4 ms·

That's all well and good, but which part should I read to understand how gravitons travel from inside the event horizon to outside of it? Or maybe your response

That's all well and good, but which part should I read to understand how gravitons travel from inside the event horizon to outside of it? Or maybe your response is a nice way of saying that the question is flawed and gravitons don't actually do that or don't need to do that?

raattgift 5y ago
The question isn't flawed, but ignoring final evaporation, nothing crosses from inside the horizon to outside. Nothing. Ever. Under any circumstances. Things can only move from the outside to the inside, unidirectionally, and on a one-way trip. Gravitational radiation originates outside the horizon. It's noise in the near-horizon region caused by massive/energetic objects moving around outside the horizon (e.g. as a neutron star plunges inwards), and most of it dissipates away to infinity (a fraction settles down and serves to make a bigger, flatter horizon). Gravitons in almost every physical theory that has them are simply what you get when you look very very closely at gravitational radiation like this, just as photons are what you get when you look very very closely at a bright flash of light. Final evaporation isn't something we need to worry about for any practical purposes (and additionally it might never happen). However, just prior to final evaporation an extremely hot, tiny, almost-fully-evaporated black hole would be surrounded by a near-horizon region of extremely dynamical spacetime, which would be the source of quite a lot of gravitational radiation (and thus gravitons); the influence of that gravitational radiation on the spacetime-filling fields of the Standard Model would also generate quite a lot of electromagnetic (and other) radiation too. If we look very closely at all these different forms of radiation we'd see lots and lots of particles. That is, you might see X-rays and gamma rays, but they are not crossing from inside the horizon to outside. They're the effect of locally strongly curved spacetime on the local parts of universe-filling quantum fields (and the intense interactions of field-content being stretched and squashed in turn induces a backreaction on the dynamical spacetime nearby).
- aaron-santos 5y ago
  Thank you for the follow up. I've asked this question throughout the years and this is the first time that virtual grativitons haven't been introduced to explain away information escaping the event horizon. Thanks for taking the time to go through a thoughtful explanation.

raattgift 5y ago

The question isn't flawed, but ignoring final evaporation, nothing crosses from inside the horizon to outside. Nothing. Ever. Under any circumstances. Things can only move from the outside to the inside, unidirectionally, and on a one-way trip. Gravitational radiation originates outside the horizon. It's noise in the near-horizon region caused by massive/energetic objects moving around outside the horizon (e.g. as a neutron star plunges inwards), and most of it dissipates away to infinity (a fraction settles down and serves to make a bigger, flatter horizon). Gravitons in almost every physical theory that has them are simply what you get when you look very very closely at gravitational radiation like this, just as photons are what you get when you look very very closely at a bright flash of light. Final evaporation isn't something we need to worry about for any practical purposes (and additionally it might never happen). However, just prior to final evaporation an extremely hot, tiny, almost-fully-evaporated black hole would be surrounded by a near-horizon region of extremely dynamical spacetime, which would be the source of quite a lot of gravitational radiation (and thus gravitons); the influence of that gravitational radiation on the spacetime-filling fields of the Standard Model would also generate quite a lot of electromagnetic (and other) radiation too. If we look very closely at all these different forms of radiation we'd see lots and lots of particles. That is, you might see X-rays and gamma rays, but they are not crossing from inside the horizon to outside. They're the effect of locally strongly curved spacetime on the local parts of universe-filling quantum fields (and the intense interactions of field-content being stretched and squashed in turn induces a backreaction on the dynamical spacetime nearby).

aaron-santos 5y ago
Thank you for the follow up. I've asked this question throughout the years and this is the first time that virtual grativitons haven't been introduced to explain away information escaping the event horizon. Thanks for taking the time to go through a thoughtful explanation.