Talk:Twin paradox/Archive 3

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Previous discussions:

A Stray Objection

 * Some might object that, while the travelling twin experiences acceleration, so does the stay-at-home twin, both by ordinary motion and by being in a gravity field. Why one has the "better" acceleration which controls the direction of time dilataion is not apparent. Also, the journey can be arranged so that the stay-at-home twin experiences exactly the same accelerations as the traveller (by moving around on a stationary gravitating planet to exactly match the accelerations of the traveller whose rocket ship always accelerates at one planet gravity).

On the one hand, this seems to me to be a reasonable objection coming from someone trying to understand special relativity. On the other hand, it is all on its lonesome, not properly integrated with the rest of the article, and it disrupts the textual flow. I will therefore remove it, but am including it here, in case someone wants to integrate it properly later on.--Susurrus 01:47, 16 May 2006 (UTC)

Twins paradox Minkowski diagram
I don't understand why the lines in the Minkowski diagram are coloured the way that they are. The terrestrial observer is supposed to be moving upwards along the y axis, yet the lines are blue on the bottom and red on the top. When the lines are on the bottom, this is when the stellar observer is moving away from the terrestrial observer. Shouldn't this mean that the lines would be red-shifted, hence red, not blue? Conversely, when the lines are on the top, this is when the stellar observer is moving towards the terrestrial observer, and the lines should therefore be blue-shifted, hence blue, not red. After all, this is the way that the lines are coloured in the two diagrams below it. --Susurrus 03:21, 16 May 2006 (UTC)


 * I don't think the colors were meant to have meaning, just to be distinguishable. —wwoods 06:43, 16 May 2006 (UTC)

Article far from perfect
I believe this article contains many errors, especially the view that time dilation is somehow a result of asymmetry due to one twins acceleration or change of inertial frame of the travelling twin. Since time dilation, according to SR, happens whether or not there is any acceleration or change of reference frames, it seems to me that both are irrevelent. And it is easy to rearrange the experiment, so that time dilation is still measured according to SR, without any acceleration. It is also possible to rearrange it so that the twin who accelerates and changes reference frames is the one that is older according to both twins (see below).

I don't think Einstein ever thought this was a real paradox, just a funny pretend paradox. The experience of the twins is asymmetrical in a very important way that has nothing to do with acceleration or changing reference frames: The twin on earth is using two reference points that are assumed to be at rest relative to him (the earth and the other star system) to measure the distance travelled and to start and stop his stopwatch. The twin on the space ship is using these same reference points for the same purposes, but they are both in motion relative to him. This causes the distance travelled to be shorter, and the time taken to be shorter, from the point of view of the space ship. Both twins would agree the twin on the spaceship was younger, because of this asymmetry.

If, for example, the travelling twin were to tow another ship behind him on a steel rod with a fixed length of 4.45 light years (which would be observed to be 2.23 light years by the twin on earth), and both twins were to use the towed ship passing earth to determine the turnaround point, both twins would agree that more time passed for the travelling twin. Again, this would be because the twin on earth used reference points that were in relative motion to him, and not because of acceleration. Again, this points out how important the reference points are. One could almost say that whichever twin is at rest relative to the chosen reference points (starting point and turnaround point) could be considered the "prefered frame", and anyone in motion relative to the chosen reference points will experience time dilation, regardless of which twin accelerated.


 * This is a version of the Pole & Barn Problem. The trick is that the moving twin and the stationary twin don't agree on where the travelling twin is at the time the end of the rod passes the stationary twin. —wwoods 05:27, 22 May 2006 (UTC)


 * This is a very good point, and illustrates how my version (not really mine, I read it somewhere) is analagous to the more common version of the Twins Paradox. In the common version, the twins would disagree about how far from earth the spaceship was when it turned around. This is normally overlooked because the problem stipulates the turnaround point as being a certain distance from earth as measured from earth. But this distance would be shorter as observed by the twin on the space ship. This is why in my version, I stipulated the length of the rod as measured by the twin on the space ship. And it would be shorter as observed by the twin on earth. And although the twins will disagree about how long the rod is, and how far away they are when the end of the rod passes earth, if they are both familiar with SR, the twin on the space ship can figure out when to turn around, ie, when the earth bound twin will see the end of the rod reach him, even though they will also disagree about when this event occurs. This is analagous to the fact that in the common version, the twins disagree about when the ship turns around as well as how far apart they are at the time.Alan Hill 20:57, 22 May 2006 (UTC).

