Talk:Twin paradox/Archive 10

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Twin Paradox without acceleration

This link: http://www.sysmatrix.net/~kavs/kjs/addend4.html goes through the twin paradox without acceleration and to me it seems closer to what Einstein was originally saying - that this all had to do with the speed of things in relation to each other, not acceleration - at least I hadn't heard him talk about acceleration being the key here. What think ye? --Rcronk 17:04, 16 May 2007 (UTC)

That astronauts don't accelerate in this example, the but clocks do. As it is the clocks that are being tracked, it is their acceleration that matters. --EMS | Talk 17:22, 16 May 2007 (UTC)

The clocks aren't accelerating; they're just being set as they pass each other.

—wwoods 17:52, 16 May 2007 (UTC)

The above article is a masterpiece of deception, the time dilation of the earthbound clock from the point of view of the outgoing clock+observer is completely discarded, at the point of intersection with the incoming clock+observer. It is then replaced with a new value which is 1.5 years greater. Basically it is saying that when the two 'moving' clocks intersect, the time on the third earthbound clock, which is 1 light year away appears to jump forward by 1.5 years. And in the end as if by magic, the numbers show an asymmetry in time dilation. ---Swanzsteve 01:11, 19 August 2007 (UTC)

See Lorentz transformations and relativity of simultaneity. You are correct the the outgoing point-of-view is discarded, but that is because the observer is now incoming and has a different point-of-view due to the change of velocity (also called an acceleration) and the Lorentz transformations. Also be advised that what has jumped is not the earthbound clock but instead the event on the eathbound clock's world line which is simultaneous with the "traveling" observer. The earthbound clock still needed 1.5 years of proper time to go between those same two events. --EMS | Talk 02:36, 19 August 2007 (UTC)

I trust that you now see why I was getting so unhappy with drilling into this on talk:Herbert Dingle, as it leads directly into this issue and beyond. However, please do be advised that this thread cannot be a debate either: You wanted an assurance that the article is correct, and you now have it. --EMS | Talk 02:36, 19 August 2007 (UTC)

EMS - I'm afraid you are completely wrong, this article's conclusion is easily disproved, you need to look at it more carefully. ---Swanzsteve —The preceding signed but undated comment was added at 03:23:36, August 19, 2007 (UTC).

Slowing down?

I'm not exactly sure how it would actually be, but what would be the result of the traveling twin slowing down with reference to the original inertial frame?

For example (and please excuse me if this would not be a viable example), what if he somehow managed to depart from the earth and remain stationary relative to the sun, perhaps by riding on a space-station-like statite? If I am understanding things correctly, he is not accelerating, and is instead slowing down relative to the Earth's natural movement.

Now, my initial reading of this article has it suggest that any change in velocity would result in a time-lag - no matter whether the astronaut speeded up or slowed down, he would be younger.

(NOTE: Everyday English has "acceleration" as referring to "speeding up" only, but in scientific circles it equally refers to "slowing down" so that all the physical changes in speed and direction necessary to get the rocket to come back—slowing down, stopping, turning around, speeding up again—can be covered by the umbrella term "acceleration". This is the way the word is used in this article.)

This seems to be contradictory to how the situation is later explained, as to that point, why couldn't the earth-bound twin be considered the one undergoing acceleration?

This has probably been asked over and over, and I will probably receive flame for asking a question I could probably have answered by doing my own work and looking for it - in that case, just tell me so. You don't even need to point me to the answer, I'll find it on my own and save you the trouble of removing my ignorance. Thank you for your time.KrytenKoro 08:05, 28 July 2007 (UTC)

You are right, of course, that in physics acceleration can refer to either "speeding up" or "slowing down," because what appears to be the former in one reference frame may be the latter in another. (For example, if I am going 100 kph in a car, and I throw a ball backward at 30 kph, from my perspective in the car I "sped it up" to 30 kph, but from the perspective of someone watching by the side of the road I "slowed it down" to 70 kph.) But the object that is accelerating is not in question; all observers agree that the ball's velocity changed by 30 kph in the direction opposite from the motion of the car.

It's the same thing in your example; you've just made things more complicated by introducing the motion of the sun and the earth into it. In truth, the earth is always accelerating, because it's moving in a circle around the sun. (Something moving in a circle is accelerating toward the center of the circle; see uniform circular motion.) The sun is also accelerating, because it (and the earth with it) are orbiting our galaxy. And the galaxy is accelerating too, being pulled by other galaxies and galaxy clusters! But none of this motion is enough to create noticeable effects due to special relativity. Thus if you stay in the solar system you need very special instruments to detect the difference in the twins' ages. But which one accelerated is still absolute, so the resolution of the apparent paradox still works. (More likely the both accelerated, but that just makes the math harder without changing the concepts.)

