[stupid question alert] I think I understand now how galaxies are not moving apart. The space is expanding in all directions making it appear from ANY given point that every other point is moving away from you. I've heard it said that this is over "large scale" distances as in those between galaxies. Does this expansion of space have a limit in terms of smaller distances? Is our galaxy itself expanding? Are the atoms in my desk slowly getting further apart?

If the amount of matter in the universe remains constant and the volume or space of the universe continues to expand, the average density of the universe is decreasing, right? Is the density of my desk also decreasing? If not, what is the limit where space ceases to be expanding?[/stupid question alert]