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Mass–energy equivalence
Intermediate
Mass is a form of energy.
E = mc²Mass is a form of energy: E = mc². A tiny mass change releases huge energy: 1 g is 9×10¹³ J, about 21 kilotons of TNT.
The Sun loses about 4 million tonnes of mass per second.
Not "mass turns into energy"; the system's mass changes when its energy changes.
In more detail
Einstein's equation E = mc² states that mass and energy are equivalent. A small amount of mass corresponds to a very large amount of energy, because the speed of light squared is huge.
Real-world uses
- Nuclear reactors release energy from the small mass difference in fission.
- Nuclear fusion in the Sun converts a small fraction of mass into energy.
- Nuclear power stations convert a tiny mass loss into a huge amount of energy using E equals mc squared.
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Frequently asked questions
Does mass really turn into energy?
In nuclear reactions, the mass of the products is slightly less than the reactants, and the difference appears as energy.
Why is c squared so important?
Because the speed of light is very large, so even tiny masses correspond to enormous energies.
Does mass really turn into energy?
In nuclear reactions the total mass drops slightly and that mass appears as kinetic and radiant energy, consistent with E = mc².
Related topics in Work, Energy & Power
Work done by gravity on incline · Heat as energy transfer · Mechanical equivalent of heat · Sources of energy · Renewable energy · Conservation of energy in collisions