4 ms·

Gravity's Most Extreme Effects Can Now Be Tested In A Laboratory

34 points by randomname2 11y ago

rubidium 11y ago
I recall reading the first experimental paper on analog gravitational black holes being created using bose einstein condensates(http://journals.aps.org/prl/abstract/10.1103/PhysRevLett.105.240401 http://journals.aps.org/prl/abstract/10.1103/PhysRevLett.105...), and was happy to see the work continuing here (see referenced paper in the article: http://arxiv.org/abs/1510.00621 http://arxiv.org/abs/1510.00621). What was very surprising was that it was a single author paper (only the prof of the group). These sort of research efforts are usually Prof+possible postdoc+a few grad students. Not sure if prof is leaving grad students out (I hope not!), or is toiling alone at this work.
dave_sullivan 11y ago
I keep running into sonoluminescence lately (https://en.wikipedia.org/wiki/Sonoluminescence https://en.wikipedia.org/wiki/Sonoluminescence), this kind of reminds me of that? Sonoluminescence reminds me of gravitational collapse, but I think that's probably because I need to read up more... Very interesting stuff going on with applied physics though--the most immediate application is probably materials science (and hopefully better computers/information processing devices). "Simulating the universe better" may come to be linked with better general information processing systems too, as in discoveries in one helps the other. For instance, more work along these lines: http://arxiv.org/abs/1510.03776 http://arxiv.org/abs/1510.03776
genug 11y ago
120 years ago, people thought that experimental results on wave propagation in continuous media could be used to make statements about wave propagation in electrodynamics. That's how we ended up with ether theories, which were eventually falsified with interferometric experiments. To my mind, we should take this as a lesson that the notion of analogue systems (e.g., using results from fluid dynamics to make statements about gravitation) is bogus. The ether episode seems to indicate that if we want to make statements about gravitational Hawking radiation, we need to do tests on a system where the gravitational dynamics are important (e.g., a black hole), not an unrelated system that just happens to be governed by an identical set of equations in some regime. Another example of people incorrectly conflating properties of an analogue system with the real system of interest is the Nature monopole paper: http://www.nature.com/nature/journal/v505/n7485/full/nature12954.html http://www.nature.com/nature/journal/v505/n7485/full/nature1... The actual result contained in the paper is that you can make a BEC whose vorticity field has regions of nonzero divergence. It is mathematically similar to (but fundamentally unrelated to) actual magnetic monopoles. Nonetheless, the paper contains the phrase "Dirac monopoles" in the title and then spends half the abstract talking about actual magnetic monopoles, as if the result is somehow relevant to actual magnetic monopole searches (which it isn't).
- Ono-Sendai 11y ago
  All ether theories weren't really falsified, just discarded on a metaphysical basis as being redundant.
  - CamperBob2 11y ago
    I wouldn't say that. The Michelson-Morley experiment demonstrated that if there was a luminiferous ether, it had no measurable inertia. That pretty much falsified the ether as anything that we'd recognize as "real."
    - Ono-Sendai 11y ago
      I've never read about the ether needing to have inertia. Also, a modern version of the ether is pretty well accepted - quantum fields that occupy all of space. Particles etc.. are disturbances in this field. Ether is something of a tainted term these days so quantum fields are not referred to as ether.
      - chc 11y ago
        Quantum field theory doesn't seem very much like the luminiferous ether. This seems like finding a new species of grasshopper that lives on a mountain, and saying, "Ah-ha, I've found Zeus! Zeus is a thing that lives on a mountain and has never been seen before, so this must be Zeus!"
  - deleted 11y ago
    [deleted]
- chakademus 11y ago
  As a counterpoint: what about the efficacy of condensed matter physics informing developments in quantum field theory? Of course analog systems must be treated carefully, but I think we shouldn't rush to do away with the practice entirely. Naturally, we do want to study black holes directly (with experiments like LIGO, LISA, etc.), but this is very expensive, difficult, and time consuming. If a small lab wants to try out some gravitationally analogous system, why not?
mrfusion 11y ago
Couldthis be useful for testing the emdrive? I heard one theory is it might be emitting gravity waves.

