4/16/07atoms and stars, class 131 atoms and stars ist 2420 class 13, april 16 winter 2007...

4/16/07 Atoms and Stars, Class 13 1

Atoms and StarsIST 2420

Class 13, April 16Winter 2007

Instructor: David BowenCourse web site: www.is.wayne.edu/drbowen/aasw07


Agenda

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

o Notes for Class 13o Final Where-Is

• Upcoming assignments• Emphasizing main points one more time• Lab 11: The Orbiting Bottle


Changes in Lab Schedule

• Changes to Syllabus lab schedule: o Lab 11 tonighto We will not do Lab 4 (we went over the content

last class)


Upcoming …

• April 23 (last regular class)o Essay 2 dueo Review for Final Exam

• April 30: nothing that night but the Final Exam

• Opportunities for extra help for Final Exam:o 5 – 6 PM next week (April 23)o Review Session next week during classo 5 – 6 PM before Final (April 30)o Telephone, email, set up a time


Semester is Ending!• All work to be counted in regular course

grade must be in by class on April 23.• If you have been relying on being able to

turn work in late, it is time to get goingo 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!


16ths on the Final

• Doing the math for converting 16ths (inches, ounces) to decimal (inches, pounds)o If this type of problem is on the Final, there will

also be a table of all divisions by 16, with a few non-16ths extras thrown in

• 1/16 = .0625, 2/16 = .1250, 3/16 = .1875, 3/7 = .4286, 4/16 = .2500, etc.

o So the result of the division will be there, but you will have to know what you are looking for.


Experiment 11• Some reports did say that the formula for the

ellipse was trusted more than the experimental measuremento The power of authorityo Also, not trusting your techniqueso But in this case, the authority was not trustworthy

• Many said no use in repeating measurementso Results would be the same

• No! Every technique has a limit, will have variations when you push that limit. Where is the limit of the string technique?

• It is never easy, but scientists will eventually come down on the side of experiment


Experiment 7

• Should find V of block V of displaced water (Archimedes was correct)o Can be large error because of small height of

displaced water• Should find S.G of wood % below water

o Large error in estimating % below water• Dumbbell – should find

W in air W in water + W displaced watero Errors were larger than I thought, may be a

problem


Later Evidence for Atoms (Q10d)

• 1895 Boltzmann and Gibbs with Statistical Mechanics – success of Atomic Theory

• But Atoms still seen as perhaps just a theoretical convenience, perhaps no actual existence

• 1905 Einstein analyzed Brownian motion to find density of atomso Experimentally confirmedo More convincing


Later Evidence for Atoms (Q10d)

• 1911, Rutherford discovered electron and nucleus, components of atomso Atomic Theory adoptedo But atoms are not elemental (they have parts),

even though atoms are still called elements• Similar definitive evidence since then• Individual atoms seen in 1970s (~) using

electron microscopes and similar devices


Big Bang background

• Big Bang proposed 1922• First evidence: entire universe is expanding,

receding away from us: 1931, Edwin Hubbleo How is this evidence? “Run movie backwards.”

• Computer simulationo How do we measure this recessional velocity?

• Doppler Effect: Red shift.– computer simulation #1 computer simulation #2

• Each type of atom has its own characteristic colors, these were all red-shifted in stars.

http://www.is.wayne.edu/drbowen/Class-Room_Models/Big_Bang.htm

http://www.phy.ntnu.edu.tw/~hwang/Doppler/Doppler.html

http://www.falstad.com/ripple/ex-doppler.html


Big Bang background

• Red Shifto When light source

is moving awayo All stars moving

away from uso More distant

stars are recedingfaster

Stationary Receding(e.g. Sun) (e.g. star)

Lines: specific colors from atoms


Big Bang background

• Second piece of evidence: Cosmic Microwave Background Radiation - 1965o Flash of light left over from Big Bang explosiono Started traveling about 400,000 years after Big

Bang, then about 4,900˚Fo Has now cooled off to about -450˚Fo Why has it cooled off – expansion. In-class demo

(blowing on your hand)


