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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

#101

Post by baseballdork »

maronato wrote: post #99
skhunted wrote: post #92

Earlier quoted context omitted.

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.

It was called out because OP used "Inshallah". The argument is that it's cultural, and complaining about it is silly.

Re: It might be possible to detect gravitons after all

#102

Post by skhunted »

maronato wrote: post #99
skhunted wrote: post #92

Earlier quoted context omitted.

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.

The point I was making is that this phenomenon occurs in other languages. Arabic and its phrases involving "allah" first came to mind. So how was this "needlessly"? I needed to give an example of this occurring in another language.

Re: It might be possible to detect gravitons after all

#103

Post by philipov »

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!

There are some ideas that spacetime is an emergent phenomenon. One such proposal is that it is produced by the large-scale presence of entanglement between particles: that entanglement creates spacetime. Where entanglement between regions of spacetime is stronger, the space is closer together, and where that entanglement is cut things get farther apart. This idea is known as "ER=EPR" [0].

That's the link bridging gravity as a particle (small-scale) and gravity as a feature of a manifold (large-scale). Physicists are trying to find a way to make spacetime emerge from quantum field theory, or make both emerge from some common framework.

0: https://en.wikipedia.org/wiki/ER_=_EPR

Re: It might be possible to detect gravitons after all

#104

Post by GranularRecipe »

DemocracyFTW2 wrote: post #57

I choked on this part: > The discussion recalls a messy, largely forgotten episode from the dawn of the quantum era. In 1905, Einstein interpreted experimental data to mean that light is “quantized,” coming in discrete particles now called photons. Others, including Niels Bohr and Max Planck, thought that the classical, wave nature of light might still be saved. [...] Most physicists presume that everything in the wo…

It's not an inshallah, it's a masha'Allah.

Re: It might be possible to detect gravitons after all

#105

Post by gosub100 »

7373737373 wrote: post #77
DemocracyFTW2 wrote: post #57

I choked on this part: > The discussion recalls a messy, largely forgotten episode from the dawn of the quantum era. In 1905, Einstein interpreted experimental data to mean that light is “quantized,” coming in discrete particles now called photons. Others, including Niels Bohr and Max Planck, thought that the classical, wave nature of light might still be saved. [...] Most physicists presume that everything in the wo…

Re. 2), what word should be used instead? "Massive concerted/collaborative effort"?

Quest, undertaking, chapter.

Re: It might be possible to detect gravitons after all

#106

Post by whatshisface »

gus_massa wrote: post #74
whatshisface wrote: post #17

Earlier quoted context omitted.

Our ability to solve integrals is much more limited when the dx represents a slight change in a function, rather than a small change in a real number. As a result, a lot of things that are easy to say in English such as "quantized curvature in spacetime," or "strongly coupled gauge theory," turn into a big mess when they're written down more precisely. One of the consequences of this limitation is that we have a mode…

> The model of non-self-interacting gravity is a particle we call a "graviton," and it probably describes reality very well when the gravitation involved is so weak that its self-interaction is undetectable. I disagree with that part. For the strong force we have the "gluons" and they are considered particles and they have a strong self-interaction. The strong self interaction makes it a huge mess and a lot of things…

The thing is, no particle is defined when it interacts. At our present level of understanding the only defined particles are the individual green's functions that appear in perturbation expansions, the lines in Feynman diagrams.

We see interacting particles in detectors, but since nobody can write down what field configuration they mean by "a photon," I can defend my phrasing - but you can defend yours too because I know what a bird is even if I don't know how they work.

Re: It might be possible to detect gravitons after all

#107

Post by DebtDeflation »

marcosdumay wrote: post #100
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.

Rather, the existence of black holes demonstrates that gravity is not renormalizable.

The last sentence in the paper:

"It seems that gravity is a low energy effective field theory description of something else that is not a quantum field theory."

QFTs like QED and QCD are renormalizable. This is a technique used to eliminate the infinities that arise in calculations from self-interaction. For a very long time, renormalization was viewed as hocus pocus (including by the person who discovered it). Later, mathematicians were able to provide a solid theoretical foundation for it.......but only as an effective field theory valid at particular size and energy scales.

Net net, the standard model is an approximation of something more fundamental. Gravity being nonrenormalizable shows that "something" is not a QFT.

Re: It might be possible to detect gravitons after all

#108

Post by 1234letshaveatw »

evantbyrne wrote: post #88
DemocracyFTW2 wrote: post #57

I choked on this part: > The discussion recalls a messy, largely forgotten episode from the dawn of the quantum era. In 1905, Einstein interpreted experimental data to mean that light is “quantized,” coming in discrete particles now called photons. Others, including Niels Bohr and Max Planck, thought that the classical, wave nature of light might still be saved. [...] Most physicists presume that everything in the wo…

You seem to be frequently flame posting about America. Are you going to be okay?

It is a cringeworthy hallmark of angsty teens and people who base their entire identity on their political leaning

Re: It might be possible to detect gravitons after all

#109

Post by sroussey »

skhunted wrote: post #94
Smithalicious wrote: post #89

Earlier quoted context omitted.

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".

The “war on Christmas” was thought up by a think tank and agreed upon by a group of conservative media that meet weekly to decide agenda to push across talk radio, tv, online. Truly an American phenomenon.

Re: It might be possible to detect gravitons after all

#110

Post by itishappy »

choilive wrote: post #46
itishappy wrote: post #14

Earlier quoted context omitted.

They can detect an interaction, but they can't prove that it's quantized without (I believe) sub-Poissonian statistics[0], which requires detecting enough events and with enough certainty that it would require planet-scale machinery. > Now graviton chasers find themselves in a peculiar position. On the main facts, everyone is in agreement. One, detecting a quantum event sparked by a gravitational wave is — surprising…

It sounds like the article is saying we could detect many events without using a planetary scaled detector It mentions a single detector being a 15kg Be bar chilled to near absolute zero. Certainly very very difficult, but not in the realm of sci-fi.

Right, but this event just confirms gravitational radiation exists (which we already know). It can't tell us how it behaves (is it quantum? it it classical?) without detecting many events in sequence to be able to run statistics on (and if you miss one, your stats are wrong). One bar has a very low probability of detection, we'd need many, hence the expectation of planet-scale machinery.
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