NOTES:

1
NOTES Proofs of the Hot Big Bang (of
Georges LeMaitre) 1. The red shift of distant
galaxies. 2. The cosmic microwave background.
Penzias and Wilson 1976. A black body curve
at T 2.7 K results from electrons combining
with protons to make hydrogen. Ultraviolet
stretched to microwave with the expanding
universe. This has small lumps in different
directions of about 1 part in 10,000
indicating early inflation. 3. NucleosynthesisBur
bidge, Fowler, and Hoyle in 1960 calculated
Big Bang made 75 He, 25 Heobserved in
unrecycled material.
Georges LeMaitre theorized The Big Bang in
1927 two years before Hubble observed it.
2
Proofs of the Hot Big Bang 1. The red shift
of distant galaxies
Implies Hubbles Law
3
Proofs of the Hot Big Bang 2. The cosmic
microwave background. observed and
identified by Penzias and Wilson in 1965.
Predicted by Cosmologist George Gamov in 1948
4
A black body curve at T 2.7 K results from
electrons combining with protons to make
hydrogen. Ultraviolet stretched to microwave
with the expanding universe.
5
WMAP Satelliteobserves the microwave Background.
This has small lumps in temperature in different
directions of about 1 part in 10,000 indicating
early inflation.
6
Proofs of the Hot Big Bang 3.
Nucleosynthesisin 1960 Burbidge, Burbidge,
Fowler, and Hoyle calculated Big Bang made 75 H,
25 Heobserved in unrecycled material.
7
For about a second, the Big Bang was hotter than
10 million K, and fused 25 of H into He.
8
The primordial soup Was thus 75 H and 25 He
by mass.
9
Post-1998 Cosmology A funny energy in space At
the present epoch the velocity of receding
galaxies is given by Hubbles Law v Ho d ,
where Ho is the Hubble constant. 1. This holds
only for galaxies at moderately low distances.
10
In actuality, the straight line of Hubbles law
curves gently downward at greater distances as
indicated by supernova Ia measurements of
explosions up to about 11 billion years ago
(Perlmutters and Schmidts groups --post 1998).

Saul Perlmutter, Berkeley
Brian Schmidt, Harvard (at first)
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At first, it was East Coast vs West Coast!_at_!
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a) The velocities are given by the redshifts of
the galaxies they are in. b) The
distances are given by standard peak luminosity
of supernovae Ia, which is always the same.
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The data implies the universe is speeding up.
15
The universal expansion is accelerating. It will
expand forever in such a way that it implies
a) The mass in the universe is not sufficient to
turn the expansion around, even with
dark matter included,
If I throw my keys up, they slow down. gravity
normally decelerates!
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b) There is a funny energy in space (usually
called dark energy) driving the acceleration like
a compressed sponge when released.
17
If Einsteins General Theory holds, this energy
may be in the form of Einsteins cosmological
constant, ?. In 1917, he postulated that this
constant outward force was necessary in a static
universe to keep the galaxies from falling into
each other.
The universe was not found to be expanding until
1929.
18
Dark energy may also be a time varying component
of space called quintessence--the fifth element.
However, for now, data closely matches the
cosmological constant.
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Cosmic History
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10-32 sec
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1 second
Big Freeze Out                            
                                                  
                                                
The First Atomic Nuclei
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Decoupling of light and matter. 380,000 years
ABB (After Big Bang)
D
The decoupling era (recombination) H atoms can
form, because light escapes.
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