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I have a couple of questions about general relativity
Дата публикации: 11-10-2026 12:30:20



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  • Thread starter Thread starter Uri Zlatnik
  • Start date Start date Oct 10, 2026
Uri Zlatnik
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Could general relativity be wrong and quantum mechanics on the right track in figuring the true cause of gravity and how it's connected to electromagnetism?
From a very young age, we are often told that space is a vacuum and a vacuum contains no matter and energy.

What we are also told from a very young age is that something cannot come from nothing.

So if a vacuum contains no matter or energy or even nothing at all then how can it curve or contain any fabric at all?

Also since we don't have a theory of quantum gravity, meaning we don't know how quantum mechanics and general relativity are connected, does it mean it could be a bit misguided to trust a theory written in 1916 which was 111 years ago?

Personally I would a bit hesitate to trust a theory written 111 years ago during War World 1 when people back then were probably ignorant of what time, energy, space, dimensions and what these things really are and what they really mean.

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I don't know about you, but if I look around I see stuff. Do you not?
It is true that we don't have a working theory of quantum gravity, but we have a working theory of how the quantum field theories work inside classical background gravity. This is called quantum field theory in curved spacetimes. It is only expected to break down when, roughly, gravity is "important at Planck scales".
Why?
Quantum mechanics is maybe 10 years younger than GR if you count from Heisenberg and Schroedinger's formulations. It's older than GR if you start from the Photoelectric effect or from Planck or Bohr.

Do you let age guide all your decisions?

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Imagine that tomorrow we find a complete Grand Unified Theory. There would be no new physics to discover. In a hundred years, would you mistrust it because it was old? In a thousand?

Old theories have survived all the tests that have been thrown at them - it's like the old saying about being wary of an old man in a young man's game. There's a reason that they survive in it. Similarly, GR remains a highly precise model that we've never caught making an incorrect prediction, which is why we continue to use it.

On the substantive question, only popsci describes spacetime as a fabric. Physicists certainly don't. And it is described as curved because the parallel postulate (initially parallel straight lines do not cross) does not hold. It is certainly possible that this is an effect of something we don't understand, but until we work out what that is, we continue with our best model.
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Yes. And then when we learn General Relativity, we learn that "no matter or energy" means that the stress-energy tensor is zero, but that in itself does not prevent spacetime from being curved, because there are solutions of the Einstein Field Equation with zero stress-energy tensor that are curved.
Yes. And then when we learn General Relativity, we learn that this means that the stress-energy tensor satisfies a conservation law: its covariant divergence is zero. This is enforced by the Einstein Field Equation, whose LHS is the Einstein tensor, whose covariant divergence being zero is a mathematical identity, and whose RHS is the stress-energy tensor, whose covariant divergence must then be zero because it's equal to the Einstein tensor (times a constant that depends on your choice of units).
That's what we learn General Relativity to explain. See above.
This is not quite true. We can do quantum field theory in curved spacetime, so we have some ways of connecting QM and GR.

What we don't have is a comprehensive theory that allows for quantum amplitudes for multiple different spacetime geometries.

Not at all. GR has plenty of experimental confirmation within its domain of validity. All we can say because of the lack of a theory of quantum gravity is that we expect GR's domain of validity to be limited to spacetime curvatures that are well below the quantum gravity scale (which most physicists assume to be the Planck scale). That covers a lot of ground.
Personally i would be very, very hesitant to make such pronouncements without first becoming very familiar with the extensive experimental confirmation of the theory.

Also, do you have a smartphone? Does it have GPS? Does the GPS tell you your location accurately? If so, you have strong evidence of GR's validity in a fairly wide domain, which includes the vacuum region around the Earth, where spacetime, even though it's vacuum, must be curved the way GR says in order for GPS to work.

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Uri Zlatnik
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I want to completely apologize to Einstein and to all of you guys for being completely wrong about general relativty. I'm really sorry guys.

I was never so good at math and apparently I'm not as smart and bright as Albert Einstein and never will be.

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[…]From a very young age, we are often told that space is a vacuum and a vacuum contains no matter and energy.

[…]

So if a vacuum contains no matter or energy or even nothing at all then how can it curve or contain any fabric at all?


You may perhaps have a too rigid definition of vacuum. Even the interstellar medium is not a true vacuum. Close yes but not completely.

(Sorry for using Wiki in here but it seemed correct in this case.)

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I meant of course to answer the OP and not pretend I could learn @Dale anything. :smile:
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