What is Rest energy?
'''Rest energy''' (E<sub>0</sub>) is the energy equivalent of a resting (i.e., immobile) particle. Based on [[Theory of relativity|relativity theory]], an [[:en:Mass-energy_equivalence|equivalence relation]] exists between [[mass]] and energy. The energy is equal to the product of mass and the square of the [[speed of light]]: E = mc<sup>2</sup>&nbsp;. For example, the rest energy of a [[proton]] is {{val|938.27208943|u=''MeV''}}. The rest energy of a 1 g mass is about {{val|2.5|e=7|u=''kWh''}}. [[Category:Relativity]] {{physics-stub}}