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Sun's light beam and diffraction grating

  1. Aug 4, 2012 #1
    Hello.

    Lets say we have 2 small holes (1&2) which makes tiny light beam from the Sun's light.
    (similar to laser beam)
    ...........................1|......................|2...
    (Sun) -> >-------------------------------------|dg|-----{order 0}-------(Earth)
    ...........................1|......................|2...

    |dg| is diffraction grating perpendicular to the light beam.
    Holes and grating moves together with the Earth.

    Will this grating effect direction of light propagation and how much?
    Lets consider only order 0 for simplicity.

    I mean the Earth is moving around the Sun.
    How this will effect the result?

    Thanks.
     
    Last edited: Aug 4, 2012
  2. jcsd
  3. Aug 4, 2012 #2

    Drakkith

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    I don't think the light that is in order 0 is affected at all.
     
  4. Aug 4, 2012 #3

    mfb

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    It modifies the position where you see sun in the sky (more interesting for other stars, however). In your setup, it does not matter. Your can view your lab as inertial system. In theory, if your experiment is extremely precise, you could measure the rotation of earth. But I think this is just a theoretical option.

    Order 0 just appears in a straight line behind the holes.
     
  5. Aug 5, 2012 #4
    Thank you.
    But still would be nice to talk with someone who would like to make this experiment.
    I mean small possible deviation up to 0.1mm per 1 m.
    At good laboratory I suppose it would take only 15 minutes of time,
    but difficult to reach necessary acuracy without specific equipment.
    Of course instead of holes some optics can be used to form narrow beam from the Sun.
     
  6. Aug 5, 2012 #5

    sophiecentaur

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    You don't need to do an experiment. You can calculate what happens. If the grating has zero thickness then the 0th order spectrum surely must involve no change in angle because the path distance for the beam will not change. What are you expecting and what is your justification, in theory?
     
  7. Aug 5, 2012 #6
    Some old theories suggest some difference between direction of light propagation
    and perpendicular to wave front for this setup.
    Diffraction grating likely would be sensitive to detect such difference.

    So why just not make measurements to be sure?
    Especially because it is extremely cheep and quick experiment for people who already have necessary equipment.
     
  8. Aug 5, 2012 #7

    sophiecentaur

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    Which old theory? Do you have a ref?
     
  9. Aug 6, 2012 #8

    You know before relativity there was 3 main views to photon:
    ballistic photon, wave in motionless ether and wave in entrained ether.
    This experiment is for comparison relativity with entrained ether.
    See picture:
    http://img196.imageshack.us/img196/1410/entrainedether.png [Broken]

    If we have observer on the Earth light from the Sun is coming a little diagonally
    (due Earth motion)
    By classical view wave front 1 is still parallel to the surface of the Earth.
    Because ether movement do not effect impulse of the photon
    light will hold his initial direction after coming to Earth's ether.
    So entrained ether will not contradict to stellar aberration (opposite to widely prevalent misunderstanding), but there is unclear situation with waver front 2.

    If front of individual photon equals to front 2 we have strange photon
    where line of movement differs from perpendicular to its wavefront.
    This can be detected by simple initially described experiment with diffraction grating.

    But still this experiment is not very clear, because we are in atmosphere and photons many times re-emits by atoms of it.
    Re-emitted photons may have usual orientation of wave front (perpendicular to line of motion).
    Therefor ideally would be nice to make such experiment on a satellite (outside atmosphere)
    and to use only holes and diffraction grating to avoid mentioned re-emitting inside optical instruments.

    I hope this is what you asking for.
    I do not know who initially proposed entrained ether,
    but I know this version was widely discussed by science community of that time
    and was made some mistake with stellar aberration.
    And I really do not know any other contradictions to experiment,
    (please say if you know)
    but this branch was dropped somehow without future development prior to relatyvity.
     
