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Thread: The two postulates of special relativity are . . . . . .

  1. #1 The two postulates of special relativity are . . . . . . 
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    The two postulates of special relativity are bound together.

    1. - The laws of physics are the same in all inertial frames of reference.
    2. - The speed of light c is the same in all inertial frames of reference.

    http://en.wikipedia.org/wiki/Postulates_of_special_relativity
    ===..
    My opinion.
    1. -
    It is correct that:
    The laws of physics are the same in all inertial frames of reference.
    2. -
    It is correct that:
    The speed of light c is the same in all inertial frames of reference.
    3.
    It is also correct that such formulation have nothing to do with the essence of SRT.
    Why?
    All inertial frames of reference ( Earth and another planets of solar system and galaxies )
    have gravity-mass. And SRT is theory without gravity-mass.
    ( About gravity Einstein wrote GRT in 1915)
    All inertial frames of reference ( Earth and another planets of solar system and galaxies )
    have very low speed and therefore enough to use only Galileo transformation
    to explain that the laws of physics are the same in all inertial
    frames of reference. But the basis of SRT are Lorentz transformations.

    The name of SRT was : On the Electrodynamics of moving Bodies.
    Not about Earth and another planets of solar system and galaxies the theory
    was talking, but about micro particles like light quanta.
    The essence of SRT is explanation the behaviour of light quanta.
    ==================...
    Maxwell needed a mechanical model to understand interaction between
    electro and magnetic fields. Later this mechanical model was thrown out.
    Einstein needed different inertial reference frames, clocks, observers, trains, .. . etc
    to understand the relations between space and time. All these different inertial
    reference frames, clocks, observers, trains, .. . are secondary factors.
    They are garbage for building blocks '
    If we throw them out, then we have Lee Smolin's trouble:
    " Einstein's special theory of relativity is based on two postulates:
    One is the relativity of motion, and the second is the constancy
    and universality of the speed of light.
    Could the first postulate be true and the other false?
    If that was not possible, Einstein would not have had to make two
    postulates. But I don't think many people realized until recently
    that you could have a consistent theory in which you changed only
    the second postulate."
    / Lee Smolin, The Trouble With Physics, p. 226. /
    ===.

    Israel Socratus


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  3. #2  
    Moderator Moderator Markus Hanke's Avatar
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    All inertial frames of reference ( Earth and another planets of solar system and galaxies )
    Earth and the planets of the solar system are not inertial frames, except perhaps locally as an approximation.

    All inertial frames of reference ( Earth and another planets of solar system and galaxies )
    have gravity-mass. And SRT is theory without gravity-mass.
    Of course. That is why you use the full formalism of General Relativity, as opposed to SRT. Even something as common as the GPS does that.

    Could the first postulate be true and the other false?
    No.

    But I don't think many people realized until recently
    that you could have a consistent theory in which you changed only
    the second postulate."
    If you abandon the second postulate, then inertial frames are no longer related by standard Lorentz transformations. The claim that such a theory is still self-consistent requires mathematical proof, which you have failed to cite here.
    There is also the small matter of empirical evidence showing us that inertial frames are in fact related by Lorentz transforms...


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  4. #3  
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    Quote Originally Posted by Markus Hanke View Post
    All inertial frames of reference ( Earth and another planets of solar system and galaxies )
    Earth and the planets of the solar system are not inertial frames, except perhaps locally as an approximation.

    All inertial frames of reference ( Earth and another planets of solar system and galaxies )
    have gravity-mass. And SRT is theory without gravity-mass.
    Of course. That is why you use the full formalism of General Relativity, as opposed to SRT. Even something as common as the GPS does that.

    Could the first postulate be true and the other false?
    No.

