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It might be possible to detect gravitons after all

quantamagazine.org

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Re: It might be possible to detect gravitons after all

#91

Post by AnimalMuppet »

NitpickLawyer wrote: post #39
cryptonector wrote: post #34

Earlier quoted context omitted.

That gravity is curvature of spacetime is one view of two equivalent views, but it is the standard view. The other view is that you have flat spacetime with different distortions (of things other than spacetime) than the distortions you get in curved spacetime. The Schwarzschild metric essentially lets you do exactly that projection of curved spacetime to flat, and vice-versa. When you watch an animation like https:/…

I last took a physics course when Pluto was a planet, so excuse my possibly outdated question, but isn't the detection of gravitational waves proof of gravity being a force? I follow a few educators/communicators in this field and I have a feeling they're using this "gravity isn't really a force" to bridge the gap between their deep understanding and us mortals that don't poses the language / understanding to get the…

Consider centrifugal force. In a non-rotating reference frame, it doesn't exist. In a rotating reference frame, it does, that is, it shows up as a term in the equation of motion.

You wouldn't expect to find quantums of centrifugal force in a rotating frame of reference, and no quantums of centrifugal force in a non-rotating frame of reference. They're both describing the same situation; either quantums exist in both frames, or they exist in neither.

So either gravity really exists as a force, or it doesn't. If it does, then I would expect gravitons, and expect them in all frames of reference. If it doesn't, then I would expect no gravitons in any frame of reference.

Except... If I understand correctly, static electric and magnetic fields are not carried by photons - they just sit there. It's only changing E/M fields that are carried by photons. So maybe only changing gravitational fields are carried by gravitons, and the static fields are just curved space-time?

Re: It might be possible to detect gravitons after all

#92

Post by skhunted »

wizzwizz4 wrote: post #85
skhunted wrote: post #78

Earlier quoted context omitted.

Please spare me that "war" simile, it only shows you're an American who can not write too well. It’s understandable that you don’t like the desensitization of war that comes from our over usage of the word. Perhaps it speaks to a defect in American culture but this is how we communicate in our language. I think Arabic has too much emphasis on allah related phrases. But that’s how they speak. Nothing I can do about it…

English has a lot of "oh my god", "god-willing", "oh god", "god no", too.

It was pointed out that in American English we overuse "war". I pointed out a language that overuses a different word. I imagine most languages have a bunch of phrases involving an overused word. My point was that this phenomenon isn't unique to American English.

Your response is that English also overuses another word. I don't understand the point you are trying to make.

Re: It might be possible to detect gravitons after all

#93

Post by AnimalMuppet »

Wololooo wrote: post #45
NitpickLawyer wrote: post #39

Earlier quoted context omitted.

I last took a physics course when Pluto was a planet, so excuse my possibly outdated question, but isn't the detection of gravitational waves proof of gravity being a force? I follow a few educators/communicators in this field and I have a feeling they're using this "gravity isn't really a force" to bridge the gap between their deep understanding and us mortals that don't poses the language / understanding to get the…

So the main issue here is how people were presenting it, in Quantum field theory, as stated by other people, each force is associated with a field and has at least one force carrier, the exact number is linked to the specifics of the mathematical framework underlying it To that extent you can build 3 fundamental forces, electro magnetic, weak (that are called together electroweak) and the strong force. You have an ex…

> neutrinos have mass and this in itself is a problem because the Higgs mechanism doesn't provide mass to them ...

The Higgs mechanism doesn't provide all mass, even of the things that it provides mass for. They each have a "bare" mass, that is, a mass without any Higgs interactions. They just have a much greater mass because of the Higgs interaction. (And maybe that's why neutrinos have so little mass...)

Re: It might be possible to detect gravitons after all

#94

Post by skhunted »

Smithalicious wrote: post #89
skhunted wrote: post #78

Earlier quoted context omitted.

