This New Idea to Detect a Quantum of Gravity Might Just Work

Correction to the screen text at 05:04: It's in the range of microgram. What I say is correct, the text isn't. Sorry about that.

Gravitons are one of the most sought-after particles in physics. They could help physicists combine quantum physics with gravity to create a theory of "quantum gravity." We thought until recently they were for all practical purposes impossible to detect, but now scientists are coming up with some ideas for how graviton-detecting experiments could work for real. Let’s take a look.

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#science #sciencenews #physics #gravity

[SabineHossenfelder]

You can now create your own quizzes on my website and embed them into your website or add them to your own videos. It's free -- just set up an account and a creator profile.

[igorpikovski]

Hi Sabine, thank you for covering our work! I am glad you found it interesting, and it was a nice explanation! But one point of clarification: We don't need to use 1 ton of mass. Rather, ideally one would have around 10kg of Beryllium, this would be the ideal detector to catch a single graviton from a neutron-star-merger event (maximal probability to absorb only a single graviton). Cooling close to the ground state in this mass range has been achieved. Nevertheless, detecting a single quantum jump of exactly one graviton energy is still difficult at these masses, so it certainly requires significant effort for the sensing part. But it can be done in the kg mass-range.

[markdowning]

Thanks Sabine.
1\ Physicists sometimes say that gravity is not a force, but the curvature of space. So why would it be expected to have particles as the three forces do?
2\ You said micrograms but your graphics guys said mg (milligrammes). 😲

[Thomas-gk]

Dr. Sabine must be a large source of high energy motivons by working through all these 🦄- papers for us.👌

[hugegamer]

I’m afraid my motovons are quantized and I never have enough energy to pump them into an excited state. This channel explains life so well.

[SpaceFrogFromOuterSpace]

Quantum computing, fusion reactors, and graviton detection are all possible, but we're just not cool enough yet.

[arctic_haze]

I no longer know whether we need gravitons at all. But this experiment would still be a great thing. This is something that can't be solved without using empirical data.

[markmoore]

I'm sure you've already caught this, but at about 5:03 the screen says milligrams (mg) but your voice says micrograms (µg)

[ThomasGutierrez]

The CUORE experiment at the LNGS has cooled down about a tonne of tellurium dioxide crystals to under 10mK and kept it stable for years, so the cryogenic technology is definitely there

[TheOriginalNinetyEight]

This sounds like revisiting the history of gravitational antennae. First, Weber tried giant metal cylinders but thermal noise drowned out any signal. The obvious next thing was to cool them to cryogenic temperatures. But stresses captured in the metal slowly released in random pings producing false signals. Then Braginsky concluded that a perfect crystal cylinder (still cryogenic) was needed to ring for a long time after a wave hit it and aluminum oxide(sapphire) was a good material. At this point I no longer remember the quantities accurately but I think his engineers had gottten to the point of being able to produce 5kg crystals and were striving towards 10kg with 25kg the eventual goal.
At this point the story gets amusing. Someone located a company in the US was already producing suitable 15kg crystals. Their current equipment could attain 20kg but no one had previously asked for one that size. As for 25kg, they would merely need to build a bigger oven. All the techniques would be the same.
And who were the customers for these perfect crystals? Manufacturers of armored cars. They made excellent windows, clear and tough.
This was in the late seventies and I heard no more until LIGO eventually made the effort somewhat moot.

[innuendo]

I occasionally write fiction, and sometimes the lore of my fiction becomes indistinguishable from this kind of " it should exists because it fits" science to the point that some of my more excitable readers actually told me I should use my lore to write a quantum physics paper. Of cause I won't, for one because aI made that shit up out of nothing and the sole purpose of lore and world building is to make shit fit to things like intergalactic portals, not to JWT observations or other real things, and secondly that I'm just an engineer with applied science credentials in electrical engineering, computer forensics, and computer statistics, I'm nothing close to an astrophysicist or particle physicist, so even if it wasn't completely made up fiction, I couldn't write a quantum physics paper to safe my life. One thing however that I feel stands out from the discussions I've had is it feels like the real physicists seem to only consider "emergent" as an absolute last option, while these excitable readers seem to exactly cling to the "it's emergent, stupid" way of thinking. I got triggered by this subject because in my fiction gravity is emergent (in short, there is a quantum chrono field with chronotons, no gravitons), but the same avoidance of considering emergent properties other than as last resort is there when you discuss things like free will. This really makes me wonder: Sabine, why are emergent properties always at the end of the line when it comes to physics hypothesis creation and testing?

[lotharschwab]

Sabine - your dry humor and eloquent articulation make me laugh and learn at the same time. Brilliant!

[BryanBrookesSmith]

3:36 finally we get to see Sabine from the waist down

[martinwettig]

1:35 I see Ricky Gervais is now doing stock footage.

[Valecan]

Okay, maybe I am missing something here. Will have to read the paper, but this is just a modified version of the existing experiments for gravitational wave called resonant mass detectors which have been used since the 60s. The issue with those detectors was the dimensions of the solid cylinders used in the detectors would have a narrow range of frequencies it could detect because you needed a strong enough passing gravity wave at the exact resonant frequency in order to have a chance to detect anything. And that is after you isolated it from all the outside sources of noise. If I recall correctly, the last generation of these detectors use to keep the temperature at 4 K, but in the 90s there was a proof of concept experiment that maintained a temperature of 50 mK or so. If they are able to maintain a low mK environment with high quality vibrational isolation, you will still have the issue of narrow frequency bandwidth and how do you separate the quanta measurement from the bulk wave? I need to read this paper.

[hermaeus_jackson]

It's exciting that people are coming up with ideas to test quantum gravity that are, like, remotely possible. Cooling a tonne of metal to near absolute zero might be out width our current abilities, but its almost certainly doable. It has a foundation in a sensible theory, and doesn't rely on sci-fi level megastructures in space, and travelling to neutron stars and other garbage like that.

[pokerandphilosophy]

I once found a graviton on the beach and I brought it back home. My girlfriend thought it was a tick and she threw it away.

[JarkkoToivonen]

Thanks for the new information Sabine . You must work hard for this channel, thanks for your hard work.

[barontau]

This metal would also need to be monocrytalline for enhanced absorption into the phonon modes. A large, perfect, monocrystalline metal is very difficult to make. Additionally 1 ton would certainly reorganize due to the strain in Earth's gravity. Most dark matter searches take advantage of a high Q resonance to make the response less broadband and their responses all would look like gravity if you don't have dark matter.

[giulas]

I love the easy-to-understand way you talk about physics and your "Sheldonresque" humor...