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Scientists observe Einstein's gravity in the quantum world
https://www.youtube.com/watch?v=CfjnTJos_no https://www.youtube.com/watch?v=CfjnTJos_no
- hammock 12d agoThere is a GREAT, accessible video about this experiment here: https://www.youtube.com/watch?v=CfjnTJos_no https://www.youtube.com/watch?v=CfjnTJos_no
- dang 9d agoThanks! We'll put that link in the toptext as well.
- deleted 9d ago[deleted]
- canadiantim 9d agoAny explanation by Roger Penrose is bound to be good
- thrance 9d agoExcept when he's rambling about quantum consciousness or other nonsense, which happens a lot nowadays.
- randomImmigrant 9d agoYou know, I pooh poohed his theories. Still do in sum. But there’s a there there that’s building. Damn Deepak Chopra and his ilk of idiots for making any conversation of quantum mechanics and biology tinged with pseudoscience. Hopefully we’ll keep getting experimental evidence as we go that it’s not at all absurd to consider quantum effects in biology. That said, those effects are going to look nothing like sustained coherence for long periods of time.
- MarkusQ 9d agoThey didn't start the fire. Quantum + biology → Woo has been with us since the 1960s at least.
- yreg 9d agoHave you actually hear him talk about it? It is very far from rambling and he will be the first to tell you that he is not sure he is right. We need physicists to come up with and develop novel ideas to consider no matter how many of them might be entirely wrong.
- GoblinSlayer 9d agoIf mind was random, people would miscalculate 1+1 with 50% probability. So earth might be flat, but it's unlikely.
- yreg 9d ago> If mind was random, people would miscalculate 1+1 with 50% probability. That does not follow at all.
- GoblinSlayer 9d agoMiscalculation doesn't follow from randomness?
- yreg 9d agoIf you run an LLM (with temp >0) and use a true random generator for seeds, it will still tell you 1+1 is 2.
- GoblinSlayer 9d agoYou mean mind is deterministic and cancels all noise? Then what quantum physics would do there?
- yreg 9d agoYou don't need to cancel all the noise to solve 1+1 correctly. The model in the example is non-deterministic. I don't know Penrose's view deeply enough to defend it further (view which I for the record do not share).
- qsera 9d ago>quantum consciousness or other nonsense Can you tell me why it is non-sense? We, through our senses perceive a world. This world we try to understand using physics. But these perceptions itself stands on top of consciousness. So consciousness is at least, as real as the world that physics conventionally tries to reason about. It could be even more fundamental, because you can have only consciousness in this universe, but still could sense a whole universe with "things" inside it. But without consciousness, and just a universe with "things", there is no "sensing"... Point is, physics should include study of consciousness...
- deleted 9d ago[deleted]
- shevy-java 9d agoSo do we finally have one unified theory or are we still none the wiser?
- swiftcoder 9d agoFrom the article: "The result does not unite quantum mechanics and gravity, nor does it show that gravity itself is quantum". I must say, it's actually quite refreshing to read an article about a science topic that conveys the caveats and limitations of the study. Far too many of these studies get filtered through the news outlet hype-machine
- Mizza 9d agoIf you'd learn about a proposed experiment to test the quantum nature of gravity, this is a cool video: https://www.youtube.com/watch?v=Uey_mUy1vN0 https://www.youtube.com/watch?v=Uey_mUy1vN0 Hopefully we'll see a result in the next decade
- rhdunn 9d agoThe article says that this proves that Einstein's equivalence principle (resulting in relativity) holds in this test of a falling quantum particle (where gravity results in a phase shift in the quantum state). It doesn't show/prove how general relativity and quantum mechanics interact. NOTE: The Dirac equation and Quantum Electro Dynamics (QED) unify quantum mechanics and special relativity (non-accelerating frames of reference). So the remaining piece is either to extend QED/QCD to accelerating frames of reference or to quantize general relativity. That would likely predict the phase shift observed in this experiment.
- pdonis 9d ago> The Dirac equation and Quantum Electro Dynamics (QED) unify quantum mechanics and special relativity And more generally the Standard Model, which includes the weak and strong interactions. The SM is a quantum field theory, which, as you say, unifies QM and SR. > (non-accelerating frames of reference). No, SR and QFT are not limited to non-accelerating frames. They are limited to small enough regions of spacetime that spacetime curvature is negligible. This experiment is an illustration of that: it compares an accelerated atom with a free-falling atom to show the phase shift between them, and the lab frame in which it is done is accelerated--but the SM and SR work just fine. But the experiment does not show any effects of spacetime curvature. > the remaining piece is either to extend QED/QCD to accelerating frames of reference No, that's already done. See above. > or to quantize general relativity. That's the big missing piece, yes. We know how to write the QFT of a massless spin-2 field (which is our naive expectation of what a QFT for gravity would look like), and we know that the classical limit of that QFT is the classical GR we have now. But we know that QFT has to be just an effective theory, just like the Standard Model; it can't be the final answer. > That would likely predict the phase shift observed in this experiment. The theories we already have (Standard Model + the equivalence principle are all we actually need) are sufficient to predict that. Of course any more comprehensive theory will have to reproduce that prediction, yes.
- ck2 9d agoso many great PBS Space Time on this concept * https://www.youtube.com/@pbsspacetime/search?query=graviton https://www.youtube.com/@pbsspacetime/search?query=graviton
- hyperhello 9d agoUnfounded speculation, but is it possible that every particle could have a different individual light speed, and the one we know is just the average speed that they have to drop or speed up to, the way a car needs to travel at the same speed as the highway?
- exe34 9d agoWhat measurable predictions does this hypothesis make that would differ from the existing models?
- hyperhello 9d agoWell, yeah. Perhaps if this experiment was expanded for a chain or a filter of cause and effect then it could be shown that one event affects another.
