To keep it as simple as possible, Einstein’s Theory of Relativity equates energy with mass, meaning that mass contains energy, and the more mass, the more energy, but is not equally proportional.
If it was proportional, then we would have a simple formula of E=M; however, this is not correct, as there is an additional component that causes this equation of mass and energy to be unsymmetrical and this component is light.
The amount of energy is not equal to the same amount of mass. The amount of energy / mass can be found by the formula E=Mc2. That is, for a certain amount of mass, there is a certain amount of energy and that energy is equal to the mass times the (power) of the speed of light squared.
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*Jay Taub is not associated with this production.