User talk:Harald88/sandbox

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One-way speed of light, relativity of simultaneity and the second postulate

Start collecting references:

  • 4 Pauli 1921 "Relativitätstheorie" for the "Encyclopädie der mathematischen Wissenschaften" (see [1]): "The velocity of the light is independent of the motion of the light source"
  • 5 Ives, "Extrapolation of the Michelson-Morley experiment" in the JOSA vol.40, no.4, april 1950 pp.185-191 : there he demonstrates the relativity of simultaneity between two stationary clocks with slow clock transport
  • 7 Erlichson 1984, link.aip.org/link/?AJPIAS/53/53/1 "A proof that absolute synchronization is impossible is sketched."
  • 9 Modern derivations of SRT (thanks to Bill Hobba):

http://arxiv.org/abs/physics/0110076, and ancient, but I still think excellent post by Tom Roberts http://groups.google.com/groups?hl=en&lr=&c2coff=1&selm=54jfst%24glp%... and chapter 10 of http://www.courses.fas.harvard.edu/~phys16/Textbook/

  • 10 (the "modern" coordinate free formalism, according to Pjacobi 19:13, 8 May 2006 (UTC))
  • 11 " according to a recent article in the American Journal of Physics" (--Alfred Centauri 21:48, 16 May 2006 (UTC)): "In the years immediately preceding 1905 and in Einstein's seminal paper, the phrase 'the constancy of the speed of light', meant only that the speed of light is independent of the source's velocity" [..] "having taken from the idea of light waves in the ether the one aspect that he needed, he declared early in his paper, to quote his own words, that “the introduction of a ‘luminiferous ether’ will prove to be superfluous.”"
  • 12 "Banesh Hoffmann, who worked with Einstein in the 1930s, in his book, Relativity and Its Roots: The second of the two principles in Einstein’s paper said that the motion of light is not affected by the motion of the source of light. Nothing, it would seem, could be more orthodox and obvious. For if a source of light generates light waves in the ether, once the waves are launched they are no longer linked to their source; they are on their own, moving at the rate set by the elastic properties of the ether…."
  • 13 "Superficial consideration suggests that the essential parts of Lorentz's theory cannot be reconciled with the relativity principle. According to Lorentz's theory, if a light beam propagates through space, it does so with a speed c in the resting frame K of the ether, independently of the state of motion of the emitting object. Let's call this the invariance of the speed of light principle." - Einstein 1909, The Development of Our Views on the Composition and Essence of Radiation

[edit] Discussion, summarizing the referenced articles

[sorry if this wasn't clear: this is not meant to be a Wikipedia editor's discussion page, but a condensed summary of the arguments in the relevant parts of the references; it should serve as a first version of a corresponding version for the Special Relativity article!]

As far as light's measured speed is concerned, an atomic clock has only the single physical property of intrinsic atomic vibration. Therefore, once a clock has been given a constant speed through space, its intrinsic atomic vibrational rate is set, and nothing more can happen to the clock to alter its recorded time (given an SR environment).

Similarly, as far as light's measured speed it concerned, a ruler has only the single physical property of intrinsic length, and once a ruler has been given a certain constant velocity through space, its unique physical length is set, and nothing more can be done to alter any of its recorded distance measurements (given an SR environment). [I agree but I didn't see this argument in the references. Thus: REFERENCE AND PAGE PLEASE! ]

Suppose we are given that clocks physically slow and rulers physically contract as the move through space. Supposed they change according to the formula
1/sqr(1 - v2/c2),
where v/c is the ratio of a clock's or ruler's speed v through space to light's speed through space c (as per Maxwell's equations).

Only if we are given these (or similarly physically distorted) rulers and clocks can light's round-trip, one-clock speed be c in all directions in all inertial frames.

However, even given slowed clocks and contracted rulers, light's one-way, two-clock speed will still vary with frame velocity according to the formula w = c2/(c - v), as long as the clocks are "absolutely synchronous", according to [REFERENCE AND PAGE PLEASE!]

Thus argues [???], one-way, two-clock variance must occur when absolutely synchronous clocks are used, even if clocks are slowed, and rods are contracted; and it proves that the only way to obtain SR's one-way invariance (using two same-frame clocks) is by replacing absolutely synchronous clocks with absolutely asynchronous clocks, and then setting (forcing) the latter to get "c" one-way via a definition, as did Einstein.

After noting that round-trip invariance/isotropy was given (for all practical purposes) by the Michelson-Morley experiment (even though their names were omitted), Einstein [1905] noted that the time portion of light's one-way speed must be given by definition because we have no means of absolutely synchronizing clocks. He also noted in his book that light's one-way speed would be c ± v if synchronous clocks were used. [ON WHICH PAGE IN THAT BOOK?]

Einstein also noted in his book Special Relativity, 1961 Edition, page 27: "... if we discard [the assumption of absolute time or absolutely synchronous clocks], then the conflict between the law of propagation of light in vacuo and the principle of relativity disappears."

Clearly, Einstein's definition of clock "synchronization" is a vital part of light's one-way speed. [AUTHOR, PUBLICATION] asserts that light's one-way speed is the only speed about which special relativity could have postulated, given round-trip invariance via experiment.

[edit] Editor's comments and clarifications

[not to put in the article; instead a summary of the essentials may be put on the article's Talk page]

Does the WIKI relativity article's second postulate section mention anything about a definition of "synchronization"? Does it mention that light's one-way speed would vary given absolutely synchronous clocks? Does it mention that Einstein was forced to discard synchronous clocks, and then had to force clocks via a definition to obtain one-way invariance? Does it mention the fact that even given slowed clocks and shrunken rods and round-trip invariance, light's one-way speed can still vary as long as truly or absolutely synchronous clocks are used? Cadwgan Gedrych 15:22, 5 June 2006 (UTC)

What is meant with "light speed" is open for interpretation.
In order to spare fresh readers we will devote the above section to this matter, instead of a few loose and debatable remarks in the intro. IMO it should be made clear in this section that OWLS relative to objects is frame dependent, just as time. Too many people fail to understand that.
Note also that some of the articles that special relativity points to treat much of that subject; linking to those will save space.
But as according to the theory no "absolute synchronity" can be established, it is IMO not useful to linger on that concept. The references don't do that either. Harald88 18:18, 5 June 2006 (UTC)