The No-Acceleration Scenario Does NOT Resolve the Twin "Paradox"

Discussion in 'Physics & Math' started by Mike_Fontenot, Dec 31, 2017.

  1. Xelasnave.1947 Valued Senior Member

    Messages:
    3,645
    No I dont think that at all.
    I believe SR was formulated without any physical observation.
    However I can understand why you would arrive at that conclusion.
    Certainly when I think about it I really dont know from what point I see an extrapolation.
    Perhaps what I seek is simply more use of physical experiments and observation.
    Yes I was reasonably aware of the history but thank you for such an excellent summation.
    Absolutely, so is there any value in talking about the twins given there is no opportunity of observing if the prediction matches reality.
    You have no need to appologise and certainly I am glad you showed kindness to take the time to help me understand.
    Alex
     
  2. Google AdSense Guest Advertisement



    to hide all adverts.
  3. Neddy Bate Valued Senior Member

    Messages:
    1,482
    I don't either, but your comment about aliens and tree height demonstrated nothing more than the limited predictive power of extrapolation.

    So you are not impressed that a theory developed on theoretical grounds managed to boldly predict a specific quantity for something as bizarre as time dilation, something totally unheard of in its time, which was then measured to extreme accuracy in numerous physical experiments. You want more than that, just in case someone wasn't paying attention in physics class. Okay. Maybe it would be easier to list the experiments which you are familiar with, rather than list the ones with which you are not familiar.

    You keep repeating that you do not understand that we are talking about time itself, not just "time for human twins". Physics does not have different definitions of time for different things, there is only one definition: That which is measured by ideal clocks.
     
  4. Google AdSense Guest Advertisement



    to hide all adverts.
  5. Xelasnave.1947 Valued Senior Member

    Messages:
    3,645
    Thank you that was my point even if perhaps it did not apply to the discussion.
    To be honest I am not impressed.
    If one made an observation and then provided the theory I would be happier.
    I dont want to upset you but you seemed to seek my opinion so as humble as it may be I presented it to you.
    You need not expend any effort to show my opinion is wrong as it is mere opinion.

    The philosophy of science dictates that a theory makes predictions and that on the one hand is reasonable but I wonder if observations could not be seized upon to support a theory rather than reviewing the observation without perhaps quickly fitting it to a theory already existing.
    Well substitute your twins with ideal clocks you still can not physically test what you discuss is my point.
    You say certain things will happen I say you can never know because you can not send a twin or a clock on the journey you discuss.

    Anyways dont let me side track the thread with my questions.
    Thanks again for your replies.
    Alex
     
  6. Google AdSense Guest Advertisement



    to hide all adverts.
  7. Neddy Bate Valued Senior Member

    Messages:
    1,482
    Thank you for your honesty.

    So you admit that you are not impressed by Einstein's theory of relativity because you do not understand that the observation that the speed of light is a physical constant came first, (as you require), and then the theory was provided afterward by reformulating Gaileo's equations of motion to fit the observation (as you require).

    Because if you understood that, then you would be happy with it, by your own criteria.

    Oh wait, no, you said you already understood all that, and the reason you are not impressed was that you don't like that the theory had predictive power, and the predicted time dilation was subsequently tested and confirmed. You would prefer if the predicted time dilation had been observed first, then the theory formulated, predicting a constant speed of light which could be observed later.

    Oh no wait, if that happened, you would not be impressed because you would rather that the constant speed of light was observed first, and then the theory formulated around that, predicting time dilation.

    Oh no wait, if that happened, you would not be impressed because you would rather that the time dilation was observed first, and then the theory formulated around that, predicting the constant speed of light.

    Oh no wait, if that happened, you would not be impressed because you would rather that the constant speed of light was observed first, and then the theory formulated around that, predicting time dilation.

    .

    .

    .
     
    Last edited: Jan 2, 2018
  8. Xelasnave.1947 Valued Senior Member

    Messages:
    3,645
    To Neddy Bate
    First of all thank you for taking the time to help me focus upon the various issues.
    I dont know that I can provide complete answers but I will try.
    I dont think I said that.
    I presume that what I said must infer same.
    My point was as stated even if unfair and as I said my opinion.
    I think what I said was that I felt although the philosophy of science requires theory to make predictions, which I see as reasonable, when a new observation is made it could be seized upon to support a theory, fitting the predictions of that theory, rather than the observation being considered on its own such that further consideration of any other possibility is not excluded.

    Clearly you have shown my ignorance and I am sorry you had to waste your time to do so but my point is rather simple and contained in my last question.