Readings – Big Bang

Emails on Big Bang• #1 from George Gale (1999)

o Kansas school board rejected Big Bang and radioactive dating along with evolution

o “Young earth creationists” – 6,000 years in past for age of earth Vs 4.5 billion years from radioactive dating (Q14)

o (DB) 6,000 years ago is a reasonable scientific date for writing and the development of records


Evidence for Big Bang

• #2, Neil De Grasse Tysono “Theories” instead of “Laws” – humble nowo 1929 Edwin Hubble, galaxies receding, further

galaxies receding fastero Gravitational lenses – focused object receding

faster than focusing object (further away)o “Time dilation” from Einstein’s Special Theory

of Relativity – time slows down if motion faster


Evidence for Big Bango “Time dilation” from Einstein’s Special Theory

of Relativity – time slows down if motion faster• Distant supernovae do explode and age more slowly

compared to near ones (Big Bang says moving faster)o Cosmic Microwave Background predicted ,

discovered 1965• A peak location and spectrum (shape of intensity Vs

wavelength) that matches measurements• Has a distant source – we see it heated when passes

through matter



o Cosmic Microwave Background predicted , discovered 1965 (cont’d)

• Molecular “thermometers” show background radiation hotter from distant (older) galaxies

o Also consistent with mix of atomic species• Consistent with accelerator laboratory experiments

o But background radiation too uniform• “Inflationary universe” explains this, and more• (DB: some non-uniformity observed 2006)


Evidence for Big Bango But required mass is missing

• (DB: dark matter is being discovered – see update)

• #3: Gregg Esterbrooko Modern science chance-based, seems not to

require God, also predicts death of the universeo 1999 conference at Berkeley CA

• Astronomer Allan Sandage: majesty of Big Bang helped make him a believer

• Ian Barbour: physical law seems to favor life (Anthropic Principle)


Evidence for Big Bang• #3: Gregg Esterbrook (cont’d)

o Consilience by E.O.Wilson: can reconcile technical and spiritual, along with other books

o Creation “ex nihilo” consistent with latest Big Bang theories

o (Q14) Parallel between God creating existence from “waters” with H being most abundant element

• (DB) Water necessary for life (at least life like us), life on earth did come from life in water

o “Existence may be … prewired … for life”o If we came late, still may be early in time span

of universe



• #4: Thomas Dianao More and more can be explained without the

action of Godo Ancients had gods, each with own areao Geocentric theory – we were at center of

universeo Now we are displaced from central positiono Quantum Mechanics lets Big Bang be created

from empty space (quantum fluctuations)



• #4: Thomas Diana (cont’d)o At one point, science said life impossible

without extraordinary coincidences in physical constants (Anthropic Principle)

• Now inflationary theory of universe makes this less necessary

o How to retain belief? (Q14)• Not a belief in anthropomorphic God, but one that

transcends as science transcends the ordinary• Scientific mastery of universe results in separation


Evidence for Big Bang• #4: Thomas Diana (cont’d)

o How to retain belief? (Q14)• Scientific mastery of universe results in separation• Separation has led some to seek immanent God

– “immanent” (Theology): present throughout the universe, as opposed to transcendent (existing apart from the universe)

• We can achieve this – experience power greater than ourselves

– Rituals– Gazing at starlit sky – experience not diminished by

knowledge


The Big Bang…

Big Bang, expansion of universe• 3-D analogy to a rising loaf of raisin bread

o Expansion with no center (but this bread has edges, unlike the universe)

o http://www.is.wayne.edu/drbowen/aasw05/BigBangAnalogies.htm

• 2-D analogy to the surface of an expanding balloono http://www.astro.ucla.edu/~wright/Balloon2.html

http://www.is.wayne.edu/drbowen/aasw05/BigBangAnalogies.htm

http://www.astro.ucla.edu/~wright/Balloon2.html


The Big Bang…

Big Bang, expansion of universe

• 3-D analogy to a rising loaf of raisin breado Expansion with no

center (but this bread has edges, unlike the universe)