    Last edited by a moderator: May 6, 2017
  10. Aug 6, 2012 #9

    mfb

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    I do not see why this should give a 0. maximum anywhere but in the straight line behind the holes.

    It is possible to develop aether theories which make the same predictions as special relativity. But they are needlessly complicated, and therefore they are not used any more. In addition, SR is not about light only - we have so many effects which agree with SR very well.
     
  11. Aug 6, 2012 #10

    sophiecentaur

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    I should have thought that the Michelson Morley experiment would have been a much more sensitive way of showing that there is no motion 'through an aether' and it works on the same principle as the suggested 'diffraction grating' method - namely trying to detect an effect on a diffraction pattern due to wave motion through some sort of 'medium'. MM showed there is none.
     
  12. Aug 6, 2012 #11
    In case if such wave exist where perpendicular of wave front differs from direction of propogation two adjacent slitts of diffraction gratings would be reached not simultaneously.
    I mean when difraction grating are exactly perpendicular to light patch.
    So light would bend a little.

    I do not state here that SR is wrong by curent experiments.
    But you can not be sure eactly 100% that situation will not change.
    If you are interested purely in nature, not in current status you can not be sure 100%.
    At least a little little less.
    But alternative views , even wrong views can suggest better experiments
    because you start thinking in terms of differences.
    I do not mean differences between Newton and SRT.
    I mean differences between SRT and the best current alternatives you can find.
    Even not excepted by science community.
    From these differences can be generated ideas for interesting experiments.
    Without these alternatives you would not find even ideas for such experiments.
     
  13. Aug 6, 2012 #12
    Lets made mind experiment.
    Lets put all MMX to photo sensityve matierial and run ether wind with velocity v.
    You will have hologram with periods
    l1=l0 * sqrt (1-v^2/c^2) along perpendicular arm and
    l2 = l0 * (1-v^2/c^2) along arm parallel to ether wind.
    This is some type of standing wave formed by not sinusoidal sum of two rays mowing back and force. But nice point is that they will form sinusoidal hologram.
    This is easy to test on a simulator.
    Now why not to guess that hard bodies are also standing waves.
    If so they must contract in ether wind by the same amount.
    So MMX can not measure anything from this point of view.

    Similar point was proposed by H.Lorenz in his LET, but with the same amount of relative contraction l2/l1 = sqrt (1-v^2/c^2)

    Again I am not saying that SRT is wrong by current data, but if alternative view gives so close results it is much easier to look for better experiments in terms of differences.
     
  14. Aug 6, 2012 #13

    mfb

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    It does not matter - you can use a diffraction grating with any direction if incoming wave fronts. The 0th maximum will be where the light spot would be without grating.

    That would be a silly statement ;).

    You can never be, as always in science.

    I just do not see where other theories would predict other results, at least for the 0th maximum.

    I do not know any (interesting) theory which agrees with SR in all experiments within the current precision, but predicts measurable deviations somewhere. As far as I know, most tests of SR just look for any deviation, without testing a specific theory. With GR, things are different, and there are theories like MOND.
     
  15. Aug 6, 2012 #14

    sophiecentaur

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    You can't test an idea like this on a "simulator" because the simulator would have your basic idea already built into it.

    MMX, surely, demonstrated that there is no "wind" so how would a non-existent wind produce any effect?
     
  16. Aug 7, 2012 #15
    Yes , length contraction is some type of ad-hoc.
    But it looks enough realistic.
    It comes from analysis how simplest hologram (a single mirror and photo sensitive surface on it)
    would look like if ether wind would really exist.
    It is easy to find that ether wind would not destroy the hologram, just periods would become shorter
    by mentioned proportions.

