Title

16 points

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?

permalink
report
reply
43 points
*

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.

permalink
report
reply
12 points

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.

permalink
report
parent
reply
2 points

I always forget quantum physics exist, then someone mentions quantum gravity, and my brain explodes.

permalink
report
parent
reply
49 points

What kind of shower do you have that allows you to conduct observations in space? Not to mention write up a paper on it.

permalink
report
reply
77 points

A: A meteor shower!

permalink
report
parent
reply
7 points

Well played.

permalink
report
parent
reply
1 point

You win the internet for today.

permalink
report
parent
reply
32 points
*
  1. We have no conclusive evidence to suggest that gravity is propagated by particles. Currently, we think that it very likely might be, but we have not come up with models to quantize gravity. U would win a Nobel prize if u did that.
  2. Watch this
permalink
report
reply
8 points

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?

permalink
report
reply
16 points

I’m relatively certain we’ve established that gravity travels at the speed of light

permalink
report
parent
reply
23 points

Only in a vacuum, in water it travels much more slowly. That’s why you can float on water.

permalink
report
parent
reply
7 points

Archimedes is going to get really angry when he reads your comment

permalink
report
parent
reply
16 points

permalink
report
parent
reply
3 points
*

A WITCH!

permalink
report
parent
reply
2 points

Lol nope

permalink
report
parent
reply
1 point

Isn’t it the same speed electromagnetic fields propagate through space?

permalink
report
parent
reply

Showerthoughts

!showerthoughts@lemmy.world

Create post

A “Showerthought” is a simple term used to describe the thoughts that pop into your head while you’re doing everyday things like taking a shower, driving, or just daydreaming. The best ones are thoughts that many people can relate to and they find something funny or interesting in regular stuff.

Rules

  • All posts must be showerthoughts
  • The entire showerthought must be in the title
  • Posts must be original/unique
  • Be good to others - no bigotry - including racism, sexism, ableism, homophobia, transphobia, or xenophobia
  • Adhere to Lemmy’s Code of Conduct

Community stats

  • 6.3K

    Monthly active users

  • 1.3K

    Posts

  • 44K

    Comments