(hint: let N be the number of stars in cubic galaxy; . If each star is separated by a distance D = 5LY, then the total volume of the cubic galaxy is . Now the number of civilizations in the galaxy is = 100. Let each one of them be surrounded by an "empty" cube of volume = in which there are no other civilizations--on the avg. So x is the avg distance between these civilization.)Quote:

assume that the galaxy is a group of 400 billion stars distributed along a cubic lattice, each star separated from it's nearest by about 5LightYear. If 100 currently signaling civilization are randomly distributed somewhere in this galaxy

from the hint I got Vgal = = .Quote:

How far away in LY is the nearest civilization likely to be?

I'm not sure how to solve the rest.