Is a length contraction just a visual thing?

Discussion in 'Pseudoscience' started by absolute-space, Feb 22, 2016.

  1. exchemist Valued Senior Member

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    Obviously not, because in the relevant frame of reference (that of the 2 coils) there is no length contraction.
     
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  3. river Valued Senior Member

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    Of course

    To the object relativity means nothing .

    This to me is what is lost about relativity . Relativity is about the observer , observing an object . Relativity is about the perspective of the observer . NOT about the object its self .

    To the objects physics , form , geometry , not one of those properties changes at all .
     
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  5. ajanta Registered Senior Member

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    Hmm !! It is not only that I assumed but many thoughts that are may be dark to you. Now I'm trying to light them....

    May be your posts for me is stress to learning English properly, but I'm trying to do better over 10 years and no development

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    Its not only about English but many things that are not gonna develop cause of mental stress of misbehaviour( of me and others)

    Whatever

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    So now I give importance to behaviour rather than learning English and many things. Sorry for that.

    I know theory of relativity is not simple to understand so sometimes I use diagrams and short description. I will must discuss it ... Thanks.
     
    Last edited: Apr 2, 2017
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  7. ajanta Registered Senior Member

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    If any observer travels at perfect relativistic speed to correct direction when the two coils are on stationery reference frame.

    Now the observer(of moving reference frame) will observe that the length or distance between two coils is constructed. On stationery frame of reference, primary coil is not able to transfar energy to secondary coil, so from the moving reference frame (observation), the length or distance construction can minimize the distance or length between two coils.

    Can the construction help to transfer energy from primary coil to secondary coil ?
     
  8. ajanta Registered Senior Member

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    Construction is wrong word but it is constraction. And there are few correct sentences in my 580 posts.
     
    Last edited: Apr 3, 2017
  9. ajanta Registered Senior Member

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    595
    Yes, And me too.
    But we need not make relativistic spacecraft to observe different event, because we have particle accelerator and many more cosmic rays of different directions. So there are different events for moving particles around the particle accelerator that(events) are dark for people around particle accelerator. Some times I think that switching is possible to observe some interesting events from stationery frame of reference, because the length is variable.
     
  10. ajanta Registered Senior Member

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    595
    So we can trigger a switch to electromagnet that will affect the moving electrons of electron beam, but the magnetic field of electro magnet is dark to the observer around the electron beam.
     
  11. exchemist Valued Senior Member

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    I'm not sure what you are driving at, but I suppose one could legitimately ask how an observer, moving at high speed relative to the coils, would interpret the laws of electromagnetism applying to the coils he is observing.

    The lengths in the direction of relative motion will all appear contracted, and the passage of time will appear dilated. As I understand it, the overall principle of special relativity is that these two effects will be complementary and should lead back to the same overall result as if there were no relative motion. But I must admit I have not tried to look at this scenario of yours and see how to apply it.

    Is this what you are asking about?
     
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  12. ajanta Registered Senior Member

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    595
    And it will make you to believe in flat earth too.
     
  13. Q-reeus Valued Senior Member

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    2,497
    To cover general interaction behaviour, those two are not enough. Additionally, field transformations (pure E or B field in one frame transform in general into mixed E & B in another frame, and vice versa). And non-simultaneity - signals emitted simultaneously in one frame in general are non simultaneously emitted in another. Ajanta, instead of filling up pages with idle speculation and pointless banter, why not knuckle down and study the subject? The internet is filled with resources on this topic. Just type in e.g. 'relativistic electrodynamics', or 'relativistic electromagnetism' and follow the links. Wikipedia will be a very good start.
    To get anywhere useful, you will need a bit of math background, but if it's particularly weak, go for a graphics oriented YouTube vid as starter. Using those search terms.
     
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  14. DaveC426913 Valued Senior Member

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    River is correct. (!!)

    Another way of phrasing this: 'relativity is what happens to others - never about what happens to onesself'.
     
  15. Q-reeus Valued Senior Member

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    2,497
    At best, that needs careful qualification. Harmless levels of say microwave radiation experienced in one frame may become lethal levels of x-rays in another frame ultrarelativistic wrt the first one. Only if there are no interactions can it be said relativity 'is never about oneself'. In which case one only has inferred properties. Any observation i.e.measurement between entities in different frames implies interactions relativistically effected by the relative motions.
     
  16. DaveC426913 Valued Senior Member

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    It is X-rays impinging upon the observer.

    No other frame has any better claim on what freq the EMR "really" is.

    Whether it is something else in some other frame is really about what's happening somewhere else.
     
