Question

Under what conditions can energy become mass? ​

Answer 1

Explanation:

Mass never "become" energy. But mass can be quantified as a certain amount of energy thanks to the famous Einstein's formulae:

E=mc2

or more exactly:

E2=p2c2+m2c4

Answer 2

Question ⤵

Under what conditions can energy become mass?

Answer ⤵

The conversion of energy, kinetic or electromagnetic, to particles with rest mass is experimentally observed only when the energy comes in big enough clumps to create a massive particle, when the energy is low, this is going to be the lightest charged particle, the electron.

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