34 points by randomname2 11y ago

I recall reading the first experimental paper on analog gravitational black holes being created using bose einstein condensates(http://journals.aps.org/prl/abstract/10.1103/PhysRevLett.105.240401 http://journals.aps.org/prl/abstract/10.1103/PhysRevLett.105...), and was happy to see the work continuing here (see referenced paper in the article: http://arxiv.org/abs/1510.00621 http://arxiv.org/abs/1510.00621). What was very surprising was that it was a single author paper (only the prof of the group). These sort of research efforts are usually Prof+possible postdoc+a few grad students. Not sure if prof is leaving grad students out (I hope not!), or is toiling alone at this work.

dave_sullivan 11y ago

I keep running into sonoluminescence lately (https://en.wikipedia.org/wiki/Sonoluminescence https://en.wikipedia.org/wiki/Sonoluminescence), this kind of reminds me of that? Sonoluminescence reminds me of gravitational collapse, but I think that's probably because I need to read up more... Very interesting stuff going on with applied physics though--the most immediate application is probably materials science (and hopefully better computers/information processing devices). "Simulating the universe better" may come to be linked with better general information processing systems too, as in discoveries in one helps the other. For instance, more work along these lines: http://arxiv.org/abs/1510.03776 http://arxiv.org/abs/1510.03776

genug 11y ago

120 years ago, people thought that experimental results on wave propagation in continuous media could be used to make statements about wave propagation in electrodynamics. That's how we ended up with ether theories, which were eventually falsified with interferometric experiments. To my mind, we should take this as a lesson that the notion of analogue systems (e.g., using results from fluid dynamics to make statements about gravitation) is bogus. The ether episode seems to indicate that if we want to make statements about gravitational Hawking radiation, we need to do tests on a system where the gravitational dynamics are important (e.g., a black hole), not an unrelated system that just happens to be governed by an identical set of equations in some regime. Another example of people incorrectly conflating properties of an analogue system with the real system of interest is the Nature monopole paper: http://www.nature.com/nature/journal/v505/n7485/full/nature12954.html http://www.nature.com/nature/journal/v505/n7485/full/nature1... The actual result contained in the paper is that you can make a BEC whose vorticity field has regions of nonzero divergence. It is mathematically similar to (but fundamentally unrelated to) actual magnetic monopoles. Nonetheless, the paper contains the phrase "Dirac monopoles" in the title and then spends half the abstract talking about actual magnetic monopoles, as if the result is somehow relevant to actual magnetic monopole searches (which it isn't).

Ono-Sendai 11y ago
All ether theories weren't really falsified, just discarded on a metaphysical basis as being redundant.
- CamperBob2 11y ago
  I wouldn't say that. The Michelson-Morley experiment demonstrated that if there was a luminiferous ether, it had no measurable inertia. That pretty much falsified the ether as anything that we'd recognize as "real."
  - Ono-Sendai 11y ago
    I've never read about the ether needing to have inertia. Also, a modern version of the ether is pretty well accepted - quantum fields that occupy all of space. Particles etc.. are disturbances in this field. Ether is something of a tainted term these days so quantum fields are not referred to as ether.
    - chc 11y ago
      Quantum field theory doesn't seem very much like the luminiferous ether. This seems like finding a new species of grasshopper that lives on a mountain, and saying, "Ah-ha, I've found Zeus! Zeus is a thing that lives on a mountain and has never been seen before, so this must be Zeus!"
- deleted 11y ago
  [deleted]
chakademus 11y ago
As a counterpoint: what about the efficacy of condensed matter physics informing developments in quantum field theory? Of course analog systems must be treated carefully, but I think we shouldn't rush to do away with the practice entirely. Naturally, we do want to study black holes directly (with experiments like LIGO, LISA, etc.), but this is very expensive, difficult, and time consuming. If a small lab wants to try out some gravitationally analogous system, why not?

mrfusion 11y ago

Couldthis be useful for testing the emdrive? I heard one theory is it might be emitting gravity waves.