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Absolute motion, is it detectable?

  1. Apr 7, 2005 #1
    What if absolute motion was detected, would this mean to Einstein's theory of special relativity?

    Callisto
     
  2. jcsd
  3. Apr 7, 2005 #2

    turbo

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    It would require a rework. The Unruh effect arises from this kind of absolute motion with respect to the local vacuum. The anisotropies seen the the WMAP data may be another example of this, resulting from the motions of the Earth around the Sun, the Sun's proper motion through the Galactic arm, the rotation of the MW, and the MW's proper motion toward M31. Of course, until the 2nd year WMAP data are released and mapped over the 1st year data, we won't know. Do we have to wait for a generation of cosmologists to die before we get to see WMAP2? It is a publicly-funded program. Maybe it's subject to the Freedom of Information Act? :devil:
     
  4. Apr 7, 2005 #3

    DaveC426913

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    Well, the new theory would have to come first, since, without a working theory, how would we deduce that we've detected a motion that's absolute?
     
  5. Apr 7, 2005 #4

    Chronos

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    Motion is only meaningful with respect to 'something' that you arbitrarily define as stationary for measurement purposes. Absolute motion implies the existence of an absolutely stationary reference frame. How would you know if you found such a thing? Would it not look the same to all observers regardless of their velocity? Relativity says there is no such thing and it has enjoyed a great deal of success. The CMB is a convenient reference frame, but hardly stationary.
     
  6. Apr 7, 2005 #5

    turbo

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    Motion is meaningful with respect to the ground state. A canoe in a stream can be in motion with respect to the bank, but stationary with respect to the stream. Relativity is successful in a lot of ways, but it does not address the source or the nature of the CMB. These are concepts that were overlaid later.

    You may be interested in knowing that physicists predicted the ~3 degree vacuum temperature when steady-state cosmology was in the vogue, long before the Big Bang was conceived. You may also be interested in the Unruh effect and others that arise from proper motion in respect to the local vacuum. It is entirely possible that the CMB is not cosmological. It is possible that the 2.7 degree glow is the ground state of our universe, and that the WMAP anisotropies are artifacts of the WMAP probe's (and those of our planet, Sun, galaxy, etc) movements relative to the local vacuum field. When 2nd year WMAP data comes out, we'll know just how "cosmological" the glow is. Everyone who expects small-angle anisotropies to map nicely with 1st year data, raise your hand.
     
    Last edited: Apr 7, 2005
  7. Apr 8, 2005 #6

    Chronos

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    Scientists apparently overlooked that fact when forming the consensus that the CMB had discredited steady state theory... or perhaps it was because steady state theory could not explain the perfect black body spectrum of the CMB.
    It is highly improbable [as in ET landing in your back yard and Elvis jumping out] the CMB does not have a cosmological origin. It is even more improbable the CMB anisotropies have anything to do with the Unruh effect. The Unruh effect only applies to accelerating bodies. The only acceleration worth mentioning in collecting WMAP data is the centripetal acceleration of the satellite in orbit - around 3400 m/s^2 in a geostationary orbit. That works out to an Unruh temperature of roughly 3E-17 degrees kelvin. That probably explains why the WMAP team forgot to factor it into their data.
     
  8. Apr 8, 2005 #7

    JesseM

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    Isn't the Unruh effect only about accelerated observers seeing the vacuum differently from inertial ones? Two inertial observers won't see the "local vacuum" any differently, will they? If so, note that acceleration is absolute in special relativity too, but this doesn't support the notion of absolute velocity, which is what people usually mean by "absolute motion".
     
  9. Apr 8, 2005 #8

    Stingray

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    CMB anistotropy due to our motion with respect to it is by far the dominant effect (by a couple orders of magnitude). All of the pretty pictures you see have already had this subtracted out. This is just a simple application of the Doppler effect...

    And, as JesseM stated, the Unruh effect deals with acceleration, not velocity. The magnitude of something's (4-) acceleration is unambiguous in relativity, so there is no contradiction.
     
  10. Apr 8, 2005 #9

    pervect

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    It depends a lot on what you mean when you say "absolute motion". Note that the unruh effect that some posters brought up does not detect "absolute motion" via the usual meaning.

    A more-or-less standard definition of absolute motion is that there would be some experiment you could perform in a closed room without looking "out the windows" to determine the room's velocity.

    Your question is really a little to vague to answer in any detail, unless you like very general answers like "detection of absolute motion would violate the principle of Lorentz invariance which is the foundation of relativity". If you want a more specific answer, you need to ask a more specific question, I'm afraid, one could imagine a lot of hypothetical ways in which Lorentz symmetry could be violated. Also, since experimental evidence strongly supports Lorentz invariance, the most likely candidates would be physics which almost preserves Lorentz invariance. It's unclear though what sort of scenario you are thinking about from your question.
     
  11. Apr 10, 2005 #10
    It did not anger many people when compared with the whole.Why not be a true agnostic instead of evangelizing atheistic vieupoints.The search for truth should remain unbiased.Any bias only hurts your credibility.
     
  12. Apr 10, 2005 #11
    If motion could be detected relative to the ether, we could say that that it is a type of absolute motion, from which all observers could measure their speed against.

    If this ether were in motion to another ether on the other side of the universe, then we would say that our measure of absolute motion is local to the ether in which we reside, so it's a type of "local" absolute motion. And I think that's the best you'll get. You cannot measure true absolute motion because you need something to measure, and if that something were moving, how would you know!

    Einstein's relativity has for the past 100-years beaten the ether theorists over the head with a very big club. Now if someone builds a device in a box that can detect motion relative to ether (local absolute motion), then it would not be unreasonable for the ether theorists to pickup that club and beat relativity over the head. Just deserts :smile:
     
  13. Apr 10, 2005 #12
    If we could measure the virtual particle flux in all directions at the same time, I would say that measurment of absolute motion would be possible.

    The particle flux in the direction of motion would be measured greater than that perpendicular to such direction.

    This measurement would not hurt SR that much. It would just give a universal reference frame to which all measurements could be related.

    juju
     
    Last edited: Apr 10, 2005
  14. Apr 10, 2005 #13

    JesseM

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    What exactly is the "virtual particle flux?" Virtual particles are introduced in quantum field theory, but quantum field theory is Lorentz-symmetric, so there can't be anything in the theory that would distinguish one inertial frame from another.
     
  15. Apr 11, 2005 #14
    Hi JesseM

    Still, you would have a greater flux per unit time in the direction of motion than in the perpendicular direction due to your velocity.

    juju
     
  16. Apr 11, 2005 #15

    JesseM

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    Not according to quantum field theory you wouldn't. It's not like virtual particles are little grains of dust in space which all share a common rest frame (or even have a single average rest frame), if that's how you're thinking of them.
     
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