4/19/06 Atoms and Stars, Class 14 1

Atoms and StarsIST 2420

and IST 1990

Class 14Winter 2006

Instructor: David BowenCourse web site: www.is.wayne.edu/drbowen/aasw06IST 1990 Moodle: techtools.culma.wayne.edu/moodle

4/19/06 Atoms and Stars, Class 14 2

Agenda

• Assignments, passbacks, initial signin sheet• Pick up:

o Notes for Class 14• Class information

o Special Grade Request if much work will be late• Review of readings• Emphasizing main points one more time• Updates: natural disasters & bird flu• Lab 11: The Orbiting Bottle

4/19/06 Atoms and Stars, Class 14 3

Upcoming …

• Tonight is the last regular classo Essay 2 dueo Review for Final Exam

• April 26: nothing that night but the Final Exam

• Opportunities for extra help:o Review Session during classo 5 – 6 PM before Final (April 26)o Telephone, email, set up a time

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My new cell phone number

• 248-376-9848• This is the number to call during 5 – 6 PM

office hours

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Semester is Ending!

• If you have been relying on being able to turn work in late, it is late!o Alternatives: D, E, I, X, drop – see counselor!

• Getting ready for Final:o Read Information Sheet carefully – a lot of

information thereo Look at Final Topics carefullyo Use Review Session!

• Final Where-Is handed out at the previous class

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Course Grades• If you are turning a bunch of work in at the

end, I may not get it graded in time for the regular grades (see the Syllabus).

• If this is you (turning it in late), what grade do you want for the regular grade? E, X, I

• Fill in the Grade Request form (get a copy from me) to let me know – otherwise it’s my choice.

• You can withdraw (W) through April 25• Medical Withdrawal

4/19/06 Atoms and Stars, Class 14 7

Your Current Status

• Grades I have for you:o Online Grade Report, link off the course web

site (see first slide)o Enter first name, last name, password the get

report• Grade you are headed for:

o Grade What-If on course web site• Ask for help with these if you are having

problems

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Makeup for Final Exam

• Let me know by email that you want a makeup, within 24 hours after the Final (University regulation)

• Date / Time Friday May 26 6 PM on campus

• Watch for later email about building and room (but I won’t send you an email unless you send me the email at the top bullet)

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Lab 7 Questions at end

A. Weight does not set flotationB. Specific Gravity < 1 (water) floatC. Ice floats Specific Gravity < 1D. Specific Gravity useful in deciding what

material an object is made ofE. Archimedes right, displaced volume =

object volumeF. If S.G.object < S.G.liquid, then object floats in

liquid. dumbbell floats in Mercury.

4/19/06 Atoms and Stars, Class 14 10

Lab 11: Orbiting Bottle

• If your two results (A & B) for the horizontal (inward) force, FH, agree, then your data are consistent with Newton’s Laws (including Universal Law of Gravitation).

• See Theory section for the proof of this

4/19/06 Atoms and Stars, Class 14 11

Brain Candy…Wormhole• A theoretical possibility within Einstein’s

General Theory of Relativity (1916)o A shortcut through 4-D space-time that could

dramatically speed travel between points connected by the wormhole, and into the future

o Requires an undiscovered form of exotic matter that may not exist, with negative energy density – a “white hole,” contrasts with a black hole

o Wormhole could collapse on the traveler• http://en.wikipedia.org/wiki/Wormhole

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Wormhole

From Wikipedia (see link on previous slide)

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Global Warming (cont’d)• What to do? Options:

o Nothing. Live with it. (Physical and ecosystem consequences not known)

• Humans can adapt quickly, natural world cannot – evolution is slow, but humans are free of evolution

• Many past examples of disasters from warming• Natural world is too complex for us to make good

predictions in from our present scienceo Cosmetic actions. Cite uncertainty in effects,

call for more research• May never have 100% certainty of the effects

o “Invisible hand” of market• Trade CO2 permits

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Global Warming (cont’d)

• Options (cont’d):o Limit CO2 production

• Increase energy efficiency, use waste energy, switch to low-carbon fuels (natural gas) away from coal and petroleum

o Remove CO2 once it is generated• Sequestration – pressurized underground or under

deep ocean (will warming release it?)• (DB) Recent poll says US thinks scientists

are confused about Global Warming. NOT!o Deliberate confusion caused by industry groups

opposed to controls – citing 2 or 3 out of 2,500

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Readings: Icecaps and Hurricanes