    One thing more if you could help if you dont wish to answer my question re replacing twins with clocks and the problem I suggest that such an experiment can never be made, is this...
    Given the small time variations when were clocks developed that could measure these small scales or fractional time differences.
    Or perhaps suggest which experiments would be worthwhile reading about.


    Moreover please dont let my ignorance of what went into SR upset you. I have read about it for many years but frankly I still understand little.
    I find it is not an easy subject to become familar with and I also am not a maths person such that I could work out various problems or exercises.

    Really my question turns on what is the point in speculation if one can not observe the speculation playing out in reality.

    Thanks again I really appreciate you taking all this time and although I understand very little simply find both The Theory of Special Relativity and The Theory of General Relativity most interesting.

    Alex
     
  9. Neddy Bate Valued Senior Member

    Messages:
    1,482
    For you and I, the relativistic effects we are discussing here are never noticeable in our lives. There is absolutely no reason for the average person to concern themselves with relativistic things in order to get through their day-to-day living. But the same thing could be said of any formal laws of physics, unless you happen to need to calculate something about them. Some of us just want to be able to calculate them, because we like math and physics.

    But you seem to be disparaging the entire scientific method. What would you replace it with? Folks who don't know anything about physics are already free to chime in lectures saying they don't need it day-to-day, and inquire presumptuously whether anyone has ever, ever, ever thought it might be wrong. As if that is not the underlying assumption of the scientific method. We don't scrap whole physics theories just because people are frowny-faced over it. We test and verify over years and decades until a better theory emerges. Do you know how long it was between Newton and Einstein?

    Do you really expect everyone in this thread, people who have studied relativity extensively, to simply say, "Yeah, Alex is right, to hell with this nonsense. Let's learn to cook beans instead!"
     
    Last edited: Jan 2, 2018
  10. Xelasnave.1947 Valued Senior Member

    Messages:
    3,645
    I think you form a very incorrect impression.

    If you have read any of my posts where scientific method has been discussed you would know that I am entirely supportive of the scientific method.

    Yet I make one, only one, comment as to a partial concern as to the down side of predictions and from that you make a large leap to assume I have some overall problem with the scientific method.

    You assume most incorrectly and you make that assumption on no basis...not very sciencey are you.

    I suggest you are simply wrong and if you are legitimately fixed on that wrong opinion sort through any of my posts on this forum and point out specifically any post where I have been in the least way critical of scientific method.

    I can make such a challenge because I know that you will find no such thread, or post or any hint at all of the wild claim you make, what you will find is various posts where I have pointed out to various folk how science works and in particular the philosophy of Karl Popper who I absolutely agree with.

    You are wrong and even you can prove that you are wrong.

    Your observation was made on one comment, which if you took the time to consider exactly what I said and not proceed with a notion of what you think I said, you may find somewhat reasonable.

    You may disagree, but to do so without really thinking about the negative implications of theories claiming observation as opposed to considering observations somewhat in an open arena, seems somewhat more in the mood of avoiding open enquirey. And to simply say...oh yes this is what we expected to support our theory...seems not right.

    Nevertheless your reaction is out of the reality which is my position.

    You ask this question based on your incorrect assessment of my position.

    I see no difficulty in taking into account my caution with absolutely no change, which I never suggested, to the current scientific method.
    Let me know when you can form a rational thought and I will respond.

    In the mean time I will let you battle the army of straw men you have constructed rather than address the inoccent questions that I asked re substituting twins with clocks and any experiment you in your wisdom could recommend.
    I certainly did not expect any such thing and perhaps if I said anything vaguely resembling your erroneous representation of anything that I have said I would be able to conclude you could have a point.

    But you do not have a point and what you say is dishonest...and if you want to make a valid point perhaps use facts rather than blowing off steam and making little sense.

    Look if you do not want to answer my simple question just say so, but please for your sake read what I have written rather than go off half cocked. Have you been drinking because you are raving like a drunk person.

    My initial respect for you has gone from hero to zero as you act, rather perform, like a fool.

    Moreover I have been polite with you and yet you seem to have little ability to respond politely with well reasoned arguement.

    Still I am not mad at you but I am disappointed.
    I expect you have had a bad day and perhaps that has caused you to lash out and if so I can understand.
    Better me than upset someone close to you so if it helps you thats ok by me.

    You have choices but I wont list the appologies that a reasonable man would make but if you want to get back to hero status you better say something to explain your terrible behaviour.

    I get it that folk like to discuss maths and physics what I dont get is your over the top stupid reaction.

    If you want to bicker I am fine with that and if you get off on insulting me thats ok as I dont care what you say and most often insults are close to the truth.

    And remember we are all on a path to enlightenment.

    Alex


     
  11. geordief Registered Senior Member

    Messages:
    625
    X-man(hope you like it

    Please Register or Log in to view the hidden image!

