5 ms·

Honestly, we might as well not post any of these. No one without a Phd in physics can remotely understand what's being conveyed, let alone any nuance.

Cthulhu_ 5y ago
I don't have a PhD in physics and found this article pretty easy to follow - it's an accessible pop sci translation of a paper [1] that DOES require a PhD or at least a serious interest in physics to follow. [1] https://arxiv.org/pdf/2109.12238.pdf https://arxiv.org/pdf/2109.12238.pdf
matt123456789 5y ago
I think that the following paragraph cuts to the heart of an important question linking GR to QM: “Take the case where a massive object is put into a superposition of two possible locations at the same time. General relativity says that any object with mass should bend the fabric of space-time. But what if that object is in a superposition? Is the geometry of space-time also in a superposition?” I don’t have a PhD in anything let alone physics, but it seems to me that answering the above question could potentially lead to a reformulation of GR in a way that gracefully incorporates quantum mechanics, which is worth getting excited about. But yes, you’re correct that the nuance is lost on me. Still, there seem to be plenty of people who find it interesting.
- rytill 5y ago
  I don’t understand. Isn’t that a pretty basic hypothesis? There’s no way we’ve gone almost 100 years and no one tried that.
  - tom-thistime 5y ago
    It's too difficult to actually carry out in practice. You increase the mass, it quickly becomes impossible to distinguish the states.
  - matt123456789 5y ago
    https://www.google.com/search?q=can+spacetime+geometry+be+in+a+superposition https://www.google.com/search?q=can+spacetime+geometry+be+in... Seems like there is a lot of theory discussions around the Internet but not seeing any experimental evidence one way or the other in the first few results.
  - pm_me_your_quan 5y ago
    It is. We haven't had the necessary experimental equipment to be able to measure it until recently. You need an extremely precise clock that you can put into a quantum superposition- that's difficult to make.
  - AnimalMuppet 5y ago
    Creating an object that is 1) massive enough to observably bend spacetime, and 2) still can be put in a quantum superposition is... not easy.
    - Enginerrrd 5y ago
      True... but you might be able to put an object in superposition with another object and separate those a bit within an existing gravity well and observe the implications.
- deleted 5y ago
  [deleted]
- nanomonkey 5y ago
  They key part here that is not easy to set up in an experiment is "massive object in superposition". Superposition is generally something that we observe in mass-less objects (bosons) like photons on a macroscopic level. The spin state of an electron or any other massive objects (fermions) isn't going to effect it's mass distribution observably on a macroscopic level as far as I understand it...these things usually collapse upon interaction with other particles. The curious thing in my opinion is how this will effect quantum computing. If gravity causes decoherence, then it is likely difficult to maintain coherence in large qubit devices that aren't in microgravity.
  - mrami 5y ago
    A bit of a tangent, but boson vs. fermion is not a massless/massive split. There are massive bosons. Rather, it's a split on the qualities of the objects' spin, and thus whether they obey the Pauli exclusion principle. https://en.wikipedia.org/wiki/Boson https://en.wikipedia.org/wiki/Boson
    - nanomonkey 5y ago
      Ah yes, you're correct. I see that I remembered that incorrectly.
- sharikous 5y ago
  First of all what you said is correct. Physics is looking for a quantum theory of gravitation and of course that would allow for superposition. The first problem is that a quantum theory of gravity is not straightforward. It's not "just" a spacetime with superposition, it probably has an even richer structure, the way QED has a richer structure than an EM field with superposition. And from the little hints we have it might have "spin 2" representation, and thereshould be some quantum very complicated field that acts like the metric GR field at low energies. But not only there are many possibilities for that, they are also very complicated, basically untreatable, or have