90% of Astronomers work in the big bang model assuming the
cosmological principle. i.e. that the universe is isotropic and
homogeneous.
Evidence for the big bang is that a) the Universe is expanding -
Hubble's law.
The cosmic microwave background radiation (detected by Penzias and Wilson)
Measured in more detail by COBE
and found to be at T=2.73 K as predicted
And the amounts of light elements - Big Bang Neucleosynthesis (Alpher
Bethe and Gamov).
What is the fate of the Universe? Depends on what is in it. Until
recently, thought just mass and then there are three criteria.
I don't have slides on this but there is no 'evidence' from Super nova
that the universe contains something else - dark energy. We believe
the Universe is flat (from CMB) but only 30% is mass.
W_t = W_baryons (5%) + W_dark matter (25%) + W_dark energy (70%)
The Big bang model has had it's successes but also there are problems -
the horizon problem, the flatness problem
and the structure problem.
Inflation was postulated to overcome this.
The Universe was hot. This allowed protons and electrons to
form. These came together and formed atoms of H (and also He, Li and
Be). Heavier elements didn't have time to form. This time was called
recombination. After this period, the photons were free to travel and
on average didn't encounter an atom of hydrogen (the universe is
empty). The universe is expanding so the hot radiation (photons)
cooled to T=2.73 K.
We can simulate the universe!