By the way, you can ask questions like this on Wikipedia:Reference desk/Science. -- SCZenz 19:05, 28 July 2007 (UTC)

This is not a dumb question at all. I dont know the answer. I suspect no one else does either. Perhaps it explains why papers continue to be published regarding the solution of the paradox. Apparently, not all the questions have been answered by the claimed "solution" of it.Electrodynamicist 14:38, 28 July 2007 (UTC)

You're right that it's not a dumb question, but your suspicion that no one else does either is incorrect. See my answer above, and try to remember that Wikipedia is not a soapbox. -- SCZenz 19:05, 28 July 2007 (UTC)

Correction. What you meant to say is that it is not a soapbox, except for its editiors.71.251.179.21 23:49, 28 July 2007 (UTC)

Not so. We have to have reliable sources to back up changes we make to articles. (I admit I didn't post any such links for my answer to KrytenKoro's question, but I was just doing him a quick favor.) Besides, anyone can edit Wikipedia. -- SCZenz 07:17, 29 July 2007 (UTC)

Okay, but wouldn't the homebody's "trip" around the sun involve constant acceleration in order to create an elliptical orbit? As well as rotation of the Earth? Granted, the astronaut twin is drastically changing his speed by changing the speed he was going at when he left Earth, but hasn't the homebody, in his yearlong trip, had his speed changed much more? Or do the speed changes of an elliptical orbit cancel out? (These both seem hard to comprehend - on one hand, my mind really doesn't want to let go of "speed up-clock slow, speed down, clock fast", but the canceling out bit seems odd, as why would time wait for the full trip to happen in order to compensate for lag - in fact, wouldn't the "cancelling" out thing require my original slow-down fallacy to be true?) Basically, I cannot figure out how the small change of the astronaut overrides the seemingly huge change of the homebody.KrytenKoro 10:05, 29 July 2007 (UTC)

The Earth is constantly accelerating, but that's de minimis for this thought experiment. The Earth's speed around its orbit is 30 km/s, while the traveling twin is moving out and back at some large fraction of 300,000 km/s. If it bothers you, put one twin on a space station coasting through intergalactic space, and the other twin on a spaceship which goes away from the station and back, real fast.

—wwoods 14:16, 29 July 2007 (UTC)

After reading this article, it is obvious that the writer didn't understand the solution at all. It doesnt make sense, and it clearly can not be understood by the average reader. So it is basically useless as solution to the problem and unhelpful to a Wikipedia user. If this is an example of what accepted peer reviewed physics is, then it must be nonsense and we should not beleive it. 71.251.179.21 12:34, 29 July 2007 (UTC)

How does Acceleration solve the twin paradox?

SCZenz clearly doesn't like this question which is why he keeps archiving it. How does acceleration solve the twin paradox? I have yet to see the mathematics of this. (217.43.69.32 19:00, 1 August 2007 (UTC))

Actually, you have yet to look at and understand the mathematics of this, but this is not a classroom, remember. DVdm 19:12, 1 August 2007 (UTC)

DVdm, you supplied your own original research articles as an attempt to explain it. I read your articles and concluded that they were rubbish.

Acceleration is every bit as symmetrical as velocity. All of you have totally avoided this issue. (217.43.69.32 21:05, 1 August 2007 (UTC))

Sorry, forgot to emphasise... Make that "look at and understand". DVdm 21:08, 1 August 2007 (UTC)

Cheers, DVdm 21:08, 1 August 2007 (UTC)

No DVdm, you can't simply write rubbish and then console yourself with the idea that the fault lies with those who can't understand it.

You have a very simple task in hand. Show me why acceleration is not symmetrical. (217.43.69.32 21:17, 1 August 2007 (UTC))

See a USENET posting of mine which explains the asymmetry and does the math. --EMS | Talk 22:18, 1 August 2007 (UTC)

I know the explanation for the assymetry. You claim that time only slows down for the clock which experiences non-gravitational forces.

I saw nothing in the maths that limited the acceleration terms to only those caused by non-gravitational causes. (217.43.69.32 14:49, 2 August 2007 (UTC))

I think that you would do well to actually read my USENET posting. However:

1. There is no gravitation in SR, which is the domain of this exercise.
2. Even if the turnaround was caused by whipping around a star, the same change of viewpoint would have occurred betweent he entry to and exit from the star's gravity well. So the issue is the overall acceleration and not its cause.

--EMS | Talk 22:47, 2 August 2007 (UTC)

Lets Resolve This Argument Now!

This dispute has a simple solution. All that has to be done is to state the facts as they are. That the textbooks assert there is a solution. That the textbook solution is disputed, and there is no agreement about it. That physics journals continue to publish papers investigating alternative solutions to the problem, and no alternative has been universally agreed upon. It should also be stated what the criticism of the claimed solution is, so that readers can make their own informed decision about it. Further references and links should be given that represent both points of view. Finally, stop insulting people who have a reasonable reason to disagree with your personal opinion. Electrodynamicist 15:17, 2 August 2007 (UTC)

The following statements above are false:

• the texbook solution is disputed, and there is no agreement about it — it is not disputed by any qualified physicists that I know of
• physics journals continue to publish papers investigating alternative solutions to the problem — no, since SR is not a current area of physics research. However, some education-oriented journals continue to publish alternate presentations of the "paradox" and its resolution.
• it should also be stated what the criticism of the claimed solution is — this would only be true if there were self-consistent criticism written by an expert; however, all such criticism I am aware of is fallacious or based on a fundamental misunderstanding of the explanation being criticized
• Further references and links should be given that represent both points of view — Nope, read Wikipedia:Neutral point of view more carefully, especially the section on "undue weight"

I agree there's no need for insults. — SCZenz 15:25, 2 August 2007 (UTC)

SCZenz, The textbook solution is disputed by numerous academics in university positions. (217.43.69.32 19:04, 2 August 2007 (UTC))

Physicists? Cite some. — SCZenz 19:13, 2 August 2007 (UTC)

SCZenz, I'm not going to bother giving you the definitive list but I'll mention a few that immediately spring to mind. Prof. Howard Hayden of the University of Connecticut. Prof. RA Waldron from some UK university who used to write into Radio and Electronic Engineer. There was Prof. Eric Laithwaite of Imperial College in London. Professor Stanislaw Kosowski in Warsaw. Dr. Rothwarf. Prof. Assis in Brazil.

