4 ms·

An important fact about the luminiferous aether is that it was abandoned as an idea because it was inconsistent with experiments. In contrast, dark matter has c

An important fact about the luminiferous aether is that it was abandoned as an idea because it was inconsistent with experiments. In contrast, dark matter has continued as an idea and become a popular explanation because new experiments have always fit very well with what it would predict. We don't know what dark matter is, or if it even is a kind of matter rather than e.g. modified gravity (though modified gravity has many problems of its own), but I think it is a common mistake that people are so eager to associate it with aether on the grounds only of what they find 'elegant'. Edit: Also, the notion of a kind of matter that can hardly be observed is not particularly weird or 'arcane'. For instance, neutrinos have many of the right properties. I think they are ruled out as dark matter candidates mainly because their mass is too low to fit with observations.

cozzyd 11y ago
Standard model neutrinos are ruled out because they are relativistic and cannot play a role in structure formation (see http://en.wikipedia.org/wiki/Hot_dark_matter http://en.wikipedia.org/wiki/Hot_dark_matter )
Dylan16807 11y ago
>An important fact about the luminiferous aether is that it was abandoned as an idea because it was inconsistent with experiments. Is it? As I understand it the concept of an aether is not so much provably wrong as utterly meaningless; once you factor in various dilations there is no effect that would be caused by an aether. Nothing could possibly measure it, and it has no impact on predictions.
- marcosdumay 11y ago
  The Aether was proved wrong, and Special Relativity (that makes different previsions) was only developed after that.
  - JoeAltmaier 11y ago
    I understand it was simply proved irrelevant - it cancelled out of the equations. Until recently, when Maxwells Equations were re-derived using some quantum field as the Aether, which yielded many surprising (and true) results. So maybe now, not so irrelevant.
    - qwerty33467 11y ago
      Can you give a citation for the Maxwell Eq. aether paper?
      - JoeAltmaier 11y ago
        Fudge. It was an article listed here. I'm paging down, not finding it.
        deleted 11y ago
        [deleted]
        platz 11y ago
        btw, this was posted a few days ago on HN, http://www.independent.com/news/2012/jul/20/higgs-field-new-ether/ http://www.independent.com/news/2012/jul/20/higgs-field-new-...
  - Dylan16807 11y ago
    http://en.wikipedia.org/wiki/Lorentz_ether_theory http://en.wikipedia.org/wiki/Lorentz_ether_theory >Many aspects of Lorentz's theory were incorporated into special relativity (SR) with the works of Albert Einstein and Hermann Minkowski. >The introduction of length contraction and time dilation for all phenomena in a "preferred" frame of reference, which plays the role of Lorentz's immobile aether, leads to the complete Lorentz transformation (see the Robertson–Mansouri–Sexl test theory as an example). Because the same mathematical formalism occurs in both, it is not possible to distinguish between LET and SR by experiment.
  - andars 11y ago
    Disclaimer: I'm no physicist Are you thinking of the Michelson-Morley experiment? Interestingly, even after the development of special relativity, Lorentz and Einstein [1] continued to discuss the possibility of an ether. Dirac also discussed the topic in 1951 [2]. The fact that it continued to be discussed by these scientists has always made me wonder whether the idea would ever return. [1]: http://en.m.wikisource.org/wiki/Ether_and_the_Theory_of_Relativity http://en.m.wikisource.org/wiki/Ether_and_the_Theory_of_Rela... [2]: http://www.researchgate.net/publictopics.PublicPostFileLoader.html?id=5307e6ddd2fd64c2528b464e&key=9c9605307e6dd83eef http://www.researchgate.net/publictopics.PublicPostFileLoade...
    - marcosdumay 11y ago
      Technically, the Aether was only proved to be isotropic to an Earth bounded reference frame, and only locally here at Earth's surface. That the Aether does not exist is only the simplest explanation (by a huge margin), but there are infinite possible theories that satisfy the experiments. Also, as the anisotropy is the only relevant characteristic of the Aether, thus most people prefer to consider the case settled.
- Strilanc 11y ago
