The real twin paradox.
in [Relativity]
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From: colp on 26 Nov 2007 13:00 On Nov 26, 10:38 pm, Bryan Olson <fakeaddr...(a)nowhere.org> wrote: > colp wrote: > > On Nov 24, 11:27 am, Bryan Olson <fakeaddr...(a)nowhere.org> wrote: > >> colp wrote: > >>> Bryan Olson wrote: > >>>> Colp's theory is that somehow he gets the time-dilation of SR, but > >>>> the effect of changing inertial frames somehow does not count. > >>> You are unable to show that the effect of changing inertial frames > >>> solves the paradox. > >> Paradox solved here: > > >> <12q1j.19192$4V6.17...(a)newssvr14.news.prodigy.net> > > > That is a link to this thread. You haven't show a solution. > > It's the message ID of the post. You can also find it at: > > http://groups.google.com/group/sci.physics.relativity/msg/1694288bbb6... Your post is not relevant. The issue is not that the twins will be the same age when they return to Earth (that was made clear in the OP), but that the clock time of the other twin as predicted by SR will not equal the proper time of the twin from his frame of reference. > > >> Part of SR that colp ignores, making his theory contradictory: > > >> http://www.bartleby.com/173/9.html > > > Relativity of simultaneity is not relevant because the paradox can be > > demonstrated from a single frame of reference (the outgoing leg) which > > has spatial and tempoaral symmetry with the inbound leg. > > Let's try that. Let's choose the outgoing frame of twin A as > our inertial frame of reference, and stick to it. Note that > given the outgoing/inbound symmetry you specify, the outgoing > frame of one is the in inbound frame of the other. > > Outbound, twin A is in the frame of reference, so clock A runs > normally. Twin B's is time-dilated to run slow. After they turn > around (meaning reverse direction for the trip back), twin B is > in our inertial frame of reference, and twin A is moving > according to our frame of reference, making clock A run slow. > We're not talking about what twin A observes; we sticking to our > one chosen frame of reference, just as you suggested above. Nice try, but I was talking about the outgoing leg by itself. Outbound, twin A is in the frame of reference, so clock A runs normally. Twin B's is time-dilated to run slow, as you said. When the twins reach the original turnaround point twin A will be older than twin B from twin A's frame of reference. If the twins had been sending clock ticks by radio to each other, then SR predicts that twin B will have sent fewer ticks than twin A sent. Since the twins are symmetrical cases of each other, the number of clock ticks sent must equal the number of clock ticks received. Thus SR predicts a false result. > > For each twin, one leg is in the frame of reference, the other > is time dilated. They arrive back at Earth showing equal time > having passed. That was made clear in the original thought experiment. > > Try sticking to any other single inertial frame of reference, > and you'll get the same answer. False. You had to use 2 legs to get a sensible result. A single leg demostrates the paradox. > So where is the paradox that you > just said this should demonstrate? The paradox is that SR predicts time dilation of a twin B is observed from the frame of reference of twin A when the twins are symmetric instances of each other. > > >>>> Colp's theory leads to a contradiction. > >>> It's not my theory. It is standard special relativity. > >> As we still lack any citation attributing the wrong theory to > >> anyone else, I stand by my description of it as Colp's own. > > > The essential element of the paradox is time dilation as observed by > > one of the twins. This time dilation is standard SR > > >http://en.wikipedia.org/wiki/Time_dilation > > If we stick to one inertial frame of reference, then there's no > paradox. The paradox exists as shown in this post. > If we take a twin's point of view and change frames, we > account for our far-away twin's age being different in the new > frame, and once again there's no paradox. If the change of frame is excluded the paradox becomes clear. > > Only colp-theory says we can change inertial frames and somehow > be immune to the relativity of simultaneity. Colp-theory makes > no sense; it leads to contradictions. It's not my theory, it is standard SR. > > >>>> In SR, the relativity of > >>>> simultaneity implies that each twin's view of his far-away sibling's > >>>> age changes upon the turn-around. > >>> The turnaround cannot affect the observed time of the remote clock. > >>> A radio clock signal from the remote twin does not change just because > >>> the spacecraft rotates. > >> "Turn-around" refers to change of direction, not orientation. > > > Your statement is ambiguous. Please clarify. > > Rotation is irrelevant. Turn-around refers to a twin changing > direction: when the outbound leg is done, he turns around and > heads back to Earth. That's when he changes inertial frames. > > What age does twin B reach simultaneously with twin A's > turn-around? The answer is different in different frames. Let's > not hear more nonsense about SR not saying such a thing, because > look - there it is: > > http://www.bartleby.com/173/9.html >
From: colp on 26 Nov 2007 13:06 On Nov 27, 1:05 am, "harry" <harald.vanlintelButNotT...(a)epfl.ch> wrote: > One last attempt ... > > "colp" <c...(a)solder.ath.cx> wrote in message > > news:81a29c49-6048-4f2d-87fd-b59380b5dd98(a)b40g2000prf.googlegroups.com... > > > > > On Nov 25, 5:54 am, stevendaryl3...(a)yahoo.com (Daryl McCullough) > > wrote: > >> colp says... > > >> >The point is that a paradox exists due to the time dilation expected > >> >by SR. > > >> No, there is no paradox in the sense of contradiction. > > > The contradiction between SR prediction ant reality is described > > below: > > > This thought experiment is like the classic twin paradox, but in this > > experiment both twins leave earth and travel symmetric return trips in > > opposite directions. > > > Since the paths taken by the twins in this experiment are symmetric, > > they must be the same age when they meet on their return to earth. > > In this experiment the twins maintain constant observation of each > > other's clocks, from when they depart until they return and find that > > their clocks tell the same time. > > Sure. > > > Special relativity says that each twin must observe that the other's > > clock is running slow, and at no time does special relativity allow > > for an observation which shows that the other clock is running fast. > > There is no need for that, and this has been explained to you from the very > start. What has been explained from the very start?
