Sure, but you can also rip off electrons from atoms by rubbing them or bending a piece of wire. The energy needed to trigger fission in uranium is less than a picojoule, it just needs to be focused enough to knock away the part of the atom, which is why neutrons are the most common way.
Here is a chart with the rate of fusion for two hydrogen atoms at various temperatures.
Sure, but you can also rip off electrons from atoms by rubbing them or bending a piece of wire. The energy needed to trigger fission in uranium is less than a picojoule, it just needs to be focused enough to knock away the part of the atom, which is why neutrons are the most common way.
Here is a chart with the rate of fusion for two hydrogen atoms at various temperatures.
https://en.m.wikipedia.org/wiki/Nuclear_fusion#/media/File%3AFusion_rxnrate.svg
This chart bottoms out at a few million degrees, since the probability is extremely low.