The Light Speed Postulate and its Interpretation in Derivations of the Lorentz Transformation

Discussion in 'Pseudoscience' started by tsmid, Apr 24, 2016.

  1. Confused2 Registered Senior Member

    Messages:
    500
    My little holiday is over. All I have time for is...
    I don't think you read much of my posts.

    The analysis at constant velocity would be 'fit for purpose' if you had any interest in the principles involved.
    The support comes from the experimental results. See (for example) http://hyperphysics.phy-astr.gsu.edu/hbase/relativ/muonex.html#c2 . I think you underestimate me. I have in the past been through every step of the experiment from counting to velocity measurement. Unfortunately those posts have been lost - I don't think my time would be well spent on this occasion if I
    were to collect up that information again. It is there for you to find if you want to.
    No comment.
     
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  3. expletives deleted Registered Senior Member

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    @ Confused2:

    Actually, I have enough respect to make sure I did read all of your posts. So you are mistaken and it may be (by some but not me) uncharitably construed as not showing me the respect you expect from others.

    If the 'purpose' was to play at SR scenarios for their own sake. Sure, it's 'fit for purpose'. But if the purpose was to actually understand the "reality" situation as you allude to, then it is patently not fit for that purpose, as the need for further GR and acceleration considerations and information (in the SR twins scenario) makes clear it wasn't 'fit for purpose' as it stood in purely SR terms which made no sense until the GR acceleration info was introduced to the analysis.

    The experimental results are data. That data is then interpreted according to theory and models. It is the latter part of the process that is in question as to its fitness for purpose. If the abstract model and interpretations of that data is made within, and remains within, a strictly SR framework, then that's all you can get out of it (just as in the SR Twins case). But if it's understanding of the "reality" you allude to, then it requires going outside that SR analysis construct and consider, as I said, both entities' actual inherent properties and parameters re motion, acceleration etc. Only then will there be any chance of understanding the whole picture rather than being satisfied with the relative SR views which actually do not explain what is really happening in what we are observing and measuring as the data.

    The purpose is different when the aim is to understand and not just calculate one or other SR perspective and make assumptions and interpretations and explanations; only when those things take into account the real GR aspects to inform same will the analysis make sense in real physical reality (and not just in abstract SR) terms.

    I trust I have clarified enough to dispel your own possible misreading of what I have said on the matter you raised in discussion that I addressed in the spirit of objective discussion between us (especially re the Muon lifetime aspect). Thanks. Best.
     
    Last edited: Aug 30, 2016
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  5. rpenner Fully Wired Registered Senior Member

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    Bullshit. SR completely handles the case of the Twin Paradox in flat space-time. The geometry of flat space-time in both SR and GR is such that a straight time-like path is the longest time-like path connecting two events. Ergo, a non-straight (and therefore non-inertial, and therefore accelerated) path between two events has a shorter elapsed proper time.

    Everything else is bafflegab, including such distractions as the twin's point of view.

    Now if you want specifics of measurable quantities in a given conjectural setting, SR again, suffices. If you want a simple formula for proper elapsed time, SR suffices in flat-space time.

    Finally, if you want details about particle lifetimes at such-and-such a relative velocity, SR suffices completely for horizontal particle beams and to very high precision for terrestrial particle beams of any appreciable momentum. Terrestrial particle physics tests of GR have been slim to the point that no one has measured the fall of antimatter yet. SR suffices for the vast majority of experimental particle physicists. Astronomical particle physics effects that are uniquely tied to GR include the as-yet unobserved Hawking Radiation, and little else.

    Further, the pedagogy of SR has numerous "paradoxes" associated with relativity of simultaneity (or equivalently, the incompatibility of intuitionist notions of absolute time with physics). The Barn and the Pole paradox is only called such in that the notion of both doors closing at the same time seems like a reasonable part of the setup only to those coached in Newtonian preconceptions antithetical to proper understanding of SR phenomena. Mastering SR is a necessary step to understanding GR.
    You green-eyed monster of a rat. Can you take no pleasure in the intellectual progress of another?
    If paddoboy shows up here, you (likely both) are getting a 20 point warning.
    Actually, the twin paradox is most commonly given as an unrealizable thought experiment. Most macroscopic implementations are done at the same order of magnitude as the non-inertial rotation of the Earth's surface and involve change of altitude so that GR effects are not entirely negligible. But there are near perfect SR implementations in muon storage rings.
    http://www.nature.com/nature/journal/v268/n5618/abs/268301a0.html
    http://www.sciencedirect.com/science/article/pii/055032137990292X
     
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  7. PhysBang Valued Senior Member

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    One doesn't need GR to resolve the twin scenario, because one an recreate it without any acceleration at all, just using fortunately coincident clocks. The resolution is that the "traveling" twin cannot use one consistent inertial frame of reference that covers every point of space. So there is a clear difference between the two twins.

