Einstein's Definition of Mass: m = E/c^2

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SUMMARY

Einstein's equation, expressed as m = E/c², defines mass in terms of energy within the framework of special relativity. The equivalence of mass and energy is established through the principle that when a body emits energy (E), its mass decreases by E/c². This relationship underscores the fundamental nature of mass and energy as interchangeable, a concept central to modern physics. The discussion clarifies that both forms of the equation are used interchangeably by Einstein, emphasizing their equivalence.

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nikkor180
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Greetings: I hope I am posting in the appropriate forum. I understand that in special relativity, Einstein expressed e = mc^2 as m = e/c^2. Is this his way of defining mass? If not, can you explain how he came to this conclusion?
 
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I am not sure if I understand your question. ##E=mc^2## is the same as ##m=E/c^2##. Are you confused about that equivalence or are you asking for a derivation of it?
 
Are you referring to a specific paper in which the equation in the form ##m=E/c^2## appears? If so, please cite the paper so we understand the context. Otherwise, I'm sure Einstein used the equation in both forms regularly.
 
nikkor180 said:
Is this his way of defining mass?

No, rest energy and mass are equivalent. That's what he's saying.

If not, can you explain how he came to this conclusion?

He showed that if a body gave off an amount of energy ##E## its mass would be reduced by ##E/c^2##.
 
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