system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: If the sun is a big nuclear reactor, why does it not explode like a massive nuclear bomb?
gpt
It basically _is_ exploding like a massive nuclear bomb, endlessly and repeatedly in one giant reaction. What keeps it together, so that it can _keep_ exploding, is its massive gravitational field. Nuclear bombs don't have that, so they go in one big burst and then the reaction stops.