There is no reason to consider acceleration, since it doesn't change anything. And we certainly don't need GR to explain it. Although I can see why some would prefer GR, I would think most people would prefer a simple SR solution that clearly points out the asymmetry of the situation.

I edited the article to include my view as an alternate, but I did not delete anything else, even things I think are huge errors, mainly because my writing skills are not good enough to rewrite the entire article, and I am sure someone would change it back if I did. And because I believe it is important to have opposing points of view.

I would appreciate any comments or corrections, Alan


 * Alan I removed your suggestion from the article and put it here. See below for reason and comments. --Pjacobi 00:07, 22 May 2006 (UTC)

Alan's Alternate Resolution with non-accelerating twins
Consider an alternate example: A space ship plans to go to the nearest star system a distance $$d = 4.45$$ light years away, at speed $$v = 0.866 c$$ (i.e. 86.6% of the speed of light). Assume that this star system is at rest relative to earth. This space ship first travels in the opposite direction from this star system, then turns around and passes earth at speed $$v = 0.866 c$$ and both twins record the time of this pass. A space station has already been set up at this destination that will record the time of arrival of the space ship, and relay a message from the travelling twin to earth containing all of his measurements. There will be no acceleration of the space ship between earth and the nearest star system. The one way trip will take $$t = d/v = 5.14$$ years in Earth time. Those on earth expect the travelling twin to be 0.5&times;5.14 = 2.57 years older when he reaches the space station than he was when he passed earth.

The ship's crew calculate how long the trip will take them. They realize that the distant star system and the earth are moving relative to the ship at speed $$v$$ during the trip. Therefore, the distance between the earth and the star system will be shortened (by the length contraction) to $$ \epsilon d = 0.5d$$ = 2.23 light years. The journey takes $$ 2.23/v$$ = 2.57 years. The twin on the space ship aged 2.57 years, just as those on Earth expected. This information, along with the time of arrival as measured by the space station is relayed back to earth by the space station. Of course there will be a delay in this transmission of 4.45 years. This will not matter as long as both twins do their calculations correctly.

Notice that this example is almost identical to the first example given above. The main difference is that neither twin accelerates or changes reference frames between the time that the spaceship passes earth and the time it passes the space station. Yet the effect of time dilation is exactly the same. And there is no reason for the twins to reunite, since all of the measurements taken on the space ship is relayed to earth in a message. Obviously, in this example the difference in the amount of time that passed for each twin cannot be due to acceleration or either twin changing reference frames, yet this example is still not symmetrical.

Notice that both twins use earth and the space station as reference point for the distance travelled, and that this space station is in the same inertial frame as the earth. The twin on earth is using reference points in his own reference frame to measure the distance traveled and mark the start and stop times. The twin on the space ship is also using the same reference points, but they are in relative motion to him. The fact that these reference points (earth and the space station) are at rest relative to one twin and in motion relative to the other is the reason for the asymmetry. The twin on the space ship will measure the distance travelled to be shorter, and the time it took to be shorter than that measured by the twin on earth.

Also notice there is no reason to use General Relativity, since Special Relativity can account for the asymmetry of the twin paradox, while ignoring any acceleration or change of reference frames, and show that there is no paradox at all.


