https://interestingengineering.com/science/gravity-particle-detection-within-reach
Scientists propose a groundbreaking method to detect single gravitons, the elusive particles believed to be the building blocks of gravity.
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If gravity is a particle, and that's a big "if", then the inescapable attractive force of a black hole would be the result of that particle's action, so what exactly would it be escaping? Itself?
I briefly worked in this area of physics, it's complicated and depends on your definition of a particle and which quantum gravity model you're talking about.
To simplify things you can just ask the same thing about non-quantum gravity. Why does gravity escape the black hole? The painfully mundane answer is that the black hole is gravity, it's not escaping itself. Gravitational waves can't be emitted from inside the black hole but that's because those are a form of radiation and not the structure of spacetime.
This is specifically important because even quantum gravity (the kind with gravitons) still has this distinction. Particles belong to a field and are excitations of it, the gravitational field itself is not made of those particles. The force associated with that field is mediated by gravitons, but what that really means is complicated and honestly possibly just the result of a cool mathematical trick. It also comes with a bunch of crazy behaviour where you have particles that can break the laws of physics by just kinda doing it so quickly that nature blinks and misses it.
The point is, the quantum gravitational field is enough for the black hole to do its job when objects come by, gravitons don't actually need to escape, though they are involved in complicated ways.
I always forget quantum physics exist, then someone mentions quantum gravity, and my brain explodes.
Almost none of this applies in the case of something like loop quantum gravity, which I understand very little of but I don't believe it's possible to discuss it using the language of QFT like I have above.
What kind of shower do you have that allows you to conduct observations in space? Not to mention write up a paper on it.
Thank you, finally somebody asks.
Also, other important question: What are the differential equations that describe how the Gravity Field propagates through space? In other words, at what speed does gravity propagate?
Only in a vacuum, in water it travels much more slowly. That's why you can float on water.
As far as I know (I'm not a physicist), it's not all that clear that gravity is caused by a particle. It makes sense to assume it is, because of parallelisms with the other fundamental interactions, all of which (other than gravity) are caused by particles that have been thoroughly observed and studied.
So we kinda know what a graviton would be like and what to look for, but so far it hasn't been found, and its existence hasn't been conclusively determined. There are some alternative hypotheses that in fact gravitons don't exist at all, and gravity is just a consequence of the shape of space-time, which I think is what's going on with black holes.
(source: trust me bro I saw it on the Internet)
I think that's the understanding of gravity for sizes of an atom and larger, which fall under the theory of relativity. In relativity, gravity is not a force; spacetime is a fabric that is bent by the presence of matter. For things smaller than an atoms, the leading theory is quantum mechanics. Quantum mechanics hasn't definitely explained gravity. One of the leading subtheories to quantum mechanics uses a hypothetical particle called a graviton to communicate gravity. No one has been able to unite the two leading theories in physics (relativity and quantum mechanics) with any experimental success. In the meantime, we just treat (a) things smaller than atom and (b) everything larger as two different worlds.
Maybe gravitons aren't affected by gravity, the same way photons aren't affected by em interactions (which they carry).
If that was the case, we would already have a quantum theory of gravity. The fact that "gravitons" (here I mean the particles of a second quantisation of GR) can interact with themselves makes the theory almost completely useless.
It's technically possible to write down such a theory, but the only way to get results out of it is to first perform an infinite number of experiments.
Or maybe they do interact with each other and that's how they escape: they're forced out by interactions with all the other gravitrons in the black hole.
