermanastronomerKarlSchwarzschild.22TheSchwarzschild solution gives a good description of ordinary black holes.However, theSchwarzschild solutiondoesnot changewith time.On theotherhand,Hawking’sevaporatingblackholeschangerapidlywithtime.

While Iwasat theUniversityofTexas, I learned that an IndianphysicistnamedVaidya had found a solution of Einstein’s gravitational field equations

thatcouldrepresentarapidlyevaporatingHawkingblackhole.ThissolutioniscalledtheVaidyasolution.Asitturnsout,theinflationarystageofGuth’stheoryis described by de Sitter’s expanding solution of Einstein’s gravitationalequations. It occurred to me that since Hawking’s primordial black holes arecreatedintheearlyuniverse,therapidexpansionofGuth’sinflationaryuniversecouldaffectthebehaviorofanevaporatingblackhole.IknewthiswouldrequirefindinganewsolutionofEinstein’sgravitationalequationsthatwoulddescribebothHawking’sblackholesandGuth’sinflationaryuniverse.

In order to find a new solution, I looked carefully at the physics behindGuth’s inflationary universe. In the inflationarymodel of the universe, a termappearswhichiscalledthe“cosmologicalconstant.”ThisisthesametermthatIhadencounteredwhenIhadstudiedthedeSitterexpandinguniverseaspartofmyPh.D. thesisatPennState. I thought that if IcouldsomehowcombinethecosmologicalconstantintotheequationoftheVaidyasolution,whichdescribesthe Hawking evaporating black holes, then I would have the new solution Isought.Afterweeksofworkingwith the equations, I succeeded in finding thenew solution, which I set out in a paper entitled “Radiating Vaidya MetricImbeddeddeSitterSpace,”publishedin1985inthePhysicalReview.

Thatworkledmetomoreresearch,resultinginapaperonthe“Evolutionof Evaporating Black Holes in an Inflationary Universe,” published thefollowingyear.Inthispaper,Ishowthattheinflationoftheuniversedecreasesthe radiation from aHawking black hole. In otherwords, due to inflation, anevaporatingblackholewouldactuallylivelonger.

Thiswasahighlyproductiveperiodformeintermsofconductingoriginalresearch,andIgiveduecreditforthesynergismandresultantburstofcreativitytothatinvaluableyearIspentintheorbitofoneJohnA.Wheeler.In1987,Iwaspromotedtofullprofessor.

Inthemid-1980s,IhadthegoodfortunetocomeincontactwithabrilliantgraduatestudentnamedKristineLarsen.Krishadrecentlygraduatedmagnacumlaude with a bachelor’s degree in physics from Central Connecticut StateUniversity. After attending a talk I had given at Wesleyan University, sheshowedupatmyofficeandsaidshehaddecidedshewanted todoherPh.D.thesisatUConnundermysupervision.Shedidnotyethaveatopicinmind,andwediscussed a number of possibilities.Nothing immediately jelled.Then, shementionedthatshewasinterestedintheworkofStephenHawking,andplannedtoattendanupcomingconferenceinChicagowherehewasscheduledtospeak.As it turnedout, Iwasplanning toattend thesameconference.Wedecided to

comparenotesaboutapossiblethesistopicforherafterhearingHawking.The conference was an astrophysical symposium on relativistic

astrophysics.KrisandImetthere,andwenttoHawking’stalktogether.Hewascompletely wheelchair-bound at this point and could only communicate via acomputer-generatedvoicewithamenuchosenonacomputerconsoleattachedto his wheelchair. That apparatus was soon forgotten as one listened to theelegant science.AsHawkinghassaid,“Iwould ratherbeknownasa scientistwho happens to be disabled than as a disabled scientist.” Beyond a doubt,StephenHawkingisfirstandforemostascientist.

Afterabanquetonthefinalnightoftheconference,Ireturnedtomyroom.Tiredfromseverallongdays,Iwenttobedearly.Aboutanhourlaterthephonejarredmeawake.ItwasKris.

“Ron,getdowntoroom520now!”“Why?”Iasked.“It’sHawking’sroom,andwe’rehavingaparty.”Needlesstosay,itdidn’ttakelongformetodressandruntotheparty.In

fact,Kris,inretellingthestorythroughtheyears,wouldclaimthatImusthaveexceededthespeedoflightingettingtoHawking’sroom.23

WhenIarrived, therewasalreadyacrowdofpeopledrinkingwine,beer,and mixed drinks. Everyone, including Hawking, seemed to be enjoyingthemselvesgreatly.Hawkingwasfriendlyandexpressive.Hislargeheadrolledtoonesideandhiseyes,whichweremagnifiedbyhisglasses,seemedtotwinklewith a certain mischievousness. Having read that he enjoyed music, I asked,“Whoisyourfavoritecomposer?”Hecommunicatedviahiscomputerconsolebyhighlightingwordsandphrasesfromamenuwithacursor.Aftertappingonhisconsole,hisanswercameforth:“Wagner.”(Ilearnedlaterthatshortlyafterhe was diagnosed with ALS, Hawking became depressed and spent hourslistening to Wagner’s Götterdämmerung [Twilight of the Gods]. It seemsHawkingandIshareanotherinterestbesidesmusic.IamtoldhehasonthewallofhisofficepicturesofMarilynMonroe.)

Not long after, Kris and I, along with some other UConn colleagues,attendedaphysicsseminaratYaleUniversitywhereweheardatalkgivenbyacollaboratorofAlanGuth’s.ThelecturewasaboutGuth’srecentworkon“childuniverses.”Guthhadtheorizedthatontheothersideofblackholesawholenewuniversemaybeintheprocessofcreation.Sincetheblackholewaslocatedinouruniverse,thenewuniversewasdubbedbyGuthtobeachilduniverse.AsIsaw it, theproblemwas that since the childuniversewas createdon theother

sideofablackholeandwecan’tseeintoablackholehowdoweknowifachilduniverseisreallybeingcreated?

Atthatpoint,IturnedtoKrisandsaid,“Thiscouldbeyourthesis.”Decidingtogodirectly toGuthandaskwhathe thoughtabout the idea,I

spokewithhimataconferenceheldatHarvard.ItoldhimthatIwasconsideringhavingmy graduate studentwork on the problem of theoretically determiningwhetherachilduniversecouldbeobservationallydetected.Thiswouldbedonebylookingatchilduniverses thatwereformedontheothersideofaHawkingradiatingblackhole.Theprocessofcreationofthechilduniverseshouldaffecttheradiationfromtheblackholethatweseeinouruniverse.

Guth,friendlyandoutgoing,listenedintently,andsaidhethoughtitwasagoodidea.Furthermore,hesaidthatasfarasheknew,noonehadworkedontheidea before. He then generously offered that, if wewished,my student and Icouldvisithimfromtimetotimetodiscusstheprogressofthework.

When I toldKrisaboutGuth’s response, shewas thrilled.She startedherresearchwhileworking in thephysics department as a teaching assistant, thenreceivedapaidgraduateassistantshipwhichallowedher todevoteherself fulltimetoherresearchwithoutanyclassroomduties.

On a regular basis, Kris and I made a pilgrimage toMIT to discuss herlatestresultswithGuth.Althoughhecouldbeintensewhendiscussingquestionsofphysics,Guthhadaneasy smile andwasenjoyable to spend timewith.HeseemedtohaveafondnessforCoca-Cola,ashisofficewaslinedwithstacksofemptycans.

Inabrillianttourdeforce,Kriswasable—usingthesolutionofEinstein’sgravitational equations that I developed earlier that studied evaporating blackholesintheearlyuniverse—toshowthattherewasindeedaverycharacteristicchange in the radiationrateofanevaporatingblackholeduring theprocessofchilduniversecreation.Guthlikedherresults,whichwerepublishedinPhysicalReview in 1991 in a paper entitled “Radiation and False Bubble Dynamics.”KrisreceivedherPh.D.in1990.Evenbeforeshefinishedherdoctorate,shewasofferedapositiononthephysicsfacultyofheralmamater,CentralConnecticutStateUniversity.

IwasproudofKris’s thesisworkandof thefact that itwasbasedon thenewsolutionofEinstein’sgravitational field equations that Ihad found inmystudyofHawking’sradiatingblackholesinanexpandinguniverse.ThissolutionhadrequiredthatIdevelopanexpertise insolvingEinstein’sequations.Likeastepping stone, it was this knowledge that would prove to be crucial to my

eventualbreakthroughindevelopinganewtheoryoftimetravel.Beforereachingthatpinnacleofmylife’swork,however,Iwouldhaveto

findmywaythroughsomeblackholesofmyown.

Eleven

BackfromtheBrink

Sincemy father’s death I have been a loner. That life-altering event notonlychangedmypersonality,italsotriggeredmyfirstlastingdepression.Atthetime,Ihadfoundadegreeofsolaceonlyinbeingalone,readingsciencefiction,anddaydreamingincessantly.

InhighschoolIsufferedanotherdepression,althoughitmighthavebeenalong, continuous one since childhood.After experiencing some exhilaration atbeingawayfromhomeandintheairforce,Isunkintoadepressivestatewhilein the service.Feeling antisocial, I tried to cutmyself off from the rest of theworld, which was one reason I volunteered for the graveyard shift in thecomputer control room. Once again, I found escape in books, and also inacademics.Itwasn’tuntilIenteredPennState,andmetMarjorie,whocametorepresent the ideal of beauty and brains, that I began to see the possibility ofhavingafullerlife.

Now, after a rewarding decade during which I became a full professor,conductedoriginalresearch(muchofitpublished)thatincreasedmyknowledgeof science relevant to time travel, and enjoyed a stable marriage, I harboredgrowing feelingsofdiscontent. Iwas filledwithquestions I couldnot answer.WouldIeveraccomplishmylife’sgoal?WasIlosingmyway?OnelessonIhadtaken from the sudden loss ofmy fatherwas that someopportunities exist foronlyafinitetimeandonehastotakeadvantageofthemwhenevertheypresentthemselvesorpossiblylosethemforever.HadIledafantasy-fueledlifealltheseyears?HadIwastedmytimestudyingsohardforsomethingthatIwouldneveraccomplish?Gradually,Islidintoafull-ondepression.

Attheuniversity,IhidmydarkmoodsasbestIcould.Puttingonefootinfront of the other, I taught classes, prepared course work, attended meetings,interactedwithcolleagues,andguidedstudents—allthewhilefeelingwretched.Athome,Iwasmoroseandmelancholy.Reminiscentofmyearlierdepressions,allIwantedwastobeleftalone.WithoutsayingawordtoDorothy,Iwouldgetupfrommychairinthelivingroom,gointothebedroom,shutthedoor,turnoffthelights,andlie in thedarkstaringat theceiling.Ifearedthesumofmylifehadfallendrasticallyshort,notonlypersonallybutprofessionally.Certainly,my

dream to accomplish breakthrough time-travel research and build a workingmachinehadnotcometofruition,andattimesIfeltaboutasfarawayfromthatgoalasIhadbeenatagetwelve,whenIbuiltmyfirstrudimentarytimemachinein the basement of our homewithmy father’s tools using illustrations from acomicbookasmyblueprint.

During these low periods, the only thing that helped were positivememoriesofmychildhood,alwayssetintheyearsbeforemyfatherdied.Overandover, I reranscenessuchasDadshowingme the insideofaTVsetashepatientlyexplainedhowtheyokesupportsthepicturetube.Therewasmuchhedidn’t have a chance to showme, andmanyquestions that I didn’t get to askhim.

Mydepressiontookitstollonourmarriage.Dorothy,agentlewomanwhohadalwaysrepresentedsecuritytome,triedtohelp.Whenshesawmegrievingformyfather,shewouldsayoutofsympathyandexasperation,“Can’tyouletthe spirit of BoydMallett rest in peace?” But I couldn’t. Even though I hadalwaysfeltasenseofsafetywithDorothy,therewaslittleshecouldnowsayordo that had any impact onme.Hitting rock bottom emotionally, I yearned toescape and be alone, as I had in the past.We never had arguments; I simplywithdrew fromDorothy and our marriage, which deeply hurt her.We finallyagreed that a separationwas in order and I should getmy own apartment. Inhindsight, itwould have beenwise forme to see a therapist. But at the time,leavingseemedtheonlyoption.Beforethefallsemesterstartedin1989IrentedasmallapartmentinManchesterandbeganlivingaloneforthefirsttimeinmorethantwentyyears.

DorothyandIchecked inwitheachother regularly,andmetperiodically.ShelongedformorestabilityinherlifethanIwasabletoprovideatthattime.Itbecameapparentweweregrowingapart.WedivorcedinJanuary1991.Missingherfamily,shemovedbacktoPennsylvaniaafewmonthslater.Notlongafterthemove, shemet a successful businessman; they eventuallymarried, happilyso.

DuringmyyearsoflivingaloneItookupthepiano.Listeningtoclassicalmusic had always been a source of comfort forme. Atmy first piano lessontherewassomethingabout the formand flowofmusicalnotesona score thatreminded me of mathematical equations. My piano teacher, Judy Rodwell,predicted that, because of the mathematical basis for the laws of musicalharmony, my background would serve me well in learning to play. I soondevelopedapassionforthekeyboard,andwouldspendmanyhourseachweek

practicing. I eventually experienced the satisfaction of mastering Chopin’sPrelude in E Minor. This somber piece spoke to me of longing and loss.Somehow, it gave my feelings an avenue of expression. Playing the pianobecamecathartic.Cominghomefromwork,Iwouldsitatthekeyboardandplaynonstop,sometimesforgettingtoeatoreventurnonthelights.Slowly,thanksinlargemeasure tomusic, the hole inmy soul began to close back up. In smalldosesIstartedenjoyinglifeagain,seeingoldfriends,makingnewones.

Thedaycame,afterfouryearsofbachelorhood,thatIwasreadytoventureforth.Rather systematic in everything I do, I enrolled in a course called FiftyWays to Meet a Lover. Thereafter, I took out a singles ad with the title“Adventurous Astrophysicist Seeks Interesting Terrestrial Female.”Nevertheless,ImetDeborahMcDonald,anintelligentandsophisticatedwomanwith two children, the old-fashioned way: at a church social. Although I hadalwayswantedmyownoffspring, thatwasnot tobe.Thebestalternativewasfinding a loving, supportive partner who arrived in my life with an instantfamily.Deborah (thenworkingasa state lobbyist foranonprofitgroup)and Imarried the following year (1993), and I happily became stepfather to Sarah,sixteen,andAndrew,thirteen.

Therewas awonderful closeness betweenDeborah and her children thatshe willingly let me become part of. One of our most memorable summervacations as a family was a visit to Einstein’s home at 112Mercer Street inPrinceton,NewJersey.SarahandAndyknewthatmyworkattheuniversitywassomehowconnectedtoEinstein’sideas,andtheywereexcitedandproud.Eventhough the housewasn’t open to visitors, the four of us stood together on theporchandhadourpicturetaken.SarahandAndywerethebestkidsastepfathercouldwant.Iamproudthattheybothbecameteachers.

One summer evening in 1996, as Deborah and I were finishing a pizzawhilewatchingamovieathome,Ifeltanexcruciatingpressureonmychest.Itried to relax,hoping itwouldgoaway.When it didn’t,Deborahdroveme toManchesterMemorial.Atthehospital,Ihadthegoodfortunetocomeunderthecare of an astute cardiologist, Dr. Parveen Khanna, who recognized from theelectrocardiogramthattherewasamajorproblemwithmyheart.Heorderedanangiogram,anddeterminedthatIhadwhatisreferredtoasa“widowmaker,”ablockageofthemajorarterygoingintotheheart.Inmycase,itwas95percentblocked. Angioplasty surgery was done and a stent inserted in the artery tocorrecttheproblem.AlthoughphysicallyIsoonfeltasgoodasnew,Istruggledwithnewfeelingsofmortality,commonamongheartpatients.

Mymother—awidow for the second time and still residing in the samehouseinAltoona—hadprovidedmewithaddeddetailsaboutmyfather’shealth.Unbeknownst to me when he was alive, my father had a heart condition forwhichhetookmedication.Shealsoconfirmedthathehadattimesbeensadanddepressed over the possibility of an early death like his own father. As Iprocessed that information, I could become angry at him for abusing hisweakened heart with a two-pack-a-day habit. Didn’t he know about the linkbetweenheartdiseaseandsmoking?Orhadthatinformationnotyetbeenwidelydisseminated in the 1950s?And yet I had never smoked cigarettes and I washaving heart problems at fifty years of age.Was I, too, doomed to die early?AggravatingmyfeelingsofmortalitywasthedeepdisappointmentIfeltatmycontinued lack of progress in time-travel research. Irrespective of how long Ilived,IknewIdidnothaveallthetimeintheworldtorealizemydream.

Providence eventually intervened, providing a crossing of pathswith oneFred Adams, professor of physics at the University of Michigan, at a 1998conferenceheldattheUniversityofKentucky.Wehititoffimmediately.AdamsandImetforbeersoneeveninginthehotelbar.Aworld-renownedtheoreticalastrophysicistwhohad studied star formations and cosmology,Adams tackledbigquestionsliketheoriginsofexistenceoftheuniverse.Wetalkedaboutourwork and careers. Adams is an easygoing guy with a friendly demeanor andquicksmile,andsoonIwasrecitingthewholestoryofhowIbecameinterestedin time travel and my very personal motivation for becoming a physicist. IacknowledgedhowIhadbeenkeepingmostof thisclose tomyvest foryearsandhadonlytoldahandfulofintimates,afraiditwouldamounttoprofessionalsuicideinacademia.Hesaidtherewasalotofworkgoingonintimetravel,andhe encouraged me to “check the literature.” He thought I should get back topursuingmylongtimegoaltodesignandbuildaworkingtimemachine.

It’s strange how it happened—at a low point having my inspirationrekindledbysuchachancemeeting.IleftKentuckydeterminedtomakeanewandconcertedefforttoreviewallthecurrentliteratureandresearchhavingtodowith time travel. Over the course of the next year and a half, I was franklysurprised at howmuchworkwas being done in the field by others, includingsomeofthebiggestnamesinscience.

InsearchingtheliteratureIcameacrossanarticlepublishedin1974inthePhysical Review entitled “Rotating Cylinders and the Possibility of GlobalCausality Violation,” by Frank J. Tipler (presently at Tulane University). ByanalyzingasolutionofEinstein’sgravitationalfieldequationspublishedin1937

byUniversityofEdinburghphysicistW.J.vanStockum,Tiplerfoundthat theregion outside an infinitely long, rapidly rotating massive cylinder contained“closedtimelikelines.”AswiththesituationinvolvingGödel’srotatinguniverseandKerrrotatingblackholes,thepresenceofclosedtimelikelinesindicatedthepossibilityoftravelingintimetothepast.