  You're being downvoted but your right. It's unfortunately hard to not sound like a crackpot on this sort of issue, because there are a lot of relativity-is-wrong crackpots. As far as special relativity goes, the aether ends up being equivalent to a having preferred rest frame. It's not wrong, but it's unnecessary. You still have the light speed limit and length contraction and time dilation and all the same math (which is an unfortunately post-hoc insight), they just take on a different philosophical character. PhysicsForums has a good summary [1]: > Both BU and LET use the Lorentz transform, etc., to make all of their experimental predictions, and therefore they are scientifically indistinguishable, making the same experimental predictions in all cases. Because of this experimental equivalence, there is little if any serious ongoing debate between the two in professional physics circles (although the philosophy literature does have ongoing debate). For me the intuition pump for BU=LET was reading The Strange World of Classical Physics [2]. Notice that, by the end, as more things are considered, it's sounding more and more like relativity... All that being said, I agree with the PhysicsForums policy. It's a pointless debate. Switching between BU and LET might give you some intuitive understanding, but day to day you end up using special relativity because it's a lot more mathematically elegant. Plus I have no idea how you'd make the aether work with general relativity. 1: https://www.physicsforums.com/threads/what-is-the-pfs-policy-on-lorentz-ether-theory-and-block-universe.772224/ https://www.physicsforums.com/threads/what-is-the-pfs-policy... 2: http://www.aetherambler.net/strange.htm http://www.aetherambler.net/strange.htm
JackFr 11y ago
I am not a physics expert, but isn't dark matter simply a plug because mass of galaxies and large scale astronomical structures calculated from light and other electromagnetic radiation, doesn't agree with mass calculated by observing they're gravitational interaction? That is, we assume that both models (radiation & gravity) are correct, and that 90+% of the universe is made up of matter which has never been directly observed and is radically different than any matter we observe directly. The whole thing seems ludicrous -- but for the problem that no better explanation has yet been put forth. One gets the feeling though that one day in the future 'dark matter' is gonna look a lot like 'epicycles'.
- inclemnet 11y ago
  > isn't dark matter simply a plug because mass of galaxies and large scale astronomical structures calculated from light and other electromagnetic radiation, doesn't agree with mass calculated by observing they're gravitational interaction? One might more generously say that dark matter is a proposed explanation for many measurements deviating from predictions based on visible matter in a way very consistent with the existence of large amounts of non-electromagnetically-interacting matter. I don't think there's anything fundamentally ridiculous about this. For instance, while you characterise it as 'radically' different to any matter that we observe directly, the neutrino has most of the relevant properties, and e.g. supersymmetry has been noted to include dark matter candidate particles. While one may doubt that supersymmetry is actually correct, I think it demonstrates that the combination of properties (massive + electromagnetically inert + maybe weak force interacting) isn't necessarily a problem.
- JonnieCache 11y ago
  It's not just galaxy rotation. That's how people first noticed it. Since then there's stuff like this: http://en.wikipedia.org/wiki/Bullet_Cluster http://en.wikipedia.org/wiki/Bullet_Cluster Also there's apparently information about the universe's composition to be gleaned from the CMB anisotropies; its all somewhat beyond me, but that curve certainty seems to fit extremely well, I'll give them that. http://www.astro.ucla.edu/~wright/CMB-DT.html http://www.astro.ucla.edu/~wright/CMB-DT.html The combination of all this stuff is apparently pretty convincing. EDIT: I see that your comment is actually referring to the bullet cluster more than the rotation curves. It's all pretty tenuous in the grand scheme of things, I agree, but then so much of cosmology is. I guess they have the benefit of the string people next door making them look reasonable by comparison.
deleted 11y ago
[deleted]

