Final Hints Spring 2008

Final Hints Spring 2008 - Hints on cosmology question 1....

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Unformatted text preview: Hints on cosmology question 1. Friedman equation 8π G 2 ρa 3 This can be solved for the scale factor a(t), given the dependence of the energy density ρ on the scale factor a(t). For example, for a universe dominated by matter, ρ ( a ) = ρ 0 / a 3 , a2 = where ρ 0 is the current density of matter. 2. The photon temperature of the universe is given by T = T0 / a , where T0 = 2.73 K is the current temperature. 3. The photon energy density is given by ργ = 2.6 ×105 (T / T0 )4 eV/m3 ...
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