    ) your point seems to be that ,doubting Thomas like until you see the fabled twin return with wide eyed disappointment at the disappeared Earthly landscape you will only accept the fundamentals of the prediction on spec.

    The maths are presently beyond me but I find no difficulty in extrapolating from equivalent predictions based on smaller objects and timescales.

    If we did not extrapolate the corollary would be that our biological makeup was at a disconnect with its constituents (the protons and whatever are used in these relativistic experiments and verifications.)

    So I am not the doubting Thomas I suggested you might be save in the way that the scientific method obliges us all to be.

    Perhaps one day soon we can construct a little life imitating nano biological robot (or a some very small organism) that we can send at relativistic speeds to and from ProximaCentauri and measure its age on return.
    http://www.scienceforums.net/topic/109770-journey-to-alpha-centauri/
     
    Last edited: Jan 2, 2018
  12. Mike_Fontenot Registered Member

    Messages:
    23
    According to the third person ("he"), the home twin ("she") is always ageing half as fast as he is. Therefore, since she ages a total of 40 years during the entire scenario, he says he "ages" a total of 80 years during the whole scenario. But he is only 20 years old at the end of the scenario, so that means that he was born 60 years after the beginning of the scenario!
     
  13. Mike_Fontenot Registered Member

    Messages:
    23
    Of course I would have no objection to that, because an instantaneous acceleration when the twins are co-located has no effect at all ... that can most easily be seen from the delta_CADO equation, with the variable "L" = 0.
     
  14. Mike_Fontenot Registered Member

    Messages:
    23
    The muon example has nothing to do with to the twin "paradox". Many people get a paradoxical feeling when they first hear that each of two perpetually inertial observers will conclude that the other observer is ageing more slowly, and that there is no CONTRADICTION in that fact. That paradoxical feeling is resolved by the the relativity of simultaneity: the fact that different inertial observers have different "nows". The muon example is experimental verification of the time dilation result. The importance of the twin "paradox" lies in what happens during the acceleration of an observer, and that doesn't happen in the muon example.
     
  15. Mike_Fontenot Registered Member

    Messages:
    23
    I think this is as concise as I can make my argument:

    The following is ALL from the perspective of the traveling twin:

    The traveling twin ("he") originally says that the home twin ("she") will be the younger when they are reunited, because he originally (and wrongly) implicitly assumes that she couldn't possibly suddenly age by a large amount during the single instant of his turnaround, and therefore he believes he is entitled to use the time dilation result during his ENTIRE trip. But at the reunion he finds out that she is the older, and that is his paradox. He resolves his paradox by realizing that the she DOES suddenly age by a large amount during his instantaneous turnaround.

    In the third person scenario, everyone is inertial. No one expects the home twin to be the younger at the end of the scenario, and no one is surprised when she is the older. No one sees anything paradoxical. There is no paradox to resolve. So the alternative scenario has nothing to do with resolving the twin "paradox".
     
    Last edited: Jan 2, 2018
  16. phyti Registered Senior Member

    Messages:
    267
    Let s be the static, a the outbound, and b the inbound observers, respectively.

    In this version, the age of b is irrelevant since he is only timing the duration of the path from the reversal (when passing a) to rejoining s, without any acceleration.

    The inbound speed is equal to the outbound speed. This shows the time dilation for the 2-path trip is greater than the single path, and involves only inertial motion.


    The clock hypothesis states that the tick rate of a clock when measured in an inertial frame depends only upon its velocity relative to that frame, and is independent of its acceleration or higher derivatives. The experiment of Bailey et al. referenced above stored muons in a magnetic storage ring and measured their lifetime. While being stored in the ring they were subject to a proper acceleration of approximately 1018 g (1 g = 9.8 m/s2). The observed agreement between the lifetime of the stored muons with that of muons with the same energy moving inertially confirms the clock hypothesis for accelerations of that magnitude.

    • Sherwin, “Some Recent Experimental Tests of the 'Clock Paradox'”, Phys. Rev. 129 no. 1 (1960), pg 17.
    He discusses some Mössbauer experiments that show that the rate of a clock is independent of acceleration (~1016 g) and depends only upon velocity.
     
  17. phyti Registered Senior Member

    Messages:
    267
    Tests using particle accelerators have confirmed the time dilation effects predicted by the relativity theory.
     
  18. Confused2 Registered Senior Member

    Messages:
    475
    Instead of one traveling clock and one stay-at-home clock imagine the traveler is moving through a region of space full of clocks all Einstein synced to the stay-at-home twin's clock. Your sudden aging of the stay-at-home frame suggests that the traveling twin can make a discontinuous jump between between a region where the clocks show one value and another region where they show some other value. This might be possible by a sudden acceleration to c in the stay-at-home frame followed by deceleration back to less than c at a new location - can you suggest another way - or is your space not continuous?
     