Furtherstudyledmetoa1988paperbyCaltechphysicistKipThorneandhiscollaborators,M.MorrisandU.Yurtsever,inPhysicalReviewLetters.Themanuscript was entitled “Wormholes, Time Machines, and the Weak EnergyCondition.”Wormholeshavea longhistory thatgoesback toa1935paperbyEinsteinandNathanRosen, inwhichtheyfoundasolutionof thegravitationalfieldequationsthatallowedforthepossibilityofatunnelbetweenouruniverseandanotheruniverse.ThetunnelwascalledanEinstein-Rosenbridge.In1955,JohnA.Wheelerhadsuggestedatunnelnotbetweentwodifferentuniversesbutbetween two different parts of our universe, and had coined the term“wormhole”todescribethistunnel.

Awormholecanbethoughtofasashortcutbetweendifferentpartsoftheuniverse, essentially through space and time. A wormhole has at least twomouthswhichare connected to a single throat. If thewormhole is traversable,mattercantravelfromonemouthtotheotherbypassingthroughthethroat.

A demonstration of a wormhole can be accomplished by using a smallrubberball.First,markonepointontheballaspointA.Then,marktheoppositeendoftheballaspointB.NowdrillaholedirectlythroughtheballfrompointAtopointB.Therearenow twoways toget fromA toB: the longwayaroundgoingalong the surfaceof theball or a shortcutdirectly through theball.ThetunneldrilleddirectlybetweenAandBislikeawormhole.Inthesameway,awormholeisadirecttunnelbetweendifferentpointsthatdoesnotliealongthesurfaceofspace.

Intheory,awormholecanbeusedasarapidtransitroutefromonepartofspacetoanotherthatwouldtaketoolongbygoingalongthesurfaceofordinaryspace. This was the basis for mankind’s first contact with an extraterrestrialcivilizationinCarlSagan’sscience-fictionnovelandmovieContact.Thismodeof travel was suggested to Sagan by his friend Kip Thorne as scientificallyplausible.

In their 1988 paper, Thorne, a former student of Wheeler’s, and hiscollaborators showed how awormhole could be used as a timemachine, onebuiltbynatureratherthanman.Thiscouldbeaccomplishedbyacceleratingoneendofthewormholerelativetotheother;relativistictime-dilation(thetimeona

clockmovingnear the speedof light is slower than thatof a stationaryclock)would result in less time having passed for the accelerated wormhole mouthcompared to the stationary one. This means that an object which entered theacceleratedwormholemouthcouldexitthestationaryendatapointintimepriortoitsentry.Suchapaththroughawormholeiscalleda“closedtimelikecurve.”Awormholewiththispropertycouldbethoughtofasaholeintime.

Continuingmyliteraturesearch,Iturnedupyetanothermodeoftimetravelintothepast thathaditsroots in theoriginofouruniverse.In1991,PrincetonphysicistJ.R.GottpublishedaPhysicalReviewLettersarticleentitled“ClosedTimelike Curves Produced by a Pair of Moving Cosmic Strings: ExactSolutions.” By then, everyone in the physics community knew that a “closedtimelikecurve”wascodefortimetravelintothepast.Essentially,Gott’spaperwasaboutacosmic-stringtimemachine.

Cosmic strings can be thought of as fault lines in the structure of theuniverse leftoverafter theBigBang.Thesestringsare infinitely longmassivethreadsthatcouldexistanywhereintheuniverse.Gottconsideredtwoinfinitelylongparallelcosmicstringsmovingtowardeachother.Asthestringspasseachothertheycreateaclosedloopintime.Itisalongthisloopthattimetravelintothepastcantakeplace.

The papers ofThorne,Gott, andTipler had a liberating influence onme.Here were well-known, highly regarded members of the physics communitypublishingpapersabout themethodsandmeansof timemachines in respectedscientificjournals.Ifeltinspiredtorenewmyeffortsand,forthefirsttimeinmycareer,workopenlyontheproblemoftimetravel.However,duetomyteachingandotheracademicresponsibilities,Ilackedthetimetocompletelyengagemyenergiestothistask.Thatwasabouttochangeunexpectedly.

One gratifying characteristic of the UConn physics department is itscollegiality.I’vealwaysfeltcomfortableamongthefaculty,staff,andstudents.DanMcLaughinwasaformergraduatestudentinthedepartmentwhowasnowinhisfortiesandteachingat theUniversityofHartford.I likedDan.Hewasabigmanwithareadysmileanda largebushymoustachelikemenworein thelatenineteenthcentury.Havingrecentlybeenmarried,Danwasclearlyenjoyinglife.JustbeforeChristmas1998Iranintohimoutsidemyoffice.Wetalkedforawhile,thenwishedeachotherhappyholidays.

Twoweekslater,Ireceivedaphonecallfromanadministrativeassistantinthe physics department. Tearfully, she toldme thatDan had died of a suddenheart attack. I couldn’t believe it.Hehad looked so alive andwell twoweeks

earlier.Nowhewasdeadandgone?Emotionsconnectedwithmy father’s suddendeathwere stirredup inside

me.Panicsetin.MyownheartconditionmademethinkthatI,too,mightsufferafatalheartattack.Sureenough,Isoonbegantoexperienceseverechestpains.Afterconsultingwithmycardiologist,andwiththeapprovalofmydepartmenthead,Iwasgrantedasix-monthmedicalleaveofabsence.

AtfirstIspentmytimeathomeinafamiliarstateofdepression.Noteventhepianoseemedtohelp.Constantlyconcernedaboutmyheartgivingout,Iwasconsumedwiththoughtsofdeath.Thenoneday,stillinmyrobeandsleepers,Iwanderedintomystudy.IbegantoporeoverwhatIhadlearnedaboutvarioustime-travel theories. Over the course of several afternoons, I became engagedwithmyfavoritesubjectagain.IstarteddoingcalculationsonpadsofpaperthatIkeptaroundthehouse,includingnexttomybed.Thestressthatseeminglyhadcontrolofmybodyreleaseditsgripandstartedtofallaway.

Now free of my normal academic responsibilities for months, I foundmyselfwithallthetimeIneededtofocusmyattentiononthetopicoftimetravelto thepast.After a coupleweeksof extensive reading, Iwas left curious, andwondering:Wasthereanotherapproach,besidesthemethodsIhadstudied,thatmightleadtoanewconceptofatimemachine?

Iwentbacktobasics.Inordertoknowwhereatimemachineistraveling,itis necessary to know the direction of time. In relativity, light is the basis forseparatingthepastfromthefuture.Whenyoustrikeamatch, the lightspreadsoutinalldirections.Eventhoughlightmovesatafastclipof186,000milespersecond, it still takes time for the light from the match to spread out like theoutwardmovingripplesinapond.Thefuturedirectionoftimeisdeterminedbyhowfarlighthasmovedfromthematch.Thespreadingoflightfromthematchcanberepresentedasanexpandingcircleincreasingwithtime.Astimegoeson,the circlegets larger and larger.Linesdrawnalong the edgeof the expandingcirclesformacone.Theconewouldlookjustlikeanice-creamcone.Infact,ifyoutookapieceofstringandthreadeditthroughthetipoftheice-creamcone,theforwarddirectionoftimewouldbethedirectionofthestringfromthetipoftheice-creamconetotheopenmouthofthecone.Thespreadingconeoflightiscalledalightcone.Thewideningofthelightconeisthedirectionofthefuture.

Inspecialrelativity,spaceandtimeareflat.Thismeans that the timelinethat goes from the past to the present to the future is a straight line that isthreadedthroughthelightcone.Theapexofthelightconerepresentsthepresentmoment(forexample,themomentyoustrikeamatch).Anypointalongtheline

after the apex of the cone as itwidens represents a future event,whereas anypoint along the line before the apex of the cone represents a past event.As apersonmovesintothefuture,theapexoftheirlightcone(thepresentmoment)moves forward. It’s likemovingan ice-creamconealonga straight string thathasbeenthreadedthroughthetipofthecone.Itwouldbevitalformetokeepthe direction of time in mind as I worked toward developing a theory forbuildingaman-madetimemachine.

During this period, I also studied Caltech physicist Richard C. Tolman’sclassic 1934 textbook Relativity, Thermodynamics, and Cosmology. InNewton’s law of gravity, only matter can produce a gravitational field. Forexample,theearthproducesagravitationalfieldthatkeepsyouanchoredtotheground. In his text,Tolmanpointed out the surprising result that inEinstein’sgeneral theory of relativity not only matter but also light can be a source ofgravity. Tolman considered the gravitational field ofwhat he called a straight“thin pencil of light.” In Tolman’s era,24 a thin pencil of light could not beproduced.Lightspreadsout fromallnatural sourcesandeven the light fromaflashlight beam fans out from the opening. As a laser produces an extremelynarrow beam of light, I wondered if thismeant thatmodern laser technologycouldbeusedtoproduceTolman’sthinpenciloflight.

As I pondered this, I thought about the common denominator amongGödel’s rotating universe, Kerr rotating black holes, van Stockum-Tiplerrotatingmassivecylinders,Thorne’swormholes,andGott’scosmicstrings.Withthe exception of the wormhole, a common factor in them seemed to be therelativerotationofmatter.ItwasthenthatIhadaEurekamoment.

IknewfrommytimeworkingwithlasersatUnitedTechnologiesthattherewasadevicecalledaringlaserthatcouldproduceanintenseandcontinuouslycirculating narrow beam of light. It occurred to me that this continuouslycirculating light beam might produce gravitational effects similar to that ofrotatingmatter.

My earlier studies ofKerr rotating black holes indicated that the rotatingmatterof theblackholeresulted inadraggingofspacearound theblackhole,ratherlikearotatingappleinavatofmolasses.Thisdraggingofspaceiscalledframe dragging. In addition, the rapidly rotating black hole also leads to theformationofclosedloopsintime.

Studying the mathematical structure of the rotating black hole in moredetail,Inoticedthatpartsoftheequationfortherotatingblackholethatledtoframedraggingalsoappearedintheequationforablackholethatledtoclosed

timelikelines.Thissuggestedthatframedraggingwasrelatedtoclosedloopsintime. That was important. If I could show that the gravitational field of acirculating lightbeamina ring lasercouldproduce framedragging, thiscouldalsoimplythatthecirculatingbeamoflightcouldleadtoclosedtimelikeloops.

Calculating the gravitational field of the circulating light beam wouldrequire all the skills I had developed in solving Einstein’s gravitational fieldequationsinmyearlierworkonblackholesandcosmology.Ibegantheprocessoffindingasolutionforthegravitationalfieldoflightinaringlaser.

Bynow,Ihadbecometotallyimmersedintheproblem,andwasnolongerconsciousofmyphysicalstate.This isusuallywhathappenstomewhenIamtryingtosolveaproblem.Iateandslepterratically,andoftenworkedinto theweehoursofthemorning.Idon’trememberdreamingabouttheequations—asIhaddonepreviouslyatsuchtimes—butIdorecalllyingawakeinbedtryingtofigureouthowtocalculateaparticulartermintheequations.

To do the calculations I chose a standard form of the ring laser. Thisconfigurationconsistedofa squarewithamirrorat eachcornerof the square.Oneofthemirrorsissemitransparentwhiletheotherthreemirrorsarereflecting.A laser beam enters the square through the semitransparent mirror. The laserbeam is then reflectedbyeachcornerof the squareand returns to theoriginalmirrorwherethebeamonceagainisreflectedtotheothermirrors.Inthisway,acirculating beam of light is created around the square by the continuousreflectionofthelightfromeachcornerofthesquare.

Asketchoftheringlasergeometry

Day after day, I scribbled furiously on endless pads of paper inmy den,workingatsolvingthegravitationalfieldequationsfortheareainsidethesquareof the laser ring.To simplify thecalculations, I studied the situationwhen thegravitational field is weakest. This involved using a standard approximationscheme for Einstein’s equations in a weak gravitational field. Sometimes,physicists use mathematical techniques called “approximations” to simplifyequations. If the effects they are looking for are small enough they can skipadditional terms in an equation. For example, consider an equation with twonumbers: .1and .0001.Because thesecondnumber in theequation issomuchsmallerthanthefirstnumber,itcanbedisregarded.Thatisanapproximation.

In Einstein’s gravitational field equations, if the gravitational field issufficiently weak it is possible to simplify the calculations by skippingeverythingexceptthelargesttermintheequation.So,Ifirstappliedthestandardapproximation for a weak gravitational field to Einstein’s equations, reducingthenumberoftermsintheequations.Then,tocalculatethegravitationalfieldofthe ring laser, I separated the square that formed the ring into four segments.

Using a mathematical summation technique called integration, I found thegravitationalfieldduetotheenergyandflowofthelaserlightforeachsegment.Putting the individual segments back together, I could then find the totalgravitationalfieldforanypointinsidetheringlaser.

To judge the effect of the gravitational field, I considered what wouldhappen if I placed an electrically neutral mass spinning inside the ring. Thismeant calculating equations for the spinning particle in the gravitational fieldthat I hadworked out for the ring laser. The calculationswere tedious, and Imadesomemistakesalongtheway,whichmeantredoingthecalculation.AsIworked outmy results, I would often listen tomusic fromRichardWagner’soperaticmasterpiece,TheRingof theNibelung.Thefact thatWagner’sheroicscoredealtwithamysticalringgavemeaddedinspiration.

AfterseveralweeksofintensiveworkIfoundthatthelightbeaminaringlaserproducedagravitationalfieldthatlooked—mathematically,atleast—likeavortexor twistingofspacenotunliketheswirlingwatergoingdownabathtubdrain. This twisting of space resulted in the dragging around of a subatomicparticle, such as a neutron, when placed at the center of the laser ring. Mycalculationsshowedthatthegravitationalfieldofacirculatinglightbeamcould,in fact, produce one of the important effects associated with the gravity ofrotatingmatter:framedragging.

Irecheckedmycalculations,findingnomistakes.My solutions proved something new and revolutionary. While frame

draggingdue to thegravitational fieldof a rotatingmassivebody (suchas theearth) had been predicted as early as 1918, no one before had showngravitationalframedraggingduetoacirculatinglightbeam.

Thepresenceofframedraggingwassignificantsinceitwaslinkedinblackholes to the formation of closed timelike loops. It was logical to expect thatframedraggingbyacirculatinglightbeamcouldalsobelinkedtoclosedloopsintime.IknewthatwasthedirectionIwouldnexttakemywork.

Eagertosharemynewscientificpredictionswithmypeers,Iwroteupmyresults and submitted them to Physics Letters A. This entailed my having tocompress nearly a hundred pages of calculations into a four-page paper forpublication.Inscientificpapers,theauthorshowsonlythestartingequations,ageneral outline of the calculations, and the final results. The details of all thecalculationsarenevershown,astheywouldtakeuptoomuchspace.

InApril2000(Ihadreturnedtoteachingthepreviousfallsemesterandwasno longer having chest pains or experiencing any other physical ailments) I

receivedword from the science journal thatmymanuscript hadbeen acceptedforpublication.Iknewthismeantthatananonymousrefereewhoisanexpertinthefieldhadcheckedtheequationsandfoundnomistakes.(Ifanymistakeshadbeenfound,thepaperwouldhavegonetoasecondexpert.Ifthesecondexpertalsofoundmistakes,thenthepaperwouldhavebeenrejectedforpublication.)

On May 8, 2000, my paper “Weak Gravitational Field of theElectromagneticRadiationandaRingLaser”appearedinprint.Onceanarticleispublished, it iswidely readby thephysicscommunityat large.Todate,myfellowphysicistshavenotpointedouterrorsinmymathorscience.Thisworkrepresentedmyfirstbreakthroughintime-travelresearch.Althoughtherewasnomention of “time-travel” in the published paper, the researchwas a necessarysteppingstoneinmyattempttodevelopthetheoryanddesignforaman-madetimemachinebasedonacirculatingbeamoflight.

Mylifelongdreamseemedtobeatthethresholdofbecomingareality.Yet,Iwasnotfinished.

Twelve

TheSweetnessofTechnology

Mydepartmenthead,WilliamStwalley, saidhe thoughtmynewresearchwould be a “novel test” of Einstein’s general theory of relativity. Anotherdepartmentcolleague,WinSmith,paidthehighestcomplimentonephysicistcangiveanotherwhenhedescribedmypublishedworkas“elegant.”BothStwalleyandSmith, however,wanted to knowmore about themagnitudeof the space-twisting effect; specifically, under what conditions would the effect be largeenoughtomeasure?Iexplainedtothemthatsincetheequationsshowedthattheeffect depended on both the laser power and ring-laser size, I was studyingdifferentconfigurationsinordertobestmaximizetheeffect.

InFebruaryof 2001, I received a call fromFredAdamsof theMichiganphysicsdepartment.Hewantedtoknowaboutmyprogresssincewehadchattedover beers in the Kentucky hotel bar three years earlier. I gave him a briefsummaryofmyresearch,and toldhimaboutmyPhysicsLettersAarticle.Heasked if I would give a talk about my work at his physics department’scolloquium.BecauseIfeltIowedAdamsforthenudgehehadgivenmeintheright direction, I acceptedwithout thinking about the ramifications.We talkedabouttitlesformytalk.

Conservativebynature,Isuggested“TheGravityofCirculatingLight.”“You’veappliedthisresearchtotimetravel,”Adamssaid.“Let’sputthatin

yourtitle.”Ipointedout that Ihaddoneonly the firstpartof thework,showing that

circulatinglightleadstothetwistingofspace,andwasnowworkingonwhetherit would also lead to the twisting of time, “a necessary requirement for timetraveltothepast.Ihaven’tfinishedallmycalculationsyetonthesecondpart.”

“That’s okay,” Adams said. “You can explain that your work is still inprogress.Why don’t we call it ‘TheGravity of Circulating Light: A PossibleRoutetoTimeTravel.”’Suchatitle,heexplained,would“jazzup”thetopicand“attractmoreattention.”

“Fine,”Isaid.Itwas,afterall,hisdepartment’scolloquium.As it turnedout, that title attractedmoreattention thaneitherofus could

havepossiblyanticipated.

ThephysicsdepartmentattheUniversityofMichigan,AnnArbor,iswellknowninternationally.From1928through1941itwasthehomeofthefamoussummersymposiaontheoreticalphysics,whichbroughttoAnnArborthelikesof Paul Dirac (1902–1984), famous as the creator of the complete theoreticalformulation of quantummechanics; Enrico Fermi (1901–1959), winner of the1938NobelPrizeinPhysicsforhisworkoninducedradioactivity,andnotedforthedevelopmentofthefirstnuclearreactor(Fermiiswidelyregardedastheonlyphysicist of the twentieth century who excelled both theoretically andexperimentally);KasimirFajans (1887–1975), aPolish-bornU.S. chemistwhodid pioneering work on radioactivity and isotopes; and many other scientificnotables, including Wolfgang Pauli, Werner Heisenberg, Neils Bohr, and J.RobertOppenheimer.DavidDennison (1900–1976), thediscovererof the spinoftheproton,spenthiscareeratMichigan.Theworld’sfirstbubblechambers—devicesfordetectingsubatomicparticlesbymeansofastringofbubblesleftinachamber of liquefied hydrogen—were developed at Michigan by DonaldGlaser,25 forwhichhewas awarded the1960NobelPrize inPhysics.Oneofmanynotablealumni,SamuelC.C.Ting(born1936),whoearnedhisPh.D.inphysicsatMichigan,won the1978NobelPrize inPhysics (alongwithBurtonRichter)for“pioneeringworkinthediscoveryofaheavyelementaryparticleofanewkind.”

