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- How does rest mass become energy? 3 answers
Where does $c$ squared come into play in the equation $E=mc^2$. Multiplication obviously but how does energy equal mass times the speed of light?
This mass–energy relation states that the universal proportionality factor between equivalent amounts of energy and mass is equal to the speed of light squared. This also serves to convert units of mass to units of energy, no matter what system of measurement units is used. To find out how much energy an object has, multiply the mass of the object by the square of the speed of light. Now we multiphy by $c^2$ because when mass is converted into energy, this energy is by definition moving at $c$. Pure energy is understood in terms of electromagnetic radiation which always moves at the speed of light