Thread: Expansion vs collision

How is it possible that 1) the universe is expanding (i.e every galaxy is moving farther away from every other galaxy) and yet 2) it is possible for galaxies to collide or for one galaxy to be "eaten" up by another?Thanx,RedStripe

It is possible because: although the Universe IS expanding (and increasing the rate of expansion) due to the mysterious "Dark Energy" of empty space, NOT every galaxy is moving away from every other one. Gravitation (of the baryonic matter plus Dark Matter that the galaxies are comprised of) outweighs the effect of Dark Energy between accumulations of sufficient mass at sufficiently close range. Most of the galaxies in our Local Group will eventually merge together.