Also, check up and see whether or not this guy agrees with Einstein's theories or not. http://en.wikipedia.org/wiki/Friedwardt_Winterberg

Don't just be so sure that there is no opposition to relativity amongst academia. (217.43.69.32 10:54, 3 August 2007 (UTC))

Herbert Dingle was a reputable physicist, definitely smarter than you, and he refuted the twins paradox. He was supported by L. Essen an expert on time at the NPL. Are you really as dumb as you seem??? You dont know anything at all. You guys need to fix this problem now. You need to resolve the problem as I said above. Your resistance only shows what fools you are.Electrodynamicist 12:15, 3 August 2007 (UTC)

Do you realize that your collective insults actually sound like the rantings of a creationist? Don't you think you would feel much better with an entirely different but less demanding hobby? Think about it honestly. DVdm 12:29, 3 August 2007 (UTC)

I can't speak for Electrodynamicist, but I'm defintely getting a new hobby. I have realized that I am not intelligent enough to comprehend the concept of two clocks both going slower than each other. I really wish I was as intelligent as DVdm. He obviously takes this concept in his stride. I'm sure that if there had never been an Einstein, DVdm would have supplied us all with the theory of relativity anyway. (217.43.69.32 15:22, 3 August 2007 (UTC))

Although this page is not for discussions about your intelligence, indeed, after I explained the following (about two clocks in relative uniform motion - i.e no returning, no turnaround or going back) to your Electrodynamicist identity:

According to you, your clock has one second between two ticks. According to me, your (moving) clock has more than one second between two ticks, so in a sloppy way, I say that your clock is "running slower than mine".

According to me, my clock has one second between two ticks. According to you, my (moving) clock has more than one second between two ticks, so in a sloppy way, you say that my clock is "running slower than yours".

Note that measuring when an event takes place on a local clock is very easy and straightforward: just take the reading. On the other hand, measuring when an event takes place on a remote clock is far less easy. It takes (1) having sent a light signal, (2) receiving an echo, reading the times of those two local events on your local clock, and taking the average of those times. So, measuring a time interval between two events on a remote (and possibly even moving) clock takes four local events.

It's really all a question of how things are defined and measured. A useful (and probably less surprising) analogy: when we look at each other through a small gap between our fingers, according to me, you have a smaller opening angle than I have, and according to you, I have a smaller opening angle than you have.

... which you entirely failed to understand, you probably realized quite correctly, and maybe you should draw an appropriate consclusion.

Cheers, DVdm 15:43, 3 August 2007 (UTC)

Troll alert!!! Here is one!!! Troll alert!!! Lurking under the bridge!!! —The preceding unsigned comment was added by 71.251.189.123 (talk • contribs) 21:29, August 3, 2007 (UTC)

Here is another USENET posting of mine called "Which clock is slower?" which answers the concerns expressed here (not that I think that the anti-relativists will agree). BTW, my overall advice is to stop answering these challenges to relativity and just revert as needed. Unable to make an impact, the anti-relativitsts will soon quit the scene. --EMS | Talk 21:53, 3 August 2007 (UTC)

Ah.... another thread that quickly turned into an Androcles teaching debacle.

Of course you know that as soon as one of them quits the scene, an other will appear to fill the vacancy. Remember the Universal Law of Conservation of Stupidity ;-) DVdm 22:37, 3 August 2007 (UTC)

EMS, you seem to think that the anti-relativity people will quit the scenes when they realize that they are not making an impact. Is that because you have a ready battalion of relativity trolls on 24 hour vigil to ensure that all wikipedia articles are commensurate with Einstein's Theories of relativity?

You are only fooling yourself. (217.43.69.32 10:54, 4 August 2007 (UTC))

This page is watched by enough people, and Wikipedia policy is on our side here. If you want to suggest wording noting that this paradox is regularly used by anti-relativists as evidence that special relativity is wrong, then go ahead: I may consent to let it into the article if it does not change its overall tone.

