system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How can the universe be infinite in size and still ever expanding?

I have heard all the matter in the universe once occupied a single point and was thrown everywhere with the big bang

does that mean the space this matter didnt occupy is infinite? or do we only count the space the matter occupies as part of the universe?
gpt
We don't know if the universe is infinite. Thats just one of the possible options.

And it would work like this:

Imagine the universe was as wide as the natural numbers 0, 1, 2, 3, 4, ... (Go on to infinity)

Now the universe expands to twice the size so there is an additional step of space between each previous step 0, 0.5, 1, 1.5, 2, ... (Go on to infinity)

Both are infinite, but the other has double the amount of "space" between two points on the previous.