    We can use GR to create a similar scenario, but it is similar, not identical.
     
  8. expletives deleted Registered Senior Member

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    410
    @ rpenner:

    Sir, your own words (highlighted red) confirm the point I made to Consfused2; which was about the conceptual understanding of the "reality" he alluded to (as distinct from the purely maths perspectives which may be fit for purpose of prediction of purely SR type relative situation from either Twin's frame; but must be augmented with non-SR info in order to make conceptual and "reality" physical sense, as per the distinction on which I based my earlier comments and then clarified further).

    Too many "ifs" spoil the clarity and thrust of the point. Your response is conditional upon your own reframing of the point, so it is not to the point. In any case, your own words (highlighted red above) effectively admit that non-inertial acceleration information is needed beyond the original purely relative SR info/construct. This confirms my point that extension of an otherwise relative-only SR construct is required------to allow input of information obtainable only by consulting overarching GR construct involving non-inertial, accelerated (non-straight path) considerations------in order to make sense of the 'twin paradox' which otherwise arises in purely relative SR construct (which 'paradox', I hasten to add, is not a real physical paradox, but only a 'relative-only maths logical paradox' due to original limited mathematical SR relativity construct; and that the 'seeming paradox in SR' is readily dispelled in "reality" when we introduce GR construct info; as I pointed out needs be done to make real physical sense of what happens in twins scenario; and as you just effectively confirmed via your own words highlighted red above).

    I have never argued against the measurements as such. They are data. No problem. The point in discussion with Confused2 went to the "reality" understanding he alluded to; and which I responded to by observing there is no problem if SR construct is extended to allow input of non-SR (ie, GR construct) information in order to make sense of the situation. My point went to that only; and I acknowledged that relative-only SR was fit for purpose if one settles for the purpose of theoretical relative predictions; but was not fit for purpose when that purpose was to remove purely relative limitations when trying to understand the "reality" he alluded to.

    Confused2 said he was having difficulties with SR; so, as encouragement not to despair, I pointed out that those difficulties effectively 'disappear' once one moves beyond the SR construct; and considers the whole picture in GR construct, and uses its non-SR info (ie, GR construct derived info such as respective non-inertial motion histories; respective acceleration values and effects; non-straight path observed from outside the purely SR construct). That was the aim of my response to Confused2; to help dispel his seeming despairing tone because he seemed to be stuck in an SR-only relativity construct.

    There is no need for that kind of emotional and hostile language and tone, Sir. I understand you are a newbie to moderation duties here so I will overlook this unseemly lapse in a moderator and comment no further on that.

    As for the question of taking pleasure or not "in the intellectual progress of another", as you put it, I remind you that science is objective not interested in personal considerations. But, for the sake of clarity, I will ignore the underlying emotional and hostile tone, and answer your question as put. Sir, I take pleasure when discussion arrives at a resolution where everyone concerned has been able to make "intellectual progress" which is based on science not personal understandings which may be misled by unscientific beliefs and assumptions which some treat as sacrosanct (to judge by the emotional attachment and hostility displayed by some). I contribute what scientific scrutiny and argument I can as one applying the dictates of the scientific methodology and principles of objectivity and relevance. If my questions elicit hostile and emotional responses in place of reasoned and calm addresses of the points I raise, then that is not my problem and I should not be expected to put up with arrogant assertions based on obviously partisan attachment to some idea or theory which is fair to question and observe upon as I have done in strict and personally disinterested adherence to science method and site rules.

    Again Sir, you help make my point to Confused2. That twin paradox was and always would remain an un-resolvable scenario while ever it remained solely in the purview of the original purely SR-only relativity construct. But as I point out, once we go beyond that limited purview and introduce the GR construct overview and use the non-SR-only type info to inform the SR-only twins scenario, we resolve the paradox which was only a seeming paradox because it was originally posed in the purely relative SR-only construct. That is why I felt compassion for Confused2 when he admitted to having difficulties with relativity. And so encouraged him by advising him to leave behind the limited purview of SR-only construct, and move beyond to GR overarching view which involves information on properties and parameters inherent to both twins in actual-effective GR informed terms and not just in relative-effective SR terms.

    The above is my own understandings and opinions based on my own researching of the relevant science matter. I make no claims but rather point out certain things for the benefit of the person with whom I was discussing in good faith adherence to science and politeness principles. Thanks rpenner (and Confused2). Best.
     
