Letters

Galactic collisions explained
Perhaps you can explain why Andromeda and the Milky Way are going to collide “Milky Way will be hit head-on,” (SN: 7/14/12, p. 10). Galaxies, as is always written, are rushing away from each other at ever-increasing speeds. How do things collide when there is never anything to collide with? Either galaxies are rushing outward in all directions with the same impetus from the point of the Big Bang, or they are not.