  17. Q-reeus Valued Senior Member

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    2,497
    Your point above is moot. It's perfectly ok to perform relativistic transformations involving say a closed system (that doesn't interact with a given observer) such as to arrive at consistent physics between frames. But it's not true - as per example I gave, to say relativity is never about oneself. Relativity is a general framework covering a great many situations that may or may not involve effects on a given proper observation frame or observer within.
     
  18. DaveC426913 Valued Senior Member

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    5,640
    I think you're missing the point.

    The observer is always stationary.
    At .9999999c relative to the background of stars, the stars are compressed along the length of travel.
    The observer does not see himself as having any relativistic distortion; it is the stars that are distorted as they move past him.
    Again, the observer is always stationary (as far as the physics is concerned).

    That's the implication of relativity: stars squished into flat discs along the direction of travel. (Yes, we know that it may make more sense that the observer is moving past the stars, but that is an arbitrary frame of reference.)


    The fact is, as per relativity, it is X-rays impinging on the stationary observer. Microwaves are somebody else's observation. Because they are moving at relativistic velocity.
     
  19. Q-reeus Valued Senior Member

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    2,497
    You effectively gave carte blanche endorsement of everything written in #542. But apart from being poorly worded, that post focused exclusively on the obvious fact proper length and clock-rate are frame independent. But relativity is not limited to such a triviality or mere observations of other objects having relative motion. Read what I wrote in #550. YOUR experience (read - interaction with) of being immersed in an EM field very much depends on relative motions. YOU may burn to a crisp or feel nothing depending on relative velocity wrt some background - even just CMBR.

    Even in pure vacuum, if undergoing proper acceleration (which SR handles without issue), according to most physicists, YOU will experience so-called Unruh radiation.
    I'm not interested in continued quibbling over semantics. If you wish to continue to endorse carte blanche river's statement in #542, cite a recognized authority that defines SR as limited to what is claimed there.
     
  20. exchemist Valued Senior Member

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    5,806
    Ah OK, thanks for the clarification.

    But a question: I seem to recall that the B field can be derived from the motion of the charges that are responsible for the E field. I wonder, then, is it possible that the transformation of E and B fields into hybrids is itself attributable to the effects of length contraction and time dilation? Or is this just woolly thinking on my part?
     
  21. Q-reeus Valued Senior Member

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    2,497
    You are probably thinking of the case of a conduction current in a wire neutral and stationary in some 'lab frame' S. Which generates an azimuthal purely magnetic field B in S. Move to a frame S' having uniform linear motion at velocity v along the wire axis, then relativistic length contraction alone is enough to find that in S' the wire is no longer electrically neutral, but has a linear charge density, and ensuing radial electric field E', in addition to B' = γB. Owing to the differential in relativistic contractions of positive lattice ion spacings vs that for conduction electrons moving relative to the lattice. Thus a test charge q stationary in S' feels a purely electric force F' = qE' acting radial to the wire axis.
    Transform back into S, and the (generally only slightly different) force F = F'/γ on q is interpreted as q moving normal to the azimuthal B, thus F = -qvxB, also acting radial to the wire axis.

    That however is a special case in the sense in most situations you can't get away with simply appealing to length contraction to explain EM phenomena in general.

    One approach starts with either the 3-potentials φ, A, or invariant 4-potential A, owing to some charge/current configuration, and apply the relativistic transforms (allowing for propagation delay) relevant to the definitions E = -∇φ -∂A/∂t, B = ∇xA. This yields the Liénard–Wiechert potentials, which were developed before SR, but are relativistically correct:
    https://en.wikipedia.org/wiki/Liénard–Wiechert_potential

    Alternately, work from the fields direct and apply the usual transformations: https://www.phy.duke.edu/~rgb/Class/Electrodynamics/Electrodynamics/node140.html
    The familiar transformations start at (16.170)
     
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  22. river Valued Senior Member

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    My point in my post #542 , is that to the object realitivity means nothing .

    An example ;

    Moon to the observer , an object with an observer goes past the moon at light speed . While this observer sees the moon contract because of the speed of light , the Moon does not change its properties because the observer is going at the speed of light .

    That is my point .
     
  23. Q-reeus Valued Senior Member

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    2,497
    Won't quibble much over that highlighted, but will point out no material object can move at c relative to any other material object (excluding dubious inferences re cosmic redshift). Only asymptotically approach c, and practically, that will almost exclusively apply only to charged particles typically either cosmic rays or those generated in terrestrial particle accelerators.

    No argument with the intent of what you say now. The problem was in earlier stating SR is ONLY concerned with such things i.e observation or merely theoretical calculation of kinematic effects.
    There is far more to SR and it's application to many disciplines, from GPS to particle smashers to certain aspects of atomic spectra to practically all of EM. Which are all about interactions effected by relativistic motions. Designating observer vs observed is either completely irrelevant or arbitrary in such situations.
     

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