Evidence for Global Warming:• Thawing icecaps• Coral bleaching• Hurricanes• Melting glaciers• Desertification• Rising sea levels

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DB: That’s not all…

• Many worldwide resource issues – “the human footprint”o Water (drinking, irrigation, industrial), food,

farmland, population (6 billion 9 billion), living in unsafe places, petroleum, trash, development, health care, education, rights

• Managing the human footprint will be a major, continuing issue

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Re-emphasizing Main Points

• Two pillars of scienceo Experiment: makes science reliable

• Scientists led astray by logic (Aristotle) and belief (church and geocentrism, Inquisition)

• Experiments base science on direct experienceo Theory: makes science valuable

• Once you have a reliable theory, it tells you the answer in advance, can use it as technology

• Two quotes from Copi, Reader Pg 8

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Re-emphasizing Main Points

• I have the experiments in this course to:o Give you direct experienceo Illustrate experiments described in classo Illustrate social nature of science within the lab

groups

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Updates

• Bird flu:o Some concern over transmission via domestic pets in

rich countrieso Also being spread through smugglingo Anthony Fauci (NIH): probably no disaster here, BUT

• Natural disasters:o Hurricane season of 2005: with better measurements,

more hurricaneso In addition to hurricanes, warm Gulf of Mexico also

important in tornado formation• Tornadoes generated when warm air from Gulf meets cold air

from Northwest

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Updates (cont’d)

• Plate tectonics:o Determines location of mineral resources and

fossil fuels• Mineral resources brought near surface by old zones

of rising magma• Fossil fuels generated when organic matter covered

over before it rots, “cooked” when drawn down to warmer depths (but not hot – like baking a turkey) then brought back near surface so we can find it

– Temperatures increase going down into the earth• Plate tectonics does both of these

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Updates (cont’d)• Tenth planet?

o In Class 5, mentioned “tenth planet” 2003 UB313 nicknamed “Xena,” larger than Pluto

o That size based on inference from brightnesso New direct measurement says Xena about the

same size as Plutoo Inference from brightness fooled because Xena

is highly reflectiveo Now, Pluto and Xena will probably be either

accepted as planets or demoted, as a pairo Meaning of “planet” still being debated

4/19/06 Atoms and Stars, Class 14 22

Uncertainty Principle (Repeat)

• No practicaleffect atmacroscopic levelo A philosophical problem with The Mechanical

Universe and with “The God’s eye view” or The Clockwork Universe over age of universe

• Important at atomic and molecular levelo Uncertainties are large on atomic scaleo What underlies our reality is strange

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Readings: Knowledge or Certainty

Jacob Bronowksi• Absolute certainty is impossible in science

o Looking at an object with infrared, then visible, then x-rays should yield greater detail. Infrared is very blurry, visible is pretty good, but x-rays are too high energy to be focused. Perfect detail of “God’s-eye” view is impossible

o Statistical uncertainty in measurements - Gauss

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Knowledge or Certainty

• 1795

• Science is discussion and argument preceding knowledge

• Also Uncertainty Principal 1927 Werner Heisenberg – cannot locate particle exactlyo Irreducible uncertainty or fuzzy focus

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Knowledge or Certainty

• No practicaleffect atmacroscopic level, but a philosophical problem with The Mechanical Universe and with “The God’s eye view”

• But certainty leads to tragedy – Nazis• (DB) Certainty and power combined

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What is Science?

Moti Nissani, What Is Science?• Difficult or impossible to give a dictionary-

type definition for science• (DB) Working scientists rarely think about

the history or philosophy of science• Start with philosophy of Thales – free

inquiry

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What Is Science? (cont’d)

• Then hypothesis and experiment (Torricelli)• Falsifiability – reason and logic have not

been not sufficient to discover the truth in science (DB: belief, either)o But contradiction by experiment does not

always mean rejection of hypothesis – can lead to reexamination of experiment or modification of hypothesis

o Scientists “on the trail” have personal concerns

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What Is Science? (cont’d)

o Scientists “on the trail” have personal concerns• Argument and community lead to progress

o Semmelweiss and deaths in maternity ward• Neighboring ward far safer• Did priest’s visit scare patients?• Washing hands – doctors did dissections beforehand• This fixed the problem• Profession slow to accept this change• Even scientists can be closed-minded, resist change

