text: can you explain to me the concept of the universe being a vacuum?   the universe is not a vacuum since it obviously has stuff in it (us for example), but there are places in the universe that are pretty close to being totally devoid of any matter. all the material in the universe is attacted to all the other meterial in the universe through gravity.  the matter in the universe has gravitated towards each other forming planets, stars, galaxies, ... leaving a lot of empty space.  all this empty space is a vacuum, since by definaition, a vacuum is devoid of matter, empty.  you can ignore the fact that a true, total vacuum does not exist, not even is space.