Astro-Webseekers,

Our speaker at the July 26 Mt. Tamalpais astronomy program, Dr. Arno Penzias, announced that
the outline of his talk on the Big Bang would be on our website, so here it is. Questions for Dr. Penzias or about the astronomy program in general may be referred through our Star Program coordinator, Tinka Ross.

Jeff Price, MTIA Webmaster

A PERSONAL VIEW OF THE BIG BANG

An Outline from 7/26/03 presentation by Dr. Arno Penzias
Nobel Prize for Physics, 1978

Our Neighborhood, and Beyond

Our sun is a (middle-sized) star
~100 B stars in our galaxy, the Milky Way
~100 B galaxies in the Universe, all moving away from one another
Earth ~10,000 kilometers in diameter (1/30 light-second)
Sun's distance ~100,000,000 (10exp8) km (7 light-minutes)
To nearest star 3x10exp13 km (3x10exp18 cm) (3 light-years)
Milky Way diameter ~10exp23 km (100,000 light-years)
To nearby galaxy ~3x10exp24 km (3 million light years)
To "edge' of Universe ~10exp28 cm (14 billion light years)

 

How We Determined Sizes and Distances

Earth ? direct measurement (first done in ancient times)
Moon ? triangulation against distant stars
Sun ? earth's shadow on moon during eclipses
Nearby stars ? triangulation (earth's orbit as baseline)
Distant stars ? brightness signatures of "Cepheid variables"
Nearby galaxies ? brightness of their Cepheid variables
Distant galaxies ? compare brightness to nearby ones of same type
Very distant galaxies ? infer distance from velocity using "Hubble
Constant"

Fair Races and Expanding Raisin Cakes

Distant galaxies seen to move away from us
- velocity of recession proportional to distance (Hubble Constant)

Big Bang for Fourth Graders
- in a fair race, faster runners observed to be ahead of slower ones
- only "fair" if everyone starts at the same place and time

Expanding raisin cake-in oven, lots of yeast
- imagine yourself sitting on a raisin
- nearest neighbors seen to be moving away from you
- their (further from you) neighbors seen to be moving faster
- every raisin-sitter inside the cake reports that same result

 

Birth of Modern Cosmology

How do galaxies stay "up"?
- Newton and Einstein offered static explanations
- Friedmann and LeMaitre propose expansion

Hubble infers universal expansion from galaxy observations
- computes "age" from average distance/velocity ratio
- result: ~2B yrs for Universe (vs. ~5B yrs for Earth)

Fred Hoyle proposes "Steady-State" alternative
- widely accepted among scientists (~1950-1965)

 

"Big Bang" Battle ? Round I

Stars recognized and nuclear reactors
- energy produced from Hydrogen fusion into Helium (H. Bethe)
- too cold to produce heavier elements (G. Gamow)

Gamow crafts theory of element production
- based upon hot and dense early Universe
- cools with expansion, particles and elements emerge
- calculation linked to present-day helium and deuterium abundances
- fails for account for creation of heavier elements
- Hoyle derides "Big Bang" scenario in BBC debate

 

"Big Bang" Battle ? Round II

Gamow's student (R. Alpher) refines calculation
Confirms that buildup stops at Helium

Gamow explores relation between early temperature and density
Extrapolates thermal evolution to galaxy formation era
Summarizes results in paper with Alpher and Bethe

Alpher and Herman pursue Gamow's extrapolation
Calculate present size of heat residue
Accept (and echo) Gamow's comment on observability
Energy no bigger than cosmic rays or diffuse starlight

 

"Big Bang" Battle ? Round III

Steady State Theory Wanes in early 1960's
Galaxies too dim to have made all their helium (F. Hoyle)

Oscillating Universe alternative explored (R. Dicke)
"Bounce" calculations follow in Gamow's footsteps
Dicke sees predicted heat remnant as observable

Arno and Bob (Wilson) probe Milky Way emission spectrum
Find more "noise" than all known sources could produce
Not due to antenna, earth, atmosphere, ionosphere, sun, or galaxies
Seek explanations, link to Gamow theory via Dicke and colleagues

 

"Big Bang" Battle ? Epilogue

Princeton theorists (Dicke & PJE Peebles) prediction confirmed
Reject offer of joint publication with A&B
Agree to publish side-by-side papers

Princeton paper held up by referee, A&B's accepted
Notes failure to cite earlier work by Gamow, Alpher and Herman
Gamow's theory confirmed, he dies soon thereafter

Two groups go separate ways ? IGH, interstellar molecules, isotopes
A&B win Nobel ? Arno lectures on "history"

Theorists rework Steady State: Big Bangs spring up from eternal matrix

String Theory (now m-Theory) Used to Depict New Steady State

Theory hypothesizes (Quantum Gravity) modifications to laws of Physics
QG applies until t>1/10exp43 seconds (Planck Time)
By then, universe has grown to 1/10exp33 cm (Planck length)
Allows room for "Physics" to operate - matter, time, and space appear
(hair diameter)/(Planck length) >(dia. of Universe)/(hair diameter)
Unsuited to experimental tests - astronomer asks, "Why do we need you?"

Big Bang picture continues to grow richer and clearer with new
observations
Full sky tapestry from t=300,000 years, yields precise age, and mass
components
Detailed story of creation from Planck time onward
Big Bang alive and well-preceded by miracle, or amazingly fortuitous