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What Is Science? (cont’d)

• Theories unify many hypotheses and experimentso Price is often inaccessibility to non-scientists

• Scientists usually not concerned with these issues or with philosophical uncertainty

• Science many not be perfect, but it can still be very good

• Many use technology but not the scientific foundation

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Physical Science: Current Status

• Newton’s Laws, Maxwell’s Equations and similar classical theories (before ~ 1900) describe world we know and see

• For things the size of molecules and smaller, need Quantum Mechanics

• Very fast, need Special Relativity• Very heavy, need General Relativity• All three have weird things going on

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Special Relativity

• For fast-moving objectso Max speed = c (speed of light)o Objects foreshortenedo Time slows downo But the traveling person says the same about

you!o Space and time space-timeo E = mc2

light has mass, is bent by gravity

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General Relativity

• For very heavy objectso Space and time warp, cause gravityo Perihelion (closest approach to sun) of

Mercury’s ellipse not fixed as in Newton’s Laws, but advances 43 seconds of arc per century (observed), other effects in addition

o Light bent twice as much as Special Relativity, observed 1918

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General Relativity (cont’d)

• “Einstein Halo” – light from far galaxy bent by near galaxy

• Variation on gravitational lens

• 12 found so far• Picture: New York Times, 12/6/05,

Pg D4 (Science)

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Quantum Mechanics

• At molecular level and smaller, waves and particles merge – everything is botho Wave – spread out, cannot contain ito Particle – have it or don’to Q.M.: wave gives chance of “catching” particle

• Cannot be made certain• Uncertainty Principle

o Carries over to regular world, makes clockwork universe impossible over age of universe

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Quantum Mechanics (cont’d)

• Accounts for properties of ordinary materialso Theoretical: keeps matter from collapsingo Coloro Solid (strength), elastic, gaseouso Solid state electronics – semiconductorso Forces – due to exchanges of particles

• No Newtonian “action at a distance”• E.g. electrical force carried by photons – particles of

light

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Combinations

• Fast (S.R.) and heavy (G.R.) – OK, since Special Relativity contained within General Relativity

• Fast (S.R.) and small (Q.M.) – these two get along well – together, predict anti-particles

• Heavy (G.R.) and small (Q.M.) – conflicto No “Quantum Theory of Gravity, ” union of both

• General Relativity is the theory of gravity

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Combinations (cont’d)• Heavy (G.R.) and small (Q.M.) –

mathematical conflicto Competing theories of gravity – “embarrassing”

• G.R.: gravity caused by masses warping space-time• Q.M. – gravity due to exchange of “gravitons” (not

found yet)o “String Theory” might unite these two

• “Theory of Everything” – accelerating expansion(!)• Matter and energy composed of elemental vibrating

strings and membranes• Eleven dimensions, seven curled up too small to

experience directly – may have indirect experience• Theory still developing, no unique experimental

evidence yet

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Three waves of science?

1. Physical science – the subject of this course – mature, quantitative (95%)

• Very controversial when it was new• 1600 – 1800 AD, although very long roots & still

developing• Now pretty much settled for everyday objects

2. Biological or life science – qualitative (30%?)• Much newer, still controversial publicly, but for

scientists it is settled• 1800 – 1935 AD

• Coming into general use in society & economy• Will qualitative change to quantitative?

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Three waves of science?

3.Cognitive science – how emotions and the mind work – just starting (5%)o Will be as controversial, if not moreo Potential for controversy: Science of Desire :

The Gay Gene and the Biology of Behavior & The God Gene (spirituality) / Dean Hamer• Spirituality predestined for some, denied to others?• A single gene is unlikely to be the sole cause

o Will call into question how we view ourselves

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The end of the ride• Strong dose of the value of science here• One more time, about science:

o Two pillars – repeatable experiment (what makes it reliable) and explanatory theory (what makes it valuable)

• Developed 1600 – 1800 AD: Copernicus to Daltono Developing hypotheses and theories is creativeo Has a boundary but expands aggressively

not a complete basis for livingo Now drives technologyo We all use ito Conflicts with some, but not all, religious beliefso People of all ethnicities have been able to contribute

4/19/06 Atoms and Stars, Class 14 41

Review for Final