You can consider energy as a Universal Currency, i.e. it can be traded among its various forms such as potential energy, kinetic energy, as well as matter. So in that sense all matter is a form of energy; its trade-in value is mc˛. There are trade restrictions however. Most matter, such as a proton, does not spontaneously turn into energy. A proton can annihilate, releasing energy, if it meets up with an anti-proton, but there are not many of those around.
LeeH
(published on 10/28/2007)