infinite degrees of freedom in their definition itself. The second problem is that there is no current way of experimentally probing such behavior. You say put a massive object in superposition, but to have observable effects you need to have so massive an object that is tens of orders of magnitude above "impossible". This experiment is nice but it probes "just" the gravitational field of the Earth (a ~10^25 kg object). It is very nice for accurate time measures, and maybe for measuring gravitational fields, it comes nowhere near to probe quantum gravity effects, just quantum effects coupled to classical gravity (classic in the sense of GR but not quantum)
- throw1234651234 5y ago
  I get what you are saying, but I have no way to know whether or not it's valid to any degree. Maybe the "constructive" part of what I am trying to say is that we either need better education on the fundamentals here, better examples, better explanations, or should just admit that it's far beyond the layman. For example, I get entanglement. I can get answers to questions like "Is FTL comm possible? No." or "What is a practical application for entanglement? Quantum radar - sorting your initial emission from jamming." etc. This though? Just too abstract (for me).
Thorncorona 5y ago
What do you believe would be a good line for posts?
steve76 5y ago
Interactions occur using internals as a medium without changing externals. This was shown long ago with Planck and supported by speed of light measurements on a cosmic and subatomic scale. This causes: 1. Things like electrons, the atom using it's own internals to interact, to be smeared out. 2. The Earth having a much slower frame rate than atoms. Attach a laser and detector on Earth, it shares the same frame rate. A cloud of atoms not attached to the Earth will appear to behave differently based on their distance from Earth. The laser is the same throughout it's path. It curves, but it's the same. If you have a really good laser, and a really good detector, you can find out how it works, perhaps create a new model beyond electrons and the nucleus. Especially with new data with black holes, you can define it in terms of particle pairs producing from nothing, and a dense internal homogeneous structure with no further substructure. You can take that model and apply real life applications regarding plasma, the sun, or matter waves, particle beams in orbit.
otikik 5y ago
It's a matter of interest. I don't have a Phd in physics, but have watched enough videos in Youtube about quantum physics[1] now to understand almost everything the article says. Some details escape me, but I believe Quantum physics does that also to Phds. On the other hand, when they publish an economics article here, with the interests and the rates and the valuations of the options and whatnot, I understand almost nothing. I can't force myself to care about those things. [1] I recommend kurzgesagt, Sabine Hossenfelder and PBS Space Time
4ad 5y ago
As a physicist I find that the level of discourse around these topics among non-physicists ranges from hilarious to depressing. But I am still happy laymen are willing to have these discussions and that physics piques their interest. To be fair, non-experts have the same misunderstanding about physics as they have about any other subject -- economics, politics, medicine -- even music and arts. Hell, even programming on this very site. Should we ban people from discussing subjects outside their field of expertise? I don't think so. If anything, people should entertain more ideas, not less. There are no experts who didn't use to be noobs. That said, I do think that in general popular science articles are pretty bad, and laymen are mostly getting confusion out of them. And I do (probably?) agree with you that the people upvoting these submissions are pretty confused and I am not sure why are they upvoting them. Personally, I wouldn't post such articles here but as long as people seem to happily engage with one another I don't see any problem with such articles. To a first approximation there are the same proportion of people knowing physics here (arguably an offtopic subject) as there are people knowing real type theory (definitely an ontopic subject), so the niche aspect of it can't be a deciding factor on what to post.

