The universe is expanding and cooling.
Different physical processes and components dominate at
different temperatures and densities.
The growth of horizons means larger scale structures form later.
Looking at large distances means looking back in time.
General Features of Universe
- homogeneous and isotropic on large scales
- Olber's paradox: expanding universe, not at a special place
- Structure in the universe is evolving (was not always there,
combined with finite speed of light gives another resolution)
Going Forward in time:
- general evolutionary features
- cooling/diluting due to expansion
- structure growing due to gravitational attraction
- short history
- initial conditions (inflation)
- bbn (first 3 minutes)
- matter-radiation equality
- cmb (300,000 years)
- dark ages
- first structures
their age, fraction of age
of universe, in years
- peak of star formation and quasar activity
- today and recently
Observations are stronger starting at the time of bbn and since.
Systems which are simplest: the
CMB (where calculations are under control) and those
dominated by dark matter (which only use gravity).
Both of these will be used later as
indirect indications of the cosmological
Short statement of paradigm by M. Rees