So what is infinity?
Imagine heading off in a straight line from Earth and you just kept on going; if you travelled at a speed close to that of light, after a while (OK a very long time) you would reach the edge of the Universe and the first matter that exploded from the “Big Bang”.
Tricky, we don’t know. We have no information.
Are there lots of Universes out there? If there are it could be that they are all infinitely apart and so we wouldn’t know if they existed or not.
Or are we the only one?
The physicist or mathematician would think of infinity as existing beyond or being greater than any arbitrary large value. Unlimited in space, time, extent or magnitude.