The Law of Conservation of Energy states: Energy cannot be created or destroyed but merely change from one form to another.Einstein showed that matter is a form of energy. When a nuclear decay occurs...
Because energy can be converted into mass and vice versa. Thus, while the mass of a system is not conserved in a particular process, the mass and energy of a closed system is always conserved.
The Law of Conservation of Energy is 0 = (d/dr + Del)(E + mcV) where E is the real or Potential Energy ( electrical, gravitational, etc) and mcV is the vector energy of the mass m and c is the speed...
because it is like a rule of science that cannot be broken. it is impossible to be broken. there are theories which aren't proven yet but laws are proven already