    But I don't think many people realized until recently
    that you could have a consistent theory in which you changed only
    the second postulate."
    If you abandon the second postulate, then inertial frames are no longer related by standard Lorentz transformations. The claim that such a theory is still self-consistent requires mathematical proof, which you have failed to cite here.
    There is also the small matter of empirical evidence showing us that inertial frames are in fact related by Lorentz transforms...
    I said that formulations
    1. - The laws of physics are the same in all inertial frames of reference.
    2. - The speed of light c is the same in all inertial frames of reference.
    have nothing to do with the essence of SRT.
    Postulates of special relativity - Wikipedia, the free encyclopedia

    ==.
    1.
    Markus Hanke explained:
    " Earth and the planets of the solar system are not inertial frames, except perhaps locally as an approximation."

    Do you know any inertial frame which is not " an approximation " ?
    2
    SRT is theory without gravity-mass
    / socratus /
    Of course.
    That is why you use the full formalism of General Relativity, as opposed to SRT.
    / Markus Hanke /
    Markus Hanke easily changed subject on the song from another opera.
    ===
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  5. #4  
    Moderator Moderator Markus Hanke's Avatar
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    Quote Originally Posted by socratus View Post
    have nothing to do with the essence of SRT.
    The "essence of SRT" is the Poincare symmetry group, and hence Minkowski space-time. As such, both postulates have a lot to do with it. Your ramblings, on the other hand, do not.

    Do you know any inertial frame which is not " an approximation " ?
    No. This is why we have General Relativity, to be utilised in cases where the approximation isn't good enough. Remember that SR is just a special case of GR, where the metric tensor is taken as constant.

    Markus Hanke easily changed subject on the song from another opera.
    I have told you exactly what the situation is - if there is no gravity, and/or the frame of reference you are using can be approximated as inertial, then you use SR. Special Relativity does not deal with gravity, in fact it is inherently incapable of modelling gravity.
    If there is gravity, or the frames or not inertial, you use GR.

    How difficult is this to understand ? I am not changing "songs" at all - the relation between non-inertial frames in general, and the description of gravity are outside the domain of applicability of SR. Not that you appear to have even the first clue about any of this.
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    Quote Originally Posted by Markus Hanke View Post
    Quote Originally Posted by socratus View Post
    have nothing to do with the essence of SRT.
    The "essence of SRT" is the Poincare symmetry group, and hence Minkowski space-time. As such, both postulates have a lot to do with it. Your ramblings, on the other hand, do not.

    Do you know any inertial frame which is not " an approximation " ?
    No. This is why we have General Relativity, to be utilised in cases where the approximation isn't good enough. Remember that SR is just a special case of GR, where the metric tensor is taken as constant.

    Markus Hanke easily changed subject on the song from another opera.
    I have told you exactly what the situation is - if there is no gravity, and/or the frame of reference you are using can be approximated as inertial, then you use SR. Special Relativity does not deal with gravity, in fact it is inherently incapable of modelling gravity.
    If there is gravity, or the frames or not inertial, you use GR.

    How difficult is this to understand ? I am not changing "songs" at all - the relation between non-inertial frames in general, and the description of gravity are outside the domain of applicability of SR. Not that you appear to have even the first clue about any of this.
    Special Relativity does not deal with gravity and therefore its frame of reference
    is a flat Minkowski spacetime .
    If there is a mass-gravity in a local area of this flat Minkowski frame of reference then
    this local area is a curved Riman's sphere.

    GRT is a small Riman's local area which exist in the flat Minkowski spacetime
    of SRT ( where the metric tensor is taken as constant.)
    =====..
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  7. #6  
    Moderator Moderator Markus Hanke's Avatar
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    Quote Originally Posted by socratus View Post
    If there is a mass-gravity in a local area of this flat Minkowski frame of reference then
    this local area is a curved Riman's sphere.
    ...and hence we are no longer dealing with Minkowski space-time. SR is not valid here, except as a weak-field approximation.
    And it doesn't have anything to do with spheres either.