The Big Bang…

• 2-D analogy to the surface of an expanding balloono No edge but cannot go off

the balloon surface• (DB) (Q14) Universe

originally light, no mattero Had to cool off for matter to

exist


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 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

http://en.wikipedia.org/wiki/Wormhole


Wormhole

From Wikipedia (see link on previous slide)


Update• Inflation: Universe

expanded “exceeding quick” in first trillionth of a second, to size of grapefruit• Produces “Anthropic

Principle”• Now expansion of

universe is acceleratingo Einstein’s

cosmological constant


Readings: Black Holes (Hewitt) (Q3)

• Black hole: escape velocity at surface > speed of light, so cannot escape (Black Hole is dark)o Space collapses nearby, draws in anything nearby

• DB: can see light as indrawn objects are destroyedo Can also be seen by gravitational effect on neighborso DB: Burned-out star collapses, forms Black Hole

• Nuclear fuel burns out, star collapses• Black Hole can draw in other matter

• Theoretically possible for reappearance of this matter as white hole, but these have not been seen, so may not exist


Readings: Global Warming (Q12)

• Light comes in to earth from suno Some absorbed on surface, warming eartho Rest reflected, exits to spaceo Greenhouse gases in upper atmosphere trap

reflected light, some returned and further heats earth

• Amount of warming now about 1ºF but projected to rise rapidlyo By 2100, projections = 2.5ºF to 11.5ºF (avg 7ºF)


Atmosphere, Climate and Change by Thomas Graedel and Paul Crutzen, Scientific American Library, 1997.

4/16/07 Atoms and Stars, Class 13 32New York Times, “Computers Add Sophistication, but Don’t Resolve Climate Debate,” Science Times Pg D3 8/31/04


Global Warming (cont’d)

• Largest effect in Antarctico Snow reflects the

most, sea water the least

o Arctic ice disappearing

o Polar bears in dangero Eskimos suing US

The New Yorker, cover, 12/12/05



• 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 evolutiono Cosmetic actions. Cite uncertainty, call for

more research• Will never have 100% certainty

• Options:o “Invisible hand” of market

• Trade CO2 permits



• 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• (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


Readings: Icecaps and Hurricanes

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


DB: That’s not all…

• Intergovernmental Panel on Climate Change (IPCC) report 2007• IPCC: joint organization of climate

scientists and government leaders• We can now see the results directly,

instead of using computer models• Some areas may see initial benefit, but if

there is no end, all areas will suffer



• Insurance industry raising premiums to account for expected higher damages

• Power and auto industries expect regulation, want it soon so they know what to plan for

• Report released today on U.S. “National Security and the Threat of Climate Change”• Board of senior (retired) military• Reduced natural resources, so threats to stability• Increased needs for humanitarian aid• New sea lanes to be protected as ice melts



• Many worldwide resource issues – “the human footprint”o Population (6 billion 9 billion), water (drinking,

irrigation, industrial), food, farmland, living in unsafe places, petroleum, trash, development

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

• I am not predicting disaster – I think we (you) will manage this, but not easy.


Re-emphasizing Main Points

• Two pillars of scienceo Experiment: makes science reliable

• Scientists led astray by logic (Aristotle) and belief (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


Re-emphasizing Main Points

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

groups


Lab 11: Orbiting Bottle• Swing bottle on string

o Measure distance from finger to middle of water, convert to decimal feet (÷ inches by 12)

o Measure weight of bottle, convert to decimal pounds

o Time ten “orbits” or circles (count from zero!)o Measure angle down from horizontalo Use formulae

• Large hand motion to get bottle moving, then small hand motions to sustain motion during measurements


Orbiting Bottle

• String pulls in two directions, H and V

• Two formulae for FH

1. FV (up) balances W (down), then angle determines FH

2. Inward force to move bottle in circular orbit

• Two should agree, roughly


SET

• Course information.• Me: David Bowen• Course:

o IST 2420, Atoms and Starso 4 Creditso Section 001o CRN 23981

• Lab afterwards

4/16/07atoms and stars, class 131 atoms and stars ist 2420 class 13, april 16 winter 2007...

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