11.7 Exercise 14

(a) What Hubble constant corresponds to an approximate age of the universe of $10^{10}$ y? To get an approximate value, assume the expansion rate is constant and calculate the speed at which two galaxies must move apart to be separated by 1 Mly (present average galactic separation) in a time of $10^{10}$ y. (b) Similarly, what Hubble constant corresponds to a universe approximately $2 \times 10^{10}$ years old?