Note that under WP:NPOV we cannot just plain "ensure that all [W]ikipeida articles are commensurate with Einstein's [t]heories or relativity", but we can and will ensure that they properly reflect the current state of human knowledge, which is close to being the same thing given the overwhelming support for relativity theory in teh scientific community at this time. --EMS | Talk 17:06, 4 August 2007 (UTC)

So you are admiting that you are biased and distorting the facts about this issue to maintain your narrow opinion. The fact that the article fails to discuss the reason for the paradox proves this. That proves you are using this site to advance your personal opinions and to distort scientific knowledge. This article fails to discuss in a factual way even the most elementary aspects of the twin paradox debate. It doesn't even admit that there was and still is a debate!!! The article should be deleted. It serves no useful purpose, because no actual scientific knowledge is contained in it. Another reason to delete it is that it is useless to the average reader. As David Hilbert said: "A mathematical theory is not to be considered complete unless you made it so clear that you can explain it to the man in the street...For what is clear and easily comprehended attracts, and the complicated repels us." 72.64.58.30 10:55, 5 August 2007 (UTC)

"the twin paradox debate" ==> What you call a debate is a futile attempt to educate those who fail to understand. A debate requires symmetry. Compare with creationists calling scientists evolutionists in order to create some kind of reassuring balance. DVdm 16:36, 5 August 2007

Yes I can see that you are right that you don't understand. That is evident, from the poor way the article is written. It does not convey any understanding at all to the reader. What amazes me is that you think you are defending relativity from the ignorant hoards, but you are not presenting the correct theory of relativity at all. That is what the debate is about. The fact that you are advancing a false version of relativity. But I can see that you can't understand that you are wrong. Too bad that Wikipedia lets you continue to do this.137.155.51.208 18:51, 5 August 2007 (UTC)

Your recents attempts at changing (as 137.155.51.208 and as 72.64.58.30) show that you don't understand. I suggest you open a new section and propose the changes you have in mind in detail. DVdm 18:54, 5 August 2007 (UTC)

See previous comments.137.155.51.208 19:06, 5 August 2007 (UTC)

Anon - Either you work with us to find a way to address your concerns (which are notable if only because they come up so regularly) or you get lost. I for one agree with DVdn that you don't understand relativity, nor do you understand the current state of scientific knowledge about it. There is no debate amongst physicists that special relativity is correct, but there is this ongoing misunderstanding that you and others have. --EMS | Talk 01:27, 6 August 2007 (UTC)

Why should he work with you? You and DVdm clearly haven't got a clue about relativity and you are only defending it as an indirect means of pushing your own private research. What makes you think that anon should either have to work with you or get lost? You keep ducking the issue of how can two clocks both be going slower than each other.

I would say that anon understands the issue clearly and has researched it thoroughly, whereas you are only pretending to understand it. So why should he have to work with you? (217.43.69.32 10:05, 6 August 2007 (UTC))

"keep ducking the issue of how can two clocks both be going slower than each other" ==>

Let me repeat for third time, but this time, I will put the most significant phrases in bold:

According to you, your clock has one second between two ticks. According to me, your (moving) clock has more than one second between two ticks, so in a sloppy way, I say that your clock is "running slower than mine".

According to me, my clock has one second between two ticks. According to you, my (moving) clock has more than one second between two ticks, so in a sloppy way, you say that my clock is "running slower than yours".

Note that measuring when an event takes place on a local clock is very easy and straightforward: just take the reading. On the other hand, measuring when an event takes place on a remote clock is far less easy. It takes (1) having sent a light signal, (2) receiving an echo, reading the times of those two local events on your local clock, and taking the average of those times. So, measuring a time interval between two events on a remote (and possibly even moving) clock takes four local events.

It's really all a question of how things are defined and measured. A useful (and probably less surprising) analogy: when we look at each other through a small gap between our fingers, according to me, you have a smaller opening angle than I have, and according to you, I have a smaller opening angle than you have, so in a sloppy way of expressing, we are both smaller than each other.

That really is all there is to it. I don't think that we are to blame for your failing to understand this simple explanation. DVdm 10:50, 6 August 2007 (UTC)

And DVDm, if the Earth has gone around the Sun once from clock A's perspective, how many times has it gone around the Sun from clock B's perspective?

Are you forever going to live in the delusion that anybody who understands Dingle's question has merely failed to understand things that only bright people like you can understand?

You are trying too hard to defend the indefensible. You have obviously invested too much in bogus theory. (217.43.69.32 16:22, 6 August 2007 (UTC))

I may as well take a stab here for grins, not that I think the anons will be impressed. At the least, I see nothing "sloppy' about the statements that each clock runs slower than the other in the frame of reference of the other clock. However, note the emphasized words: "in the frame of reference of the other clock". In SR, there is a relativity of simultaneity such that events the occur at the same time in one frame of reference may occur at different times in another frame of reference. The effect is furthermore a linear function of the separation between the events in question in one of the frames of reference. So as the clocks move further and further away from each other, the differences associated with the relativity of simultaniety get greater and greater. So in the frame of clock A, t = T for clock A is simultaneous with t' = T/γ for clock B (at the position of clock B when t=T for clock A). In the same situation but in the frame of reference for clock B, t' = T for clock B is simultaneous with t=T/γ for clock A (at the position of clock A when t' = T for clock B). Note that since the other clock is reading time for its frame, that I must not only specify when the current clock's frame the comparison is being made, but also the position at which it is to be made. Anything less is ambiguous. Dingle's mistake was in not being sensitive to subtle ambiguities like that in relativity. --EMS | Talk 16:24, 6 August 2007 (UTC)

Commentary on the above incorrect statement. You need to study relativity textbooks.

According to you, your clock has one second between two ticks. According to me, your (moving) clock has more than one second between two ticks, so in a sloppy way, I say that your clock is "running slower than mine".