    Last edited: Aug 30, 2016
  9. tsmid Registered Senior Member

    Messages:
    368
    It is not about conceptual 'difficulty' here, but about conceptual consistency or inconsistency. You can for instance not justify the 'equation' 1=2 by introducing a new concept of 'relativistic mathematics' according which you weigh the left hand side by factor 2 higher than the right hand side just to suit your purpose (I don't think that a school teacher would be very impressed if a pupil tried to rationalize away his mathematical mistakes by introducing new concepts in this sense). It is about initial definitions and sticking to them. So modifying the initially agreed length and time units depending on what events you consider is therefore not permissible. If that leads to problems for you, then there must be something wrong with your initial assumptions, and in this case this is the implicit assumption (based on classical physics) that light consists of particles and that their location transforms into different reference frames by means of a velocity dependent transformation. So it is the concept of 'speed' that needs to be modified for light (but only for light), not the concepts of space and time in general.
     
  10. tsmid Registered Senior Member

    Messages:
    368
    Each observer utilizes only the clocks and rulers of hie own frame for any measurements. He is as such not interested in whatever units the other observer uses in his frame. The units of the other frame only come into play if you want to do a coordinate transformation, but the transformation must be between the native units i.e. x1,t1->x2,t2. Something like x1',t2' represents fictitious variables that have no counterpart in reality.

    I you start moving relatively to a meter stick, both ends of the latter will by definition be moving by the same amount within a given time, so the distance between the two ends will always be a meter (unless, like I said, you change your own measuring units).
     
  11. rpenner Fully Wired Registered Senior Member

    Messages:
    4,833
    That's incorrect and renders your understanding of SR highly suspect.

    SR was formulated first in Cartesian coordinates and then in pure geometry. In either, inertial trajectories are modeled as straight lines. That why "frame" is synonymous with "inertial Cartesian coordinate system." But just because straight lines are special in Eucldiean and Minkowski geometries doesn't mean that other curves are not admissible in either system. What began with straight lines and circles was generalized to conic sections, spirals and (with the invention of calculus) general curves. SR is entirely capable of handling the mechanics of acceleration motion, so your peculiar objection to treating accelerated motion in flat space time in SR seems baseless and backward.

    "Real" (meaning achievable) accelerations are not necessary for analysis of the twin paradox for the geometric fact that the straight line is the longest path remains whether the alternative to inertial travel is smooth or piecewise continuous (modelling infinite acceleration).
     
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  12. expletives deleted Registered Senior Member

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    @ rpenner:

    Sir, you have the right to suspect what you like personally; but the discussion points made will be the objective arbiter either way, irrespective of anyone's personal suspicions.

    Sir, you are preaching to the converted on all that. I have not contended against any of those things you point out. Perhaps you may be conflating me and my discussion points with some other person or points you are discussing with that involves your points and arguments?

    In any case, my point was that whatever the original SR relative-only constant-motion type construct, it had to be extended to include, by whatever means and maths, the non-SR-type info, the self-limiting to which previously made the original twins paradox so problematic when considered only as SR type scenario. The point I made was that such extension was motivated by the need to explain the real effects when all is said and done. And that real effect in the twins scenario can only be understood and explained if the GR type info is available and applied to whatever extended SR construct is the best for that purpose of dispelling the twins paradox.

    Do you see what I am constraining my point to? In short, whatever extended SR maths is applied, it boils down to the fact that eventually and effectively, the whole picture (and not just infinitesimal path lengths in curved space) has to be considered (as per the overarching GR construct) if the real effects on the one twin and not the other is to be understood irrespective of any previous SR-type maths logical 'paradoxes'.

    That is all I have pointed out, Sir.

    No Sir, I don't mean that. I meant "real" as in actual respective inherent properties and parameters (accelerations or not, etc) of both twins involved (for contextual clarification re that please refer to my earlier posts to Consfused2 regarding that. Thanks).

    And as for the modeling using calculus techniques, it makes no difference to the actual real effective outcome of the accelerations on whichever twin is affected.

    It reminds me of the Zeno Paradox which 'mathematically proves' there can be no motion at all. Obviously such techniques may be useful and fit for purpose in certain limited path length treatments in a particular construct; but eventually the whole path length needs be considered if the analysis is to make real physical sense.

    For example, one may 'treat' an infinitesimal length of the circle circumference as 'straight', but in reality overview when all the infinitesimal lengths are combined, one must have reproduced the original circle's inherent circumference properties and parameters; else one is left stuck in an analytical maths construct which makes no sense other than the limited 'fit for purpose' sort of sense within the limited construct used in exclusion of the overarching reality view of the full circle.

    Similarly, Confused2 seemed to be having difficulties because he seemed to be stuck in the original SR-relativity-only self-limiting perspective, instead of continuing beyond to the overarching GR perspective which informs and expands the understandings, even though the limited view was 'fit for purpose' for what limited understandings purposes it was originally designed for but which is now made more realistic by the GR overview. As I pointed out.

    I trust you now understand that that was all I pointed out. I have had no argument at all with the other things you now raised above which were beside the point I was making, Sir. Thanks. Best.
     
    Last edited: Aug 30, 2016

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