Originally Posted by dalem

You are wrong. Every galaxy is not moving away from every other galaxy within a bounded and fixed enclosure called "the universe". Instead, every galaxy has its own intrinsic velocity vector and the space through which they move, called "the universe", is also expanding.

The best way I've ever read it explained is roughly as follows:

1. Take a spherical balloon.

2. Inflate it just enough so that it has a spherical shape.

3. Take a black magic marker and randomly dot the surface of the balloon with spots.

4. Begin inflating the balloon.

5. Think of the dots as galaxies, the surface of the balloon as a 2-dimensional model of the 3-dimensional space of the universe, and the radial distance "r" between the center of the balloon and the surface as time.

6. Note that as the balloon inflates, the surface of the balloon expands and the absolute distance between the dots increases. To tune this model further, assume that each black dot is instead a very slow-moving ant that crawls on the surface of the balloon.

7. As long as the rate of expansion is greater than a certain value, the surface of the balloon, our universe, expands so fast that even two ants crawling towards one another on the surface will always become farther apart.

8. Also note that the universe has no "beginning" or "end" in terms of physical distance - the surface is continuous, i.e. "infinite".

So the universe itself is indeed expanding, and everything is indeed moving away from everything else.

-dale