Take and assume

PHYSICS · Subjective · Fermi University Physics · Relativity & Gravitation · Astrophysics & Cosmology · Einstein's field equations

The Geometry of Gravity, Ch FRW cosmology as an exact solution

Problem

Take

H_0 = 67.7\ \text{km s}^{-1}\text{Mpc}^{-1}

and assume, as an approximation, that the Universe is flat and matter (dust) dominated only, both today and for all future time, so that

a(t) \propto t^{2/3}

with

a(t_0)=1

at the present time

t_0

. Estimate the additional cosmic time, beyond

t_0

, needed for the scale factor to double to

a=2

. State the idealisation this estimate ignores.