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Inertial Frames

  1. Jan 27, 2010 #1
    Hello... learning to post and into the appropriate forums. Also, can you delete previous post and how?

    Quick question: Since time as we know it does not or can not 'stop'... Is there such a thing as an intertial frame at 'absolute rest'?

    Thank you for any and all responses.
  2. jcsd
  3. Jan 27, 2010 #2


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    No. Pick two observers moving relative to each other. Your frame cannot be at rest with respect to both of them, so there is no "absolute" rest frame. Any frame is as good as another.
  4. Jan 27, 2010 #3


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    As long as the "edit" button still appears under the post, then yes. You can only edit or delete posts during the first 24 hours. (I don't know if you can delete a post that started a new thread after people have replied to it. It would be weird if you could).
  5. Jan 28, 2010 #4
    It was believed by Maxwell, Poincare and others that all of space is filled with "the ether," and that this was the "primary" (at absolute rest) inertial frame, with all others in motion relative to it. The lesson learned from the Michelson/Morley experiment was that it is impossible to determine whether or not one's inertial rest frame is one and the same as the ether rest frame. Owing to Fitzgerald/Lorentz length contraction, Lorentz time dilation and the way clocks at rest in a given frame are synchronized, it is as if Nature conspires to hide the ether rest frame. Poincare observed that a complete conspiracy of Nature is a LAW of Nature. Einstein and others simply disavowed the existence of the ether. At present it IS possible to determine the motion of one's chosen inertial rest frame relative to the Big Bang background, black body radiation, and some are carefully suggesting that the whole matter of an absolute rest frame merits reconsideration.
  6. Jan 29, 2010 #5
    Nothing is absolute, relative is as good as it gets.
  7. Jan 30, 2010 #6

    There is a reason I am asking these questions..maybe to try and build a 'little' something in the way of conversation and or understanding.

    If you are at the center of a black hole which is 'beyond' the event horizon 'time' as you know it stops.

    If that is the case then no movement takes place in or across the space-time/continum. (abbrev. sp/t/con). Therefore..you have a 'place' or 'point' in the sp/t/con. or a 'region' of the sp/t/con...where no motion takes place. Question: Is this region of the sp/t/con. at absolute rest?

    Is an inertial frame a region of the sp/t/con where no motion takes place? Or..is it a region of the sp/t/con where a person can make 'objective' measuments about objects in other region's that are moving..'relative' to each other?

    In practice..it will not be possible to make objective measurements from such a region..but could I be wrong? Is this not an inertial frame in the sp/t/con that is at 'absolute' rest?...that for not because of its 'condition' such measurements could be made?

    Funny thing...could not this region of the sp/t/con not change its position to other regions of the sp/t/con? ie. providing or causing other regions of the sp/t/con to be influenced by its unique condition?

    Sorry about any vagueness to these questions...hopefully you can provide worthwhile answers.

    Thank you.
  8. Jan 30, 2010 #7


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    That isn't true. Anything within the event horizon continues to experience time... briefly. Within the event horizon, any particle will inevitably be crushed within the singularity within a finite time. What happens precisely at the singularity is not covered with existing physics.

    Since your premise is incorrect, everything that follows is not meaningful.

    The idea that time stops at the event horizon is a misapprehension, based on the fact that no signal can get back through the event horizon to the outside. Hence what is actually observed from outside as a particle crosses the event horizon is a signal that is redshifted to infinite, and the falling body "frozen" in time before it ever crosses the event horizon.

    However, this has nothing to do whatever with what happens to the falling particle, which (for a sufficiently large hole) may not even be able to tell anything particularly different as the horizon is crossed. Furthermore, since only a finite number of photons can ever come back from the falling particle before it falls through the event horizon, you don't actually "see" any "frozen particle". You see a signal redshifted to invisibility, and then nothing.

    For more details, I recommend Falling Into a Black Hole, a web page by Professor Andrew Hamilton, at the University of Colorado.

    It isn't the case, and so the "therefore" is not valid.

    Cheers -- sylas
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