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I'll agree that experimental error is the most likely explanation by far but I think there's still a noticeable chance that the explanation is some novel effect

I'll agree that experimental error is the most likely explanation by far but I think there's still a noticeable chance that the explanation is some novel effect that doesn't actually violate conservation of momentum. If I were to give a break down on my expectations they'd probably be something like 90% Experimental error 9% Unexpected and novel consequence of current physics 1% New physics that doesn't actually violate momentum conservation ~0% Violation of conservation of momentum. But this has gone the point where even if it's experimental error I expect the mechanism will be at least somewhat interesting, as with the Italian speed of light experiment.

mahranch 11y ago
> ~0% Violation of conservation of momentum. I don't think the chance of violation of the conservation of momentum would be 0%. Unlikely? Yes. Highly unlikely? Most definitely, but not zero. Why? Because we don't yet have a "theory of everything". For all we know, (not saying this is the case, just a thought experiment/hypothetical) the string theorists have it right, and there are extra dimensions, or brane universes (a multiverse) and maybe this effect is in some way related to that (pulling/utilizing an energy from a higher 4th dimension). Granted, it goes against everything we currently know about physics, but so did a lot of things at one point. And that usually happens when we don't know enough about the area we're researching. And when it comes to quantum mechanics, we're only scratching the surface of what we know. There are plenty of things in quantum mechanics that are completely inexplicable. Things like the double slit experiment, quantum entanglement, quantum tunneling, etc.. We know those things occur, but very little or nothing at all as to the "how" and "why". They seem to defy known physics but there they are...
- mikeash 11y ago
  That squiggly line in front of the zero means "approximately," so really you're in agreement. The chances are not exactly 0, but more like 0.0000001%.
- Symmetry 11y ago
  It's certainly not impossible, which is why I put the "approximately" symbol in front of the zero. I would be very, very surprised if the TOE broke conservation of momentum but then again I found it very surprising that there's basically just one experiment that breaks reflective symmetry (I forget what it's Noether[1] equivalent conservation law is). [1]https://en.wikipedia.org/wiki/Noether%27s_theorem https://en.wikipedia.org/wiki/Noether%27s_theorem
  - mahranch 11y ago
    > which is why I put the "approximately" symbol in front of the zero. Ah, I missed that somehow... Haven't had my coffee.
    - Symmetry 11y ago
      No problem, I'm sure I've responded after similar misreadings many times.
  - gjm11 11y ago
    There isn't a Noether conservation law corresponding to reflective symmetry, is there? The situation where Noether's theorem applies is where you have a smooth family of symmetries, with one of them being the identity (i.e., the trivial symmetry where you don't change anything at all), but reflections don't fit that pattern. On the other hand, if the laws of physics are invariant under reflections then they are also invariant under rotations because you can make rotations out of reflections. So you could say that conservation of angular momentum is the corresponding conservation law. But (so far as anyone knows, I think) the laws of physics really are rotation-invariant and conservation of angular momentum really does hold.
    - JadeNB 11y ago
      > On the other hand, if the laws of physics are invariant under reflections then they are also invariant under rotations because you can make rotations out of reflections. So you could say that conservation of angular momentum is the corresponding conservation law. This is an interesting idea, but, I think, too weak. It is true that every rotation is a composition of two reflections, but there's such an important difference between rotations (orientation-preserving) and reflections (orientation-reversing) that I think one shouldn't say that invariance under the former implies anything about invariance under the latter.
yk 11y ago
I think violation of conservation of momentum is more likely than new physics. Basically, if this thing produces a general relativity effect, then it is possible that momentum is not conserved because the underlying metric does not have translation symmetry. (GR Energy Momentum conservation would still be in effect in that case, but classical momentum conservation would not.) Apart from that, I am unhappy about your percentages, I think the non experimental error explanations are an order of magnitude less likely.
- Symmetry 11y ago
  My physics education topped out at special relativity and statistical mechanics so I'll take your word for it.
- AnimalMuppet 11y ago
  > Basically, if this thing produces a general relativity effect, then it is possible that momentum is not conserved because the underlying metric does not have translation symmetry. Given the setup, it seems highly unlikely that this thing produces something that requires a GR explanation. The energies aren't high enough; there's no high gravitational field or high acceleration. > I think violation of conservation of momentum is more likely than new physics. But if GR is out, then violation of conservation of momentum is new physics.
  - yk 11y ago
    I agree, or actually I assume that the disagreement is only about words. I would not call it new physics, if, for example, we have to couple quantum fields to GR in a not straightforward way, so in the case were we already know all the parts but not the specific combination of the parts. I would only call it new physics if we have to rewrite basic textbooks.
    - AnimalMuppet 11y ago
      If this showed us how to couple quantum fields to GR, that would be pretty good. Personally, I would consider that "new physics", given how unclear it is how to do so at the moment. If doing so doesn't significantly change either GR or quantum, however (and so the basic texts are still valid), I could go with your view.

