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Galilean principle of relativity!

  1. Sep 1, 2013 #1
    Galilean principle of relativity is for sure not absolutely true, isn't it?

    Say one has a pool full of water within a spaceship, if the spaceship is accelerated and then acceleration stops, one can look at the ripples in the pool, analyze their form and then tell, up to a certain degree of preciseness, if there was acceleration, how long ago, what was the force accelerating? nop? and now say, the types of materials analyzable and measuring equipment become more and more available, then it can get to a point that some type of liquid-gas within the space ship can be analyzed by some sort of newly discovered particles, and one can tell if the spaceship was accelerated up to 100 million years ago up to a 1000 years plus minus preciseness. Is there a basic physical law that denies that possibility?

    Now, doesn't the special principle of relativity start at its very first sentences, by relying on the Galilean principle of relativity?

    If there is any well informed math-physics guy here, who also thinks that this is not a die-hard joker question-view, then, can you please try to explain to me, how does this change the very mathematical basics of SR?
     
    Last edited: Sep 1, 2013
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  3. Sep 1, 2013 #2

    PeterDonis

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    The Galilean principle of relativity doesn't say anything about accelerated motion; it only says that inertial motion (i.e., free-fall, unaccelerated motion) is locally indistinguishable from rest. The principle of relativity in SR is the same; it says nothing about accelerated motion.
     
  4. Sep 1, 2013 #3

    WannabeNewton

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    The Galilean transformations are limiting cases of the Lorentz transformations. The principle of relativity does not state that the transformations between inertial frames must necessarily be Galilean transformations. In SR, it leads to the Lorentz transformations after making an extra assumption. The principle of relativity is a statement about the non-privileged nature of inertial frames.
     
  5. Sep 1, 2013 #4
    WanabeNewton and Peter:
    1. Peter: In the scenario i presented, no measuring is done when space ship is accelerating. Only when acceleration is over and even a million years after last and only acceleration took place .
    2. Wanabe: In your comment, you are shooting over my laymen head, please speak very plainly and not these wizard incantation words such as transformation. I think that i described the scenario very clearly.
     
    Last edited: Sep 1, 2013
  6. Sep 1, 2013 #5

    PeterDonis

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    That doesn't mean that the Galilean principle of relativity requires that everything before acceleration look exactly the same as everything after acceleration. The principle doesn't say that every state of inertial motion has to look exactly the same; it only says that every state of inertial motion must obey the same laws of physics. Both of the inertial states in your scenario--the state before the acceleration, and the state after the acceleration--are valid solutions of the Newtonian laws of physics (which are the appropriate laws if we're talking about the Galilean principle of relativity); they are just different solutions.
     
  7. Sep 1, 2013 #6

    WannabeNewton

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    Peter very clearly addressed your example in post #2. If you introduce acceleration for any period of time, you are clearly breaking the symmetry (implied by the principle of relativity) amongst inertial frames. All the POR says is that inertial frames by themselves are unprivileged. It doesn't state that states before and after acceleration must be identical.
     
  8. Sep 1, 2013 #7
    Peter,
    If i can know up to a very long ago period of time and up to a very high degree of preciseness, that an inertial state object was accelerated, then this piece of data should be considered as coming from an internal quality of matter itself, nop? - then nature does not act the same between these states - then laws of nature DO NOT act the same under different inertial states.

    Of course the question is how long ago and how precise, should one be, to say this is an internal property of matter itself or is there some kind of physical principle or natural property ,that states that, no matter how precise and how long ago i will be, at measuring these ripples in the pool, still it is not an internal property of matter, because something else that has to do with SR or light or what not, always, always, always will be some degrees more precise than the hypothetical precision i am referring to.

    But then, i am saying that at least that absoluteness aura of Galilean principle is not true. If i can get in this space ship and have no windows in it (i mean outside ship radio measurement of any kind) and no active measurements made while accelerating and still i can tell where was my departure point, up to a certain degree of precision - can such a measurement ever be precise enough to conflict or change SR or would it alway 'lag' at the same precision error behind SR precision for some reason and never get the departure point better and better, as measuring equipment evolves?

    What are the mathematical boundaries that make it an internal property of matter and how can this view be mathematically expressed in relation to SR, or without relation to SR, that is what i am trying to understand.
     
    Last edited: Sep 1, 2013
  9. Sep 1, 2013 #8

    PeterDonis

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    I think you are confusing properties of the laws with properties of particular solutions. The same laws of nature can have multiple particular solutions that have different properties. There is nothing in that that is inconsistent with the principle of relativity.
     
