Can a mass be be converted into energy components only if it moves at the speed of light?

Question

Isnt mass conversion mass breaking up?

Answer 1

No, not at all.

Processes in perfectly stationary nuclei turn mass into energy. For instance, the energy an emitted alpha particle has in alpha decay from a staionary nucleus is reflected by a tiny fall in mass of the nucleus.

Conversely, as you accelerate a particle towards the speed of light, more and more of the energy you give to the particle gets converted to mass. In fact, you can never get the particle to the speed of light - its mass will go to infinity first. This is quite measurable in a particle accelerator.