In physics, mass–energy equivalence states that anything having mass has an equivalent amount of energy and vice versa, with these fundamental quantities directly relating to one another by Albert Einstein's famous formula:
E = mc²
This formula states that the equivalent energy (E) can be calculated as the mass (m) multiplied by the speed of light (c = about 3×108 m/s) squared. (Similarly, anything having energy exhibits a corresponding mass m given by its energy E divided by the speed of light squared c².) Because the speed of light is a very large number in everyday units, the formula implies that even an everyday object at rest with a modest amount of mass has a very large amount of energy intrinsically. Chemical, nuclear, and other energy transformations may cause a system to lose some of its energy content (and thus some corresponding mass), releasing it as light (radiant) or thermal energy for example. Wikipeda, mass-energy equivalence
"Matter is bound up energy and energy is liberated matter." [Keely, 1893]
See Also