I know that energy is recognized through motion. Even in the mass-energy equivalence a velocity is present even though it is a rest-energy (Not really sure if this would count as a potential energy since there is no 'field' of acceleration that the mass is in)
So does kinetic and potential energy make up all other forms of energy by definition?
Best Answer
Originally even thermal energy was neither kinetic nor potential. Of course with the acceptance of the mechanical theory of heat we can interpret it as a manifestation of kinetic energy. Roughly, the distinction between kinetic and potential energy in classical mechanics reflected the difference between intrinsic energy of an object, and energy of interaction between objects, with the former reduced to the energy of mechanical motions (macroscopic or microscopic).
In this sense special relativity introduced a new form of energy based on the Einstein's mass-energy equivalence. In hindsight, the energy of electromagnetic field studied earlier by Lorentz and Poincare was a particular case. Another manifestation is energy released in nuclear reactions. One could say that as with the thermal energy this new energy microscopically "reduces" to the energy of subatomic motions and interactions, so it may not be that new. However, there is still a difference with classical statistical mechanics and thermal energy. When excited atom emits a photon we can not say that energy of some motion or interaction "in" the atom got "transferred" to the photon, which did not even "exist" before the emission, such classical parsing simply loses its meaning in quantum theory. Moreover, mass-energy equivalence assigns this internal energy even to truly elementary particles (with no parts that can move or interact) that are at rest.