system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5:how can the universe be infinite if it started from a single point

how can something which was said to be the size of a watermelon at one point be infinite?
gpt
There are infinitely many numbers between 0 and 1, but the size of this interval is only 1.

Somewhat similarly the universe at the beginning was infinitely dense but compressed down to a singularity. If something is infinitely dense you can expand it out to an infinite size.