    Here is some picture (full animation maybe would be too big to place here)
    http://img507.imageshack.us/img507/6130/wave.png [Broken]
    Lets asume ether wind from right to left with velocity v
    If we have mirror on left side then incoming wave :
    y1 = k*sin(x/(2*pi(c+v)) +t)
    and reflected wave
    y2 = k*sin(x/(2*pi(c-v)) -t)
    (both are gray on the picture)
    Then y1+y2 = k*sin(x/(2*pi(c+v)) +t) + k*sin(x/(2*pi(c-v)) -t)
    (black line) which also moves.
    But it moves only inside static zones surrounded by static violet sinusoids.
    y3 = 2*k*sin( x/( 2*pi*c*(1-v^2/c^2) ) ) and
    y4 = -2*k*sin( x/( 2*pi*c*(1-v^2/c^2) ) )

    So it forms sinusoidal hologram, but with shorter periods compare to the case when v=0.
    Here are no any ad-hocs up to this point, just calculations how hologram would look if ether wind would exist.

    Then comes ad-hoc idea: maybe hard bodies are some type of standing waves also.
    If so they must follow the same rules (must contract by the same amount).
    In this way even 0.9c ether wind will be not detectable with MMX setup, because of contraction of paralel arm by factor (1-v^2/c^2) and perpendicular by factor sqrt(1-v^2/c^2).
    Nothing much new here compare to LET, because relatyve contraction stays the same,
    but maybe here is a little better motyvation why hard bodies could contract.
    Yes, this analogy/relation between hologram and hard body can be seen as an ad-hoc,
    but also can happen that it is a good guess.
    But at least we need same alternatyve views to find good experiments based on differences.
    I think there is no big problem if alternatyve view is not vell developed in all posible areas.
    But still it is worth for mentioned purpose (to look for experiments) if it has good agreetment with experiments in areas where it is already developed and if we are scientific minded (not sure 100% with any even the best curent theory).

    By the way it looks this idea also can be aplied to explain life time of unstable particles.
    Smaller moving particle (perpendiculary smaller by factor sqrt(1-v^/c^2))
    may move longer until it hits with some virtual particle or dark mater particle or something else. Ant it looks this explanation fits numerically to known experiments also.
     
    Last edited by a moderator: May 6, 2017
  17. Aug 7, 2012 #16

    sophiecentaur

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    MMX had to be done long before holography had been invented but precisely the same thing is involved. I can't see why you want to re-do (effectively) the experiment, bearing in mind that there are hoards of experiments which are done nowadays which both demonstrate and use the non-existence of an aether. I'm talking about all the interferometry that's done between satellites and on the ground etc.
    No simulation can be used to 'prove' anything so it would be a waste of time.
    The rest of your post is getting a bit speculative, I'm afraid. I ran out of steam on the way through it.
     
  18. Aug 7, 2012 #17
    There are two different statements:
    relativity do not contradict to all known experiments
    and
    ether of light still exist.

    I think these two statements do not exclude each other,
    but there is no way to prove it without discussions
    (private discusion also would be ok, 1 email per week would be enough).
     
  19. Aug 7, 2012 #18

    sophiecentaur

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    Personally, I prefer to stick to open forum conversations.
    There is "no way to prove it" without measurements, I think. There have been many discussions (and measurements) already. If you are interested in finding out more then perhaps you need to read around more.
     
  20. Aug 7, 2012 #19
    Yes, in data of real measurements I am interested most of all.
    But here is such problem, I am interested in measurements only where my view for sure provide results different from current theory. But such experiments still was not done.
    Most known real experiments which have relation with c do not contradict to my view.
    For the rest (like Probe B for example and more) my math skills is not strong enough.
    You can test with any particular known experiment where math is not too complex.
     
  21. Aug 7, 2012 #20

    ZapperZ

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    I don't get it.

    There are dozens of other similar measurements that are WAY more sensitive than this (Kennedy-Thorndyke, for example) to detect such variations, if any. They haven't detected any. What makes you think that this particular one, that is considerably coarser than those experiments, is any better? Are you saying that your set up is more sensitive than LIGO or LISA, for example? How?

    Zz.
     
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