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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

#61

Post by tsimionescu »

DemocracyFTW2 wrote: post #58

Another goodie: > You need huge masses — think planets — to significantly warp space-time and generate obvious gravitational attraction. By way of comparison, a credit card-size magnet will stick to your fridge. By way of comparison, even an Olympic pool-size balloon of hot air will float.

It's not clear what problem you have with that comparison. It's a classical example of just how weak gravity is compared to the electromagnetic interaction. A whole planet's worth of mass is weaker than the EM field generated by a tiny magnet. And the strong and weak nuclear interactions are even stronger still.

Re: It might be possible to detect gravitons after all

#62

Post by lazide »

gradschoolfail wrote: post #29
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…

This needs to be emphasized more, by the TFA too — most (theoretical) physicists think that detecting gravitons is an engineering exercise that has no implications* for quantum gravity (as understood by the public) >The model of non-self-interacting gravity is a particle we call a "graviton," This needs to be emphasized even more, because it has >when the dx represents a slight change in a function *see the discussio…

Because they don’t want to run the risk of being wrong, eh?

Re: It might be possible to detect gravitons after all

#65

Post by DebtDeflation »

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.

Re: It might be possible to detect gravitons after all

#66

Post by actionfromafar »

whatshisface wrote: post #17
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!

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…

I don't know if it was just sheer luck that your comment fit my particular flavor of ignorance perfectly, but it struck me as great writing! I think I learned a little thing today. When I read the article I thought, too bad I can't ever understand anything of this, but now my personal model of the universe is just a little bit richer.

Re: It might be possible to detect gravitons after all

#67

Post by tecleandor »

DemocracyFTW2 wrote: post #58

Another goodie: > You need huge masses — think planets — to significantly warp space-time and generate obvious gravitational attraction. By way of comparison, a credit card-size magnet will stick to your fridge. By way of comparison, even an Olympic pool-size balloon of hot air will float.

But the whole atmosphere is pushing it up, isn't it? (Well, not the "whole" atmosphere, but...)

Re: It might be possible to detect gravitons after all

#69

Post by cryptonector »

trevordixon wrote: post #52
stouset wrote: post #42

Earlier quoted context omitted.

My naïve understanding is that you can model gravity as a force in a flat, static spacetime. Equivalently you can model gravity as a forceless distortion of curved spacetime. Both models can be translated faithfully into one another, so you can solve problems related to gravity in either domain.

My naive understanding is that forceless spacetime distortion predicts somewhat different things than the old model. That's how general relativity finally explained the procession of Mercury's orbit for example.

GP means that you can take the Einstein field equations (and their solutions) and use the metric tensors to map between flat and curved spacetime, with either way being equivalent. GP did not mean that those tools map from Newtonian flat spacetime to curved.

Re: It might be possible to detect gravitons after all

#70

Post by Seb-C »

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.
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