This is indeed very sloppy. This statement says that the second clock is fast, because during the one second on my clock your clock ran faster to read more than one second. You have to get this right.

According to me, my clock has one second between two ticks. According to you, my (moving) clock has more than one second between two ticks, so in a sloppy way, you say that my clock is "running slower than yours".

Again the clock is running fast not slow because is indicates more than one second for a reference time of one second. You again have it wrong.

Note that measuring when an event takes place on a local clock is very easy and straightforward: just take the reading.

Well since you did not get it right it really is not that easy.

On the other hand, measuring when an event takes place on a remote clock is far less easy.

Hey you never said anything about a remote clock. So this doesnt count. You need to be more careful in definitions.72.84.64.196 21:21, 11 August 2007 (UTC)

Actually... you should re-read what is said. If the moving clock takes more than one second to go from 12:00:00 to 12:00:01 (between two ticks) that means it's running slow, not fast. Gscshoyru 21:36, 11 August 2007 (UTC)

Since it is not clear at all which clock is moving and which is not, I can't tell anything at all about what is or is not meant here. Further, since either clock can be the rest or moving one, I can pick either one I want as opposed to what he says. It all boils down to the problem of perception, and my perception is different. So you need to say which is the rest clock and stick to that definition. Be clear about it.72.84.65.8 20:48, 12 August 2007 (UTC)

A very strange situation: I ask the people to clearly express, what they think and that is OR! So please take care: a clock is never running slow or fast. A clock is just running. A second is always a second. A single object can change his state. That is, why "time goes by". Two objects can never be in one place. That is, why they have a distance. But how can object be in touch without beeing in one place? Therefore they have a finit size. To watch a local clock you must have a "ticker" and an counter. The counter counts the ticks. Counter and ticker are in one place while the ticker ticks. That is: they are at (in?) (relative) rest. If the counter and ticker are not in one place (their distance is greater then their size) it needs an communication mechanism. This mechanism follows own (known) rules. We have to establish a counting instrument, that comprises two counters, a comparator and a communicator. Only than we can compare two tickers to determine their tickrate. Two tickers are said to be identical, when the comparator can not see a difference and the distance is not changed. Today we know, that the tickrate changes, when the distance changes continuously, that is, there is relative movement. This effect is also influenced by the communication mechanism, but these influences can be compensated, the effect still takes place. Anybody, who does not aggree with this should not take part in the discussion on the twin paradox. So, if this is the common basis, we can answer the question, where the dispute comes from! Anyway, if these statements are not clear or faulty, they should first be clearified and corrected. ErNa 20:54, 12 August 2007 (UTC)

I see that the above writer is trying to clarify the issue. This is very much needed because of the poor discussion of the twin paradox in this article. It is evidently not useful because it does not address the issues but merely gives a textbook answer. That solves nothing. This is why the article needs to be changed. The above comments certainly need to be addressed so that the issue of clocks and time measurement is discussed in the article so that a clear understanding of the issue will be provided to the reader.Electrodynamicist 13:49, 14 August 2007 (UTC)

But it makes no sense, to discuss with those people, that can not see, what type of clock a simple atom is. If I would delete everything, I do not understand, Wikipedia would be nearly empty. So, it is better, those, who understand nearly everything, go on deleting, what I belive to understand ;-> ErNa 17:00, 14 August 2007 (UTC)

Electrodynamicist - Under the reliable sources policy, we should be presenting the textbook answer (or answers). I will admit that I do not like the lack of a clear statement of the paradox, and IMO it may be reasonable to include a breif statement that this is considered by some to be an invalidation of SR. OTOH, your request regarding the issue of clocks and time measurement at best needs a specific proposal and more discussion. This may be an issue which is better dealt with over at time dilation and special relativity and should only be breifly touched on here. Certainly that issue is central to special relativity itself, but this page is about the twin paradox and IMO dealing with these (admitedly underlying) issues may be a disctraction in the context of this article.

I also worry that you are trying to impose your own anti-relatvity POV here. Note that this article by its nature will assume the correctness of special relativity, and that under WP:UNDUE little if any space can be devoted to the anti-relativity interpretation of this paradox --EMS | Talk 17:15, 14 August 2007 (UTC).

You are being inflamatory instead of addressing the issue of how to improve this article. You seem to think that improving the article will make it less biased towards your view of it so you resist that. Apparently your certainty that the textbook answer is correct is in doubt. If that answer is correct, then why not actually prove it? What are you afraid of EMS? How can a few extra facts hurt the truth, unless it really isn't true?Electrodynamicist 18:13, 14 August 2007 (UTC)

Kindly stop making accusations and start making specific suggestions. There is room for improvement here. I support there being a clear statement of the claim of self-contradiction that is behind this paradox. I also am amenable to there being a mention of your viewpoint. I fail to see how those changes cannot be improvements and yet which also support your viewpoint. Kindly get to work and let's see what you come up with. I cannot make you any guarentees that myself and others will find your suggestion acceptable, but if not it may still be possible to generate consensus wording that will satisfy all of us. "Nothng ventured, nothing gained." IMO, you can contribute, but please be aware the in this context your personal POV is of limited usefulness. --EMS | Talk 18:50, 14 August 2007 (UTC)

