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- Thread starter derek.basler
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HallsofIvy

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[tex]\frac{m_0}{\sqrt{1- \frac{v^2}{c^2}}}[/tex]

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alxm

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Sounds weird. I was always told I'd _lose_ weight by jogging. :)

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Mass, length, time, kinetic energy are all relative.

Electric charge and potential energy seem fixed. And I still wonder about potential energy.

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Relativistic (like in this thread) or Invariant mass?

I was told in this forum that in modern physics mass=invariant mass as relativistic mass is just a synonym for E/c^2 and is useless.

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The mass needs to be useful. One useful application should be for gravitational force calculation.

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jtbell

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Yes, the invariant mass [itex]m_0[/itex] which can be calculated fromIs there a mass that stays invariant no matter what reference frame you observe it from?

[tex]m_0 c^2 = \sqrt {E^2 - (pc)^2}[/tex]

has the same value in all inertial reference frames.

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That does seem to be a convention favored by some here, yet in books I read by Smolin, Hawking, Penrose, Greene, Randall and others, they seem to routinely use relativistic mass....I don't see it as a big deal either way...I was told in this forum that in modern physics mass=invariant mass as relativistic mass is just a synonym for E/c^2 and is useless.

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Ich

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True. The Earth loses invariant mass during this process. It's a pity that pervect is no longer around to give a short lecture on the meaning of "mass" in GR.derek.basler said:The lost potential energy is then radiated as heat, and therefore the Earth loses energy. And since energy and mass are inter-related, the Earth thereby loses mass.

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The big deal is that people get replies without specifying the meaning of the "mass".That does seem to be a convention favored by some here, yet in books I read by Smolin, Hawking, Penrose, Greene, Randall and others, they seem to routinely use relativistic mass....I don't see it as a big deal either way...

The same person can get inconsistent replies in parralel threads, like "is mass conserved? yes", "is mass invariant? yes"

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Are they textbooks of physics currently used at university? Because if they were, it would be serious; if they are not, then I suggest you to look up in physics textbooks.That does seem to be a convention favored by some here, yet in books I read by Smolin, Hawking, Penrose, Greene, Randall and others, they seem to routinely use relativistic mass....I don't see it as a big deal either way...

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