Due to the renownof theMichiganphysics department, events andpressreleases are tracked by the news media, nationally as well as abroad. Oneafternoon in February, two months before I was scheduled to appear in AnnArbor, I received a call from London. PhysicistMichael Brooks, an editor atNewScientist,theinternationalequivalentofScientificAmerican,wascallingtofindoutmoreaboutmyscheduledtalkatMichigan.Afteranumberoflengthyphoneconversations,BrooksdecidedtodoafeaturearticleaboutmyworkthatwouldcomeoutafterIspokeatMichigan.

Inthemeantime,Ihadreturnedtomyresearch,findingasmuchtimeforitas I could fit in with my academic responsibilities. Historically, mostbreakthroughsinsciencearemadeatuniversitieswhereprofessorshaveteachingresponsibilities.TheexceptionistheInstituteforAdvancedStudiesatPrinceton(Einstein,Godel,etal.),whichisdesignedstrictlyforresearch.

Having only partially worked out the gravitational effects of circulatinglightbeams,Iturnedtotheaspectthatwouldleadtotimetravelviaclosedloopsintime.Toworkoutthelatterhalfofmytheorywouldrequirelookingatstronggravitationalfields.

InsolvingEinstein’sgravitationalfieldequationsfortheweakgravitationalfield of the ring laser, I had used a standard approximation scheme. To findclosedloopsintimegeneratedbycirculatinglight,Iwouldnotbeabletoresorttoapproximations.Thecompletesolutionoftheproblemwouldrequirefindingwhat are known as “exact solutions” of the Einstein field equations. FindingexactsolutionsofEinstein’s fieldequations isanotoriouslydauntingproblem.Hoping tosimplify theproblem,Iconsidered twobeamsof lightcirculating inoppositedirections. In thisway, I arrived at a tentative solution. Iwasuneasywithhavingdeviated frommyoriginal ring lasermodelwitha singlebeamoflight going in one direction, but decided to seewhere themodel of two lightbeamsmovinginoppositedirectionswouldtakeme.26

InApril (2001) I flew to AnnArbor, which has a population of slightlymore than 100,000 people and an additional 40,000 students. I settled into acomfortable hotel near the campus. The nextmorning,my host, FredAdams,pickedmeupandtookmetothelecturehallwhereIwastogivemyfirstpublictalkonmynewresearch.Aboutfiftypeoplewerealreadypresent.Iknewfromhaving attended other colloquiums that theywould be predominately graduatestudentsandfacultyfromthephysicsdepartment,althoughtheycouldbefromall over the spectrum—solid-state physics, nano technology, atomic andmolecularphysics,etc.Thebestpresentationsatsucheventsapproachedatopicfrom themiddle ground—not overly technical, and yetmore scientific than apopular-leveltalk.

Adamsgavetheaudienceabriefintroduction.AsIstoodwaiting,Icomposedmyselfwithseveraldeepbreaths.Irealized

thatIwasabouttocomeoutoftheclosetIhadsequesteredmyselfinforyears.Oncethedoorwasthrownopen,therewouldbenogoingback.

Sincetheaudiencewascomposedmainlyofphysicistsinotherspecialties,Ibegan with a brief background of Einstein’s special and general theories ofrelativity. I reminded them that in the special theoryEinsteinhad showed thattimeslowsdownforamovingclock.Inaddition,thegeneraltheoryofrelativityindicates(inpart)aslowingdownoftimeinagravitationalfield.27

In the general theory, gravity results from the bending of space by amassivebodylikethesun.Theearthandtheotherplanetsmovearoundinorbitsguidedbythecurvedspaceproducedbythesun.IpointedoutthatinEinstein’stheory, even light,which does not havemass, has energy and that energy cancausespace tobend.Since lightcanbendspace, thismeans that lightcanalsoproduce a gravitational field. I explained that this gravitational effect of light

wasthekeytomydiscoveries.Ithendescribedhowthecirculatinglightofaringlasercausedatwistingof

space.Iillustratedthisbyusingoneofmyfavoriteanalogiesofaspooninacupofcoffee.Imagine,Isaid, that thecoffeeinthecupwaslikeemptyspace,andthespoonislikethecirculatinglightbeam.AsIstirredthecoffeewiththespoonyou could see how the coffee swirled around. In exactly the same way, thecirculatinglightbeamiscausingastirringofemptyspace.Ifyouplacedasugarcube in the coffee it would get swirled around because the coffee is gettingstirredbythespoon.Similarly,ifyouplacedaspinningsubatomicparticlelikeaneutron in theemptyspacesurroundedbyacirculating lightbeam,youwouldseetheneutronbeingtwistedaroundlikethesugarcubeinthecoffee.

Next,IpointedoutthatinEinstein’sgeneraltheoryofrelativity,spaceandtime are connected. If space gets twisted, time gets twisted. I explained that Iwasworking on a solution of Einstein’s gravitational field equations,which Ihopedwouldshowthattwolightbeamscirculatinginoppositedirectionswouldlead to time being twisted in a loop, and that this in turnwould lead to timetravelintothepast.“However,”Isaid,“thisresearchisnotyetcomplete.”

WhenIfinished,theresponseoftheaudiencewascautiouslypolite,andIwasn’tsurewhattomakeofit.Therewereonlyafewquestions,andnoonehadanyobjectionstothephysicsorthemathematics.

WhenIreturnedhome,IgotacallfromMichaelBrooks,wantingtoknowhowmy lecture went. I gave him a summary and suggested he contact FredAdams.Shortlythereafter,Ireceivedane-mailfromBrookstellingmethatNewScientisthaddecidedtodoacoverstoryaboutmytimetravelwork.TheMay19, 2001, issue of New Scientist hit the newsstands with a cover headline:“Flashback: Presenting the World’s First Time Machine.” The article began:“RonaldMallett thinks hehas found a practicalway tomake a timemachine.Mallett isn’tmad.None of the known laws of physics forbids time travel. ...”The article went on to give an overview of my research, along with thesecommentsbyFredAdams regardingmy talkatMichigan: “The receptionwascautious and skeptical. But there were no holes punched in it, either. Thesolutionisprobablyvalid.”

When I turned onmy computer that evening to checkmy e-mail, I wasshocked to see dozens ofmessages frompeople I didn’t know—andwho hadapparentlygottenmye-mailaddressfromtheUConnWebsite—inquiringaboutmy time-travel research. It took hours for me to answer them. The next day,therewere dozensmore e-mails. Itwas then that I began to realize the deep-

seatedinterestmanyotherpeoplehaveintimetravel.That sameweek Iheard fromBenBowie,adocumentary filmdirector in

Englandwhohad read theNewScientist article.Bowie,who toldmeMichaelBrookswasafriendandneighbor,saidhethoughtmyresearchwouldmakeforagooddocumentary.HewantedtoflytotheU.S.tomeetme.Wearrangedforarendezvousthefollowingweek.Havingneverdreamedmyresearchwouldserveas thesubjectofadocumentary, I looked forward tomeeting thedirector.Butalmostimmediately,Iwasfilledwithdread.

MichaelBrooksdidnotknowthatIwasblack,andtheNewScientistarticledidnotmakereferencetomyrace.IknewthatBenBowiewouldalsonotknow,as my phone conversation with him would not have given away my ethnicorigin.Infact,IhadoncebeentoldbyanAfrican-AmericanadministratorthatIdid not “sound black” over the phone. My experiences growing up in whiteAmericahadtaughtmethatnomatterhowhighIclimbed,itcouldneverbehighenough for somepeoplesimplybecause Iamblack. I feared thatwhenBowiesawme,hemightfindsomereasonnottocontinuewiththeproject.

Asitturnedout,myfearswerebaseless.Bowiewasunhesitatinglyfriendlyandinterestedinmywork,notinthecolorofmyskin.Aswetalked,itwasclearthat he thoughtmy ideaswere sound, and could lead to the development of aworking time machine. It was important to him that my work was based onEinstein’stheoriesofrelativity,andBowiefeltthatasuitabledocumentarycouldbe made discussing Einstein’s general and special theories of relativity whilehighlightingmyresearchintotimetravel.ThusbeganafruitfulenterprisewhichresultedinTheWorld’sFirstTimeMachine,awell-craftedsciencedocumentarythat first aired in2003onTheLearningChannel, andat the same timeon theBBC inEngland.Using state-of-the-art animationsand real-life sequences, thefilm covers Einstein’s special and general theories of relativity and quantumtheoryandmyowntime-travelresearch.

Newspapersandmagazineswerenowcallingonaregularbasis.AfteryearsofkeepingmumaboutmyinterestintimetravelbecauseIfearedbeinglabeled“the crazy professor,” itwas astonishing how publicmywork had so quicklybecome.Tomyamazement,thepresscoverageextendedtothatarbiterofrockandroll,RollingStone,whichnotedmyworkintheirAugust2001issueundertheheadline“HotTheory:TimeTravel.”

Somewhereearlyonintheprocessofbeingdiscoveredbythemedia,Iwasbeingchallengedbyareporterinaninterview.AsIrecall,IwasbeingcomparedtoDocBrown, themadprofessor inBacktotheFuturewhoinventedtheFlux

Capacitortotravelbackintime.Inexasperation,Ifinallysaid,“Look,I’mnotanut. This is not Ron Mallett’s theory of matter. It’s Einstein’s theory ofrelativity.I’mnotpullingthingsoutoftheknownlawsofphysics.”Incasetherewas any doubt, I was basing not only my theories but also my career andreputationonthefoundationsbuiltbyEinstein.

AreporterfortheWallStreetJournalinterviewedme,whichresultedinalengthyarticle,“PhysicistsAreLookingatHowWeMightTakeaTripThroughTime.”InthearticleIexplainedaboutmylong-timeinterestintimetravel,andhowIhadkeptquietanddidnotcome“outofthetimetravelcloset”foralongtime.Thereporterthennoted:“Theclosetisemptyingfast....”

Andhow.TheBostonGloberananeditorial titled“TimeandAgain,”whichreadin

part:Time is a straight line formost people—yesterday, today, tomorrow. It’s

whatthewatchsays,whattheguyontheradiosays,orwhattheticketsays.Itcanseemtoraceordrag,butthesearestatesofmindratherthanpermutationsoftheoldlinear24/7.ButwhatiftheclockwereasmalleableasGumbyandtimemachinesascommonasairports?Whatifwecouldhopinandfly?

RonaldMallett,professorofphysicsattheUniversityofConnecticut,feedsthissciencefictionfantasy,whichiswhyhepacked200peopleintoaMuseumofSciencelecturehallonarecentFridaynight.Traffic-weary,gravity-weighted,skeptical,andcurious, theycame tohear fromsomeoneboldenough,orcrazyenough,tosuggestthattimetravelcouldhappeninthiscentury....

Soonafterward,aBostonTVstationcontactedmeaboutdoingastory.ThestationalsocalledAlanGuthatMITtoaskhimaboutmywork.Ireceivedane-mailfromGuthsuggestingthatwegettogethertodiscussmycurrentresearch.On a hot and sticky August day I traveled to Boston and met with Guth, ajourneythatIhadtakenseveraltimesbeforeandalwaysenjoyed.

Guth, still the friendly, intent listener I remembered from my previousvisits, immediatelygrasped thebasic ideaofmyring laser-gravitywork in thePhysics Letters A paper.With that published theory, he did not see any realproblems.Ontheotherhand,asIsatinhisofficetellinghimabouttheongoingsecondpart ofmyworkdealingwith possible loops in timegeneratedby twolightbeamscirculatinginoppositedirections,hestoppedme.

GuthsaidthathecouldseehowloopsintimecouldhappenifIbasedthispartofmytheoryonthemodeloftheringlaserinmyPhysicsLettersAarticle,wherein I had the light beams circulating in only one direction.But he didn’t

believe that two beams of light circulating in opposite directionswouldwork.Hisintelligentcritiquestruckachord.

Inthebeginningofmyrecentwork,Ihadbeenuneasyaboutthepointhewasnowmaking.Foronething,Iknewthatwithtwolightbeamscirculatinginoppositedirections, the frame-draggingeffectcouldpotentiallycancelout.Forobjectssuchasrotatingblackholes,theframe-draggingeffectandclosedloopsin time seemed closely aligned. Guth’s comments brought me back to myoriginalconcerns.Iwouldhavetoattackhead-ontheproblemofcalculatingthestrong gravitational field of a light beam circulating in only one direction. IthankedGuthandleftBostonknowingthatIhadmoreworktodo.

Strugglingwith an appropriatemodel to calculate the stronggravitationalfieldofalightbeamcirculatinginonlyasingledirection,Iconsideredhowthelight might be channeled. One method I looked at was an optical fiber,essentiallyalightpipe.Justasawaterpipeisusedtochannelwater,anopticalfiber is used to channel light. Because of their capacity for huge amounts ofinformation transfer, optical fibers have found wide-ranging applications,including telephonecommunications.These lightpipes seemed tailor-made formyuse.ToincreasetheeffectofasinglecirculatingbeamoflightIconceivedofwrappinganopticalfiberaroundahollowtubeinahelicalspiraltocreateasortofcylinderoflight.WiththisIfeltIwasbeginningtoapproachamodelIcoulddealwith.

Interest inmy research had been steadily increasing among students andfaculty and it was suggested that I give a physics colloquium at my ownuniversity aboutmy latest research.My talk to about150 students and facultymembers was similar to what I had given at Michigan with one importantdifference:Ioutlinedtheneedforcalculatingthestronggravitationalfieldofalight beam circulating in a single direction for the creation of closed loops intime. The lecture was well received, and helpful comments came from mycolleagues, as well as my former department head, Ralph Bartram. Feedbackfrom respected colleagues was a powerful reason, I realized, for a scientistinvolvedinongoingresearchtomakesuchpresentations.

Inmyworkontheweakgravitationalfieldofaringlaser,Ihadconsideredasingleneutronspinninglikealittletopatthecenterofthelaserring.Bartram,a solid-state theorist, suggested that Imight consider a beam of neutrons. Bysending the beam through the stronger gravitational field of a light cylinder,Bartram thought Imight see an intensified frame-dragging effect inwhich theentire beam of neutrons would be turned around as they moved along the

cylinder. I felt thatBartram’s suggestionmight beworth trying at some pointwhenwereachedtheexperimentalstage.

Unlike other scientific disciplines such as chemistry and biology, physicshas a formal division of labor between theory and experiment. A theoreticalphysicistusesmathematicalrelationstoexplainatheory,whileanexperimentalphysicist sets up whatever apparatus is required and makes the actualmeasurementsthatconstituteaphysicaltestofthetheory.Tobesuccessful,anexperimentalphysicistmusthaveafacilityfordesigningsophisticatedapparatusandtakingprecisemeasurements,whileatheoreticalphysicistmustbeskilledinusingmathematicaltechniquestoexplaintheworkingsofnature.Traditionally,thereexistsanatural tensionbetween the twodisciplines. Ifa theoristbelieveshehasthecorrectequationortheory,heisnotthrilledbynegativeresultsofanexperiment that disproves his work. In the world of an experimentalist, anegativeresultcanbejustasimportantasapositiveone.

Thepredictionofaphysicalbehaviorofnaturecanfirstbemadethroughanexperimentand/orobservation,but,also,thetheoryforaphysicalbehaviorcancome first. In the realworldofphysics, itworksbothwaysaboutequally.Anexample of the former is the discovery of the photoelectric effect byexperimentalistPhilippLenard,28whoobservedthatchangingthecoloroflightthat isshoneonametalsurfacechangesthespeedofelectronsthatareejectedfromthesurface.Usingquantumtheory,Einsteinlatercameupwiththetheoryand equations for showing how the increasing frequency (color) of light gavemoreenergyofmotiontotheelectrons,workforwhichhewonhisNobelPrize.An example of the latter is Einstein’s mathematical derivation of the famousequation E =MC2 that predicted that a small amount of mass (m) could beliberated to provide an enormous amount of energy (E). Einstein was neverinvolvedinexperimentstoprovehistheory.Infact,althoughmosttheoristsareinterested in having their work verified, Einstein was largely indifferent toexperiments to prove his theories. (For security reasons due to his Germancitizenship,EinsteinwasnotallowedtobepartofthemostfamousexperimentalverificationofhiscelebratedE=MC2equation:theManhattanProject.)

Asatheoreticalphysicist,IlearnedlongagothatIdidnothavetheaptitudeforexperimentalwork.However,thetimemachinewastooimportantformetowaituntilexperimentersdecidedtheywereinterestedinmytheory.Asaresult,Iwaskeenly interested inbeingclosely involved in theexperimentalsideof theproject. I knew, however, that to adequately testmy theory, Iwould need thehelpofanexperimentalistwhopossessedspecificscientificskills.

Such qualified assistance came from close at home in the person of aninnovativeexperimentalphysicist,ChandraRoychoudhuri,researchprofessorofphysicsatUConnwhorunstheuniversity’sprivatelyfundedresearchlaboratoryset deep in the woods several miles away from the main campus. Born andeducatedinIndia,RoychoudhurigraduatedfromJadavpurUniversity,Calcutta,thencametotheUnitedStates.HereceivedhisPh.D.in1973fromtheInstituteof Optics at the University of Rochester in New York. Roychoudhuri hadattendedmyUConncolloquiumandafterwardcameup tomeandcommentedabout the “underlying symmetry” of my theory. He was familiar with theprediction from Einstein’s general theory of relativity that matter has agravitational effect on light, verified byArthurEddington in his famous 1919observation of the bending of distant starlight by the gravitational field of thesun.Chandra,aspecialistintheexcitingnewfieldofphotonics,toldmethatheliked the notion that light also has a gravitational effect onmatter. Photonicsdoes for light what electronics does for electrons. Just as electronics is thecontroloftheflowofelectrons,photonicsisthecontroloftheflowoflight.Thescienceandapplicationsofphotonicsareusuallybasedonlaserlight.29

Chandra thought my theory broke new ground on light and matterinteractions,andshouldbesetupexperimentally.Hesuggestedacollaboration.Realizing that Chandra’s background in photonics—and specifically lasers—madehimanidealcollaboratortotestmytheories,Iwholeheartedlyagreed.

