Anyway.
1/Ho =13e9yr, they say.
Cephid variable stars pulse in proportion to their luminosity (so the latter is easily known). These luminosities then can be used to calculate range. Velocity of course is known from redshift, and thus we can correlate one to the other. Range x Ho = V. A good (terse and childish) explanation of the universe's age is here, at the WMAP satellite site. WMAP calls the universe 13.7b yrs old.
Nucleosynthesis in the early universe considers the relative expected proportions of elements as a function of how hot it was. ("Hot" being the relative proportion of energy to mass in the early universe.) This plot, from about 3 minutes? shows the ratio of He to other elements eg Li, we find now, & thus calibrates the early energy density. They believe all the heavy elements were formed in stars or supernovae.
The Inflaton Field Theory supposes something more violently expanding happened right at first, as an answer to the problem of relics (where are the magnetic monopoles a hot cosmic soup would have created?) and the problem of flatness (some stars look older than 1/Ho)
Just some numbers...
- Critical density is 5 protons / m^3, and we are nowhere near that: where is it all? This is the motivation for the search for dark (unseen) matter & energy.
- Planck density = 10^93gm/cm^3
- Age of universe 13.7b yr
- Age of transparency 350,000 yr. (? ...from memory)
- Black hole density= (1.8x1016 g/cm3) x (Msun / M)2 ,usually M is 10x solar masses.
- Schwarzchild radius= (3x105 cm) x (M / Msun), this, from here.
