Why nuclear fusion results in energy?

Question

So every other kind of energy we can get is from splitting molecules (combustion) or splitting atoms (fission)
So how come we can get energy from fusing atoms together?

In: Physics

Answer 1

Your assumption is wrong. We get energy by going from a higher energy state to a lower energy state.

Combustion isn’t splitting molecules, but rather rearranging them: if you burn methane you go from CH4 + O2 to CO2 + H2O. The resulting molecules “contain” less energy than the second ones, the difference gets released.

For fission and fusion it’s the same. You start from something (a heavy atom or two hydrogens) and end up with something else that contains less energy in total, the difference gets released.