If you were to divide the presentday universe into cubes whose sides are 10 million lightyears long, each cube?

would contain, on average, about one galaxy similar in size to the Milky Way. Now suppose you travel back in time, to an era when the average distance between galaxies is 0.22 of its current value, corresponding to a cosmological redshift = 3.6 . How many galaxies similar in size to the Milky Way would you expect to find, on average, in cubes of that same size? In order to simplify the problem, assume that the total number of galaxies of each type has not changed between then and now.