cozzyd 11y ago

Standard model neutrinos are ruled out because they are relativistic and cannot play a role in structure formation (see http://en.wikipedia.org/wiki/Hot_dark_matter http://en.wikipedia.org/wiki/Hot_dark_matter )

Dylan16807 11y ago

>An important fact about the luminiferous aether is that it was abandoned as an idea because it was inconsistent with experiments. Is it? As I understand it the concept of an aether is not so much provably wrong as utterly meaningless; once you factor in various dilations there is no effect that would be caused by an aether. Nothing could possibly measure it, and it has no impact on predictions.

marcosdumay 11y ago
The Aether was proved wrong, and Special Relativity (that makes different previsions) was only developed after that.
- JoeAltmaier 11y ago
  I understand it was simply proved irrelevant - it cancelled out of the equations. Until recently, when Maxwells Equations were re-derived using some quantum field as the Aether, which yielded many surprising (and true) results. So maybe now, not so irrelevant.
  - qwerty33467 11y ago
    Can you give a citation for the Maxwell Eq. aether paper?
    - JoeAltmaier 11y ago
      Fudge. It was an article listed here. I'm paging down, not finding it.
      - deleted 11y ago
        [deleted]
      - platz 11y ago
        btw, this was posted a few days ago on HN, http://www.independent.com/news/2012/jul/20/higgs-field-new-ether/ http://www.independent.com/news/2012/jul/20/higgs-field-new-...
- Dylan16807 11y ago
  http://en.wikipedia.org/wiki/Lorentz_ether_theory http://en.wikipedia.org/wiki/Lorentz_ether_theory >Many aspects of Lorentz's theory were incorporated into special relativity (SR) with the works of Albert Einstein and Hermann Minkowski. >The introduction of length contraction and time dilation for all phenomena in a "preferred" frame of reference, which plays the role of Lorentz's immobile aether, leads to the complete Lorentz transformation (see the Robertson–Mansouri–Sexl test theory as an example). Because the same mathematical formalism occurs in both, it is not possible to distinguish between LET and SR by experiment.
- andars 11y ago
  Disclaimer: I'm no physicist Are you thinking of the Michelson-Morley experiment? Interestingly, even after the development of special relativity, Lorentz and Einstein [1] continued to discuss the possibility of an ether. Dirac also discussed the topic in 1951 [2]. The fact that it continued to be discussed by these scientists has always made me wonder whether the idea would ever return. [1]: http://en.m.wikisource.org/wiki/Ether_and_the_Theory_of_Relativity http://en.m.wikisource.org/wiki/Ether_and_the_Theory_of_Rela... [2]: http://www.researchgate.net/publictopics.PublicPostFileLoader.html?id=5307e6ddd2fd64c2528b464e&key=9c9605307e6dd83eef http://www.researchgate.net/publictopics.PublicPostFileLoade...
  - marcosdumay 11y ago
    Technically, the Aether was only proved to be isotropic to an Earth bounded reference frame, and only locally here at Earth's surface. That the Aether does not exist is only the simplest explanation (by a huge margin), but there are infinite possible theories that satisfy the experiments. Also, as the anisotropy is the only relevant characteristic of the Aether, thus most people prefer to consider the case settled.
Strilanc 11y ago
You're being downvoted but your right. It's unfortunately hard to not sound like a crackpot on this sort of issue, because there are a lot of relativity-is-wrong crackpots. As far as special relativity goes, the aether ends up being equivalent to a having preferred rest frame. It's not wrong, but it's unnecessary. You still have the light speed limit and length contraction and time dilation and all the same math (which is an unfortunately post-hoc insight), they just take on a different philosophical character. PhysicsForums has a good summary [1]: > Both BU and LET use the Lorentz transform, etc., to make all of their experimental predictions, and therefore they are scientifically indistinguishable, making the same experimental predictions in all cases. Because of this experimental equivalence, there is little if any serious ongoing debate between the two in professional physics circles (although the philosophy literature does have ongoing debate). For me the intuition pump for BU=LET was reading The Strange World of Classical Physics [2]. Notice that, by the end, as more things are considered, it's sounding more and more like relativity... All that being said, I agree with the PhysicsForums policy. It's a pointless debate. Switching between BU and LET might give you some intuitive understanding, but day to day you end up using special relativity because it's a lot more mathematically elegant. Plus I have no idea how you'd make the aether work with general relativity. 1: https://www.physicsforums.com/threads/what-is-the-pfs-policy-on-lorentz-ether-theory-and-block-universe.772224/ https://www.physicsforums.com/threads/what-is-the-pfs-policy... 2: http://www.aetherambler.net/strange.htm http://www.aetherambler.net/strange.htm

JackFr 11y ago

I am not a physics expert, but isn't dark matter simply a plug because mass of galaxies and large scale astronomical structures calculated from light and other electromagnetic radiation, doesn't agree with mass calculated by observing they're gravitational interaction? That is, we assume that both models (radiation & gravity) are correct, and that 90+% of the universe is made up of matter which has never been directly observed and is radically different than any matter we observe directly. The whole thing seems ludicrous -- but for the problem that no better explanation has yet been put forth. One gets the feeling though that one day in the future 'dark matter' is gonna look a lot like 'epicycles'.

inclemnet 11y ago
> isn't dark matter simply a plug because mass of galaxies and large scale astronomical structures calculated from light and other electromagnetic radiation, doesn't agree with mass calculated by observing they're gravitational interaction? One might more generously say that dark matter is a proposed explanation for many measurements deviating from predictions based on visible matter in a way very consistent with the existence of large amounts of non-electromagnetically-interacting matter. I don't think there's anything fundamentally ridiculous about this. For instance, while you characterise it as 'radically' different to any matter that we observe directly, the neutrino has most of the relevant properties, and e.g. supersymmetry has been noted to include dark matter candidate particles. While one may doubt that supersymmetry is actually correct, I think it demonstrates that the combination of properties (massive + electromagnetically inert + maybe weak force interacting) isn't necessarily a problem.
JonnieCache 11y ago
It's not just galaxy rotation. That's how people first noticed it. Since then there's stuff like this: http://en.wikipedia.org/wiki/Bullet_Cluster http://en.wikipedia.org/wiki/Bullet_Cluster Also there's apparently information about the universe's composition to be gleaned from the CMB anisotropies; its all somewhat beyond me, but that curve certainty seems to fit extremely well, I'll give them that. http://www.astro.ucla.edu/~wright/CMB-DT.html http://www.astro.ucla.edu/~wright/CMB-DT.html The combination of all this stuff is apparently pretty convincing. EDIT: I see that your comment is actually referring to the bullet cluster more than the rotation curves. It's all pretty tenuous in the grand scheme of things, I agree, but then so much of cosmology is. I guess they have the benefit of the string people next door making them look reasonable by comparison.

deleted 11y ago

[deleted]