Chandra, of medium height and possessing a warm smile that he showsoften,hasagreatsenseofhumorandalso loves toget into longphilosophicalconversations.Hislabissituatedinwhatusedtobeacafeteriaanddininghall;theentirestructureispaintedinstitutionalgreen.Linedupinsidetheexpansivespaceareaboutadozenoptical tables,onwhichanynumberofdifferent laserexperimentsarealwaysbeingcarriedoutforvariousprivateindustries.Chandraisrenownedforhisworkwithhigh-poweredlaserdiodes,whicharetinylasers(about.006incheshigh,whichisonlysixtimesthewidthofahumanhair)thatcanproducepeakpowerof100watts.

During regularmeetings to talk shop,Chandra and I considered photoniccrystalsasapossiblealternativetoopticalfibersasameansofchannelinglightalong a helical path to form a light cylinder. The study of photonic crystalsoriginatedwiththe1987workofEliYablonovitchatBellLabsinHomdel,NewJersey,andSajeevJohnattheUniversityofToronto.Agemstonesuchasopalisan example of a naturally occurring photonic crystal. The particular iridescentcolor of opal is the result of the way light is channeled through the crystal

structure of the gemstone. Armed with the knowledge that optical fibers orphotoniccrystalsmightbeused toproducea lightcylinder, Idecided touseacirculatingcylinderoflightasthebasisofmytheoreticalcalculation.

Since they can be written in a single line, Einstein’s gravitational fieldequations look deceptively simple. However, when taken out of the highlycompressed tensor calculus notation, they represent a set of ten extremelycomplexequations.Todothecalculations,Ireachedbacktomyexperienceoffinding an exact solution for the Einstein field equations for the stronggravitational field of an evaporating black hole in an inflationary universe. Inthat case, ithadbeennecessary forme tocombine twosolutionsofEinstein’sequationstoformanewsolution.IhadcombinedtheVaidyablack-holesolutionwith the de Sitter cosmological solution to produce the Vaidya–de Sittersolution.Myexperiencewiththistechniqueprovedtobeofsignificantvalueindealingwiththepresentproblem.

Idecidedtodispensewithtryingtomodelmathematicallyeitheranopticalfiber or a photonic crystal. Instead, for the sake of generality and to keep thelight beam on a cylindrical path, I elected to use a geometric constraint. Thisconstraintwas representedbyastatic (nonmoving) linesource.Lightnaturallywantstotravelalongastraightline.Theonlypurposeofthelinesourceinmycalculations was to act as a general constraint to confine the circulating lightbeam to a cylinder. (Set up experimentally, the line source could look likewrapping a piece of string around a maypole, with the string being the lightbeamandthemaypoleservingasthelinesource.)Thelightbeamitselfwouldbeconceived of as a mass less fluid flowing in only one direction around thecylinder.Thismeantthatthesolutionreallycontainedtwosolutions:oneforthecirculatinglightandoneforthestaticlinesource.

In March 2002, as I was still working on solving the field equations, IreceivedaninvitationtogiveatalkaboutmyresearchattheJunemeetingoftheInternational Association for Relativistic Dynamics (IARD) Conference inWashington,D.C.,inthreemonths.TheconferencewasbeinghostedbyHowardUniversityandwouldbeattendedbyexpertsinrelativitytheoryfromaroundtheworld.Excitedly,Iacceptedtheinvitation.Thiswouldbethefirsttimemyworkwould be exposed to specialists in my field. Since I had yet to finish mycalculations, the opportunity presentedwas both exciting and nerve-racking. Inowhadadeadline,andthepressurewason.

In trying to solve Einstein’s gravitational equations for the stronggravitationalfieldofacirculatingcylinderoflight,thetaskwasmadeevenmore

difficultbythefactthatthefullEinsteingravitationalfieldequationsarehighlynonlinear differential equations.Unlike linear differential equations, forwhichstandard techniques of solving the equations exist, every nonlinear differentialequationhastobeconsideredonacasebycasebasis.Inalinearequation,2+2=4.Foranonlinearequation,itcanhappenthat2+2≠4,wherein≠means“notequalto.”Nothingcouldbetakenforgranted.

TherehavebeenmanyexactsolutionsoftheEinsteinfieldequationsdonebyothers.However,most of the solutionsdonot have aphysicalmeaning; inother words, there is no identifiable source for the gravitational field of theequation. A few of the exact solutions with identifiable sources are theSchwarzschild solution for the gravitational field outside of a nonrotatingsphericalmassivebody,theKerrsolutionforthegravitationalfieldoutsideofarotating spherical massive body, and the de Sitter solution for an expandinguniverse.

IwasattemptingtofindanexactsolutionoftheEinsteingravitationalfieldequations for thegravitational fieldofacirculating light cylinder.Without theaid of a computer, I set about solving each of the ten nonlinear differentialequations for the areas outside and inside the light cylinder. I spent everyavailable moment I had attempting to solve these time-consuming equations,oftenworkingtwelvetofifteenhoursaday.SometimesafterworkingnearlyallnightIwoulddragmyselftotheuniversitytogivemylecturesafteronlyanhourortwoofsleep.Simultaneouslyexhaustedandcharged,Ihadneverworkedsohardinmylife.

After twomonths, I finally had an exact solution of the field equations.Withgreatanticipation,Ibeganstudyingthetemporalpropertiesofthesolution,in otherwords, those that related to time. It didn’t take long forme to noticethere was a term in the solution that ordinarily looked like a circle in spaceoutside the cylinder of light. When I worked the numbers and the frame-draggingeffectofacirculatinglightcylinderbecamestrongenough,thecircleinspaceturnedintoacircleintime.Thismeantthattherewereclosedloopsintimeoutside the circulating cylinder of light thatwould lead to time travel into thepast.

“Closedloopsintime...”Iputmypencildownandrubbedmytemples.Theclockonmydeskshoweditwasafter3:00AM.Inowhadacompletedtheoryfortimetraveltothepast.

Turningoutthelights,Iwenttobed.

*

As the airliner descended towardRonald Reagan InternationalAirport inWashington,D.C.,onJune25,2002,Ipeeredoutthepassengerwindowatournation’scapital.Notwithstandingadegreeofanxiety,Ifeltreadytopresenttheresults ofmywork to the annualmeeting of the InternationalAssociation forRelativisticDynamics.

Once inside the airport terminal, Iwalkedover the coveredbridgeway totheMetro station. After transferring to the green line, I got off at the Shaw-HowardUniversityexit,turnednorth,andwalkedsixblockstothemaincampusof Howard University. It seemed strangely coincidental yet wonderfullyappropriate that this august international group which convened at differentworldwidelocaleseachyear(thepreviousyearatTelAvivUniversityinIsrael)washavingitsmeetingthisyearatHowardUniversity,withitsrichtraditionofprovidingeducationalopportunitiesandexcellence toAfrican-Americans sinceshortlyaftertheCivilWar.Thisyear—myyear,andhereofallplaces—Iwouldstandbeforesomeoftheworld’smostrespectedphysiciststopresentthewholeofmyworkandlife’sambition. Iwouldbeoneof threeAfrican-Americans intheroom;another,TepperGill,wasaHowardUniversityfacultymember.

Inside the lecturehall I lookedupat the rowsofoccupied seats that roseupwardfromthepodium.Someofthebiggestnames(aswellasbrains)inmyfieldawaitedme.Aftercatchingmybreathfollowingthejokeabouthavingnomorethansixtytransparenciestoshow(Ihadtwenty-six),IbeganbyexplaininghowmytheoriesweresolidlybasedonEinstein’sgeneralrelativitytheory.

I went over the details of how closed time loops were formed in thegravitational field circulating cylinder of light. Pointing to relevant equationsprojectedonanoverheadscreen,Ishowedthatthesametermthatledtoframedragging in space was needed to generate the closed loops in time. “Thecirculating light beam causes a swirling of space that produces a swirling oftime,whichinturnresultsintheformationofclosedtimeloops.”

In the course of my presentation, I projected on the screen variousillustrations, equations, and final solutions, all for thepurposeof showing thatspaceandtimecanbemanipulatedinawholenewwaythatwouldleadto thepossibilityoftimetravelintothepast.

Thefinaltransparency,however,wassomethingdifferent.Itwasofaphoto

takenlongagoofmyfamilyattheBronxParkwithmysmilinghandsomefatherholdingmylittlebrother,Jason,whileIstoodnexttomybeautifulmother.(Myyoungerbrother,Keith,hadnotyetbeenborn.)

Iconcludedthe talkbytellingthegroupaboutmyoriginalmotivationforbeinginterestedintheproblemoftimetravel,explaininghowaftermyfather’sdeathIwasinspiredbyH.G.Wells’booktoonedaybuildarealtimemachine.

“Myoriginalmotivationforeverything—learningmathandscience,goingtocollege,becomingaphysicist—wassoIcouldseemyfatheragain.”

Thenthelecturewasover.Therewasasilencefromtheaudience that lastedsomewhat longer thanI

wouldhaveliked.Iwasn’tsurehowtotakeit.Inretrospect,Ibelievethegroupwasstunnedbythesuddenpersonalturnmytalkhadtaken,somethingthatwasnotoftenheardatsuchscientificgatherings.Then,theapplausecame.

AsIexpected,someperceptivequestionsfollowed.Onehadtodowiththecircumstances under which the frame-dragging effect could be observed. Iexplained that my experimental colleague, Chandra Roychoudhuri, waspresently studying practical designs for the implementation of neutron-beamexperimentstotestthegravitationalframe-draggingeffect.

When there were no more questions, Bryce DeWitt, the legendarycofounderofthequantumtheoryforgravitywhosepresenceatmytalkhadleftmebothanxiousandawestruck,cametohisfeet.

I still had amongst my books one by DeWitt, Relativity, Groups andTopology,whichwaswellwornandhadhelpedmeyearsagowithfundamentalunderstandingscrucialtothecompletionofmyPh.D.thesis.

Ididn’twaitwithbatedbreathsomuchasIrefusedtobreathe.“I don’t know if you’ll ever see your father again,” DeWitt said, his

eyebrowsraisedashepeeredintentlyatme.“ButIdoknowhewouldhavebeenproudofyou.”

DeWitt’scommenthadaprofoundimpactonme,andnotonlybecause itwassaidbyamanwhomIgreatlyrespected.Ihadbeenconcentratingsomuchon close-up equations that I hadn’t taken time to see the wider focus. Mylifelong thirst for knowledge, my science education, my university teachingprofession:yes,Dadwouldhaveunderstoodmydrive tobettermyself,andhewouldhavebeenproudofme.Inarealsense,hehadbeentheone—intheshorttimeweweretogetherinlife—whoputmeonthispath.Evenwithoutsolutionsonmypadofpaper,IknewthatassurelyasIknewanythingintheuniverse.

Ibegantofeelwholeforthefirsttimeinmanyyears.

*

The second half of my time-travel theory was published in the journalFoundationsofPhysicsinSeptember2003.Entitled“TheGravitationalFieldofa Circulating Light Beam,” the paper contained the new exact solutions ofEinstein’sgravitationalfieldequationsforthegravitationalfieldofacirculatinglightcylinderandshowedthatclosedloopsintimeresulted.

AnotherpartofDeWitt’scommentaftermytalkturnedouttobetrue.Asmy results indicated,when I turned off the light flow, the time loops

disappeared while the line source around which the light had circulatedremained.Theclosedloopsintimehadbeenproducedbythecirculatingflowoflight, and not by the nonmoving line source.When it came to translatingmytheory into the design for a circulating-light time machine, it was clear thecirculating flow of light would be the machine’s on-and-off switch. Per myresults,inordertoachieveclosedloopsintime,thelightsourcehadtobeon.

Closed loops in time would continuously be formed only as long as theflowoflightcontinued.Theseloopswouldstackupontopofeachotherandbeconnected to form a spiraling helix that would look rather like the familiarchild’stoy,theSlinky.Evenastheearthmovedinspace,thetimeloopsofthehelixwouldadjusttothenewlocation.Ifthecirculatingflowoflightwasleftonforayear,thenbyenteringthehelixayearfromnow,someonewouldbeabletospiralbackalongthetimeloopsofthehelixtoasfarbackasthefirstdayayearagowhenthecirculatingflowoflightwasturnedon.

Asthevariousimplicationsinvolvedinthedesignandoperationofthetimemachine began to sink in, a realization hit me:My time machine could onlycarryatimetravelerbacktothemomentthemachinewasturnedon,andnotonesecondbefore.WhyIdidn’tseethissooner,Idonotknow.Perhapsitwasagainamatterofbeingtooclosetotheequationstoseethebigschemeofthings.Whatit meant was that when the first time machine that could transport a humanbecame operational, our descendants might be able to visit us, but we couldnevervisitourancestors.

It would not be like the time-travel movie Frequency, which I had seenwhenitwasreleasedin2000,andthenboughtwhenitcameoutonvideo,andsawagain—andagain.NexttoTheTimeMachine,ithadthemostimpactofanyfilm in my life, touching on the essence of what my dreams were about.FrequencytellsthestoryofapoliceofficernamedJohnSullivanwhoisabletocommunicateacrosstimewithhisdeadfirefighterfather,FrankSullivan(played

byDennisQuaid).John’sfatherhaddiedthirtyyearsearlierfightingafireinawarehouse. During an evening of unusually intense solar flare activity, Johnturns on his deceased father’s old ham radio set. After an exchange with anunknown ham operator, John becomes aware that theman is his father. Johnrealizesthatheisinapositiontoalterhisfather’sfate.HewarnsFrankaboutthefirehehasyettofight,andsaveshim.Insodoing,Johnchangeshisownlifebyhavinghisfatherpresentforhischildhoodandbeyond.

Iwouldnevergettheopportunitytodothesame.Iwouldnotbeabletousemytimemachinetoseemyfather.Thegrownman and scientist I hadbecomecouldnow let goof the final

emotional vestiges of his shattered childhood.My father was gone, and therewas nothing I could do about it other than live my own life with pride andcourage, and fill as many days as I had left with valued people, times, andworks.

IthoughtbacktowhatJ.RobertOppenheimerhadsaidwhenhewasaskedyears after World War II about the motivation that led to the successfulcompletionoftheManhattanProject.Surprisingly,itwasn’ttobuildanatomicbomb to end the war. Oppenheimer said the scientific project had been“technicallysweet,”andclaimedthathadbeenthetruemotivationformanyofthescientistswhodidendupbuildinganewkindofbombthatendedthewar.

Eventhoughmyoriginalgoalofbeingabletotravelbacktothe1950shadmorphed into something else entirely, Iwas highlymotivated to complete theprojectoutofsheercuriosityandthesweetscienceofseeingthedevicework.Inow began to plan how I might turnmy theory for breaching the space-timecontinuumintoapracticalreality,withmyoverridinghopeandintentionthatitwouldbeusedonlyforpeacefulpurposes,neverviolent,warlikeendeavors.

Itwastimetobuildanexperimentaltimemachine.

Thirteen

BuildingtheMachine

Theoretical physicists are generally not concerned with practicalapplications of their work. Applications that lead to patents are normallyreservedforspecifictechnologicaldevices;theoriescannotbepatented.

I had, however, a somewhat different take on this after readingHow theLaser Happened, the autobiography of Nobel laureate physicist Charles H.Townes.30 In his book, Townes indicated that itwas not necessary to have aworking model of a device in order to have it patented. He suggested that aresearcherwithaconcrete theoryas tohowanewdevicewillworkshouldgoaheadandapplyforapatent.

I consulted with UConn’s Center for Science and TechnologyCommercialization.Thedirectorof technology licensingsuggested that I fileaprovisionalpatentthatwouldestablisharecordofmyideawhilegivingmetimetoworkoutafullpatent,somethingIcouldwaittodountilthecirculatinglight-gravitationalframe-draggingexperimentbeganinearnest.(Aprovisionalpatentapplicationdoesnotrequireasmuchinformationasafullpatent,nordoesitcostasmuchmoneytofile.Also,itlastsforonlyayear.)

Mygoalwasnot to be secretiveor possessivewhen it came tomy time-travel research. In fact, quite the opposite was the case. Historically, once anoriginal theory is published in the scientific press, it is common practice forother scientistsandengineers touse it in theirownwork.That ishowscienceadvances. While Einstein is credited with the theoretical discovery of thestimulated emission of radiation that is behind the laser, other researchersdeveloped the first working laser. I am sure Einstein would not have had aproblemwiththathadhebeenaroundtowitnessthedawningofthelaserage.

In studyingU.S. patent guidelines, I realized it would not be possible topatent a time machine as such. However, I could request a patent for anapplication inwhich the timemachinewas a central component.After givingthisfurtherthought,IcameupwiththeideaforadevicecalledLOTART.InmypatentapplicationfiledJuly2,2003,withtheU.S.PatentandTrademarkOffice,Iprovidedthefollowinginformationunder“DetailedDescription”:

A laser optical time machine and receiver transmitter (LOTART) is a

communication device consisting of a unidirectional circulating light beamconnected with a signal receiving and transmitting device. The time machinereceiver would be capable of receiving long-range signals from an externaltransmitting device constructed for a particular application at a specified timeandplace in thefuture.The timemachine internal transmitterwould thensendsignals to an earlier moment along closed time lines with information aboutsubsequent external conditions. For example, if at some later time a planetaryspacemissionissuccessful,thenasignalcouldbetransmittedfromthelandingmodule to the earthbound light cylinder time machine. The received signalwouldthenbetransmittedwithinthelightcylindertimemachinetothepresent.The reception of the signal would indicate, at the present time, whether thefuture mission was a success. Based on the receipt of the signal, it could bedeterminedwhetherornotitwasnecessarytochangemissionparameters.Thiscould lead to considerable savings in terms of cost and manpower of spaceexploration.

Theproposedopticaltimemachineconsistsofalaserbeamsentthroughaunidirectional cylindricalwaveguide in an appropriatemedium connected to areceiver and transmitter. The resultant circulating light beam generates agravitationalfieldthatcontainsclosedtimelines.Asignalreceiver-transmitterislocated in the region outside the circulating light cylinder. Specificelectromagneticsignalsdetectedatthereceiverwouldthenbetransmittedalongthe closed time lines from a designated later time to the moment when theLOTARTwasturnedon.

Inthe“Claims”section,IindicatedthatLOTARTwas:* A method of generating the closed time loops associated with

gravitationalfieldofacirculatinglightbeamandthereceptionofsignalssentatsomefuturetimetobetransmittedtothepresent.

*Amethodofformingaunidirectionalcylindricallightconfigurationinanappropriateopticalmedium.Thecylindricalconfigurationcanbeapproximatedby photonics crystals, optical fibers, or a stacked array of unidirectional ringlasers.

The following diagram, captioned “Light cylinder (LC) wave guide andsignalreceivertransmitter(SRT),”wassubmittedwiththeapplication:

Fig.1Lightcylinder(LC)waveguideandsignalreceivertransmitter(SRT)

ThegovernmentgrantedaprovisionalpatentforLOTARTinAugust2003.Although it had been an interesting exercise to speculate about possibleapplications in order to qualify for a patent, themost pressingmissionwas todetermine experimentallywhether a particle ofmatter or signals of some typecouldbesentbackintimeaspredictedbymycalculations.

