Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Interesting interferometer experiment!

  1. Jan 23, 2010 #1


    User Avatar

  2. jcsd
  3. Jan 23, 2010 #2

    Ivan Seeking

    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    Moved from S&D, maybe appropriate for the physics forum.

    Since we have no references I chose GD.
  4. Jan 24, 2010 #3


    User Avatar
    Science Advisor
    Gold Member

    I'm thinking one of the mirrors is changing position slightly during each revolution (longer then shorter path length) causing the change in pattern. It does make you wonder.
  5. Jan 24, 2010 #4


    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    I thought something similar, that some part of the apparatus isn't securely bolted down.
  6. Jan 24, 2010 #5


    User Avatar
    Science Advisor
    Gold Member

    That is interesting.

    If the shift in the fringe patterns was due to the apparatus bending, intuitively I would have thought the stationary points would have been when the apparatus was horizontal and under maximum strain. Martin Grusenick reports it at being when the apparatus was at 450 to the horizontal.

    The experiment should be repeated under laboratory conditions by a competent experimenter.

    Of course Self-Creation Cosmology predicts something like this.....
    Ah, well.....

    Last edited: Jan 24, 2010
  7. Jan 24, 2010 #6
    It does seem like gravity is causing some of the components to move. However, a quick Google search revealed that he has built a new interferometer that is lighter and more compact, and apparently the new rig exhibits similar interference fringe shift, though to a lesser extent. It would be nice to see this experiment repeated in a zero-g environment to further reduce the effects of gravity.
  8. Jan 24, 2010 #7
    Yes, it's pretty clear to me and I do not believe there is any new physics here : in the vertical position, he has mechanical variations due to the weight of the apparatus. Interferometers are pretty sensitive. At the very least, if he wanted to publish, he would have to provide an estimate of this effect.
  9. Jan 24, 2010 #8


    User Avatar

    I wouldn't take any position until i check it myself. All the mechanical and other sources of errors can be easily eliminated...i guess with less than 100 bucks i can build one. Maybe is better instead of rotating it to build it as a pendulum......Any other amateur...?
  10. Jan 24, 2010 #9


    User Avatar
    Homework Helper

    11.5 fringes corresponds to a roughly 6-micrometer shift in the position of the mirrors. To the engineers here: Given the construction of the device, could the mirrors have shifted by that amount?
  11. Jan 24, 2010 #10
    I'm not even an engineer and I can tell you that this thing is bunk.

    First off, the fringe shift changes based on time of day (his words).
    There are no opposite side supports to any piece of the apparatus.
    Aluminum is a pretty flexible material and I'm sure those box tubes are moving.
    It's not properly balanced linearly. That wood sure looks like it doesn't counter the laser projector.
    There are no perpendicular weights to balance the strain on the flimsy L bracket.
    It is not fastened with a bearing on both sides.
    I don't know if it really matters but that is a very high level light environment (every laser lab I've seen in the movies has black walls :P).

    I honestly don't know squat about performing experiments but this looks fishy as all hell.
  12. Jan 24, 2010 #11
    Where is the rotating experiment's center of gravity?

    What is its general relativistic (gravitational) frequency shift?

    Is the beam splitter first surface?

    Do the experimental results (interference) themselves confirm a mechanical flaw?
  13. Feb 2, 2010 #12


    User Avatar

    So i have build real quick an interferometer, one arm like 400mm the other 200mm, and i used a cheap red laser pointer. My results while testing it were that this stuff is so sensitive that the interference pattern will change even when a fly drops a fart at 5 meters from it! I obtained a clear pattern of interference just like Martin did, which wasn't too sensitive and while spinning it vertically or horizontally didn't show any visible change in the pattern. On top of this main pattern i got another interference pattern that was extremely sensitive even to my breath . My conclusion is that the effect that Martin had is too big to be accounted to any new phenomena, but rather to the not well assembled mirrors or beam-splitter. I don't say that could not be something interesting but for that its needed a very sensitive interferometer in VACUUM and if possible in zero gravity! I couldn't observe the variations of the secondary interference pattern because they are way to sensitive to any vibration or even air movement. They become visible only when the interferometer is completely still, even then they jump around from time to time.
    One interesting thing was that while the interferometer is still, in horizontal plane, from time to time the main interference pattern is changing but I'm very sure is not from the surrounding vibrations...i guess maybe is because of the lasers wavelength is not stable....
    Why the interference pattern is changing when the air its moving between the mirrors?
    I don't even understand why we actually have an interference of the light...i thought that electric field are not self-interacting...oh well
  14. Feb 8, 2010 #13
    Interesting. Hope further research is done on this.
  15. Feb 14, 2010 #14


    User Avatar

    I realised that in the movie we don't see actually an interference between the two split rays but we can see two distinct interference patterns created by the two rays with them-self, so its not a real interference that can give us a good information. I observed that if i overlapped the two distinct interferences i obtain a very sensible interference pattern characteristic to the Michelson interferometer. This interference is very very sensible to any kind of vibrations and air movement too. I build a more precise support and i spun the interferometer again and indeed you can see that the pattern is changing....but still not convinced if not because the air movement despite the fact that the change is opposite symmetrical when the mirrors are going up and when they go down. I still believe that Martin's interference is because of a poorly stabilized mirrors.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook

Similar Threads for Interesting interferometer experiment Date
Your most interesting fact about Pi Mar 13, 2018
Sound volume (life experience) Feb 25, 2018
What originally got you interested in physics? Jan 16, 2018
EE PF Projects Contests Interest Nov 26, 2017