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General relativity allows various forms of energy to participate in the gravitational force.

What observation(s)--if any--confirm general relativity's notion that the various types & concentrations of energy which are influenced by gravity (i.e. feel the effect of spacetime curves...sometimes referred to as "passive") are all the same types & concentrations that cause gravity (i.e. create spacetime curves...sometimes referred to as "active")?

I now provide links to a couple Physics StackExchange questions which arguably come close to answering the above, but don't quite answer it...with one answerer readily admitting he's unaware of any such observation(s), when it comes to light.

Thank you for your help.

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user50489
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    You may see, in one of the linked questions, that an argument has been made that QCD binding energy is properly considered to contribute to what some call "active mass." However, at least based on what's in that particular link, I still don't understand how we know, from actual experiment or observation, that QCD binding energy doesn't contribute only to "passive mass" rather than both "active" and "passive." – user50489 Mar 19 '15 at 15:00
  • Well, we put the concentrations and types of energy into the right side of the EFEs and we put gravity and the geometry of spacetime into the left side. That results in the types of energy sourcing and reacting to gravity (although saying something reacts to gravity is like saying it moves through space). Then with the EFEs, we make predictions of what observations this setup would result in. If those predictions match reality, that's good evidence that the types of energy source gravity – Jim Mar 19 '15 at 15:14
  • Thanks, Jimnosperm. So, going back to QCD binding energy for example...as far as you know, has anyone ever attempted what you just said, but only after estimating and subtracting out the QCD binding energy within each supposedly gravitating body? And if so, did the predicted movement match, or not match, what was actually observed? – user50489 Mar 19 '15 at 15:21
  • I'm not sure. I have no idea if that has been attempted or not. But I think it might require quantum gravity to successfully and completely do that. Sadly, that's outside my bailiwick – Jim Mar 19 '15 at 15:47

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  1. Eötvos-type experiments establish that QCD binding energy is exactly equivalent to mass as far as feeling the effects of gravity.
  2. Conservation of momentum is generically observed in all interactions in our universe.
  3. given 1. and 2., if energy was NOT active mass, then the force that a pound of gold exerted on the Earth would be different than the mass that a pound of hydrogen exerted on the Earth. Since they FEEL the same force from the earth, you cannot have conservation of momentum as both of them fall, since they would exert different forces on the Earth
  4. Therefore, if you believe that passive mass is different from active mass, you either have to disbelieve in conservation of momentum or the equivalence principle, both of which are exactly consistent with known experiment.
Zo the Relativist
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