- exe34 9d agoAs opposed to current models, where one event does not affect subsequent events?
- hyperhello 9d agoGood god, sorry I participated in any way. Apparently there’s a quantum physics colloquium I’m disturbing.
- exe34 9d agoI'm sorry, I thought you knew how scientific ideas were discussed, I didn't know you were just trying to bootstrap a new religion.
- setopt 9d agoProbably no, because according to quantum mechanics, photons are indistinguishable in a way that affects experiments.
- ziomerlojahsay 9d ago[flagged]
- 0x62 9d ago> Please don't use Hacker News for political or ideological battle. It tramples curiosity. https://news.ycombinator.com/newsguidelines.html https://news.ycombinator.com/newsguidelines.html
- pjungwir 9d agoI was wondering last night: are any of the fundamental forces "blocked" by an intervening object? I assume not, since there is nothing like that in the equations. But that is kind of interesting, since sometimes you hear talk of hypothetical particles like gravitons.
- EA-3167 9d agoBlocked? No. Greatly attenuated and restricted in what modes can be accommodated? Yes. More critically though the study gets into how they used a reference wave packet to establish a stationary baseline for the interferometer. Assuming the experiment is sufficiently isolated to reduce noise below the necessary threshold this can work in principle. https://www.science.org/doi/10.1126/sciadv.aec8045 https://www.science.org/doi/10.1126/sciadv.aec8045
- WaxProlix 9d ago> Blocked? No. Greatly attenuated and restricted in what modes can be accommodated? Yes. Can you give me some examples? I guess I'm thinking lead barriers or a Bose Einstein condensate but curious what you mean here.
- AlotOfReading 9d agoYour house has walls to attenuate photons.
- EA-3167 9d agoCasimir plates are a good example, although Faraday cages are probably better known along with Mu-metal.
- Ono-Sendai 9d agoThat's a very deep question. In some sense no, in some sense yes. I would say on the deepest level, no, they are not blocked.
- deleted 9d ago
- MathMonkeyMan 9d agoHere's the [paper][1] on the arxiv. I found it hard to believe that they accounted for other forces precisely enough that they could attribute the phase change to gravity, but this is beyond me so I trust the result. At first I thought "they showed that you can measure a particle falling in gravity," which seemed dumb because we already know that particles fall in gravity. But they showed that you can measure a single (aggregate) particle falling in gravity, which is pretty cool because if gravity is quantum then that means that they observed an interaction between the graviton and their rubidium atom. [1]: https://arxiv.org/pdf/2502.14535 https://arxiv.org/pdf/2502.14535
- fr2029 9d agoThere's no evidence for gravitons.
- Zarathustra30 9d ago> ...if gravity is quantum... You don't need evidence to support a premise.
- qlte 9d agoTheir point is measuring gravity's influence on a single particle is not necessarily evidence of the existence of the graviton.
- omnicognate 9d agoNobody's claiming it is.
- NuclearPM 9d ago“ if gravity is quantum then that means that they observed an interaction between the graviton and their rubidium atom.”
- hoppp 9d agoI am not very well versed in the subject but if quantum objects can fall and multiple quantum waves can occupy the same space, then why doesn't everything always collapse into a single point? Why does it only happen in black holes and outside of that quantum waves instead create emergent systems instead of just collapsing together? Does high gravitational force nullify emergence in space/time? Might be a stupid question. I don't study this subject much.
- hgoel 9d agoThey can't exactly occupy the same space due to the Pauli exclusion principle. IIRC that's believed to be the final "barrier" that prevents neutron stars from collapsing into black holes. But this is also getting into the tricky parts of wave particle duality, so the precise details are a bit difficult for me too.
- limaoscarjuliet 9d agoOnly cats can violate Pauli's principle. Anybody who had a cat can attest to the fact they can go through walls. Just close a room with a cat inside and - given enough time - the cat will escape.
- dmfdmf 9d agoI thought QM and GR were mathematically incompatible. How do you even perform an experiment without accepting one frame or the other? Sus.
- traes 9d agoSeems like they just added a linear gravitational potential term mgz to their hamiltonian and computed the phase change it would induce. They claim they experimentally confirmed the phase change. I didn't think that worked! They also claim its consistent with some kind of GR derivation, but I haven't looked at that.
- stared 9d agoIs it a subtle effect that cannot be explained by Newtonian gravity (i.e. a different potential affecting, V(z) in the Hamiltonian)?
- traes 9d agoNo. From the paper linked above [0]: > The phase of free fall is predicted in a purely quantum manner to have a dependence m/6 g^2T^3/ℏ + gmzT on the free-fall time T, where m is the mass of the object, g is the gravitational acceleration relative to the surface of Earth, and z in the spatial coordinate in the direction of gravity. This prediction follows the calculated phase accumulated by an object accelerating in a linear potential, and has been made starting from almost one hundred years ago by Darwin, Kennard and others. Apparently the phase shift is derivable from just adding a linear potential term mgz to the Hamiltonian. [0]: https://arxiv.org/pdf/2502.14535 https://arxiv.org/pdf/2502.14535
- deleted 9d ago[deleted]
- gaze 9d agoVlatko tends to show up on papers with let's say, big claims. Consider the superconducting qubit/Tardigrade paper https://arxiv.org/abs/2112.07978 https://arxiv.org/abs/2112.07978
- MarkusQ 9d agoVlatko Vedral (of Oxford) to be clear. (He's listed as V. Vedral on the Tardigrade paper you linked, and it's more common to use last names in this context.)
- miles_io 9d agoMind-bending stuff. Always wondered when we'd start seeing GR effects pop up at the quantum scale, makes sense.
- rimworld 8d ago[dead]