It is a fact, that even physicists have different understanding of simple things. If Electrodynamicist can not accept, what ems57fcva says, then, according to the principle of relativity, whether E is to simple minded to understand, or E is to sophisticated, to explain. "E"= any person. The problem is: Einstein didn't specify a physical clock. So, if I write: the clock is embodied by a hydrogen atom, this is said to be WP:OR. This is just obsurd, and it doesn't matter, if here, or in time dilation! But: The introduction of the article is correct. Not in http://de.wikipedia.org/wiki/Zwillingsparadoxon ! There is written: According to RT both twins deduce, that the other one is time dilated. But what, when they can see the other ones clock? Then they can determine, who was accelerated. And there I see a problem: If my clock is such simple as hydrogene and I observe distant, moving hydrogen, then I know, if my or that hydrogen was more accelerated. In consequence: there is a frame of absolute rest! To me, that is not a problem, for, AFAIK, the laws of physics are the same in all inertial frames. Not the speed! ErNa 18:48, 14 August 2007 (UTC)

Never ending story

[Section removed as not relevant to the talk page.]KrytenKoro 21:05, 8 August 2007 (UTC)

One Year is One Year for Everybody in the Universe

[Section removed as not relevant to the talk page. Sorry Gscshoyru—you probably weren't aware that the comment you replied to had been removed repeatedly as utterly irrelevant soapboxing by a repeated problem user. I only removed your reply because it wouldn't have made any sense without the original.] — SCZenz 12:17, 8 August 2007 (UTC)

I know... I've been watching the debate... I was attempting to reason with him, even though the past history of this makes it seem unlikely... Gscshoyru 12:20, 8 August 2007 (UTC)

More irrlevancy was removed. --EMS | Talk 19:03, 8 August 2007 (UTC)

Edit by 72.64.63.58

The anon 72.64.63.58 added to the article:

The twin paradox is a disputed problem in Einstein's special theory of relativity, in which the solutions contradict the postulates of the theory. The dispute involves a claim by A. Einstein that the passage of time is slower for physical processes that occur in moving frames of reference. The dispute involves the extension of this claim to an example of biological life processes, so that a twin who returns from a high velocity space voyage discovers that he is younger than his brother. The dispute involves the meaning and measurement of time, the concept of biological age, and the interpretation of the special theory of relativity.

This is totally unacceptable. Items:

• The problem is not disputed in scientific circles
• The solution does not contradict the postulates of relativity.
• The slower passage of time for a moving clock is not a "claim".
• A moving clock is not in a "moving frame of reference". This statement reflects a fundamental misunderstanding of what a frame of reference is. A better wording would be that the passage of time for a clock which is found to be moving in a given frame of reference is slower than for a clock that is not moving in that same frame of reference. [Item: In the "moving" frame, the moving clock (if it is at rest in that frame of reference) will go faster than the "stationary" clock (which will be moving in this frame of reference). Do realize that in this context "moving" and "stationary" are just labels for the frames of reference.]

After the frame-of-reference business that rest of this posting fails due to its being based on what preceeded it.

I can't draft it right now, but IMO this does show the need for this article to have a good statement of the paradox. (The issue primarily is that the "stay-at-home" twin was moving for the "traveling" twin under the principle of relativity. Given that, the question is "Why was the stay-at-home twin the one that aged more?") --EMS | Talk 22:23, 14 August 2007 (UTC)

EMS, I aggree, that anons POV is very private. To me the dispute arises from a wrong usage of the principle of relativity. I will now study this article and see, if I can follow. To me it is out of question, that the earth twin passes more time. The open question is: is there a method to determine, which twin is the travelling one without a meeting on earth. That is: if two observers can determine their distance repeatedly, than they can determine the velocity of their relative movement. To make it simple: both are not accelerated. All influences of the measuring instrument (for example: runtime of signals) are known and compensated. Both assume the invariance of speed of light and express the measured relative velocity in fractions of speed of light. Then, they send this fractional value als a pulse code modulated light signal and can receive vice versa the result of the others measurement. These pulse codes can easily be compared and will show the same value. The pulse period can be different. Now they agree to use electromagnetic radiation, for example 300000 Hz. The question is: will both see the same frequency shift (doppler & time dilation) or not. If not, they can determine, who is travelling and who stayes at home. ErNa 11:35, 15 August 2007 (UTC)

Erna - I'm not sure what you are saying here. If it is that you don't believe that the Earth observer experiences more time, then you are rejecting relativity theory. That is not a good thing to do in the context of this article. --EMS | Talk 16:03, 15 August 2007 (UTC)

EMS: You misunderstood me. To me it is a fact: speed of light is alway measured to the same value, whatever you do. Therefore, speed of light is the basis of all measurements. It is a consequence, that time is no longer universal. Two objects can not be in one place. But they can be very close. They are at relative rest, when there distance doesnot change in measure and direction. Then there "timespeed" is equal. If one object is accelerated, this objects time "slows down". "peculiar", according to Einstein, not a paradox. But, a question arises: If they do not know their history, two objects seeing themselves in relative motion, can they decide, which one was accelerated by doing measurement? The twin article in the german wikipedia states, that say see the others time dilated. That is my problem, and other problem too. ErNa 17:14, 15 August 2007 (UTC)

