mfb- t1_jedt1iu wrote on March 31, 2023 at 8:16 AM

Reply to comment by DarkTheImmortal in ELi5 If the universe is expanding, what is it expanding into? by cashmoneyhash

> The universe is already infinite

We don't know if it is.

> This can ONLY happen when infinity is involved.

No. The universe could be finite, and still expand.

DarkTheImmortal t1_jeduiwg wrote on March 31, 2023 at 8:38 AM

The 2nd part you point out you skipped over something. I said an infinite universe can expand AND remain the same size at the same time. To have both of those seemingly contradictory properties at the same time requires an infinite universe. An infinite volume can get bigger, but it's still infinite.

mfb- t1_jedv127 wrote on March 31, 2023 at 8:45 AM

Yes, if the universe is finite then its volume increases. So what? Doesn't stop OP's question from being relevant, with the answer still being "it's not expanding into anything".