REVIEWS

Jonathan Simon

Learning physics from science fictionBeyond Star Trek: Physics from Allen Invasion*

to DM End of Tuiw

1997 Basic Books 176pp $2100

Many science-fiction authors try to use ideasfrom the cutting edge of science beforeexploring the human and technologicalconsequences of these ideas. It is, however,rarer to see an author go in the oppositedirection - in other words, one who startswith popular ideas from science fiction,before tackling the relevant physics.

It may sound somewhat surprising thattopics such as unidentified flying objects(UFOs) and extrasensory perception shouldhave any relevant physics, but they do. Andanyone who wants to evaluate such phenom-ena even remotely seriously will find thatthere is physics one needs to be aware of andunderstand - even if one expects to eventu-ally dismiss the ideas. In his last book, ThePhysics of Star Trek (HarperPerennial 1996),Lawrence Krauss - a particle astrophysicist

Physics, but not as we know It - Starship Enterprise

fun and also serves a higher purpose. Histechnique is to bring up a specific science-fic-tion idea and then discuss the relevant phys-ical principles. In this way the reader ends upunderstanding some solid physics. For ex-ample, anyone who wants to investigate thepotential mechanisms by which extrasensoryperception might be transmitted and re-ceived - assuming, for the moment, that itexists in some form - should first have a goodworking knowledge of electromagnetdsm.

"Newton's second lawbecomes interesting whenyou try to apply it to UFOs."at the Case Western Reserve University inthe US - explored topics from contemporaryphysics in the context of the science fictionscries Star Trek. This sequel continues in thesame vein, boldly going where no physicswriter has gone before, to paraphrase thefamous opening lines of the series.

In addition to Star Trek itself, Krauss thistime looks at the movies Independence Day andStar Wars, as well as the television series TlieX Files. (I should point out, however, thatone docs not need to have seen Star Trek,Independence Day, Star Wars or The X Files toenjoy the discussions.) There arc also generalreferences to other concepts that are familiarfrom science fiction and fantasy. For exam-ple, Krauss addresses the physics of interstel-lar trawl, the frequency of extrasolar planetsand the potential mechanisms behind extra-sensor)' perception. He also looks at how thelaws of physics would need to be obeyedeven if time travel were permitted.

The easiest way to approach the physics ofscience fiction would be to find flaws in thescience-fiction physics, and then explain thefallacies. Krauss has taken a more difficultroad that is at least as interesting, still lots of

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Of course, diere are plenty of good rea-sons why extrasensory perception is unlikelyto be D'ansmitted by classical electromagnet-ism. But before one can understand diesereasons, one must first learn some basic elec-tromagnetism, and extrasensory perceptionis at least an entertaining motivation to doso. Similarly, to understand the limitations ofspaceships, one needs a grounding in New-tonian propulsion theory (and a few tidbitsof general relativity). However, in the handsof the wrong teacher in a lecture hall, thistopic could be a bit on the dry side. Butdelivered by Krauss, in the context of space-ships, it takes on a whole new attraction.

Another almost insidiously delivered les-son is in probability and statistics, whichtakes place while the author evaluates thelikelihood of finding extrasolar intelligentlife. Krauss introduces, describes and thencritiques die Drake equation, which esti-mates the number of intelligent civilizationsin the galaxy. This estimate is calculated asthe number of stars in die galaxy, multipliedby the probability diat such a system has anEarth-like planet, multiplied by the probab-ility of the star being stable long enough for

life to evolve, multiplied by die probability of1 life evolving into intelligence, and so on.; Of course, most of diese probabilities areunknown, but the equation at least allowsone to compartmentalize our ignorance.Krauss also points out that many of diescprobabilities are not independent, andshould not therefore be merely multiplied.This leads into an intelligent, entertainingdiscussion on the distinction betweenabsolute and conditional probabilities, andby the time the chapter is over, the readerhas learned much more than originallybargained for.

While reading and thinking about popu-lar ideas in current science fiction, such asUFOs and extrasensory perception, one canlearn a lot of interesting and fundamentalphysics. To die average science-fiction fan,the physics of Newton's second law palesnext to ideas like die particle-wave dualityof quantum mechanics or the space-timc-warping physics of general relativity. ButNewton's second law suddenly becomesinteresting when your try to apply it toUFOs that make instantaneous right-angleturns at supersonic speeds. Basic electro-magnetism, meanwhile, becomes intriguingwhen applied to extrasensory perceptionmessages transmitted from one person'sbrain to another.

Often the same person enjoys science fic-tion and science itself, since both can inspirethe imagination in similar ways. Indeed,someone who is not (or not yet) a profes-sional scientist may find diat exploring onearea enhances die exploration of the other.The ideal readers for this book will thereforebe curious science-fiction fans and - to aslightly lesser extent - professional (or stu-dent) physicists who fancy a bit of sciencefiction. The book should also, I believe, bemandatory reading for science-fiction wri-ters. Both physics novices and physicsexperts alike will find the physics discussionsinteresting and amusing. And experts inbotii physics and science fiction will findpleasingly little to quibble about, since dieauthor obviously knows both subjects well.

Johnathan Simon Is a postdoctoral researcher In

computational neuroscience at the Institute for

Systems Research at the University of Maryland,

US. He originally trained in theoretical general

relativity and wrote "The physics of time travel" in

the December 1994 issue of Physics World

PhysicsWebBooks reviewed in PhysicsWorid can beordered on-line at http://physicsweb.org/

PHYSICS WOULD J«»U«RY 1998