# E = mc² : mass or internal energy

The internal energy of an object is defined as the energy of that object at rest. This energy is related to its mass M and the square of the speed of light c², by the Einstein formula E = mc². It is also called by physicists mass energy. In normal conditions, the mass energy is very large compared to other energies such as kinetic energy, given the value of the speed of light (300 000 km / s), which enter by its square in the formula.

## Similar definition(s) :

Binding energy

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