Cthulhu_ 5y ago

I don't have a PhD in physics and found this article pretty easy to follow - it's an accessible pop sci translation of a paper [1] that DOES require a PhD or at least a serious interest in physics to follow. [1] https://arxiv.org/pdf/2109.12238.pdf https://arxiv.org/pdf/2109.12238.pdf

matt123456789 5y ago

I think that the following paragraph cuts to the heart of an important question linking GR to QM: “Take the case where a massive object is put into a superposition of two possible locations at the same time. General relativity says that any object with mass should bend the fabric of space-time. But what if that object is in a superposition? Is the geometry of space-time also in a superposition?” I don’t have a PhD in anything let alone physics, but it seems to me that answering the above question could potentially lead to a reformulation of GR in a way that gracefully incorporates quantum mechanics, which is worth getting excited about. But yes, you’re correct that the nuance is lost on me. Still, there seem to be plenty of people who find it interesting.

rytill 5y ago
I don’t understand. Isn’t that a pretty basic hypothesis? There’s no way we’ve gone almost 100 years and no one tried that.
- tom-thistime 5y ago
  It's too difficult to actually carry out in practice. You increase the mass, it quickly becomes impossible to distinguish the states.
- matt123456789 5y ago
  https://www.google.com/search?q=can+spacetime+geometry+be+in+a+superposition https://www.google.com/search?q=can+spacetime+geometry+be+in... Seems like there is a lot of theory discussions around the Internet but not seeing any experimental evidence one way or the other in the first few results.
- pm_me_your_quan 5y ago
  It is. We haven't had the necessary experimental equipment to be able to measure it until recently. You need an extremely precise clock that you can put into a quantum superposition- that's difficult to make.
- AnimalMuppet 5y ago
  Creating an object that is 1) massive enough to observably bend spacetime, and 2) still can be put in a quantum superposition is... not easy.
  - Enginerrrd 5y ago
    True... but you might be able to put an object in superposition with another object and separate those a bit within an existing gravity well and observe the implications.
deleted 5y ago
[deleted]
nanomonkey 5y ago
They key part here that is not easy to set up in an experiment is "massive object in superposition". Superposition is generally something that we observe in mass-less objects (bosons) like photons on a macroscopic level. The spin state of an electron or any other massive objects (fermions) isn't going to effect it's mass distribution observably on a macroscopic level as far as I understand it...these things usually collapse upon interaction with other particles. The curious thing in my opinion is how this will effect quantum computing. If gravity causes decoherence, then it is likely difficult to maintain coherence in large qubit devices that aren't in microgravity.
- mrami 5y ago
  A bit of a tangent, but boson vs. fermion is not a massless/massive split. There are massive bosons. Rather, it's a split on the qualities of the objects' spin, and thus whether they obey the Pauli exclusion principle. https://en.wikipedia.org/wiki/Boson https://en.wikipedia.org/wiki/Boson
  - nanomonkey 5y ago
    Ah yes, you're correct. I see that I remembered that incorrectly.
sharikous 5y ago
First of all what you said is correct. Physics is looking for a quantum theory of gravitation and of course that would allow for superposition. The first problem is that a quantum theory of gravity is not straightforward. It's not "just" a spacetime with superposition, it probably has an even richer structure, the way QED has a richer structure than an EM field with superposition. And from the little hints we have it might have "spin 2" representation, and thereshould be some quantum very complicated field that acts like the metric GR field at low energies. But not only there are many possibilities for that, they are also very complicated, basically untreatable, or have infinite degrees of freedom in their definition itself. The second problem is that there is no current way of experimentally probing such behavior. You say put a massive object in superposition, but to have observable effects you need to have so massive an object that is tens of orders of magnitude above "impossible". This experiment is nice but it probes "just" the gravitational field of the Earth (a ~10^25 kg object). It is very nice for accurate time measures, and maybe for measuring gravitational fields, it comes nowhere near to probe quantum gravity effects, just quantum effects coupled to classical gravity (classic in the sense of GR but not quantum)
throw1234651234 5y ago
I get what you are saying, but I have no way to know whether or not it's valid to any degree. Maybe the "constructive" part of what I am trying to say is that we either need better education on the fundamentals here, better examples, better explanations, or should just admit that it's far beyond the layman. For example, I get entanglement. I can get answers to questions like "Is FTL comm possible? No." or "What is a practical application for entanglement? Quantum radar - sorting your initial emission from jamming." etc. This though? Just too abstract (for me).

Thorncorona 5y ago

What do you believe would be a good line for posts?

steve76 5y ago

Interactions occur using internals as a medium without changing externals. This was shown long ago with Planck and supported by speed of light measurements on a cosmic and subatomic scale. This causes: 1. Things like electrons, the atom using it's own internals to interact, to be smeared out. 2. The Earth having a much slower frame rate than atoms. Attach a laser and detector on Earth, it shares the same frame rate. A cloud of atoms not attached to the Earth will appear to behave differently based on their distance from Earth. The laser is the same throughout it's path. It curves, but it's the same. If you have a really good laser, and a really good detector, you can find out how it works, perhaps create a new model beyond electrons and the nucleus. Especially with new data with black holes, you can define it in terms of particle pairs producing from nothing, and a dense internal homogeneous structure with no further substructure. You can take that model and apply real life applications regarding plasma, the sun, or matter waves, particle beams in orbit.

otikik 5y ago

It's a matter of interest. I don't have a Phd in physics, but have watched enough videos in Youtube about quantum physics[1] now to understand almost everything the article says. Some details escape me, but I believe Quantum physics does that also to Phds. On the other hand, when they publish an economics article here, with the interests and the rates and the valuations of the options and whatnot, I understand almost nothing. I can't force myself to care about those things. [1] I recommend kurzgesagt, Sabine Hossenfelder and PBS Space Time

4ad 5y ago

As a physicist I find that the level of discourse around these topics among non-physicists ranges from hilarious to depressing. But I am still happy laymen are willing to have these discussions and that physics piques their interest. To be fair, non-experts have the same misunderstanding about physics as they have about any other subject -- economics, politics, medicine -- even music and arts. Hell, even programming on this very site. Should we ban people from discussing subjects outside their field of expertise? I don't think so. If anything, people should entertain more ideas, not less. There are no experts who didn't use to be noobs. That said, I do think that in general popular science articles are pretty bad, and laymen are mostly getting confusion out of them. And I do (probably?) agree with you that the people upvoting these submissions are pretty confused and I am not sure why are they upvoting them. Personally, I wouldn't post such articles here but as long as people seem to happily engage with one another I don't see any problem with such articles. To a first approximation there are the same proportion of people knowing physics here (arguably an offtopic subject) as there are people knowing real type theory (definitely an ontopic subject), so the niche aspect of it can't be a deciding factor on what to post.