Fromtheoutsetofourcollaboration,myexperimentalcolleague,ChandraRoychoudhuri, and Idecided to initiallyconcentrateondemonstrating the firstpartofmytime-traveltheory:thatthegravitationalfieldofacirculatingbeamoflightwouldleadtoatwistingofspacewiththeresultantframedragging.Therewerepractical aswell as theoretical reasons for thisdecision.On thepracticalside,all thatwasneeded for framedraggingwasaweakgravitational field. Incontrast, a strong gravitational field was required to produce closed time-likeloops.Since less energywas required to produce aweakgravitational field, itmadesensetofirstlookforframedragging—aneasierexperimenttosetupandanecessaryconditionfortimetraveltooccur.

From a theoretical standpoint, the equations showed that closed loops intime were generated at higher energies by frame dragging. If we could notexperimentallyproduceframedragging,itwouldbepointlesstolookforclosedloopsintime.

Themachinewouldbebuiltinphases.Thefirstphasewouldbetodesignequipment to verify that a circulating beam of light at low energies did twistspaceasIpredicted.Onlywhenspacetwistingwasobservedbymeansofframedraggingwouldthesecondphasecommence.Thesecondphaseentailedgoingtohigherenergiestocreateclosedloopsintime.

Tobegin the firstphasewehad todevelopapracticaldesign for the ringlaser, anduse it onanappropriate testparticle.Theparticlewechosewas theneutron,asubatomicparticlethatmakesup(alongwithprotons)thenucleusofmostatoms.Aneutronhasapropertycalled“spin”thatwouldmakeitusefulinthe experiment. Any rotating object is said to be spinning. The earth, forexample,isrotatingaroundanaxisthroughtheNorthPole.Therefore,theearthcan be said to be spinning about its axis. The neutron also has an axis aboutwhich it rotates or spins. Normally, the direction of the neutron spin doesn’tchange.However,mytheoryshowedthatiftheneutronisplacedatthecenterofa ring laser, the gravitational fieldwill cause the spin direction to be draggedaround.Thechange in thedirectionof theneutronspin iscalledprecession.Akey result I had derived frommy calculationswas an equation for the frame-draggingprecessionofaspinningneutralparticlesuchasaneutron:

In this equation,Ω represents the rateatwhich theneutron spindirectionchanges.Theequationcontainstwofundamentalconstantsofnature,Gandc.Giscalledtheuniversalgravitationalconstantandcisthespeedoflight.Therearetwo variables, ρ and a, in the equation that can be changed according to theexperimentalsetup.ρistheintensityofthelaserbeamandthevariableaisthelengthofanysideofthesquarethatmakesuptheringlaser.Theequationshowsthat increasing the intensity of the laser or decreasing the ring laser size willincreasetherateatwhichthespindirectionoftheneutronchanges.Thismeansthattheexperimentshouldbedesignedtoachievethelargestpossibleintensitiesforthesmallestpossibleringsize.

In my original ring laser-gravity paper in Physics Letters A I had usedmirrors to establish a circulating light flow. This configuration had severelimitationssince,onapracticallevel,thesizeofthelaserringislimitedbythesizeofthemirrors.Mirrorscouldbemadeonlysosmall.ChandraandIrealized

thatsomethingelsewasneeded.Wecameupwithanalternativeschemetousefourseparatebut intersecting laserbeams to formasquare.Thesymmetricallyfocused laser beams from the four corners of the square would simulate theeffectofahigh-intensityringlaser.Theintersectingbeamscouldbeadjustedtoachieveextremely small ring sizesof about .000001meters (.00004 inches) inlength.

It also became clear that the effect of the ring laser could be furtherincreasedbystackingtheringsatopeachother.Thefinalconfigurationwouldbea laser-light towerwith each level consisting of four intersecting laser beams.Thelaserbeamsofeachlevelofthetowerwouldbeprovidedbyhigh-powereddiodelasers.Eachdiodelasercanproduce10wattsandisabout.000155meters(.006 inches)high.Thecirculating light towerwouldproducea space-twistinggravitational field.My calculations showed that an observable frame-draggingeffectwouldbeseenforatowerstackedwith10,000diodelasers,whichwouldleadtoatotaltowerheightofaboutfivefeet.

Toseethespace-twisting,frame-draggingeffect,abeamofneutronswouldbeshotthroughthecenterofthetower.Astheneutronsemergedfromthetower,the change in their spin direction would be measured. If the spin directionchanged by the amount predicted in the equation, this would prove that theneutronshadexperiencedframedraggingduetothespace-twistingeffectsofthegravitationalfieldofthecirculatinglighttower.

Itisimportantinscientificexperimentstoconsiderdifferentpossiblewaystoachieveadesiredeffect.Itturnedoutthattherewasanotherwayofobservingthe gravitational frame-dragging effect of the ring laser that did not involveparticlesofmatteratall.ThisapproachoccurredtomewhenIconsideredsomeof my earliest research, in particular what I had done with my first graduatestudent, Fred Su, who had studied the frame-dragging effect caused by thegravitational field of a rotating black hole. Thiswas done by looking atwhathappenstoalightrayasitpassesneararotatingblackhole.

Afundamentalpropertyoflightisthatitvibratesupanddownasitmovesforward.Theplaneformedbytheupanddownvibrationiscalledtheplaneofpolarization of the light ray. In Fred’s thesis, he showed that the plane ofpolarization of the light ray is twisted by the gravitational field of a rotatingblackhole.Irealizedthatasimilartwistingoftheplaneofpolarizationofalightray should happen if we sent the ray through the gravitational field of thecirculating light tower. We now had two different possible experimentalarrangementsthatcouldtestthefirstphase.

AsChandra and Iwere considering these various experimental strategies,therewasnewsaboutanexcitingsatelliteexperimentunderway.GravityProbeBwassetup to test thegravitational framedraggingcausedby the rotationofthe earth. The $700 million project was a collaboration between NASA andStanfordUniversity,withNASAproviding themoneyandStanfordservingasthe prime contractor for the mission and responsible for the design andintegrationofthescienceinstruments,aswellasformissionoperationsanddataanalysis.Theprincipal investigator for the experiment isStanfordphysicistC.FrancisEveritt.31IthoughtitmightbevaluableformetomeetwithEveritttolearn more about his frame-dragging experiment, and tell him about mine.Everittagreedtoavisit,andIflewtoCaliforniainJune2004.

This was my first visit to Stanford, located in northern California aboutfortymilessouthofSanFrancisco,andIwasstruckwiththebeautyofthetree-lined campus. Shown to Everitt’s cluttered office,my first impression of himwas that he resembled photographs I had seen of a sixtyish Albert Einstein.Everittissoftspoken,withaBritishaccent,andamopofstringyhairthatfallsto his shoulders.After some pleasantries, he gaveme a tour of the laboratorycomplex.

Everitttookmefirsttoamodelofthecryogenicprobethathousedthefourgyroscopes so essential to the experiment. The probe looked like a giantstainless-steel thermosbottle.Eachgyroscopewasaperfectly smooth1.5-inchsphere—about the size of a Ping-Pong ball. “These spheres are the roundestobjectsevermadebyman,”Everitt explained.The tinysphereswereenclosedinsideahousingchambertopreventdisruptionfromsoundwaves,andchilledtoalmost absolute zero to prevent their molecular structure from creating adisturbance.Everittclaimedtheaccuracyofthegyroscopestobe“thirtymilliontimesgreaterthananygyroscopeeverybuilt.”

Theexperimentwasnotspurofthemoment,buthadalonghistory.In 1918, three years after Einstein had published his general theory of

relativity, twoAustrian physicists, Joseph Lense andHans Thirring, predictedthat amassive rotatingbody—such as the earth—woulddrag the empty spacesurrounding its mass. This effect was dubbed frame dragging. By 1960,however, frame dragging due to a massive rotating body had still not beenobserved.

ItwasatthisjuncturethatStanfordphysicistLeonardSchiffhadanideafora possible way of observing frame dragging due to the earth’s rotation. Hesuggested that a gyroscope could be placed in polar orbit to measure the

effect.32Agyroscope is simply a rotatingor spinningobject.Sans any forcesactingonthegyroscope,thespindirectiondoesn’tchange.IfEinstein’sgeneraltheoryofrelativityiscorrect,oncethegyroscopeisinapolarorbittherotationoftheearthwillresultinatwistingofspacearoundthesatellite.Thistwistingofspacewouldchangethespindirectionofthegyroscopeasitisdraggedaroundinthe direction of the rotating earth. Therewas one problem: at the time Schiffproposedthisexperiment,thetechnologyneededtocarryitoutdidnotexist.Notonlywasitamatterofnothavingtheprecisescientificandmeasuringapparatusrequired, but theU.S. had been in the space business only a couple of years.Rocketsandorbitalsatelliteswerestillanemergingtechnology.

Later in the twentieth century satellite launches became routine, andadvancesinsuperconductivity(electricalcurrentsthatoccurwithnoresistance)andmaterialstechnologies—especiallytheabilitytoproduceperfectlysphericalspinning gyroscopes—allowed for the possibility of an experimental test ofgravitationalframedraggingbytherotatingearth.Unfortunately,Schiffdiedin1971 before the experiment could be set up. In 1981, Everitt became theprincipalinvestigatorforthesatelliteexperiment.

Twomonths before my visit, on April 20, 2004, a 21-by-9-foot satellitecarrying the probe containing four gyroscopeswas successfully launchedby aDelta II rocket fromVandenberg Air Force Base. Everitt explained that finalcalibration of the gyroscopes were, as we spoke, still being done by sendingsignals from theStanfordcontrolcenter to thesatellite inorbit.After thatwascompleted, the experimentwouldbegin. IfEinstein’spredictionswere correct,the fourultra-precisegyroscopes shoulddetect that smallamountsof timeandspace aremissing from each orbit. Tomeasure each orbit, the gyroscopes arealignedwithaguidestarusingatrackingtelescope.Amagnetic-fieldmeasuringdevicerecordsthechangesinrespecttotheguidestar.

WhenwereturnedtoEveritt’soffice,I toldhimaboutmyownwork,andmyprediction of framedragging due to the gravitational field of a circulatinglightbeam.Ihadsenthimcopiesofmytwopublishedpapers,andInowaskedhis opinion of the experimental arrangements that Chandra and I had beenconsidering to test my theories. Everitt thought that the most likely successwould come with considering the frame dragging effect on the plane ofpolarizationofalightraythatwassentthroughthegravitationalfieldoftheringlaser.Thereasonforthiswasthatlightwasfareasiertocontrolthanneutrons.The light ray could be reflected multiple times through the ring laser, whichwould considerably amplify the frame-dragging effect on the plane of

polarizationoftherayandmaketheeffectmoremeasurable.Before leaving I thanked the gracious Everitt for his time and learned

opinions,andinvitedhimtogiveaphysicscolloquiumatUConnthefollowingyear.EverittsaidthathehadneverbeeninNewEnglandduringthefallandhehadheard that the foliagewascolorful that timeofyear.Wesetadate forhisvisit in October 2005. According to Everitt, sufficient data would have beencollectedbythentocheckonthevalidityofthepredictionofframedraggingdueto the gravitational field of the rotating earth. Until then, I would be eagerlyawaiting,likeeveryoneelseinthephysicscommunity,thoseresults.33

When I returned home, I discussedwhat I had learnedwithChandra.Hefelt that Everitt was correct in his belief that greater measurability of thegravitational frame dragging effect of the ring laser would be achieved byobservingtheeffectoftheplaneofpolarizationofalightray.Nevertheless,weagreedthatthebeststrategyforthepresenttimewouldbetocontinuelookingatbothneutronsandlightrays.

In our earliest discussions, Chandra and I both acknowledged theparamount need of funding for our project. Research funding can come fromgovernment, business, nonprofit and private sources.Government funding canbe acquired by sending a proposal to an appropriate agency. Sources ofgovernmentfundingcanbeclassifiedasnonmilitaryandmilitary.ExamplesofnonmilitaryfundingsourcesaretheNationalScienceFoundation(NSF)andtheNational Aeronautics and Space Administration (NASA). Military funding isconnectedwithsuchorganizationsas theDefenseAdvancedResearchProjectsAgency(DARPA).Ihad, infact,beencontactedbysomeonewithconnectionsto DARPA. However, I felt the need for caution over the issue of receivingpossible funding support from the military. My unease came partly from thesomewhatcomplicatedhistoryofthelaser.

In 1953, Charles Townes invented a device for amplifying microwaveradiation that he called themaser (microwave amplification by the stimulatedemission of radiation). By 1957, Townes was thinking about how to build adevicetoamplifylightbasedonthemaserprinciple.Townescalledtheproposeddevice an optical maser. At the time, Townes was a professor of physics atColumbia University. Working independently, a Columbia graduate studentnamedGordonGouldbeganthinkingaboutadevicethathecalledalaser(lightamplification stimulated by the emission of radiation). In 1958,Gould left hisdoctoralstudiestoworkforasmallcompanynamedTechnicalResearchGroup(TRG).Hewasabletointerestthecompanyinhisideaforalaser.TRGwasable

to obtain a sizable military contract to work on the laser from the AdvancedResearchProjectsAgency(ARPA),theprecursortoDARPA.UnfortunatelyforGould,securityrestrictionswereattachedtothemilitarylargess,andGouldwasunable to obtain the necessary security clearance. His research notes wereclassified,meaninghecouldnotevenwriteanythingforpublication.Gouldwasshutoutofhisownproject.WhileTownes’contributiontothedevelopmentofthelaseriswelldeserved,equalcreditshouldhavebeengiventoGouldandnodoubtwouldhavebeen—perhapsalongwithashareofTownes’NobelPrize—haditnotbeenfortheinterventionofthemilitary.

There are other examples inwhich themilitary—for reasonsprofessed toinvolvenationalsecurity—hadtakenaprojectawayfromascientist.InacaseIknew about, a laser researcher lost his project when the military saw thepotential for a laserweapon to use against incomingmissiles and aircraft andtookitover.Ididnotwantthattohappentothisproject.ThelastthingIwantedwas to acceptmilitary funding only to have the work classified and snatchedaway—perhapsatthemomentthatthemilitaryrealizedtheexperimentworked.Chandra, who had also heard outrageous stories of military interference inscience,agreed.Althoughmilitaryfundingforscientificprojectsisavailableinlargeamounts,wedecidedearlyonnottoseekoracceptit.

Allmajorscientificandtechnologicalendeavorsrequiresufficientfundingtocarryouttheactualexperiments,andcertainlyChandraandIwereinthesamepositionwhen itcametobuilding thecirculating light-timemachine.Abudgethad been developed at UConn for the first phase of the time-machineexperiment,which had officially been designated as the “Space-timeTwistingbyLight” (STL) project. The budget for the initial phase—to demonstrate thegravitationalfieldofacirculatinglightbeamcausesatwistingofspace—totaled$286,000, which included the cost of personnel (postdoctoral and graduatestudents), equipment, research travel, and supplies. The University ofConnecticutFoundation,Inc.,anonprofitinstitution,hasestablishedanaccounttoreceivecontributionsandmanagefundsfortheproject.34

Inthemeantime,Ibeganconsideringpossiblestrategiesforcarryingoutthesecond phase of the time-machine experiment: to establish the presence ofclosed loops in time due to the gravitational field of circulating light. Quiteunexpectedly,asuggestionforanexperimental testcameasaresultofanothercollaboration Iwas involved in.Often, physicists find themselvesworking onmorethanoneresearchproject,andthathasusuallybeenthecaseforme.

ForanumberofyearsIhavehadaninterestinoneofthemajorproblems

confronting astrophysicists: the so-called missing matter problem. Thatsomethingwasnotquiteright in theuniversewasfirstnoticedbyobserversofthemotionsofstars ingalaxies.Onewaythatastronomershaveoffindingouthowmuchmatterisinthegalaxyissimplybycountingthenumberofstarsinagalaxy.Itisthensimplyamatterofarithmetictoaddupthenumberofstarsanddeterminethetotalmassofthegalaxy.Anotherwayofdeterminingthemassofagalaxyisbylookingatthemotionofstarsthatareorbitingneartheedgeofagalaxy.Itturnsoutthatbyobservingthevelocityofanorbitingstaritispossibletocalculatethemassofthegalaxyaboutwhichthestarisorbiting.

Ashockcametoastronomerswhentheydeterminedthemassofa typicalgalaxybyfirstcountingthestarsmakingupthegalaxyandcomparingthatmasswith the mass of the galaxy as determined by observing the motion of starsorbitingaroundit.Totheirsurprise,thetworesultsdidnotagree.Thenumberofstarscountedgaveavalueforthemassofthegalaxythatwasmuchlessthanthemassthatwasdeterminedbylookingatthemotionofstars.Inanutshell,thisisthemissingmatter,ormissingmass,problem.

A number of theoretical proposals had been suggested to resolve thisproblem. Sincewe count stars by seeing thembecause they are luminous, themostobviousanswer is that themajorityof thematter thatmakesupagalaxymustbenonluminous,meaningwecan’tseeallthematter.Becausemostofthematter is nonluminous, it is called “dark matter.” Some of this nonluminousmattercouldbeintheformofblackholes,alsoinvisible.

Afriendandcolleagueofmine,MarkSilverman,aBritish-bornprofessorofphysicsatTrinityCollegeinHartford,Connecticut,becameinterestedinthemissingmatterproblem.MarkandIfirstmet in1987ataconference thatwasheldatKingsCollege inLondon tocelebrate thehundredthanniversaryof thebirthofErwinSchrödinger,whodiscoveredthewaveequationfor theelectronin1926.MarkreceivedhisPh.D. fromHarvard in1973and is internationallyknownforhisworkonatomicandopticalphysics.Heisafriendly,dappermanofmediumheightwhosportsaratherroguishmoustacheandshortbeard.

Mark thought that the missing matter might be due to a universal fluidmadeupoflightweightparticlesofaspecialnature.Wedecidedtocollaboratebecause it appeared that the properties of these particles could be related toearlier work I had done on Einstein’s famous (or infamous) cosmologicalconstant,inwhichheattemptedtoshow—erroneously,asitturnedout—thattheuniversewasnotexpanding.TheapproachMarkandIhavetakentothemissingmatter problem is promising, and we have published a number of papers

discussingourresults.During one of our meetings, I told Mark about my work involving the

gravitationalfieldofacirculatinglightbeam,andtheformationofclosedloopsintime.Markmadeabrilliantsuggestionaboutonepossiblewayoftestingforthepresenceof theclosedtime-likeloops.Hisoriginalremarks involvedusingradioactive elements, which have proscribed life spans. Later, I modified hissuggestionandappliedittothedecayofunstableelementaryparticles.

