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

[nikkor180]

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?

 

[Dale]

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?

 

[Matterwave]

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.

 

[Mister T]

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 $E/c^2$.