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Special Relativity defined without reference to light

  1. May 11, 2012 #1
    Just saw this paper discussed (sort of) on Reddit, and wondered if it is old news.
    http://www.reddit.com/r/Physics/comments/tgvpn/a_rederivation_of_special_relativity_from_chaos/
    (the URL is truncated so it gives the wrong impression ;))
    I can't understand the maths behind it, but am very interested in the axiomatic basis of relativity, and eliminating the light speed reference is clearly a significant claim. The language of the paper is fairly idiosyncratic, and the author barely contains his utter contempt for Newton, which itself makes for an interesting read!
    I would be fascinated to hear the opinions of the wizards here, if it is correct, I would consider persevering to understand it myself. I just hope it wasn't an April Fools' joke that escaped . . .
     
  2. jcsd
  3. May 11, 2012 #2

    Ich

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    The paper is too long, so I won't read it. However, it seems to be staircase wit from someone who is especially slow on the uptake (100 years, that is).
     
  4. May 11, 2012 #3
    heh, as it happens I have that book, and read it very recently (mostly, I'm not keen on anything to do with QFT) ;) Not sure I fully understand what is meant by "staircase wit", unless it just refers to retrospective application of mathematics. If so, then would that apply to Euler, Lagrange et al with regard to Newton's work? In which case I would not consider that a criticism to worry about.
    By way of explanation, the reason I posted it in the first place was the possibility of shutting up people who think of breaking the speed of light as a mere technological problem.
     
  5. May 11, 2012 #4

    Ich

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    It's a famous quote from Minkowski, as he realized that mathematicians should have found SR long before Einstein, from basic principles. It is explained in the link.
     
  6. May 11, 2012 #5
    I did not read it (sorry). Such claims are usually half right or half wrong, depending on how you look at it. For sure relativity doesn't need to refer to "light", but it does use the speed of light c. The relativity principle alone does not suffice, it needs an additional boundary condition. The simple answer for which you don't need much math to verify: also classical (Newtonian) physics has the relativity principle, and that is not SR. But maybe his claim is merely that one can obtain SR from other postulates; and that is well known.
     
  7. May 12, 2012 #6

    Cleonis

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    There is no such thing as eliminating the significance of light speed, but what you can do (and has been done by many), is expressible as follows: "in any logical system there is great freedom to interchange axiom and theorem without changing the contents of the system."

    You can take the relativity of light speed as starting point, and derive the Minkowski metric as a logical consequence, or you can take the Minkowski metric as starting point, and derive the relativity of light speed as logical consequence.

    The logic enforces the implications, but in itself the logic does not pinpoint which elements should be set as the axioms of the system. The fact that the 1905 Einstein paper focused on light speed is how things happened to unfold, with no inherent physics significance.


    According to the summary of the Feigenbaum paper relativistic physics is arrived at purely by demanding the the most general validity of the principle of relativity.

    This result is known as 'the most often independently rediscovered result in special relativity'.
    So yeah, if that is the point of the Feigenbaum paper then it's really old news.


    Personally I quite like the concise and accessible version written up by Palash B. Pal: "arxiv.org/pdf/physics/0302045" [Broken]

    Since you are interested in the philosophy of physics axiomatization you will enjoy that discussion I think.
     
    Last edited by a moderator: May 6, 2017
  8. May 12, 2012 #7
    Thanks for that link; my understanding so far of Galilean/Einsteinian relativity is based on the relevant parts of Penrose's Road to Reality and Brown's Reflections on Relativity. Any other relevant articles welcome!
    [EDIT] Having read the article, it would appear to be exactly what I am looking for, both forms of relativity derived from the the properties of space and time, with the speed of light optionally dropped in right at the end after all the real work has been done.
     
    Last edited: May 12, 2012
  9. May 12, 2012 #8

    Cleonis

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    Also, deciding between galilean and einsteinian relativity can be done on lines of experimental evidence other than optical.

    For instance, the observation that muons created in the upper atmosphere make it all the way to the earth's surface. Usually that is mentioned as corroborating evidence, but one can just as well cite the muon observation as the experimentum crucis, and refer to optical observations as corroboration.

    Arguably the muon observation is more direct evidence. By contrast, the Michelson-Morley experiment is a null-experiment. It is argued that the fact that the Michelson-Morley experiment failed to find motion of the earth relative to the luminiferous ether counts as evidence in favor of einsteinian relativity. The muon observation is directly affirmative: it's a direct consequence of the relativistic time dilation.
     
  10. May 12, 2012 #9
    That is an even better way of putting it; Maxwell establishes both the speed of light and its source independence, then (eg muon) experiment establishes special relativity over Galilean, and simultaneously the cosmic "speed limit" itself. It is then merely a question of further experiment to confirm that this relativistic top speed is numerically equal to the speed of light. These experiments can be refined to whatever degree of accuracy a la the equivalence principle.
    Hope I have understood your comment, I think my "ammunition" is now complete!
     
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