The test would be set up as follows: consider that a circulating beam oflighthasgeneratedaclosedloopintime.Also:unstableelementaryparticlesofaparticulartypeallhaveexactlythesamelifetime.Supposethatabeamofsuchparticlesissentpastaregionthatcontainsaclosedloopintime.Thoseparticlesthatapproachtheloopontherightsidewillbeexperiencingadifferentdirectionoftimethanthoseparticlesthatapproachtheloopfromtheleft.Ifadetectorisplacedontheothersideoftheloop,thelifetimeoftheparticlesthatarriveatthedetectorwillbedifferent—dependingontheirpathintime—astheyencounteredtheclosedloopsintime.Thisshouldgiveapreciselymeasurabledeterminationofthepresenceofclosedtime-likeloops.

Thisisthekindofdefinitiveresultthatwouldconvinceotherphysiciststhatacirculatingbeamof lighthadindeedcreatedaclosedloopin time.Ifwecansendanelementaryparticlebackintime,wecansendanyothermatterbackaswell,althoughtodosowouldrequiremorelasersandmoreenergy.

Whenweareinthefinalstagesofbuildingthetimemachine,itisthiskindof experiment thatChandra and Iwill first attempt to perform at his lab. If adifferenceinthelifetimeofthedecayofunstableelementaryparticlesisindeedobserved, then the concept of a circulating light timemachinewill have beenverified—andtheageoftimetraveltothepastwillbeusheredin.

Fourteen

Time-TravelParadoxes

That my calculations predict time travel is possible only back to themomentthefirstworkingtimemachineisactivatedsolvesaproblemraisedbyStephen Hawking and others. Their question: If travel into the past becamepossible at some futuredate,whyhaven’twe received time travelers from thefuture?

This then is one possible answer: We may not have seen time travelersbecause the first working time machine has yet to be switched on. Once amachine that can transporthumans is activated,wemay indeed start receivingvisitorsfromthefuture,astheywillthenhaveaportalthroughwhichtheycanreachus.Wellbeforethen,however,wemaybeginreceivingmessagesfromthefutureviaatimemachinethatcansendandreceivemoreelemental(nonhuman)formsofmatter,suchasradiosignals.

Thereisapotentialwayaroundthelimitationsontimetravelthatmyworkpredicts, but itwould require the existence of intelligent life on other planets.Thereiseveryreasontobelievethattheuniverseisteemingwithlife.Ifitisnot,andifearthturnsouttocontaintheonlyformsofintelligentlife, thenawholelotofspacehasbeenwasted.TheSETI(SearchforExtraterrestrialIntelligence)project has for decades been searching the sky for radio signals that mightindicatethatintelligentlife,otherthanourown,existsintheuniverse.Todate,nointerstellarradiosignalhasbeenfoundthatcanbeunambiguouslyinterpretedas a message from an extraterrestrial civilization. Nevertheless, the searchcontinues.

An even more promising direction for finding life on other planets hascome from the discovery of extrasolar planets. Beginning in the 1990s, greatexcitement was generated when astronomers confirmed the observation ofplanetsoutsideoursolarsystemthatwereorbitingstarsverymuchlikeoursun.Thediscoveryoftheseextrasolarplanetswasmadepossiblebygreatlyimprovedtelescope technology. On October 6, 1995, two Swiss astronomers at theUniversity of Geneva, Michel Mayor (born 1942) and his graduate student,Didier Queloz (born 1966), announced the first definitive observation of anextrasolarplanet, a planetwhichorbits a star other thanour sun and therefore

belongstoanotherplanetarysystem.Theplanet—named51Pegasib—islocatedintheconstellationofPegasusabout47.9lightyearsfromearth.(Onelightyearisaboutsixtrillionmiles.)

Extrasolar planets are too small to be seen directly; indirect methods ofobservationarenecessary.Onemethodofdetectionof extrasolarplanets isbyobserving the gravitational influence that the orbiting planet has on the star.Anotherwayofobservinganextrasolarplanetisthetransitmethod:asaplanetcrossesinfrontofastar,theshadowoftheplanetcausesthelightofthestartodim.Byearly2006,nearly200extrasolarplanetshadbeendetected.Mostoftheextrasolar planets are much larger than the earth (around the size of Jupiter,whichis316timesmoremassivethanearth).However,onJanuary25,2006,aplanet nomore than five times themass of the earthwas found.Astronomersbelieve it is only amatter of time before an earth-like planet is detected. Theconsequencesofsuchadiscoverywouldbeprofound.Ourgalaxyalonecontainsabout100billionstars.Ifevenasmallfractionofthesestarscontainedearth-likeplanets, it is possible that extraterrestrial civilizationswhich are both less andmoreadvancedthanourowndoexist.

Idonotdiscountthepossibilitythatanalienworldexistswithtechnologysoadvancedthattimetravelhasbecomeapartoftheircivilization.Itispossiblethat one distant day, when we have developed space propulsion technologyadvancedenough,wewillreachoneoftheseworlds.35Supposetheybuiltandturnedonatimemachineafewthousandyearsago.Imaginetheexcitementofseeing ancient Egypt, Greece, Rome, and witnessing historic events we haveonlyreadaboutinhistorybooks.

Regardless of the method of travel, going backward in time opens up aPandora’sboxoftroublingparadoxes.Oneoftheobjectionsthathasbeenraisedagainst time travel into the past, by both philosophers and scientists, is that itcould lead to serious contradictions. The chief example is the so-calledGrandfatherParadox.Thisparadoxcanbe illustratedbyaparable.Consider ifyouwillthestoryofoneKeithFraser.

OnOctober 31, 2050, Ted Fraser, a bright and ambitious youngman, isfortunate enough to have an interviewwith a top legal firm in his hometown.TheseniorpartnerofthefirmisimmediatelytakenwithTed’squalificationsandpersonality. Ted is hired and eventually meets the senior partner’s attractivedaughter,Emily.TedandEmilyfallinloveandaremarried.In2052,thehappycouplehavea son,David.Tedpasses away in2074.A fewyears later,Davidmarriesandhasason,Keith.AsKeithgrowsup,Davidconstantlytellshisson

about thewonderful grandfather that he’ll never know. In 2095,Keith joins atop-secret government project that had developed advanced time travel fiftyyears earlier. Obsessed throughout the years with wanting to have known hisgrandfather, Keith volunteers to go back in time. He is transported to hisgrandfather’s hometown on the morning of October 31, 2050. Spotting hisgrandfather,whomherecognizesfromoldphotographs,Keithhollerstogethisattention.Ted,takenbysurprise,turnssuddenly,trips,andbreakshisleg.Takentothehospital,Tedmissesthejobinterviewwiththelawfirm,andthejobgoesto someone else. At this point in the story we arrive at a major paradox. Bymissing the interview, Ted never has the opportunity to meet the boss’sdaughter.Asa result,TedandEmilyneverhavea son,David.SinceDavid isneverborn,ourtimetravelerKeithisneverborn.ButifKeithisneverborn,thenhowcanhetravelbackintimetochangehisgrandfather’slife?

Thisisthecruxoftheparadox:howisitpossibletotravelintothepastanddosomething that couldwipeoutyourownexistence?Therehavebeenmanyattempts to deal with this paradox. One way to eliminate such time-travelparadoxes has been to say that nature conspires to prevent such an unnaturalchanging of history. This “prevention by nature” is related to Hawking’sChronologyProtectionHypothesis,which conjectures that the laws of physicswillsomehowpreventthesuccessfuloperationofatimemachine.Forexample,when a timemachine is turned on, it will somehow destroy itself before anyhistory-alteringeventsareallowedtotakeplace.

Another resolutionof theGrandfatherParadox is nearly as strange as theproblem itself. This resolution is based on the othermain pillar of twentieth-century physics: quantum mechanics. Unlike the classical world of Newton,which deals with certainties, the world of quantum mechanics deals withprobabilities. One application of quantum probabilities is the parallel-worldstheory of the universe, which states that at every possible decision point theuniverse splits into different parallel branches (i.e., the cheeseburger or tunasandwichdilemma).It’simportanttorememberthatthissplittingdoesnotrefertoconsciouschoices—itjusthappens,andregardlessofwhichuniverseweliveinwewouldnotknowabouttheexistenceoftheother.

Theapplicationofparallel-worlds theory to time travelwasdevelopedbyOxford physicist David Deutsch, and we can see how this theory leads to aresolutionof theGrandfatherParadoxby reconsidering theKeithFraser story.At themoment thatTed’sgrandsonKeitharrives in thepast, there isasplit inthe universe. This parallel universe is different from the universe that Keith

originally left. It is in the newparallel universe thatKeith arrives tomeet hisgrandfather. Even though Keith precipitates the events that led to hisgrandfather’smissedopportunities,itdoesnotleadtoaparadoxbecauseKeithisinanewparalleluniverseandnothinghedoes in thenewuniverseaffects theolduniverse.Intheolduniverse,hisgrandfathermakestheinterview,meetshisfuture wife, and eventually has a grandson named Keith. As bizarre as thisparallel-universescenariosounds,itisnotruledoutbythelawsofphysics.

In addition to chronology protection and parallelworlds, there is anotherintriguingpossibilityfortheresolutionoftime-travelparadoxes.Supposethatasuitable encrypted transceiver receives a message from the future. The onlyphysical reality thatwehave is thepresentmoment. Ifweacton themessage,then we will have chosen a particular future. This new future is likely to bedifferentfromthefuturefromwhichthemessagewasreceived.Inotherwords,we really will have changed the future. That said, there is a fundamentaluncertainty associatedwith our decision to act on any informationwe receivefromthefuture.Howcanwebecertainwhethertheinformationreceivedisfromour future or the future of a parallel universe? Consequently, even with aworkingtimemachine,thereexiststhepotentialforadegreeofuncertainty.

Science-fictionmovieshavesometimesdealtwiththeperilsofchangingthepastwithouthavingknowledgeof the consequences for the future.Oneof themore recent films that considered the consequences of altering the past is the2004science-fictiondramaTheButterflyEffect.Thestoryisaboutayoungmanplagued by unhappy childhood memories. He decides to change the past byusinghisabilitytotravelbackintime.Theproblemisthateverytimehealtersthepast,thefutureconsequencesbecomeincreasinglyworse.

Unlike traveling into thepast, time travel into the futuredoesnot lead tosuch paradoxes. This is because once you arrive in the future, there’s nothingyoucandotochangethepast.Youcanonlylivewiththeconsequencesofwhathashappenedduringthetimeyouweretravelingtothefuture.

Asfortravelingintothepast,Ibelieveitwillultimatelyhappen.Whentimetravel does occur, abuses will naturally arise. As with any new, powerfultechnology,timetravelwillhavetoberegulatedtopreventill-usage.Itwillbeuptosocietytoensurethattimetravelisusedforthebenefitofthehumanrace.

Thequestionofwhethertimetraveloccursbetweenparallelworlds,onlyinthisworld,orwhethernaturesomehowwillintervenetopreventtimetravel,canonly be answered after the first time machine is turned on. I believe thatsomedaymankindwillbeabletoanswerthequestion“Whathappenswhenwe

gobackintimeandchangethepast?”Time travel could allow us an unprecedented control of our destiny.

Ultimately,however,theonlythinganyofusreallyhaveisthepresentmoment.

*

IfEinsteincouldcomebackforanhourandwecouldsitonaparkbenchandtalk,IwonderwhatImightsaytohim.IthinkIwouldstartbytellinghimthathewouldn’tbelievewhatwenowknowabouttheuniversebasedlargelyonhiswork,forinstance,theBigBangtheory,andhowweknowthattheuniversestarted out as a cataclysmic event. I’m sure he would also want to know theanswerstosomequestionshewasn’tabletosolve.

“Youwereright,aunificationoftheforcesofnatureisnecessary,butthereasonyoudidn’tsolveitwithjusttwoforces—gravityandelectromagnetism—isthatwenowknowtherearefourforcesatwork.Thestrongnuclearforceandtheweaknuclearforcemakeuphalfoftheunificationsolutionthatgovernsalltheinteractionsintheuniverse.”

I would also tell him how a satellite is circling earth now to prove histheorythatalargemasscausesframedragging.Iwouldexplainmyowntheorythat shows thegravitational fieldofacirculating lightbeamalsocauses framedragging.“Weareunderstandingmoredeeplywhatyourgeneral theoryhas tosayabout thenatureofspaceandtime.”Iwould tellhimthat thegravitationalfieldofcirculatinglightisnotonlygoingtocauseaframe-draggingeffect,butthat according to my calculations it could also lead to closed loops in time,whichmeansthepotentialfortimetravelintothepast.

DoIthinkEinsteinwouldsignonformytime-traveltheory?Well, I don’t believe hewould take it for granted. I think hewould say,

“Showmethecalculations.”IwouldbeinterestedinknowingifEinsteinreadthesamebookthathadso

motivatedme:TheTimeMachine.Iwouldliketothinkthathedid.Indeed,ata1930 banquet in London where Einstein and H. G.Wells were both present,Einstein at the dais acknowledged Wells, saying he was pleased to see thenovelist“whoseviewsoflifeI’mparticularlyattractedto.”

BeforeourhourontheparkbenchwasoverandEinsteinreturnedtobeingone for theages, I’d surely say, “Dr.Einstein, thankyou foryourgeneral andspecial theoriesof relativity, and for all yourotherunbelievably incisiveworkforallofmankind.Thankyou,too,forbeingmylifelonginspiration.”

*

Mymotherisstillaliveandgoingstrongatageeighty-two.WhenIvisitedher a few months ago, she took me to her church, Mount Zion Baptist, inAltoona.Shewasbesideherselfwithprideinshowingmeofftotheotherchurchmembers,introducingmeas“Myson,DoctorRonaldMallett.”

Intruth,thelossofmyfatheratanearlyagecouldhavebadlyderailedme.Asitwas,Ibecamewithdrawn,andahabitualtruant.Wereitnotformydreamof one day building a timemachine, Imight have dropped out of school andtaken awrongpath in life. “Mydream,” I recently told an audience of youngpeople,“helpedkeepmeoutofthestatepen,andgotmeintoPennState.”

Mymotherandfather’sothersonsweredriventosucceed,too.Myyoungerbrother, Jason, always a good people person,was amember of the renownedIBMsalesforce,andretiredasanexecutive.Myyoungestbrother,Keith,alwaysadoodler,isawell-knowncommercialartistandportraitpainter.Mysisters,EveandAnita,workasacomputergraphicsartistandmedicalassistant,respectively.

OnthatvisittoAltoona,ItoldMomforthefirsttimeaboutmydreamasachildandformanyyearsthereaftertobuildatimemachinesoIcouldgobackandseeDadagain.Iexplainedsomeaboutthescienceandlasersinvolved,butIthinkshestoppedlistening.Shelookeddeeplyatme,withtearsinhereyes.

“Youlooksomuchlikeyourfather,”shefinallysaid.Wehugged,andIcriedwithher.

Mymother and father,Dorothy andBoydMallett,withme (left) andmybabybrother,Jason,attheBronxPark,1948.

Mysoldierfatherbeforebeingshippedoverseasin1944.

Visiting my grandparents’ farm in Claysburg, Pennsylvania, with mymotherandbrotherJason(left),early1950s.

Dadworkingonatelevisionset,1954.

ThecoveroftheClassicsIllustratededitionofTheTimeMachine,whichIboughtforfifteencentstheyearaftermyfatherdied.ThestorygavemehopeofonedaybuildingaworkingmachinethatwouldtakemebackintimetoseeDadagain.

Firstpageof theClassics IllustratededitionofTheTimeMachine. Iusedsuch illustrations as an elementaryblueprint to buildmy first timemachine atageeleven.

My graduation picture from Altoona Area High School, class of 1962.Withdrawnandhavingfewfriends,Iwanteddesperatelytoleavehomeandbeonmyown.Within twoweeksofgraduation, Ishippedout forU.S.AirForcerecruittraining.

DorothyFryandmeon the stepsofourapartment inBrooklyn,1968.Atthe time, Iwasworkingasa research technicianat theMarkiteCorporation inGreenwichVillage.Weweremarriedformorethantwentyyears.

In my office in the University of Connecticut Department of Physics in1989, two years after becoming a full professor. Today, the poster of an oldfriendandlongtimeinspirationisstilltapedontothesamefilingcabinetnotfarfrommydesk.

IservedforsixyearsasacampusliaisonofficerfortheU.S.NavyReserve.Onthisdayin1982,IwentonatrainingcruiseaboardUSSMiller(FF-1091),afast frigate named in honor ofDorieMiller, anAfrican-American ship’s cookwhomanned amachine gun– aweaponhe had not been trained to operate –aboard his docked ship at Pearl Harbor on December 7, 1941. Miller, whosucceeded indowningoneof the attacking Japanese aircraft,was awarded thecovetedNavyCross.

AttheInternationalCenterforTheoreticalPhysicsinTrieste,Italy,in1979with physicist Joseph Taylor and his wife, Marietta. A year earlier, Taylor’sbreakthroughresearchonbinarypulsarswithgraduatestudentRussellHulsehadbeenannounced,providing the first experimentalevidence for theexistenceofgravitational waves. For their work, Taylor andHulse shared the 1993NobelPrizeinPhysics.

VisitinglegendaryphysicistJohnA.WheelerathishomeonHighIsland,Maine,1995.Ispentmyfirstsabbatical(1982–83)asaFordFoundationfellowattheUniversityofTexas,Austin,whereWheelerwasthedirectoroftheCenterforTheoreticalPhysics.Nowninety-fiveyearsold,WheelerstillkeepsanofficeatPrinceton.

Boyd Mallett’s three sons (from left): Jason, a retired sales executive;Keith,asuccessfulcommercialartist,andme.Circalate1990s.

Inmyoffice explaining tograduate students themathematics and sciencebehind my laser-driven time machine, under the watchful gaze of the oldrelativist,2006.

Dr.RonaldMallett,professorofphysics,UniversityofConnecticut.

Endnotes

1DanishphysicistNielsBohr(1885–1962)madeessentialcontributionstothe understanding of atomic structure as well as quantum mechanics. Hereceived the Nobel Prize in Physics in 1922 for his work dealing with thestructure of atoms. (The element bohrium is named in his honor.) During theNazioccupationofDenmarkinWorldWarIIBohrescapedtoSwedenandspentthe last two years of the war in England and America, where he joined theManhattan Project and helped build the atomic bomb. In his later years, hedevotedhiseffortstothepeacefulapplicationofatomicphysicsandtopoliticalproblems arising from the development of atomic weapons. He died inCopenhagen.

2HughEverett III, born inMaryland in 1930 and raised inWashington,D.C.,leftphysicsafewyearsafterreceivinghisPh.D.,discouragedatthelackofresponsetohistheoriesfromotherphysicists,includingNielsBohr,whowasunimpressedwithEverett’sideas.Everettsoonwenttoworkasadefenseanalystandconsultantforprivateindustry,becomingamultimillionaireintheprocess.A chain-smoker and heavy drinker, Everett died suddenly in 1982 at age 51,apparentlyofaheartattack.Hisson,Mark“E”Everett,istheleadsingeroftherockbandEels.

