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I Special theory of relativity argument

  1. Mar 27, 2016 #1
    Some layman people are against special relativity and stubbornly persist on their theories.
    One man put the model that the speed of photon is c + v, where v is speed of source. In such case Michelson interferometer is not a good anti-argument.

    What is, in your opinion about the most simple and effective experimental or theoretical argument against the above model (for educated non-physicist.)
    He wishes an experiment, where source of light is moving.
    I gave an argument about the speed of OPERA neutrinos, but argumentation is not easy.
    All physics is against the above model, but anti-argumentation is not easy.
     
    Last edited: Mar 27, 2016
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  3. Mar 27, 2016 #2

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    If you rule out explaining the details of the Michelson-Morley experiment, there is not much that you can say scientifically. But you can describe the history. Just about everyone believed that the velocities should add. Or that aether existed. They tried really hard to find experiments and theories that would support that belief. The experimental results left no alternative to the speed of light being constant.
     
  4. Mar 27, 2016 #3
    It is strange to me, that no experiment exists to simply rule out c+v model. Is it something similar to OPERA, where source is moving and photons are used instead of neutrinos?
     
  5. Mar 27, 2016 #4
    I thought that was the whole argument? If c+v is one direction c-v would be the opposite direction. We simply see "c" and "v" has no effect on the results.
     
  6. Mar 27, 2016 #5

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    You might describe briefly that light behaves like a wave going through a stationary field, unaffected by the speed of the source, but that all inertial frames measure it's speed the same in their reference frame. That can lead to a discussion of the relativity of simultaneity, distance, and time.
     
  7. Mar 27, 2016 #6
    Yes, but I do not know an example where speed of light is measured from non-rest source?
    I agree, nonsimultaneity is an important argument, but not in one step.

    Or maybe, Maxwell equations are independent from speed of source, they always give result c, as speed of light?
     
  8. Mar 27, 2016 #7

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    You mean other than the Earth?
    Only if they are interested. But it is the root cause of it all.
     
  9. Mar 27, 2016 #8
    It is not important if source is other than earth, I think, if speed of source is minuscule, it can be measured.

    And my question above: Do maxwell equations always give speed of light as c? This can be an effective answer.
     
  10. Mar 27, 2016 #9

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    Transmission of radio signals between earth and spacecraft
     
  11. Mar 27, 2016 #10
    Was this speed of "light" measured precisely enough?
     
  12. Mar 27, 2016 #11

    jtbell

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    Tests of Light Speed from Moving Sources (from the FAQ on experimental tests of relativity which is linked at the top of this forum)

    What is "precisely enough"?
     
  13. Mar 27, 2016 #12

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    If the actual speed of the received signal differed from the accepted invariant velocity as a result of the speed of the source, the ground locations computed by a GPS receiver would be systematically wrong. No such systematic errors have ever been seen, and we're working with distances measured in meters after the signal has travelled hundreds of kilometers.
    So even before doing any statistical error analysis or considering interferometry measurements, we're talking about better than one part in ten thousand. More sophisticated measurements than this naive "how far down the off-ramp did I go before the GPS figured out that I took the wrong exit?" are orders of magnitude better than that.
     
  14. Mar 27, 2016 #13

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    Without corrections for relativity, GPS measurements would be wrong by about 6 miles per day.
     
  15. Mar 27, 2016 #14
    Do you think satelites, or Spacecraft? If you think satelites, you do not think geostationary satelites?
     
  16. Mar 27, 2016 #15
    This link is what I wished. Thanks.
    With "precise enough" I thougt more precise than velocity of source of light.
     
  17. Mar 27, 2016 #16
    Yes, but I think that those corrections are for general relativity, I think only about velocity of satelites, that I will not complicate.
     
  18. Mar 27, 2016 #17

    PeroK

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    Well, if Special Relativity is wrong, what hope would there be for General Relativity? It's not you yourself that is unconvinced, by any chance?

    The GPS corrections are for both SR and GR, by the way.
     
  19. Mar 27, 2016 #18
    I think I found:
    46 us/day for general relativity, -7 us/day for special relativity. This can be translated into above 6 miles/day.

    When I explain to a layman, I need as simple as possible.
     
  20. Mar 27, 2016 #19

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    Either satellites or spacecraft - they're both spacecraft, we just happen to use a different name for the spacecraft that are in semi-permanent earth orbit, and they're all equally useful as moving light sources.

    The GPS satellites are nowhere near geosynchronous, but even if they were.... A geosynchronous satellite is moving about 2.5 km/sec faster than the point on the earth's surface directly below it.
     
  21. Mar 27, 2016 #20

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    I didn't read the whole thread, but I don't know why you think that no experiment rules out the c+v model, which is commonly called emission theory.

    See for instance the PF Faq, "Experimental basis of Special Relativity", https://www.physicsforums.com/threads/faq-experimental-basis-of-special-relativity.229034/, and chase down through a couple levels of links to arrive at the section on "Tests of light speed from moving sources", http://www.edu-observatory.org/physics-faq/Relativity/SR/experiments.html#moving-source_tests. You might also want to check out the notes on "extinction" earlier in the reference.

    Basically there's plenty of tests, and they've been mentioned numerous times. But there's always someone around to ask the same old questions over again. Perhaps we'll see another question along the same lines as early as tomorrow, as someone reads the thread, and gets inspired without reading the responses. Though I can't point too much of a finger at not reading all the responses - I didn't read them all myself, as - well, I've seen this before a few times.
     
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