The expansion of the universe is causing things which are not gravitationally (or stronger) bound to get further apart. So, your later scenario is closer to true, except that some galaxies are gravitationally bound to each other. For example, Andromeda is bound to our Milky Way and will get closer for the next 2½ billion years — resulting in a collision.
The AstronomyCast podcast (http://www.astronomycast.com/) has a fairly good explanation of the expansion of the universe in several episodes. Don't recall which episode, but I'd try ep. 5 and 6 (on the Big Bang) or 11 (Dark Energy). Actually, I'd recommend the whole show.
The AstronomyCast podcast (http://www.astronomycast.com/) has a fairly good explanation of the expansion of the universe in several episodes. Don't recall which episode, but I'd try ep. 5 and 6 (on the Big Bang) or 11 (Dark Energy). Actually, I'd recommend the whole show.