Understanding E = Mc^2

In physics - in particular, special and general relativity - mass-energy equivalence is the concept that the mass of a body is a measure of its energy content. In this concept, mass is a property of all energy; energy is a property of all mass; and the two properties are connected by a constant. This means (for example) that the total internal energy E of a body at rest is equal to the product of its rest mass m and a suitable conversion factor to transform from units of mass to units of energy. Albert Einstein proposed mass-energy equivalence in 1905 in one of his Annus Mirabilis papers entitled "Does the inertia of an object depend upon its energy-content?" The equivalence is described by the famous equation:

E = m.c^2

where E is energy, m is mass, and c is the speed of light. The formula is dimensionally consistent and does not depend on any specific system of measurement units. The equation E = mc2 indicates that energy always exhibits relativistic mass in whatever form the energy takes. Mass-energy equivalence does not imply that mass may be "converted" to energy, but it allows for matter to be converted to energy. Mass remains conserved (i.e., the quantity of mass remains constant), since it is a property of matter and also any type of energy. Energy is also conserved. In physics, mass must be differentiated from matter. Matter, when seen as certain types of particles, can be created and destroyed (as in particle annihilation or creation), but a closed system of precursors and products of such reactions, as a whole, retains both the original mass and energy throughout the reaction.