You know that you have been accelerated because you will feel a force accelerating you. Another way of determining if it is you that has been accelerated in the absense of a physical acceleartion (such as if you do turnaround by passing close to a star) is to note that your perception of spacetime has changed. The change in perception is what makes things work in this case. Please look at this USENET posting of mine. It explains why the views of the twins are consistent even though each one is time dilated with respect to the other throughout the exercise. --EMS | Talk 17:39, 15 August 2007 (UTC)

You didn't see, what the core of the above situation is. You can not know, if you personally have been accelerated, that is, the atoms, you are made of. But you keep for true, that all atoms of your body are made of elementary particles with identical properties. I'll read your paper and you should try to understand the experiment, I sketched. ErNa 19:40, 15 August 2007 (UTC)

ok, I started reading your paper. "It is commonly assummed that the distance covered by the stay-at-home twin wrt the spaceship twin is therefore also the same in both the outbound and inbound legs of the trip. This is not the case." Something, that is commonly assumed, but not the case, is obviously not easy to understand. Therefore I repeat my question: is it true, that two objects, that are able to measure their distance as a function of time, and the distance increases with a certain, constant rate per time, will always measure the same velocity of their relative movement. And is it possible to extrapolate the place and time of their departure? Addentum: could we set up an experiment, where to objects come closer with constant speed 0.8c (dilation:0.6, easy to calculate), no gravitation, no external forces? (Other conditions to be determined)ErNa 20:31, 15 August 2007 (UTC)

I think that you are asking for something a bit impractical in asking for an an experiment with two clocks measuring each other at high relative speeds. However, there are a number of observations of the characteristics of particles moving at high speeds which represent time dilation at work. One is the detectin of muons from cosmic ray collisions in the upper atmosphere on the surface of the Earth. The at-rest half-life of a muon is so short that they should almost never get down the far while traveling at near lisghtspeed, but time dilation means that their half-life has not passed in their own proper time. (This can also be seen as a case of the Lorentx contraction from the viewpoint of the muon.) Slowdown of atomic vibrations are also seen in particle accelerators, along with other predicted SR effects.

BTW - The relative speeds of two objects given the same two events for both objects will always be agreed on. Velocity is a different matter since velocity is technically a vector, and the directions should be opposite in this case. (However, the word "velocity" is used in the context of "speed" in the translations of Einstein's articles.) --EMS | Talk 14:31, 16 August 2007 (UTC)

Again EMS you are merely seeking an edit war to gratify your ego. Your actions are inflamatory and betray your bad faith in previous statements you made. Please restore the statements you removed. Your reasons betray your bias and show your real purpose is to cause an edit war, promote useless argument, and provoke a confrontation, in order to prevent improvement of this article. Electrodynamicist 14:38, 15 August 2007 (UTC)

OK, EMS. Lets go on: Taken exactly, velocity doesnot matter. RT applies always. Just to detect results (differences), we have to have "relativistic" velocities. The twin experiment itself is "impractical", but that doesn't change anything. Let us have a surplus starwars laser gun. And an perfect mirror. And a single photon detector. Let us have, whatever we need! A laser, mounted perpendicular on a mirror is directed toward a distant mirror. The laser fires pulses at a fixed rate, say 1 s. The detector detects the reflected puls 1 sec delayed. Whenever he fires the next one, he sees the reflection of the last. This system can state: the distant mirror is in a fixed distance of half a light second, about 150000 km. Both systems will have the same result. This is equivalent to the statement: the systems are at absolute rest or moving at the same velocity. For there is no landmark to measure absolute velocity, there is no absolute velocity. They are allowed to say: we are in relative rest. I hope, you agree and there are no questions about the praticability. ErNa 15:23, 16 August 2007 (UTC)

That sounds like lunar laser ranging, and that has been going on since 1969 (when a proper mirror was placed on the moon by the Apollo 11 astronauts). Now there is not any "Earth ranging" going on from the Moon, but it is fully expected that if it was the results would be the same for the Earth-Moon distance at any time. Perhaps the simple answer to your query is that if you are going to the east at 100 mph in my rest frame of reference, then I am going to the west at 100 mph in your rest frame of reference.

BTW - What does this have to do with the article? We are more and more discussing the physics instead of how to improve the article. --EMS | Talk 17:21, 16 August 2007 (UTC)

Ok, and what has the article to do with the twin paradox? The introduction is sufficient, the rest gives reason for dispute. To me, before I read the article in the wikipedia, the paradox was, that twins can have different age. Or, as Einstein said: peculiar. Then I had to accept, that the paradox is different: both twin calculate and observe, that the others time is dilated. The reason is: RT is symmetrical. Only when the twins meet again, they can compare there intermediate lifetime and the stay at home twin grew older. Now I try to find a undisputed situation, that shows, that also during the journey both can decide, who's time is dilated, that is, who was accelerated. If it would be possible, to exchange information about the "actual speed of time", it would be possible to determine the acceleration without having it measured. ErNa 18:55, 16 August 2007 (UTC)

