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Lorentz contraction inverse trouble

  1. Dec 8, 2005 #1
    why Lorentz contraction transformation in the direction of motion for the problem in michelson experiment was proposed, instead of length expansion in the direction perpendicular to motion. I think that too will give the same solution. I dont know i might be crazy and silly in this argument. I have read that Professor Feynman has answered this by saying that this violates Newtons Principle of Relativity statement. But i was wondering how this violates.
    Ok i agree that its obvious that there is no reason to say for expansion in perpendicular direction to motion, but it might contract in direction of motion due to change in length of target by light due to motion. But my doubt is still there is a chance of mistery as like contraction. Ofcourse it would have led to different consequences in other things of relativity.
    I might have been wrong also, anyway i am not any professional physicst, i m a software engineer and working on physics for now as ameature. working to become a good physicst with clear understanding of nature.
  2. jcsd
  3. Dec 8, 2005 #2


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    There is a thought experiment arguing that there is no contraction (or expansion) in the spatial directions perpendicular to the motion. Essentially, it involves two identical winged objects (call them A and B) with a nail or other marking pen at the tip of each wing.
    Suppose A and B travel inertially toward each other with different speeds along a line.
    Suppose there is contraction in the perpendicular direction.
    Then, in A's frame, B's wing contraction will mark up A's wing.
    Invoking the relativity principle, in B's frame, A's wing contraction will mark up B's wing.
    Logically, both can't happen. Therefore, there can be no contraction in the perpendicular direction.
  4. Dec 8, 2005 #3
    do u mean that Lorentz transformation is under conspiracy. But still its the only solution for Michelson experiment. I dont find anything wrong with that although it looks misery.
  5. Dec 8, 2005 #4
    pls just say me why they decide to use contraction in motion instead of expansion. Was this issue raised before.
  6. Dec 8, 2005 #5


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    Are you suggesting that my own ruler expands relative to a ruler that's moving at relativistic velocities relative to me, instead of the moving ruler shrinking relative to mine? The problem is there'd be no upper limit to how much my ruler must be expanded relative to other rulers to get the ratios to work out the same as in SR--for example, relative to a ruler moving at 0.6c relative to me, my ruler would have to be 1.25 times longer than it, but relative to a ruler moving at 0.9c relative to me, my ruler would have to be 2.29 times longer than it, relative to a ruler moving at 0.99c my ruler would have to be 7.09 times longer than it, relative to a ruler moving at 0.999999c my ruler would have to be 707.1 times longer than it, relative to a ruler moving at 0.999999999c my ruler would have to be 22361 times longer than it, and so forth. And it's not like there actually have to be other rulers travelling at these velocities for my ruler to expand, my ruler should have a fixed length when it's at rest in my frame, it shouldn't suddenly expand when I see another ruler whiz by. But there's no way to choose a fixed finite length so that it'll be big enough relative to an arbitrary ruler moving past it, if you assume the moving ruler is the "normal" length.
  7. Dec 9, 2005 #6
    please have a look at
    Illustrating the Michelson-Morley experiment on
    arxiv 2005 physics education
  8. Dec 10, 2005 #7
    Thank u Mr.Jesse. I worked last night on this and understood where i mad the mistake. It was due to misinterpretation of SR in an experiment at a different context. But thank u for ur patience with such a silly question.(i m just a amature in physics and not professional)..
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