Fusion only happens in the Sun due to incredibly rare quantum tunnelling events. That is why the sun can burn for billions of years. It takes a long time for th

Fusion only happens in the Sun due to incredibly rare quantum tunnelling events. That is why the sun can burn for billions of years. It takes a long time for the energy generated to reach the surface and escape, that is why the sun has a high temperature. IIRC fusion reactors on earth use magnetic confinement to raise the temperature much higher than the sun's interior for a much higher rate of fusion reactions. I'm sure someone will be along to correct me if I got that wrong. ;0)