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Einstein in his book: Relativity: The Special and General Theory. http://www.ibiblio.org/ebooks/Einstein/Einstein_Relativity.pdf [edit] on page 56, I believe] writes, "the expression for energy" in the form $\frac{mc^2 +E_0}{\sqrt{ 1-v^2/c^2}}$, where $m$ is the rest mass and $mc^2$ the energy of the rest mass. $E_0$ is the energy added to the body (by adding photons, for instance). Then the rest mass energy, $mc^2$, and added energy, $E_0$, is divided by $\sqrt {1-v^2/c^2}$ to account for the energy of the velocity. And that, I think, produces gravity. That is my expectation. Am I right?

I am no expert on this. I welcome criticism of this post. I think this energy is what is said to curve spacetime or create gravity.

Relativistic mass, is calculated as $\frac{M_{(rest)}}{\sqrt {1-v^2/c^2}}$

I think that relativistic mass is gravitational, as is "absorbed energy".

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  • $\begingroup$ at which page? .. $\endgroup$
    – Umaxo
    Commented Aug 13, 2020 at 7:19
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    $\begingroup$ I repaired your mathjax formulas, but next time, invest some time into your question and repair your typos, make it as readable as possible and as clear as possible.It takes time and effort to give quality answer and it is only fair you make the same effort to write quality question. In this way, it will much more useful and impactful on broader audience and not just you. $\endgroup$
    – Umaxo
    Commented Aug 13, 2020 at 7:29
  • $\begingroup$ I'm just learning the mathjax. thanks for the edit. I see the proper sqrt form now. $\endgroup$
    – BruceAW
    Commented Aug 13, 2020 at 8:35
  • $\begingroup$ On page 56, if I understand correctly. It was an unmarked page, between 55, and 57.. I found it, for the purpose of quote, by searching "mass". $\endgroup$
    – BruceAW
    Commented Aug 14, 2020 at 13:47

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General relativity is, unfortunately (or fortunately, depending on your perspective), a lot more complicated than that. The curvature of space-time is directly related to the stress-energy tensor, which, roughly speaking, is a 4x4 matrix that encapusaltes the ideas of energy, momentum, and stress (the rate of flow of momentum) into one object.

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  • $\begingroup$ Is one 'complication', is that vector energy {KE, light etc.)exerts a gravitational like force in the direction of the vector? Something like 'frame drag'? – BruceAW 17 mins ago $\endgroup$
    – BruceAW
    Commented Aug 14, 2020 at 0:02
  • $\begingroup$ The complication is that energy is frame-dependent. You'll measure different energies in different frames. The energy-momentum vector is a valid geometrical object that combines energy and momentum. However, curvature in four dimensions needs a lot of numbers to describe it, so the vector isn't enough. What we end up with is a relation between a "matrix" (tensor) describing curvature and the stress-energy tensor. $\endgroup$
    – Technically Natural
    Commented Aug 14, 2020 at 1:16

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