system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How is the Universe expanding if gravity pulls things together?
gpt
Wouldn't physicists like to know.

But seriously, they dont know. At this point, all we have are some theories. Mainly, dark energy. Basically an unknown, undetectable force that pushes on everything in the universe. Locally, its not strong enough to overcome gravity, which is why stars, planets, orbits, galaxies, etc. still exist; but on a cosmic scale, it is strong enough to push all the clumps of mater (which are basically clumps of gravity), away from each other.

It's also worth mentioning that, since dark energy expands space itself, and isn't technically *moving* anything, the expansion of the universe is actually faster than the speed of light. Some galaxies are moving away from each other so quickly, that light from one galaxy would never be able to reach the other, because it cant travel fast enough.