    GRT is a small Riman's local area which exist in the flat Minkowski spacetime
    No, it is exactly the other way around. SR deals with local areas in generally curved Riemann space-time which can be considered locally flat, i.e. approximately Minkowskian locally.

    So once again ( this has been explained before ) - Special Relativity is a subset of General Relativity, not the other way around. The former is defined by a constant metric tensor, whereas the latter has a metric tensor the components of which are general coordinate functions. The names alone ought to give you a hint here. If gravity is considered, GR must be used, always.

    You may wish to take a look at my General Relativity thread, which introduces the mathematics and core concepts :

    http://www.thescienceforum.com/physi...elativity.html

    It's been made a "sticky" for a reason.
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  8. #7  
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    Quote Originally Posted by socratus View Post
    And SRT is theory without gravity-mass
    Actually, this isn't quite true. The metric of any (curved) spacetime can be coordinate-transformed to the Minkowskian metric at any given single point (assuming the spacetime is smooth at that point). Thus, all local physics is special relativity. The implication of this is that while spacetime curvature is defined locally, it cannot be measured locally (e.g. a curved surface looks flat when viewed up close).
    There are no paradoxes in relativity, just people's misunderstandings of it.
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  9. #8  
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    Thus, all local physics is special relativity.
    Exactly my point, but I think what the OP is complaining about is that SR cannot model gravity itself accurately ( which is correct, given that it is formulated in Minkowski space-time ); he claims ( if I understand that word salad correctly ) that gravity is everywhere, therefore SR cannot be a valid theory.
    Obviously he does not understand the concepts of local vs global.
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  10. #9  
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    Quote Originally Posted by Markus Hanke View Post
    Obviously he does not understand the concepts of local vs global.
    Apparently not. And then there's the equivalence principle which says that what we normally regard as gravity is not due to spacetime curvature but due to being in an accelerated frame of reference, and that what spacetime curvature does produce is the tidal effect.
    There are no paradoxes in relativity, just people's misunderstandings of it.
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  11. #10  
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    Quote Originally Posted by Markus Hanke View Post
    Thus, all local physics is special relativity.
    Exactly my point, but I think what the OP is complaining about is that SR cannot model gravity itself accurately ( which is correct, given that it is formulated in Minkowski space-time ); he claims ( if I understand that word salad correctly ) that gravity is everywhere, therefore SR cannot be a valid theory.
    Obviously he does not understand the concepts of local vs global.
    I claim that flat negative Minkowski frame of reference of spacetime
    ( zero vacuum Pseudo - Euclidian - 2D space ) is a global system and
    curved Riemann space & time is a local gravity system.
    Why am I correct?
    Because: only a few % of whole mass of Universe is a gravity-mass
    and more than 90% of mass of Universe is dark mass/energy which
    is hidden in the flat negative Minkowski frame of reference of spacetime
    ( zero vacuum Pseudo - Euclidian - 2D space )
    =.
    socratus
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  12. #11  
    Moderator Moderator Markus Hanke's Avatar
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    Quote Originally Posted by socratus View Post
    I claim that flat negative Minkowski frame of reference of spacetime ( zero vacuum Pseudo - Euclidian - 2D space )
    This is just random terms mixed together into meaningless word salad.

    is a global system and curved Riemann space & time is a local gravity system.
    It's the other way around. Gravity is everywhere, since gravitational fields extend into infinity. Minkowski space-time is hence a local approximation, whereas Riemann space-time extends globally. Do you want to see the maths ? Not that I have much confidence that you can even begin to understand them...

    Why am I correct?
    You aren't. You are just an ignorant crank who refuses to acknowledge what has already been explained multiple times.

    Because: only a few % of whole mass of Universe is a gravity-mass
    and more than 90% of mass of Universe is dark mass/energy which
    is hidden in the flat negative Minkowski frame of reference of spacetime
    ( zero vacuum Pseudo - Euclidian - 2D space )
    Again, just random words without any meaning whatsoever.
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