Chapter 23    The Beginning of Time

 

When did it all start?   About 14 billion years ago

Extrapolating the Hubble Constant backwards (allowing for acceleration)
         Universe is aging -- more distant galaxies look younger

 

"Big Bang" Theory:
         Universe started as small, dense, hot blob of matter and photons
         Expanded
         Expansion caused cooling: temperature plot

 

Grand Unified Theory GUT All forces are the same when the energy is high
Inflation -- a sudden expansion of spacetime by a factor of roughly 1030
         It flattens our piece of the universe

 

Outline of the events:
         Diagram

Table:

Time

Temp K

Event

Planck Era

10-43 s

1032

Planck time Gravity separates

GUT era:   Gravity + 3 forces

10-38s

1029

Symmetry breaking Strong separates

Electroweak era: GUTS Inflation, Quarks + leptons

10-10s

1015

Electroweak separates

Particle era: quarks + leptons, four forces

10-3s

1012

Confinement q -> p, n

Nucleosynthesis era: p+e  -> n+n

p, n -> He plus a little Li  (Start of Standard Big Bang)

3 min

109

nuclear freeze out He/H set

Era of nuclei:  H, He, electrons plasma

380,000 yrs

3000

E-M freeze out recombination
p+e -> H atom CBR released

Era of Atoms

1 billion yrs

30

Protogalaxies condense

Era of Galaxies  galaxy formation, etc

present

CMB at 3

 

 

 

Evidence

 

Cosmic Microwave Background

         Transition at 380,000 years

         What we see the CMB sky   ‘zoom’

 

H He abundance in Population II stars

         Number of neutrons sets amount of H vs. He

         Baryonic matter only about 4%

 

 

Persistent problems

         Why is the universe so smooth?  [ to about .01%]

         Why is the universe so close to the critical density

 

Solved by Inflation

         Current parts of CMB  used to be much closer

         Inflation flattens spacetime

 

Why not perfectly flat?

         Quantum fluctuations get ‘inflated’ to be the current size of the lumps

 

If all this happened we should see the lumps in the CMB and their size should tell us what the density was at that time. (Was it the critical density?)

         WMAP Sky and results  (higher resolution made it possible)

 

According to WMAP:

         The geometry is flat

         Baryonic matter is 4.4%

         Total matter is 27%

         Flatness implies dark energy makes up other 73%

         Universe age is 13.7 billion years

 

The Future
         An accelerating universe slows down
         Eventually, protons decay -- all ordinary matter falls apart
         Eventually, even black holes evaporate
         Only subatomic particles and photons are left, rattling around the vast spaces of the universe