3 H. G. Wells (1866–1946) was a biologist and his strong scientificbackgroundshowedinhiswritings.Hisearlynovels—TheTimeMachine,TheInvisible Man, and The War of the Worlds—billed as “scientific romances,”inventedanumberofthemesnowclassicinsciencefiction.ItisbelievedWellswasinfluencedbythepopularwritingsofJulesVerne(1828–1905).

4HendrikAntoonLorentz (1878–1928)was born in theNetherlands.Hewonthe1902NobelPrizeinPhysicsforhisworkonelectromagneticradiation,defining it so as to accurately explain the reflection and refraction of light. In1904 he developed his Lorentz transformations, mathematical formulas thatrelate space and time measurements of one observer to those of a second

observer moving relative to the first. As these formed the basis of Einstein’sspecial theory of relativity (1905), Lorentz is considered one of the mostprominentfiguresinthehistoryofphysicsandthespecificareaofrelativity.Amanofimmensepersonalcharm,Lorentzendearedhimselfbothtotheleadersofhisageandordinarycitizenswhocrossedhispath.

5 Georg Simon Ohm (1787–1854) was born and educated in Germany.After his breakthrough work in electricity, for which he used measuring andtesting equipment of his own design, he had hoped to receive a prestigiousuniversityprofessorship.Instead,afterhispublishedfindingsweredismissedbythescientificcommunityin1827,hewasforcedtoresignfromhishigh-schoolteachingposition and lived inpoverty for anumberofyears. In1841,hewasfinally recognized for the significance of his discovery and received a medalfrom the Royal Society of London. In 1849, five years before his death, heachieved his lifelong goal when he was appointed to a coveted position asprofessorofexperimentalphysicsattheUniversityofMunich.

6InAugust1955,inMoney,Mississippi,afourteen-year-oldNegroyouthfromChicago,EmmettTill,wasdraggedfromhisuncle’shomebyagroupofwhite men. His head was crushed and he was shot and thrown into theTallahatchieRiver.Till’smurderwasinretaliationforhisgoingintoagrocerystorethepreviousdayandwhistlingatthewhitewifeofthestoreowner.ManyconsiderthemurderofEmmettTilltohavebeenthesparkthatstartedthecivilrightsmovementinAmerica.Notuntilfiftyyearslater,inJune2005,wastherea conviction in the case, when Edgar Ray Killen, a former Ku Klux Klanmember,wasfoundguiltyofmanslaughter.

7 Joseph John Thomson (1856–1940), an English physicist known byfriendsasJ.J.,iscreditedasthediscovereroftheelectron.His1897discoverycausedasensationinscientificcircles,resultinginhiswinningaNobelPrizeforPhysicsin1906.Inperhapsthegreatestfather–sonstoryofmodernphysics,hisson,GeorgePagetThomson,wasawardedaNobelPrizeforPhysicsin1937forprovingthattheelectronisinfactawave.

8RichardFeynman,astorytelleratheart,sharedwithSin-ItiroTomonagaof Japan and Julian Schwinger the 1965 Nobel Prize in Physics for their“fundamental work in quantum electrodynamics, with deep-ploughingconsequences for the physics of elementary particles.” It turned out eachmanhaddonethesameworkindependently.WhileFeynman’sworkasexplainedbyhis diagrams was famously easy to understand, Schwinger’s overtly complexapproach rendered his writings nearly indiscernible. When informed thatSchwinger’s work was mathematically equivalent to his own, Feynmanexclaimed,“NowIhavebeentranslatedintohieroglyphics.”

9ErwinWilhelmMueller(1911–1977)wasaGerman-bornphysicistwhoinvented both the field emissionmicroscope and the field ionmicroscope, thelatter of which enabled him to be the first person ever to observe individualatoms.From1952untilhisdeath,hewasamuch-admiredmemberofthePennState Department of Physics, and received many recognitions, including(posthumously) theNationalMedalofSciencefromPresidentJimmyCarter in1977.

10Einstein’s new theories did not replace theNewtonian law of gravity,butsimplycompletedanincompletetheory.Whenthespeedofanobject,suchasamodern-dayrocket,ismuchlessthanthespeedoflight,Einstein’srelativitytheory for motion becomes the same as Newton’s theory of motion.Consequently,forweakgravitationalfieldsandrelativelyslowspeeds,Einsteinand Newton are in agreement. In fact, Newtonian gravity was all that wasneeded for man to successfully go to the moon and back. For man’s fartherexplorationsofothergalaxies,involvingrocketsflyingnearerthespeedoflight,Einstein’stheorieswillprevail.

11 Newton and German mathematician G. W. Leibniz (1646–1716)independently discovered the basis for calculus, one of the major scientificbreakthroughs of the modern era. Although Leibniz’s seminal work on thesubjectwaspublishedfirst,Newtondisclosednotesandotherevidenceshowingthat he had developed the same ideas twenty years earlier. For the last twodecades of his life,Newton fought a heated legal battlewithLeibniz over theauthorship of calculus. It is now generally accepted that Newton developed

calculusfirst,althoughitisstillunclearwhenhewouldhaveshareditwiththeworldhadnotLeibnizpublishedfirst.In1705,Newtonbecamethefirstscientisttobeknighted,andtothisdayisregardedasperhapsthegreatestscientistofalltime. Even Einstein ranked Newton number one; Einstein is usually rankednumbertwo.

12 Many years before Einstein, Austrian physicist Ludwig Boltzmann(1844–1906) established statistical mechanics as a means of showing thatquantitiesliketemperaturewereduetotheaverageenergyofmotionofmillionsof molecules. Boltzmann’s ideas were attacked by prominent physicists whodisbelieved the existenceofmolecules.Boltzmannwasamanwith a sensitivenature, and as a result of these rejections he suffered deep depression. Hecommittedsuicidebyhanging in1906whileonholiday in Italy.Thepreviousyear, Einstein had concluded his own work that would finally convince thescientific community of the existence of molecules, but in an era of slowcommunicationwordofEinstein’sworkdidnotreachBoltzmannintime.

13ThisEinstein–Lenardconnectionis ironic.In1923,Lenard,addressingtheGerman Physics Society, charged that “relativity is a Jewish fraud,whichone could have suspected from the first ... since its originator Einstein [is] aJew.” Lenard made this speech ten years before Hitler rose to power inGermany,aneventthatcausedEinsteintofleehisnativecountryfortheU.S.Inthe 1930s, Einstein helped many Jewish intellectuals living in danger inGermanytomigratesafely.Intheprocess,hebecamealeadingZionist.In1948,hewasofferedthefirstpresidencyofthenewstateofIsrael,whichhedeclinedonthegroundsthathewasnotapolitician.

14HarvardUniversityprofessorRoyJ.Glauber,eighty,wasthecorecipientofthe2005NobelPrizeinPhysicsforhisworkindevelopingasetofequationsthat accurately predict how photons behave in coherent light sources such aslasers.Astudentinthe1941graduatingclassatBronxHighSchoolofScience,GlauberattendedonlyoneyearatHarvardbeforebeingrecruitedtoworkontheManhattanProject,wherehewasassignedtocalculatingthecriticalmassofthebomb.Hewasonlynineteenatthetime.Afterworkingontheproblemfortwoyears,hewentbacktoHarvardandobtainedhisbachelor’sdegreeandhisPh.D.

15 Michael Faraday (1791–1867) is often considered the greatestexperimentalist in the history of science, even though he lacked a universityeducationandknewonlyelementarymathematics.RefusingtobelieveNewton’spremise that space is empty, Faraday, the son of a blacksmith, set up hisexperimentsinabasementinhisLondonflat.Largelyresponsibleforelectricitybecoming a viable technology, he contributed significantly to the fields ofelectromagnetism and electrochemistry. He also invented the earliest form ofwhat came to be known as the Bunsen burner, which is used universally insciencelaboratoriesasaconvenientsourceofheat.

16Atomicclockskeeptimebetterthanotherclocks;however,theyarenotradioactive,nordotheyrelyonatomicdecay.Likeordinaryclocks,theyhaveanoscillatingmassandaspringanduseoscillationstokeeptrackofpassingtime.The big difference is that the oscillation in an atomic clock is between thenucleusofanatomandthesurroundingelectrons,insteadofbetweenthebalancewheelandhairspringofaclockworkwatch.Atomicclockskeeptimebetterthanthe rotationof the earth or themovement of the stars.Without atomic clocks,GPSnavigationwould be impossible, the Internetwould not synchronize, andthepositionoftheplanetswouldnotbeknownwithenoughaccuracyforspaceprobesandlanderstobelaunchedormonitored.

17ErnestRutherford(1871–1937),anativeofNewZealand,isconsideredthefatherofnuclearphysics.HewontheNobelPrizeinChemistryin1908fordemonstrating that radioactivity is the spontaneous disintegration of atoms.During his investigation of radioactivity, he coined the terms alpha, beta, andgammarays.HistorianssuggestthatRutherfordistotheatomwhatDarwinistoevolution, Newton to mechanics, Faraday to electricity, and Einstein torelativity.

18Ihavesincecometobelievethatitisamyththattheirbestworkisdonebythetimephysicistsareintheir twenties,althoughit is truethatanumberofoutstanding contributions have been made by twenty-something physicists.However, due to the very nature of physics, which requires the accumulatedacquisition of knowledge of the physical world, physicists often make

groundbreaking contributions later in life. One need only mention Planck’squantum theory, Schrödinger’s quantum mechanics, and Einstein’s generaltheoryofrelativity;breakthroughworkconductedbythesepillarsofphysicsatages forty-two, forty-two, and thirty-seven respectively. And, of course, eachone of them contributedmightily to the discipline throughout their long lives.Einstein, in fact, was found working physics calculations on his deathbed in1955,atageseventy-seven.

19JohnA.Wheelerwasnotthefirsttopredicttheexistenceofblackholes.In1939,AmericanphysicistJ.RobertOppenheimer,whowouldlaterdirecttheManhattan Project and the building of the atomic bomb, and his graduatestudent, Hartland Snyder, published a paper in Physical Review entitled “OnContinuedGravitationalCollapse.”ThiswasthefirstpredictionusingEinstein’stheoryofgeneralrelativityregardingthefinalfateofastarsufficientlymassivethat light cannot escape it. Ironically, Wheeler initially disagreed withOppenheimer’sprediction,butlaterbecameanapostleofthisfinalstate,whichhefamouslylabeledablackhole.

20JosephH.Taylor,Jr.,bornin1941,andRussellA.Hulse,bornin1950,shared the 1993 Nobel Prize in Physics for “the discovery of a new type ofpulsar, a discovery that has opened up new possibilities for the study ofgravitation.” Today, Taylor and Hulse, formerly teacher and student,respectively,arebothprofessorsofphysicsatPrincetonUniversity.

21KipThorne,borninLogan,Utah,in1940,receivedhisBSdegreesfromCaltechin1962andhisPh.D.fromPrincetonUniversityin1965.HereturnedtoCaltech,whereheiscurrentlyFeynmanProfessorofTheoreticalPhysics.Hisresearch is focused onEinstein’s general theory of relativity and astrophysics,with emphasis on relativistic stars, black holes, and especially gravitationalwaves.More than forty physicists have received their Ph.D.s atCaltech underThorne’s personal mentorship. Thorne is known for his kind demeanor andrather modest bearing; he insists on being addressed by his first name andkeepingintouchwithhisstudentsevenwhenheisonvacation.

22KarlSchwarzschild(1874–1916)wasborninFrankfurt.Achildprodigyofsorts,hehadascientificpaperonorbitspublishedwhenhewasonlysixteen.At the outbreak ofWorldWar I in 1914, he joined theGerman army despitebeingoverfortyyearsold,andservedasanartilleryofficer.Hediedtwoyearslater,reportedlyfromanillnesscontractedwhileservingontheRussianfront.

23KrisLarsenandIbothconsiderourexperience“partyingwithHawking”to be the most unique at any of the many—and often staid—academicconferenceswehaveattended.Infact,Kris,whotodayisaprofessorofphysicsand astronomy at Central Connecticut State University and director of theuniversity’shonorsprogram,woulddescribe the incident in the introduction toher first book, Stephen Hawking: A Biography (Greenwood Press, 2005).“According to Einstein, the speed of light is the ultimate speed limit of theuniverse,” Kris wrote, “but somehow Ron managed to get dressed again andarriveatthepartyevenfaster.”

24 Richard Chase Tolman (1881–1948) was born in West Newton,Massachusetts.HereceivedhisPh.D.fromMITin1910andwasaprofessorofphysical chemistry and mathematical physics and the dean of the graduateschool at Caltech. He made many important contributions to statisticalmechanicsandcosmology,includingthehypothesisofanoscillatinguniverse(aclosed-universe model in which the expansion of the universe slows andreverses, causing a collapse into a singularitywhich then explodes into a newuniverse, repeating the cycle). Tolman was a close friend of J. RobertOppenheimer, who used mathematical techniques developed by Tolman toanalyzethefinalstateofcollapsedstars,latertobeknownasblackholes.

25DonaldA.Glaser, born in 1926, has been a professor of physics andneurobiologyintheGraduateSchooloftheUniversityofCalifornia(Berkeley)since1989.HetoldreportersinPalmCoast,Florida,wherehewasvacationingat the time hisNobel Prizewas announced, thatwinning the award created aproblem.“Itmakesitveryhardtocontinuetodoscience.It’shardtodisciplineyourselftorecognizethatthenextthingyoudowon’tbeasimportant.”

26For a time, I considered the possibility that slowingdown lightmightincrease the gravitational frame-dragging effect of the ring laser. RecentexperimentsbyLeneHauofHarvardUniversityandRonaldWalsworthof theHarvard Smithsonian Center for Astrophysics had shown that light could besloweddownfrom186,000milespersecondtoonlyafewmilesperhour.Slowlight,however,turnedoutnottobehelpfulformyresearch.

27 The special theory of relativity deals only with objects that have aconstantandunchangingvelocity,ratherlikeacarthatstaysataconstantspeedof sixty-fivemiles per hour. In contrast, the general theory ismore general innature (hence its name), dealing not only with objects that have a constantvelocitybutalsoonesthataccelerateanddecelerate.

28PhilippLenard(1862–1947)wasanAustrian-bornphysicistandwinneroftheNobelPrizeforPhysicsin1905forhisresearchoncathoderaysandthediscoveryofmanyof theirproperties.Lenardwasa strongGermannationalistandmemberoftheNationalSocialistParty.DuringtheNaziregime,hewasanoutspokenproponentoftheideathatGermanyshouldrelyon“Aryanphysics”toconquer the world, and ignored what he believed to be the misleading andfallaciousideasof“Jewishphysics,”bywhichhemeantchieflythetheoriesofEinstein.

29 Photonics as a field began in 1960 with the invention of the laser.Thereafter, it evolvedwith the development of optical fibers as amedium fortransmitting information using light beams, aswell as theErbium-doped fiberamplifier, inventions that formed the foundation for the telecommunicationsrevolutionofthe1990sandprovidedtheinfrastructurefortheInternet.

30CharlesH.Townes,bornin1915inGreenville,SouthCarolina,receivedhisPh.D. from theCalifornia Institute ofTechnology. In1964, he shared theNobelPrizeinPhysicswithtwoRussians,NicolayG.BasovandAleksandrM.Prokhorov,forfundamentalworkinthefieldofquantumelectronics,whichledtothedevelopmentofmasers(microwaveamplificationbystimulatedemissionofradiation)andlasers(lightamplificationbystimulatedemissionofradiation).

TownesispresentlyattheUniversityofCalifornia,Berkeley.

31C.FrancisEverittwasborninKent,England,in1934.HereceivedaPh.D. in physics from Imperial College, University of London, in 1959. As aresearchassociateattheUniversityofPennsylvania,Everittconductedresearchon liquid helium, which led him to become interested in using gyroscopes atvery low temperatures as apossiblemeans to testEinstein’sgeneral theoryofrelativity.Since1962hehasbeenatStanfordasaprofessorofphysics.

32Unlike an equatorial orbit, the planeof a polar orbit changeswith therotationoftheearth.Theequatorialplanerotatesarounditself,ratherlikeputtingacoinonitsedgeandrollingitacrossatable.Theplaneofapolarorbitismorelikerotating(orflipping)thecoinfromonesidetotheother.

33 On October 28, 2005, Francis Everitt spoke at UConn’s physicscolloquiumduringitsEinsteinCentennialcelebration(thehundredthanniversaryofEinstein’sspecialtheoryofrelativity).Duringaquestion-and-answerperiod,hewasadamantaboutnotdiscussingorspeculatingabouttheresultsofGravityProbeB until the data has been analyzed.He estimated that resultswould bepublished sometime in 2007. Should Everitt and his team observe the frame-draggingeffectduetotherotatingearth,itwillsupportEinstein’sgeneraltheoryofrelativity,aswellasthefoundationuponwhichmytime-travelworkisbased.If this turns out to be a negative experiment, in which Einstein’s theory isdisproved,itwouldbethemajorsciencestoryofmylifetime.Whatwillnotbeproven by Gravity Probe B is whether frame dragging also occurs in thegravitationalfieldofacirculatingbeamoflight.

34 The first contribution was made by New York composer andbusinessmanDavidZinn,whosefather,WilliamZinn,wasthemusicalarrangerforHenryMancini.BothZinnscametoUConntomeetwithme,Chandra,andfoundation director Frank Gifford for what felt like a high-energy summitconferencebetweentheartsandsciences.

35Present-dayspaceexplorationisdominatedbychemicalrockets.Theserockets have the advantage of great thrust. However, the velocities achievedmakespacetraveltodistantplanetsaverylengthyaffair.Thereareotherformsofrocketpropulsionthatarecurrentlybeingconsideredthat—whilehavinglittlethrust—burn for longperiodsof time toprovidea steadyacceleration that canleadtoveryhighvelocities.Anexampleofsuchanengineistheelectrostaticionpropulsion drive. The rocket exhaust of such an engine consists of a beam ofcharged atoms or ions. Typically, a chemical rocket could make a flybyexcursion of Pluto in forty-three years. In contrast, an ion rocket with acontinuous acceleration as small as .0001 feet per second could make thejourneyinaboutthreeandahalfyears.