From: Daryl McCullough on 26 Nov 2007 13:47 colp says... >The issue is not that the twins will be the >same age when they return to >Earth (that was made clear in the OP), but that the clock time of the >other twin as predicted by SR will not equal the proper time of the >twin from his frame of reference. SR does *not* say anything about how things look from an accelerated "frame of reference". It talks about how things are measured using an *inertial* frame of reference. >Outbound, twin A is in the frame of reference, so clock A runs >normally. Twin B's is time-dilated to run slow, as you said. To be precise: Twin B's clock runs slow as measured in A's outbound frame of reference. >When the twins reach the original turnaround point twin A will >be older than twin B from twin A's frame of reference. A doesn't have *a* frame of reference. He has *two* frames of reference: an outbound frame of reference, and an inbound frame of reference. A is older than B according to one of those frames, but B is older than A according to the other. When A turns around, he changes from a frame of reference in which A is older to a frame in which B is older. >If the twins had been sending clock ticks by radio to each >other, then SR predicts that twin B will have sent fewer ticks >than twin A sent. Since the twins are symmetrical cases of each >other, the number of clock ticks sent must equal the number of >clock ticks received. Thus SR predicts a false result. Why don't you actually try to *derive* what you are saying from the postulates of SR? As several people have pointed out, what you are calling SR is a theory of your own invention. What SR says is that, from the point of view of any *inertial* coordinate system, 1. Light has speed c in all directions. 2. Moving clocks run slow, by a factor of square-root(1-(v/c)^2). 3. Moving rods are contracted in the direction of motion by a factor of square-root(1-(v/c)^2). 4. Inertial coordinate systems are related by the Lorentz transformations, rotations and translations. It doesn't say anything (directly) about how one accelerated twin appears to another accelerated twin. You have to *derive* what each twin sees from the postulates of relativity. Suppose that your twins are sending signals to each other once per second. Then if the twins travel in opposite directions at speed v for time T, turn around, and return at speed v, the rate at which each twin receives signals from the other is given by the following: From the point of view of twin A, there are three periods with three different rates Period 1: The signals received by A from B come slower than once per second. This period lasts for half the trip. Period 2: The signals received by A from B come at the rate of one per second. This period lasts for less than half the trip. Period 3: The signals received by A from B come at more than one per second. This period lasts for less than half the trip. Add up the signals received by A from B during the three periods, and you get the same number as the number of signals sent by A to B during those three periods. -- Daryl McCullough Ithaca, NY
From: Daryl McCullough on 26 Nov 2007 13:49 colp says... >SR describes time dilation. SR does not describe time compression. That's incorrect. The Lorentz transform for time has two factors: t' = gamma (t - vx/c^2) t' can be greater than t or less than t, depending on the value of x. -- Daryl McCullough Ithaca, NY
From: Sue... on 26 Nov 2007 14:10
On Nov 26, 1:47 pm, stevendaryl3...(a)yahoo.com (Daryl McCullough) wrote: > > What SR says is that, from the point of view of any > *inertial* coordinate system, No... the inertial modifier does not appear. That issue is considered with relation to mass energy equivalence http://www.bartleby.com/173/15.html > > 1. Light has speed c in all directions. > 2. Moving clocks run slow, by a factor of square-root(1-(v/c)^2). SR says no such thing. It says moving clocks are *judged* to run slow from a different frame. "The Behaviour of Measuring-Rods and Clocks in Motion " http://www.bartleby.com/173/12.html You are making a fine argument that the principle of relativity doesn't hold true regardless of the speed of light. http://www.quackwatch.org/01QuackeryRelatedTopics/pseudo.html Sue... |