system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5 - How is it that both Fusion and Fission create energy?

My mind immediately tries to use a magnetism analogy (which I recognize is incorrect and not comparable to the strong/weak nuclear force) so I think about the energy it takes to push magnesia together or pull magnets apart. 

Furthermore, how do both separating and combining manage to create energy?
gpt
Because fusion is taking two very small atoms, and merging them into a bigger one.

While fission is taking a VERY LARGE atom, and breaking it into smaller ones.

There is a point on the atomic scale where fusion actually starts to take more energy than it produces, it’s actually around iron, which is why really heavy elements are only created as a star is dying and then a super nova, when there is lots of extra energy being expended.

This actually is why stars die, because they start trying to fuse heavier and heavier elements and it stops producing enough energy for the chain reaction to continue.