mahranch 11y ago

> ~0% Violation of conservation of momentum. I don't think the chance of violation of the conservation of momentum would be 0%. Unlikely? Yes. Highly unlikely? Most definitely, but not zero. Why? Because we don't yet have a "theory of everything". For all we know, (not saying this is the case, just a thought experiment/hypothetical) the string theorists have it right, and there are extra dimensions, or brane universes (a multiverse) and maybe this effect is in some way related to that (pulling/utilizing an energy from a higher 4th dimension). Granted, it goes against everything we currently know about physics, but so did a lot of things at one point. And that usually happens when we don't know enough about the area we're researching. And when it comes to quantum mechanics, we're only scratching the surface of what we know. There are plenty of things in quantum mechanics that are completely inexplicable. Things like the double slit experiment, quantum entanglement, quantum tunneling, etc.. We know those things occur, but very little or nothing at all as to the "how" and "why". They seem to defy known physics but there they are...

mikeash 11y ago
That squiggly line in front of the zero means "approximately," so really you're in agreement. The chances are not exactly 0, but more like 0.0000001%.
Symmetry 11y ago
It's certainly not impossible, which is why I put the "approximately" symbol in front of the zero. I would be very, very surprised if the TOE broke conservation of momentum but then again I found it very surprising that there's basically just one experiment that breaks reflective symmetry (I forget what it's Noether[1] equivalent conservation law is). [1]https://en.wikipedia.org/wiki/Noether%27s_theorem https://en.wikipedia.org/wiki/Noether%27s_theorem
- mahranch 11y ago
  > which is why I put the "approximately" symbol in front of the zero. Ah, I missed that somehow... Haven't had my coffee.
  - Symmetry 11y ago
    No problem, I'm sure I've responded after similar misreadings many times.
- gjm11 11y ago
  There isn't a Noether conservation law corresponding to reflective symmetry, is there? The situation where Noether's theorem applies is where you have a smooth family of symmetries, with one of them being the identity (i.e., the trivial symmetry where you don't change anything at all), but reflections don't fit that pattern. On the other hand, if the laws of physics are invariant under reflections then they are also invariant under rotations because you can make rotations out of reflections. So you could say that conservation of angular momentum is the corresponding conservation law. But (so far as anyone knows, I think) the laws of physics really are rotation-invariant and conservation of angular momentum really does hold.
  - JadeNB 11y ago
    > On the other hand, if the laws of physics are invariant under reflections then they are also invariant under rotations because you can make rotations out of reflections. So you could say that conservation of angular momentum is the corresponding conservation law. This is an interesting idea, but, I think, too weak. It is true that every rotation is a composition of two reflections, but there's such an important difference between rotations (orientation-preserving) and reflections (orientation-reversing) that I think one shouldn't say that invariance under the former implies anything about invariance under the latter.

yk 11y ago

I think violation of conservation of momentum is more likely than new physics. Basically, if this thing produces a general relativity effect, then it is possible that momentum is not conserved because the underlying metric does not have translation symmetry. (GR Energy Momentum conservation would still be in effect in that case, but classical momentum conservation would not.) Apart from that, I am unhappy about your percentages, I think the non experimental error explanations are an order of magnitude less likely.

Symmetry 11y ago
My physics education topped out at special relativity and statistical mechanics so I'll take your word for it.
AnimalMuppet 11y ago
> Basically, if this thing produces a general relativity effect, then it is possible that momentum is not conserved because the underlying metric does not have translation symmetry. Given the setup, it seems highly unlikely that this thing produces something that requires a GR explanation. The energies aren't high enough; there's no high gravitational field or high acceleration. > I think violation of conservation of momentum is more likely than new physics. But if GR is out, then violation of conservation of momentum is new physics.
- yk 11y ago
  I agree, or actually I assume that the disagreement is only about words. I would not call it new physics, if, for example, we have to couple quantum fields to GR in a not straightforward way, so in the case were we already know all the parts but not the specific combination of the parts. I would only call it new physics if we have to rewrite basic textbooks.
  - AnimalMuppet 11y ago
    If this showed us how to couple quantum fields to GR, that would be pretty good. Personally, I would consider that "new physics", given how unclear it is how to do so at the moment. If doing so doesn't significantly change either GR or quantum, however (and so the basic texts are still valid), I could go with your view.