  19. Neddy Bate Valued Senior Member

    Messages:
    1,482
    Mike_Fontenot, please see my posts #13, and #16. They were buried by Xelasnave's hijacking of this thread, (thanks alot Alex! *sarcasm*).

    In #13 we see that the apparent paradox can still come from the instantaneous acceleration scenario, while the non-accelerated scenario can still be useful to resolve that apparent paradox by letting the third party represent the second half of the instantaneous acceleration scenario, just without any actual acceleration. What is your objection to that reasoning, if any?

    In #16 we see that the information which you say is essential to resolve the apparent paradox, (namely that that the traveling twin must learn that the home twin will suddenly age by a large amount during his instantaneous turnaround), is in fact obtainable from the non-acceleration scenario. As follows:

    All that is required is a careful comparison of the inertial frame of the third party to the inertial frame of traveling twin, in the moment the traveling twin and third party are both in the same place, with their clocks reading the same time. By analysing both reference frames in detail (including use of Einstein synchronised clocks at rest in both frames), we can compare what those two inertial frames would say about the time on the home twin's clock in that instant of time. Compared to what the traveling twin's inertial frame would say, the third party's inertial frame would say that the time on the home twin's clock would be a ahead by a large amount. And that large amount precisely matches the large amount obtained in the acceleration scenario, in the instantaneous turnaround. What is your objection to that reasoning, if any?
     
  20. Confused2 Registered Senior Member

    Messages:
    475
    If two parties are in the same place at the same time surrounded by clocks Einstein synced to the home twin clock - can they read different values from the same clock?
     
  21. Neddy Bate Valued Senior Member

    Messages:
    1,482
    Imagine the home twin is sitting in a railroad station, and there are two very long high-speed trains running on parallel tracks past this station, both at the same speed. One train is headed east, while the other train is headed west. The traveling twin starts off standing at the station, where his twin sibling is sitting.

    But then the traveling twin decides to jump on board the eastbound train, leaving his sibling behind. The whole time the traveling twin is on board that train, he can use the Einstein synched clocks on board to ascertain that the stay at home twin's clock is accumulating fewer ticks than his own clock. At the moment when his own clock says t'=20 and he knows his sibling's clock says t=10 he decides he is getting too far away from his sibling, so he jumps from the eastbound train to westbound train to head back.

    When he lands on the other train, his own clock still says t'=20 but now he has to use the Einstein synched clocks on board the westbound train to ascertain the current time on his sibling's clock back at the station. Luckily the trains are long enough that there are still some train cars right next to the home twin. That is how the traveling twin determines that his sibling's clock now says t=70 right after the jump, meaning the stay at home twin's clock jumped ahead by 60 ticks during the instant the traveling twin jumped from one train to the other. From then on, he finds that his sibling's clock is again accumulating fewer ticks than his own clock, just as it was when he was on the other train. By the time he gets back to the station, his own clock says t'=40 and his sibling's clock says t=80.

    Note that the traveling twin did not have to jump very far through space, he jumps only a very small distance from one train to the other. I hope that helps.
     
    Last edited: Jan 2, 2018
  22. Neddy Bate Valued Senior Member

    Messages:
    1,482
    The two parties are each surrounded by clocks which are at rest in their own frame, and Einstein synched to their own clocks. Each one says his own clocks all read the same time, but find the other's clocks to be quite different. They are only the same where the two parties are, with their clocks in agreement. Since the more distant clocks disagree, they can disagree on the time on the home twin's clock, because that is very distant from them.

    Note, they do not use the home twin's Einstein-synched clocks, they use their own. If they used the home twin's Einstein-synched clock nearest them, they would see t=40, but they have no reason to believe that the distant home twin's clock says t=40 also, because those clocks are only in synch in the home twin's frame, not other frames.
     
    Last edited: Jan 2, 2018
  23. Confused2 Registered Senior Member

    Messages:
    475
    Thanks Neddy Bate, that's good but is it good enough? I'm not sure. Reintroducing my scenario of a home twin at -x, 0 in the middle where the travelers either cross or bounce back and an extra home twin at +x. We then have left twin and right twin leaving at t=0 in all frames. We place an Einstein synced clock at x=0. Left and right twins arrive at 0 at the same time (by symmetry) and must agree on the value of the clock synced in the home frame. If they don't - I think something has gone wrong somewhere. If they swap ships or bounce back off x=0 - their start time (in the home frame) for this leg of the journey is marked (for both) by the clock at x=0 synced to (either) home twin clocks.
     

Share This Page