Index

A

academia,(i)Adams, Fred, (i), (ii), (iii), (iv) Advanced Research Projects Agency

(ARPA),(i)African-Americanscientists,(i),(ii),(iii)airforce,(i),(ii),(iii)AlbertEinstein:Philosopher-Scientist,(i)algebraclass,(i)amyotrophiclateralsclerosis(ALS),(i)angioplastysurgery,(i)approximations,(i)Association for Relativistic Dynamics Third Biennial Conference, (i)

AstrophysicalJournal,(i),(ii)atomicbomb,(i),(ii)atomicclock,(i),(ii)atoms,(i),(ii),(iii),(iv),(v),(vi),(vii),(viii)Augustine,Saint,(i)Austin,Texas,(i)

B

BacktotheFuture,(i),(ii)Baldwin,James,(i)Barnett,Lincoln,(i)Bartram,Ralph,(i)Basov,NicolayG.,(i)Bathgate,John,(i),(ii)batteryvoltage,(i)BeingandTime,(i),(ii)BidTimeReturn,(i)BigBangtheory,(i),(ii),(iii)Biloxi,Mississippi,(i)binarycode,(i)binarystars,(i),(ii)blackholes,(i),(ii),(iii),(iv),(v)evaporatingblackholes,(i)primordialblackholes,(i)radiatingblackholes,(i)rotatingblackholes,(i),(ii),(iii),(iv),(v)blackpowermovement,(i)Bohr,Niels,xiv,(i),(ii),(iii),(iv),(v),(vi)Boltzmann,Ludwig,(i)

Bonis,Scott,(i)Booleanalgebra,(i)Born,Max,(i)BostonGlobe,(i),(ii)Bowie,Ben,(i)Bowie,David,(i)ABoyandHisDog,(i)Bradbury,Ray,(i)BringtheJubilee,(i)Britt,May,(i),(ii)Brooks,Michael,(i),(ii)Brown,Robert,(i)Brownianmotion,(i),(ii)bubblechambers,(i)Budnick,Joseph,(i),(ii),(iii)Bunsenburner,(i)TheButterflyEffect,(i)

C

calculus,(i),(ii),(iii)Carter,Brandon,(i)CenterforTheoreticalPhysics,(i),(ii)chemicalrockets,(i)childuniverse,(i),(ii)chronologyprotection,(i)ChronologyProtectionHypothesis,(i)circulartimelines,(i)circulatingbeamoflight,(i),(ii)CivilRightsActof1964,(i)Clark,Ronald,(i)ClassicsIllustrated,(i),(ii)clocks,(i),(ii), (iii), (iv),(v),(vi)closedtime-

likecurve,(i)“ClosedTimelikeCurves Produced by a Pair ofMovingCosmicStrings:

Exact Solutions”, (i) closed time-like lines, (i), (ii), (iii), (iv) closed time-likeloops,(i),(ii),(iii),(iv)closedtimeloops,(i),(ii),(iii),(iv),(v),(vi),(vii)closedtimeline,(i)

Colborn,Robert,(i)Collins,Joan,(i)computers,(i),(ii),(iii)TheConfessionsofSt.Augustine,(i)Contact,(i)

“OnContinuedGravitationalCollapse”,(i)cosmicrays,(i)cosmicstrings,(i),(ii)“Cosmological Considerations on the General Theory of Relativity”, (i)

cosmologicalconstant,(i),(ii),(iii)cosmology,(i),(ii)“CouplingbetweenTimeReversalandtheSpace-TimeSymmetriesof the

deSitterUniverse”,(i)cryogenicprobe,(i)CubanMissileCrisis,(i)curvedspace,(i),(ii),(iii),(iv),(v),(vi)CygnusX-1,(i)cylinders,(i)

D

Daseinconcept,(i)Davis,Sammy,(i)deSitter,Wilhelm,(i),(ii)deSittersolution,(i),(ii)deSitterspace,(i),(ii)deSitteruniverse,(i)death,(i),(ii)Defense Advanced Research Project Agency (DARPA), (i) deflection of

starlight,(i)DeltaIIrocket,(i)Dennison,David,(i)depression,(i),(ii)deuteriumatoms,(i)Deutsch,David,(i)DeWitt,Bryce,(i),(ii)dimensions,(i)diodelaser,(i)Dirac,Paul,(i),(ii)divorce,(i)“TheDynamicsofSpace-time”,(i),(ii)

E

Eddington,Arthur,(i),(ii)“The Effect of the Kerr Metric on the Plane of Polarization of an

ElectromagneticWave”,(i)TheEgoandtheId,(i)Einstein,Albert,(i),(ii)centennialofbirth,(i)cosmologicalconstant,(i),(ii),(iii)curvedspace,(i),(ii)electromagneticforce,(i)energy,(i)fieldequations,(i),(ii),(iii),(iv),(v),(vi),(vii),(viii)gravity,(i),(ii),(iii),

(iv)molecules,(i)personallife,(i),(ii)quantumtheory,(i),(ii)radiation,(i)relativity,(i),(ii),(iii),(iv),(v),(vi),(vii),(viii),(ix),(x),(xi),(xii),(xiii),

(xiv),(xv),(xvi),(xvii)stars,(i)statistics,(i)teaching,(i)tunnels,(i)Einstein,Eduard,(i)Einstein,Elsa,(i)Einstein,HansAlbert,(i),(ii)Einstein-Infeld-Hoffman(EIH)problem,(i),

(ii) Einstein–Lenard connection, (i) Einstein, Mileva Maric, (i), (ii) Einstein:ProfileoftheMan,(i)Einstein-Rosenbridge,(i)

Einstein:TheLifeandTimes,(i)electricfield,(i)electricalattraction,(i)electricalcircuit,(i)electricity,(i),(ii)electromagnetism,(i)force,(i),(ii)lighttheory,(i)radiation,(i)electronics,(i),(ii),(iii)electrons,(i),(ii),(iii),(iv),(v),(vi),(vii),(viii)electrostaticionpropulsion

drive,(i)electroweaktheory,(i)elementary particle physics, (i) “Emission and Absorption of Radiation

AccordingtotheQuantumTheory”,(i)energy,(i),(ii)Erbium-dopedfiberamplifier,(i)Everett,Hugh,(i),(ii)“TheEverettInterpretationofQuantumMechanics”,(i)Everitt,Francis,(i),

(ii)

Evolution of Evaporating Black Holes and an Inflationary Universe, (i)exactsolutions,(i),(ii),(iii)existence,(i)

expandinguniverse,(i),(ii)experimentalphysics,(i)extrasolarplanets,(i)extraterrestrialcivilizations,(i)

F

Fajans,Kasimir,(i)Faradayeffect,(i)Faraday,Michael,(i),(ii),(iii)father,(i),(ii),(iii),(iv),(v),(vi),(vii)FBI,

(i)Fermi,Enrico,(i)Feynmandiagrams,(i),(ii)TheFeynmanLecturesonPhysics,(i)Feynman,Richard,(i),(ii),(iii),(iv)

Ficker,Ida,(i)fifthdimension,(i)TheFinalCountdown,(i)Finkelstein,David,(i)TheFireNextTime,(i)Fleming,Gordon,(i),(ii),(iii),(iv)ForbiddenPlanet,(i)forcesintheuniverse,(i)Ford Foundation Senior Postdoctoral Fellowship, (i) Foundations of

Physics,(i)Fox,Gray,(i)Fox,MichaelJ.,(i)framedragging,(i),(ii),(iii),(iv),(v),(vi),(vii),(viii),(ix)Fraser,Keith,(i)Fraser,Ted,(i)Frequency,(i)Freud,Sigmund,(i)Fry,Dorothy.SeeMallett,DorothyFryFry,Ken,(i)funding,(i)Furrer,Ethelyn,(i)

G

galaxy,(i),(ii)gaugetheory,(i),(ii)Geeter,Joan,(i)generalrelativity,(i),(ii),(iii),(iv),(v),(vi)geometricconstraint,(i)Gey,Marjorie,(i)Gifford,Frank,(i)Gill,Tepper,(i)Glaser,Donald,(i),(ii)Glashow,Sheldon,(i),(ii)Glauber,Roy,(i),(ii)“Global Structure of theKerr Family of Gravitational Fields”, (i) Godel,

Kurt,(i),(ii),(iii),(iv)Gott,J.R.,(i),(ii)Götterdämmerung,(i)Gould,Gordon,(i)GrandfatherParadox,(i)grandparents,(i),(ii)“TheGravitationalFieldofaCirculatingLightBeam”,(i)gravity,(i),(ii),

(iii),(iv),(v),(vi),(vii),(viii),(ix)gaugetheory,(i),(ii)gravitationalfield,(i),(ii)gravitationalfieldequations,(i),(ii),(iii),(iv),(v)gravitationalforce,(i)“TheGravityofCirculatingLight:APossibleRoute toTimeTravel”, (i)

GravityProbeB,(i),(ii)Griswold,Doug,(i)Grossman,Marcel,(i)Groton,Connecticut,(i)Guth,Alan,(i),(ii),(iii)gyroscope,(i)

H

Hakmiller,Karl,(i)Haller,Kurt,(i),(ii)Hau,Lene,(i)Hawkingradiation,(i)Hawking,Stephen,(i),(ii),(iii),(iv)heartproblems,(i),(ii)heavy-hydrogenatoms,(i)heavyphoton,(i)

Heidegger,Martin,(i),(ii)Heisenberg,Werner,(i),(ii),(iii),(iv)heliumatom,(i)Hoffman,Banesh,(i),(ii)Horwitz,L.P.,(i)HowtheLaserHappened,(i)Hubble,Edwin,(i)HughesAircraft,(i)Hulse,Russell,(i),(ii)hydrogenatom,(i),(ii)

I

id,(i)IdeasandOpinions,(i)inducedabsorption,(i)industrialscientists,(i)inflationaryuniverse,(i)Infeld,Leopold,(i)Institute for Advanced Studies at Princeton, (i), (ii), (iii) International

Association for Relativistic Dynamics (IARD) Conference, (i), (ii), (iii)InternationalCenterforTheoreticalPhysics,(i)invisiblecompanion,(i)

J

John,Sajeev,(i)JournalofMathematicalPhysics,(i)

K

Kaluza-Kleintheory,(i)Kaluza,Theodor,(i)KeeslerAirForceBase,(i),(ii)Kennedy,RobertF.,(i)Kerrblackholes,(i),(ii),(iii)Kerr,RoyP.,(i),(ii)Khanna,Parveen,(i)Killen,EdgarRay,(i)Kimbrough,Jones,(i)Kimbrough,Pinky,(i),(ii)

Kimbrough,William,(i),(ii)King,MartinLuther,(i),(ii),(iii)Klein,Oskar,(i)

L

LacklandAirForceBase,(i),(ii)Landau,Martin,(i)Larsen,Kristine,(i),(ii)lasers,(i),(ii),(iii),(iv),(v)diode(i)holedrilling,(i),(ii),(iii)TheLearningChannel,(i)Leibniz,G.W.,(i)Lenard,Philipp,(i),(ii),(iii),(iv)Lense,Joseph,(i)Levine,SumnerN.,(i)light,(i),(ii),(iii),(iv),(v),(vi),(vii)beams,(i),(ii)circulatingbeam,(i)clock,(i)color,(i)cone,(i)cylinder(LC),(i)ray,(i)speed,(i),(ii),(iii),(iv)travel,(i)lineardifferentialequations,(i)Lloyd,Christopher,(i)LockbourneAirForceBase,(i),(ii)Lorentz,Hendrik,(i),(ii)Lorentztransformation,(i),(ii),(iii),(iv)LOTART,(i)LouGehrig’sDisease,(i)

M

magenticfield,(i),(ii),(iii),(iv)Maiman,Theodore,(i)Mallett, Boyd, (i), (ii), (iii), (iv), (v), (vi), (vii)Mallett,Dorothy Fry, (i),

(ii),(iii),(iv),(v),(vi),(vii)automobileaccident,(i)divorce,(i)marriage,(i)pregnancy,(i)Mallett,DorothyKimbrough,(i),(ii),(iii),(iv),(v)Mallett,Etta,(i)Mallett,Eve,(i),(ii),(iii)Mallett,Ira,(i)

Mallett,Jason,(i),(ii)Mallett,Keith,(i),(ii),(iii)TheManWhoFelltoEarth,(i)ManhattanProject,(i),(ii),(iii),(iv),(v)manifestcovariant,(i)Maric,Mileva,(i),(ii)MarkiteCorporation,(i)maserprinciple,(i),(ii)master’sprogram,(i)mathematics,(i),(ii),(iii),(iv)Matheson,Richard,(i)Maxwell,JamesClerk,(i)Mayor,Michel,(i)McDonald,Deborah,(i)McLaughin,Dan,(i)Michelmore,Peter,(i),(ii)Michelson,A.A.,(i)militaryfunding,(i)Minkowski,Herman,(i)missingmatterproblem,(i)ModernScienceandTechnology,(i)molecules,(i),(ii),(iii)Monroe,Marilyn,(i),(ii)Moore,C.L.,(i)Moore,Ward,(i)Morley,E.W.,(i)Morris,M.,(i)mother,(i),(ii),(iii),(iv),(v)movies,(i)moving-boundaryproblem,(i)movingclock,(i),(ii),(iii)Mueller,ErwinWilhelm,(i),(ii)muon,(i)music,(i)

N

NationalAeronauticsandSpaceAdministration (NASA), (i), (ii)NationalMedalofScience,(i)

National Science Foundation (NSF), (i) National Science FoundationTraineeship,(i)NationalSocietyofBlackEngineers,(i)navy,(i)

neutron,(i),(ii),(iii),(iv)neutronstar,(i)NewScientist,(i),(ii),(iii)Newcomb,Simon,(i)

Newton,Isaac,(i),(ii),(iii),(iv)calculus,(i),(ii)gravity,(i),(ii),(iii)motion,(i)space,(i)NobelPrizeBasov,NicolayG.,(i)Bohr,Niels,(i)Dirac,Paul,(i)Einstein,Albert,(i),(ii)Fermi,Enrico,(i)Feynman,Richard,(i),(ii)Glaser,Donald,(i),(ii)Glashow,Sheldon,(i),(ii)Hulse,Russell,(i)Lenard,Philipp,(i)Lorentz,Hendrik,(i)Planck,Max,(i)Prokhorov,AlexsandrM.,(i)Richter,Burton,(i)Rutherford,Ernest,(i)Salam,Abdus,(i),(ii)Schrödinger,Erwin,(i)Schwinger,Julian,(i)Taylor,Joseph,(i),(ii)Thomson,GeorgePaget,(i)Ting,SamuelC.C.,(i)Tomonaga,Sin-Itiro,(i)Townes,Charles,(i)Weinberg,Steven,(i),(ii)nonlineardifferentialequation,(i)nonviolentresistance,(i)normaltime,(i)nuclearfission,(i)nuclearforce,(i),(ii)

O

Ohm,GeorgSimon,(i),(ii)

Ohm’slaw,(i)opals,(i)Oppenheimer,Robert,(i),(ii),(iii),(iv),(v)opticalfibers,(i),(ii)opticalmaser,(i)TheOuterLimits,(i)

P

parallel–worldstheory,(i),(ii)parents,(i)patents,(i)Pauliexclusionprinciple,(i)Pauli,Wolfgang,(i),(ii)Pennsylvania State University, (i), (ii), (iii), (iv), (v), (vi), (vii), (viii)

Peterson,Cynthia,(i)Peterson,Jerry,(i),(ii),(iii)Ph.D.programs,(i)philosophy,(i)photoelectriceffect,(i),(ii),(iii),(iv)photonics,(i),(ii)crystals,(i)photons,(i),(ii),(iii)PhysicalReview, (i), (ii), (iii), (iv), (v), (vi) PhysicalReviewLetters, (i),

(ii)physicsclass,(i)PhysicsLettersA,(i),(ii),(iii),(iv),(v)PhysicsToday,(i)piano,(i)Planck,Max,(i),(ii)Poe,EdgarAllan,(i)polarorbit,(i),(ii)polarizationoflight,(i)populationinversion,(i)“PositionOperatorsina(3+1)deSitterSpace”,(i)positrons,(i)potentialdifference,(i)Pratt&WhitneyAircraft,(i),(ii),(iii),(iv)precession,(i)preventionbynature,(i)primordialblackholes,(i)PrincipleofRelativity,(i),(ii)Prokhorov,AlexsandrM.,(i)protons,(i),(ii),(iii),(iv)provisionalpatent,(i)pulsar,(i)

Q

Quaid,Dennis,(i)quantum electrodynamics, (i), (ii) quantummechanics, (i), (ii), (iii), (iv),

(v), (vi), (vii), (viii), (ix)QuantumPhysics ofElectronics, (i) quantum theory,(i),(ii),(iii),(iv)Queloz,Didier,(i)

R

racism,(i),(ii),(iii),(iv),(v),(vi),(vii),(viii),(ix)radiatingblackholes,(i),(ii) “Radiating Vaidya Metric Imbedded de Sitter Space”, (i) “Radiation andFalseBubbleDynamics”,(i)radiowaves,(i)

radioactivedecay,(i)radioactivity,(i)“TheRaven”,(i)Reeve,Christopher,(i)relativisticastrophysics,(i)Relativity,GroupsandTopology,(i)relativityphysics,(i)relativitytheorygeneralrelativity,(i),(ii),(iii),(iv),(v),(vi),(vii),(viii),(ix),(x),(xi),(xii),

(xiii),(xiv)motion,(i),(ii),(iii)specialrelativity,(i),(ii),(iii),(iv),(v),(vi),(vii),(viii),(ix),(x),(xi)time,

(i),(ii),(iii),(iv)Relativity,Thermodynamics,andCosmology,(i)researchfunding,(i)Reynolds,Esther,(i)Richter,Burton,(i)ringlaser,(i),(ii),(iii),(iv),(v)TheRingoftheNibelung,(i)rockets,(i)Rodwell,Judy,(i)RollingStone,(i),(ii)Rosen,Nathan,(i)rotating black holes, (i), (ii), (iii), (iv), (v) “Rotating Cylinders and the

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S

sabbatical,(i)Sagan,Carl,(i)Salam,Abdus,(i),(ii)SanAntonio,Texas,(i),(ii)Saturn5rocket,(i)Schiff,Leonard,(i)Schilpp,PaulArthur,(i)Schrödinger, Erwin, (i), (ii), (iii) Schrödinger’s equation, (i), (ii), (iii)

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T

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U

uncertainty principle, (i), (ii) unified field theory, (i), (ii) UnitedAircraftResearch

Laboratories,(i)UnitedTechnologies,(i),(ii),(iii),(iv)TheUniverseandDr.Einstein,(i),

(ii), (iii) University of Connecticut, (i), (ii) The University of ConnecticutFoundation,(i)UniversityofMichigan,(i)

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V

Vaidya–deSittersolution,(i)Vaidyasolution,(i),(ii)VandenbergAirForceBase,(i)vectors,(i)Verne,Jules,(i)“VintageSeason”,(i)Volta,Alessandro,(i)

W

Wagner,Richard,(i),(ii)Walker,Barry,(i)WallStreetJournal,(i),(ii)Walsworth,Ronald,(i)Watkins,Charles,(i)WattsRiots,(i)waveequation,(i),(ii)wave function, (i), (ii), (iii), (iv) “Weak Gravitational Field of the

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Y

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Z

Zparticle,(i)Zinn,David,(i)Zinn,William,(i)Zionism,(i)