Please spare me that "war" simile, it only shows you're an American who can not write too well. It’s understandable that you don’t like the desensitization of war that comes from our over usage of the word. Perhaps it speaks to a defect in American culture but this is how we communicate in our language. I think Arabic has too much emphasis on allah related phrases. But that’s how they speak. Nothing I can do about it…

Let's split the difference and start talking about the "jihad on drugs"

Nice. I think it would probably be more effective propaganda to say the "jihad on Christmas" than the "war on Christmas".

Re: It might be possible to detect gravitons after all

#95

Post by cryptonector »

toomuchtodo wrote: post #13
choilive wrote: post #4

> physicists are debating what it would really prove. Well, if we can detect the graviton before we have a working quantum theory of gravity, it would mean that gravity is in fact quantized and that we just need to figure it out. This would be a very big deal.

> This would be a very big deal. Gravity drive?

Nope.

Re: It might be possible to detect gravitons after all

#96

Post by mr_mitm »

mensetmanusman wrote: post #71
Seb-C wrote: post #70

Since I read the story "The Road Not Taken" from Harry Turtledove, I cannot stop thinking that we might eventually discover that the question of the conflict between the general relativity and quantum theories is something so simple and elegant that we never even considered it before.

Or, something like the simulation hypothesis is real and different models of reality are used at different length scales and the overlap is fuzzy.

The issue is that the overlap becomes large and very important near black holes (and near the big bang, but that's probably not important in a simulation).

Re: It might be possible to detect gravitons after all

#97

Post by gpsx »

ta93754829 wrote: post #10

So I thought gravity was basically the curvature of spacetime. But if there's a "gravity" particle, those two things seem mutually exclusive? Can someone who understands this please explain it to me, thanks!

Gravity is similar to an electric field here. A wave function for a field consists of an amplitude for each field configuration, where a “field configuration” refers to a value for the electric field for each point in space. In GR each field configuration would correspond to a space time geometry for the universe. We have quantized excitations as distinct “valid” solutions to the wave function, which we call a particle, though it is nothing like an electron. The notion of space time geometry holds throughout. (Edit: in practice, people never calculate wave functions for fields like electric fields. That would be too hard. Different methods are used in calculations. Second edit: the wave function wouldn’t be composed of complete space-time configurations, histories of the universe, but time slices from it, like space geometries. Maybe this can be expanded in responses/comments.)

Re: It might be possible to detect gravitons after all

#98

Post by eterevsky »

So the article says that Freeman Dyson calculated that only one graviton capture event would happen per billion years in a detector the size of the Earth. The new experiment however proposes to use 15 kg of super-cooled Beryllium.

My question is: what's the difference between the proposed Beryllium slab and Dyson's theoretical detector?

Re: It might be possible to detect gravitons after all

#99

Post by maronato »

skhunted wrote: post #92
wizzwizz4 wrote: post #85

Earlier quoted context omitted.

English has a lot of "oh my god", "god-willing", "oh god", "god no", too.

It was pointed out that in American English we overuse "war". I pointed out a language that overuses a different word. I imagine most languages have a bunch of phrases involving an overused word. My point was that this phenomenon isn't unique to American English. Your response is that English also overuses another word. I don't understand the point you are trying to make.

Your response needlessly called out Arabic for using too much “Allah”.

English overuses it the same amount, given that Allah is their word for God.

Re: It might be possible to detect gravitons after all

#100

Post by marcosdumay »

DebtDeflation wrote: post #65

The fact that QED and QCD are renormalizable while gravity is not is probably trying to tell us something deeper than we think. Relevant paper: https://arxiv.org/pdf/0709.3555 You can read the first two paragraphs of the Introduction and then skip to the last sentence of the Conclusion if you want to bypass all the math.

So... If gravity is quantized, then black holes must be only a low-energy approximation of whatever phenomenon is really happening there?

If there's some proof that they aren't black (AFAIK, the only thing we know empirically), I've missed it. All I see is a point that the current theory would be wrong.

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