Question

During the fusion process, how is mass converted into energy?

Answer 1

this is the answer of your question

Answer 2

it according to einstein equation e= mc2 (energy=mass*speed of light)

the atoms that are decayed travells in a speed of light . hence the mass can be converted into energy

AMAZING FACT INDEED
if humans travelled in the speed of light they may become a time traveller according to Einstein