You seem to be slipping in original research here, and this not appropriate. However, I will repond but breifly. First of all, look more carefully at Twin_paradox#What_it_looks_like:_the_relativistic_Doppler_shift. Secondly, relativity theory (which is waht I assume you mean by "RT") is not symmetrical once acceleration comes into play. The symmetry is for inertial motion only. In RT, an acceleration changes your view of spacetime. As I noted in the USENET post, the in the view of the traveling twin, the stay-at-home twin is suddenly viewed as being much further back in time than he was before as a result of the traveling twin's acceleration. OTOH, the stay-at-home twin sees no such change in position of the traveling twin, just the spaceship turning around once the light from the turnaround event reached the stay-at-home twin. So the twins can agree who was accerated or not based on local observations at the time. --EMS | Talk 20:50, 16 August 2007 (UTC)

No, that is not OR. But "the stay-at-home twin is suddenly viewed as being much further back in time", that to me is witchcraft. There is no difference wether the twin return momentarily (like a delta-funktion) or with limited acceleration. So, there is no need for "sudden" changes at all. You, and not only you, say: something strange happens during turnaround. But that is paradox, for it means, that things happen suddenly, they are no longer continuously. And that is not physics. Pure logic: if you can change an inertial frame, then there are at least to different inertial frames. And from this: to objects. moving inertial with changing distance, will always measure the same relative velocity, but not necessarily the same distance. But you can not agree to that. And I think, it makes no sense to go on. ErNa 21:28, 16 August 2007 (UTC)

It's not witchcraft, but it may look like it. How are coordinate drawn in SR? How do they change under acceleration? A way of "seeing" this is to consider how the light from the other twin is changed by acceleration. One effect is that the parallactic distance to the stay-at-home twin is increased simply because the light beams from that twin become more convergent. So the stay-at-home twin comes to be viewed as being further away. Since c is the same in all inertial reference frames in SR, it follows that if the other twin is now seen as being further away he his also being seen as he was longer ago.

That said, do note that there has been no time travel. The coordinates of the viewed position of the other twin have changed, but not the position itself. It's not waht you expect. It's not consistent with the simpler rules laid down by Netwon. But relativity is what it is, and Newtonian physics it is not. --EMS | Talk 02:48, 17 August 2007 (UTC)

Edit shortcut

I know, there is no time travel in the sense of science fiction. But what does "travel" mean? Time is passed. The amount of time passed is measured by counting the ticks of a clock. That implies: there is an observer and there is a clock and a counter. Newtons physics are based on the preassumption, that time is universal, that is, two independent systems of observer, clock and counter count the same amount of ticks between two comperations of the counters, whatever they do in between. Experience (measuring velocity of light) showed this preassumption can not be true and lead to the SRT. From the invariance of speed of light follows, that time passes as a function of the velocity profile of the systems. Therefore, when comparing the counters -to do this, both systems have to be in one place at relative rest), they can have different values. That should be the basis of any conversation. If we do not agree on this, we should use the right words, without changing the sense. Only than it makes sense to go on and decide, if it is possible to compare the counters without being in on place or at relative rest. Otherwise, I better drill a hole in my knee and plant a flower! ErNa 11:09, 17 August 2007 (UTC)

Einstein specified a synchronization procedure for this: A light beam gets sent out by an inertial obsrver and (at?) time t1, gets reflected at some event and returns to the emitter at time t2. The observer who emitted the light and recieved the reflections can infer that the event of the reflection occurred as time (t1 + t2)/2 in his temporal coordinate system. That is how a clock gets extended in SR. --EMS | Talk 16:12, 17 August 2007 (UTC)

Ok. And the distance of the event was (at the time of the event) d1 = c * (t1 + t2)/2. Now, at t2 he emitts a next light pulse which is reflected (event 2) and received at time t3, t3-t2 = 2* (t2-t1). Event2 occurred at time (t2 + t3)/2 = 2*t2 - t1 at distance d2. What is the velocity of the reflecting object, seen by the inertial observer? ErNa 19:41, 17 August 2007 (UTC)

ErNa - you should be able to figure that out yourself. Besides, this has nothing to do with the article itself. --EMS | Talk 20:56, 17 August 2007 (UTC)

I'm able to do that, but You are also able to. I wanted to have Your "OK", but now, I don't know, if You agree with what I wrote. And I know, that You can't see for now, what this has to do with the article. But let's go on, and we well see. Maybe, I'm wrong. But even that I have to understand. ErNa 09:36, 18 August 2007 (UTC)

Ok, EMS, you don't answer. Therefore, I'll go on: In my first reaction, I used your text and defined a second event. And now, trying to figure the velocity of the obvious movement, I found: it alway makes sense to check, what is given. How could Einstein say: ..." event of the reflection occurred as time (t1 + t2)/2"? Shouldn't it be (t2-t1)/2? What do you mean? ErNa 16:48, 19 August 2007 (UTC)

(t2 - t1)/2 half of the *difference* between the times of the events. The reflection occurs at half of the difference after t1. So the reflelction occurs at time t1 + t2/2 - t1/2 = (t1+ t2)/2. I also would point out that if stuff like this confuses you then you are in poor shape to take on relativity theory. Kindly make your point and stop beating around the bushes. In case you have not noticed, I am losing my patience with this stuff. --EMS | Talk 23:27, 19 August 2007 (UTC)

Ok, I realy was confused! Shame on me! But why do You prefer to argue with people, that insist in their mistakes? ErNa 06:00, 20 August 2007 (UTC)