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

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Discussion Overview

The discussion revolves around Einstein's equation relating mass and energy, specifically the expression m = E/c². Participants explore whether this equation serves as a definition of mass and seek clarification on its derivation and context within special relativity.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • One participant questions whether m = E/c² is Einstein's definition of mass and seeks an explanation of how this conclusion was reached.
  • Another participant asserts that E = mc² and m = E/c² are equivalent, suggesting confusion may lie in understanding this equivalence or in the derivation of the equation.
  • A different participant asks for a specific paper reference where m = E/c² is used, indicating a need for context regarding Einstein's use of the equation.
  • One participant clarifies that rest energy and mass are equivalent, stating that if a body emits energy E, its mass decreases by E/c².

Areas of Agreement / Disagreement

Participants express varying levels of understanding regarding the equation's implications and context. There is no consensus on whether m = E/c² serves as a definition of mass, and the discussion remains unresolved regarding the specifics of its derivation and application.

Contextual Notes

Some participants reference the need for specific papers to clarify the context of the equation, indicating potential limitations in understanding its historical and theoretical background.

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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