It is because the Universe is expanding.

...And the Ever Expanding Universe was created on 2009-07-14.

All the available evidence strongly indicates that the Universe is, indeed, expanding.

1. the universe continues to keep expanding 2. the universe slowly stops expanding 3. big crunch (basically the universe will stop expanding and fall back into itself)

It is not exactly expanding into anything. The galaxies are moving apart from each other, from which we can infer that the universe is expanding. Theoretically, this is a result of the Big Bang, in which the universe began when all matter was compacted into a very tiny sum, and then exploded apart in a very big bang, and as a result is still expanding today.