  10. Sep 1, 2013 #9

    PeterDonis

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    I'm not sure how I can address your issue mathematically since (a) you haven't written down any mathematical description of the issue, and (b) you are basically claiming that the math I would be using, which is based on the principle of relativity, is wrong. So I'm not sure what you're looking for here.
     
  11. Sep 1, 2013 #10

    Mentz114

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    This idea has been floated many times by folk who want there to be absolute motion and an absolute state of rest. It is pointless and adds nothing to the understanding of the universe.
     
  12. Sep 1, 2013 #11
    Mentz, yours is a philosophical statement, i think that what i am asking here, indeed with my very laymen words and understanding, are physical, experimental and mathematical questions. BTW, please refer me to a thread that its subject is exactly or as close as possible to this pool experiment i am asking about here. Thanks.
     
  13. Sep 1, 2013 #12

    Dale

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    This is a non sequitor. You are saying if we can distinguish non inertial motion from inertial motion then the laws of physics are not the same in different inertial frames. That simply doesn't follow logically.

    Take a law of physics, expressed in one inertial frame. Transform that law to a different inertial frame. If the expression in the new frame has the same form as in the old frame then that law is the same in all inertial frames.
     
  14. Sep 1, 2013 #13

    Mentz114

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    What you are suggesting is that some matter could encode all the information in its worldline from some time in the past to the present, say, and that this information will alter the way the matter behaves. It is possible in principle to build a machine that can do the path recording for a spaceship* - but how would a brick or a bowl of hot soup achieve this ?

    In what way could the presence or absence of the information affect the physics ?

    * a smartphone equipped with GPS and some software can record a rough itinerary ( worldline ) as it is carried about.
     
    Last edited: Sep 1, 2013
  15. Sep 1, 2013 #14
    If it is possible to know the local time at another inertial state, up to a certain degree, without communicating by radio waves with that other inertial state, then does it not conflict with any physical principle? Never has any relativity principle denied the possibility of knowing the time at other inertial states, without radio communication?
     
    Last edited: Sep 1, 2013
  16. Sep 1, 2013 #15

    Dale

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    No, why would it?
     
  17. Sep 1, 2013 #16

    Mentz114

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    If one could optically track the path of another body for an interval of time, then combined with knowledge of the local gravitational fields it is possible to calculate how much time would have elapsed on a clock on that path. I don't know if that counts as 'communicating' to you.

    I can't follow this, sorry.
     
  18. Sep 1, 2013 #17
    DaleSpam,

    Because of the famous example, titled, as much as i recall, 'Galilean principle or relativity', with a man waking up from deep sleep, sitting at the bottom of that windowless inertial state ship, unable to say if the ship has left harbor or not.
     
    Last edited: Sep 1, 2013
  19. Sep 1, 2013 #18
    Mentz,

    Doesn't the pool replace the need to optically or by radio wave, communicate with that other inertial state, up to a certain degree of precision? If it does, doesn't it conflict with any existing physical principle?

    Please take into account that i am referring to a case, where the two states where 'together', 'one', at a certain point back in time, and that the other state, the 'base ship' not the 'ship', did not change its state, since then ,while the 'ship' did - and the 'ship' can still use the pool to tell the local time at the 'base ship', without radio communicating to it. In this scenario, it is a negligible gravity area of space.

    Regarding the other part of what i wrote, that you said you don't follow, i have rephrased it.
     
    Last edited: Sep 1, 2013
  20. Sep 1, 2013 #19

    Mentz114

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    The recording device (your 'pool') records its own path so I don't see how it can tell you about another worldline.

    The same remark applies. When the split happens, the pools are no linger recording the same worldline.

    The only way to predict accurately the time elapsed on another worldline is to have knowledge of the worldline and details of the gravitational configuration ( which includes the possibility of no gravity).
     
  21. Sep 1, 2013 #20
    OK, so the formulas stay the same, and the term 'unprivileged' implies nothing about two identical experimental environments (ships), that all types of possible measurements becoming more and more identical between them, as more and more time passed from last non-inertial state goes by (measurements that have nothing to do with these two ships outside, only with its inside parts and material), if the whole experiment equipment tools and environment are exactly identical, but both copies are at different inertial states - 'unprivileged' will not imply that these identical experimental environments, will tend to show exactly the same measurement results, as time passes by?
     
    Last edited: Sep 1, 2013
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