system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How is the universe flat?
gpt
Flat is the wrong word but we do not have a better word for it. If the universe were one dimensional we would have called it streight, as opposed to curved or bowed. If the universe was two dimensional it would be flat and not round. But we do not have a name for a similar three dimensional shape. So we use the next best thing which is the word flat.