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Very good arguments against existence of isotropical length contraction or expansion?

  1. Feb 2, 2013 #1

    smm

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    according to special relativity theory, any object that has relative
    velocity also has lorenz- contraction L' = L0 *sqrt (1-(v/c^2))

    it sounds odd that this is only kind of length contraction known to exist.

    why there are no other kind of length expansions or contractions, or are them impossible to exist for some reason that comes from relativity- or particle physics theories?

    -For example If someone would tell you that he has observed an
    object in space with his telescope that has isotropical length expansion, could you make good argument against his claim?


    i put here some arguments against that i have found:

    1 according to lights spectral lines, supernovas and other events, all laws of nature seems to be same everywhere in observed space

    2 In particle physics experiments, no length expansions or contractions have been
    ever observed

    3 if some object would have length expansion, at least it cant move or emit light at superluminal speed - that is not possible according to special relativity theory.

    4 Does particle that have isotropic length expansion or contraction
    have more or less momentum or energy than normal particle? IF SO, where has
    the particle got its momentum from? What kind of force can have influence to
    to make the particle have isotropic length expansion or contraction?
     
  2. jcsd
  3. Feb 2, 2013 #2

    HallsofIvy

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    Re: very good arguments against existence of isotropical length contraction or expans

    Yes, this seems reasonable- and that the laws of nature are the same everywhere is a standard assumption.

    Why would particle physics experiments be important? Relativistic length contraction certainly has been observed- whether in "partcle physics experiments" or not, I don't know.

    How do you arrive at this? Length expansion, as a result of relative motion, is itself not possible according to special relativity theory. I don't know what you mean by "can't move". Every object in the universe is moving relative to some other object.

    Good! A question rather than a flat assertion! No, relativistic length contraction is not directly related to the energy or momentum of an object. However, it is true that the amount of energy or momentum an object is observed to have depends upon the frame of reference from which it is observed. If I am in a frame of reference in which the object is at rest, I see no contraction from its rest length and I see 0 kinetic energy and momentum. If another observer is in a frame of reference in which that same object is in motion, that observer will see the object contracted (never "expanded") from its rest length and see non-zero kinetic energy and momentum.
     
  4. Feb 2, 2013 #3

    ghwellsjr

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    Re: very good arguments against existence of isotropical length contraction or expans

    Keep in mind, as HallsofIvy just pointed out, it's the velocity of an object relative to a frame of reference that matters. Since we can use any frame of reference, the lorentz contraction can be different in every one.
    Yes, of course.

    1) As HallsofIvy pointed out, it's always length contraction, not length expansion.

    2) It's not isotropic. It's only along the direction of motion.

    3) It cannot be observed with a telescope or by any other means since it's different in each frame.

    You don't need any arguments against isotropic length expansion or contraction because nobody is arguing for it. What you need is to understand Special Relativity. I suggest you read lots of other threads on this forum such as the ones listed at the bottom of this thread and learn that way. Promoting ideas that debunk relativity is a good way to get banned and asking irrelevant questions is just a waste of everybody's time.
     
  5. Feb 2, 2013 #4

    smm

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    Re: very good arguments against existence of isotropical length contraction or expans

    hi - i am curious about can you say directly a very good argument that isotropic length expansion cant exist in nature? i want to clarify this at first here.

    for example can atom at rest have isotropical length expansion or contraction? I mean does some very good argument deny this atoms existence? If someone would say that he has found hydrogen atom in his laboratory that has 3 times larger radius than normal hydrogen atom, but it is a hydrogen atom -can you give very good argument against this claim?

    2 In particle physics experiments, no length expansions or contractions have been ever observed

    Why would particle physics experiments be important? Relativistic length contraction certainly has been observed- whether in "partcle physics experiments" or not, I don't know.

    i mean that no isotropical length expansions or contractions have ever observed in particle physics experiments. for example all free protons and other particles are found to be exactly
    identical in their radius except their lorenz contraction required in special relativity theory.

    3 if some object would have length expansion, at least it cant move or emit light at superluminal speed - that is not possible according to special relativity theory.

    How do you arrive at this? Length expansion, as a result of relative motion, is itself not possible according to special relativity theory. I don't know what you mean by "can't move". Every object in the universe is moving relative to some other object.

    i mean that If for example atom would have isotropic length expansion, special relativity theory at least requires that its electrons orbital velocities cant be superluminal. Also free proton that is accelerated by some force cant emit electromagnetic radiation at superluminal speed.

    4 Does particle that have isotropic length expansion or contraction
    have more or less momentum or energy than normal particle? IF SO, where has
    the particle got its momentum from? What kind of force can have influence to
    to make the particle have isotropic length expansion or contraction?


    Good! A question rather than a flat assertion! No, relativistic length contraction is not directly related to the energy or momentum of an object. However, it is true that the amount of energy or momentum an object is observed to have depends upon the frame of reference from which it is observed. If I am in a frame of reference in which the object is at rest, I see no contraction from its rest length and I see 0 kinetic energy and momentum. If another observer is in a frame of reference in which that same object is in motion, that observer will see the object contracted (never "expanded") from its rest length and see non-zero kinetic energy and momentum.

    Yes i understand that kinetic energy, momentum, time dilation, lorenz contraction and simultaneity - are all relative properties of particle while particles rest energy (that is equivalent to its mass) is nonrelative and always invariant property of particle.

    by the way what do you mean that relativistic kinetic energy is not directly related to particles lorenz contraction? i understood that special relativity gives strict connection between particles lorenz contraction and particles relative kinetic energy and momentum (although they also depend on particles rest mass and if particle consist of several moving parts they all have slightly different energies) and they both exist at same time.

    If isotropical length expansion would exist, it cant be relative propery of a particle - it cant be symmetric between two observers that have relative speed.

    i mean that for example if atom would have isotropical lenght expansion does its orbiting electrons have then more kinetic energy? or less? if so, what kind of force has acted on that particle to give it this energy or take it away? if there is no force that can do this, at least no known force can ever create isotropic length expansion or contraction.
     
  6. Feb 3, 2013 #5
    Re: very good arguments against existence of isotropical length contraction or expans

    Since Einstein, if not before, the contraction has not regarded as being a physical effect on the object, but rather the result of a coordinate transformation between the object and the observer. It's a special case of applying the Lorentz transform to the situation being examined. The Lorentz transform arises from the assumption that there are only relative motions, and that the speed of light is the same for all observers.

    So one would not expect to find other kinds of length contraction.

    Sylvia.
     
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