 * Alan, the problem here is that we cannot ignore acceleration. SR only works insofar as the matter under consideration has uniform motion (i.e. constant zero or non-zero speed, without any changing direction).  SR is called 'special' for a reason: it is a restrictive case of physical law and when unraveling the physical nature of the universe, we can only apply special restrictions when certain conditions apply.  Since the twin in the spaceship must change his/her speed to move away from the twin on Earth, and then slow down, and then turn around, and then change his/her speed to move back toward the twin on Earth, the spaceship twin is accelerating multiple times (change of speed and change in direction).  SR therefore does not, and can not, solely apply to this thought experiment.  This article accurately reflects this fact therefore.  I know this may not be a satisfying answer, but when we apply the laws of physics we must do so correctly.  If you would like to discuss these ideas further, send me an email at shale_d2010 @yahoo .com.  Let's reserve this talk page for article improvements. Cheers, Astrobayes 17:09, 21 August 2006 (UTC)

Comment
Pjacobi 00:12, 22 May 2006 (UTC)
 * I agree that the article is not perfect, the distance to perfection is debatable. But the least it needs is another way to resolve the paradox. One or two arguments are enough for an article.
 * I know the temptation to try to find the most perfect and convincing argument ever&trade; -- but please have in mind our central policy of no original research. We have to stay with arguments, which are already published by reputable sources. If you think, your argument is much better than anything which is already published, try to get it published (but not in Wikipedia)!


 * Hi Alan,
 * - What we think doesn't matter for for Wikipedia; instead, opinions of reputable sources matter
 * - The article isn't about one-way time dilation; it's about the Twin paradox
 * - The article already states that the asymmetry isn't directly caused by acceleration
 * - I think that a known variant without accelerating frame is worth mentioning, but it doesn't need so much elaboration; just a few phrases will do
 * - The article already describes that it wasn't much of a paradox in SRT, and that the SRT calculation never was a problem
 * - The article paradox explains the meaning of "paradox", and that article is already linked (third word of this article)
 * - Nevertheless the article certainly needs more improvements, see also higher up on this page (archives).
 * Harald88 00:35, 22 May 2006 (UTC)

Response to Comments
Well, first of all, thanks for all the comments. I'm surprised that this explanation could be construed as "original research". I certainly cannot take credit for that! I can't recall where I read this particular example, but the explanation I offered is based on Einstein's 1905 paper. The reason I called this an alternate view is because of the alternate (correct) source of the asymmetry. The current article repeatedly refers to acceleration and/or changing reference frames as the reason for the asymmetry. And I know lots of other sources do, too. But there are plenty of sources that don't. Clearly the asymmetry which causes the differential aging of the twins is still there even if you remove the acceleration fron the experiment all together. SR predicts that in a situation like the Twins Paradox, differential aging would occur whether or nor acceleration was involved. This is not original research, this is in Einstein's 1905 paper. Time dilation and length contraction happen because of relative motion, regardless of acceleration. Of course the article doesn't say that acceleration causes these effects, but it says that acceleration is relevent to why the situation is asymmetric, which is clearly not the case, as shown in my example.

I will try to make all of this shorter and more to the point and post it here later (not in the actual article). I'm sure most people will not read everything I wrote because it it just too long winded.


 * [To add you signature and a timestamp to your posts, type ~ . It helps to make it clear who's saying what.]


 * Without changing rest frames, there is no asymmetry. There'd just be two observers in relative motion, who each see the other's clocks running slow. The travelling twin doesn't actually have to come home, so acceleration isn't required. The spaceship can coast past Earth and then past a homebound ship which resets its clocks to match. —wwoods 09:24, 22 May 2006 (UTC)


 * I would have to disagree a little with that. It is easy to have asymmetry without changing rest frames, which I showed above. And it is easy to set up an example where no one accelerates and there is no change of rest frames, and one twin will age less according to SR. That was my entire point. Alan Hill 20:56, 22 May 2006 (UTC).


 * If you use a single frame as Einstein did in 1905, then the Twin that moves around ages more. Is that your point? That was understood from the start and isn't really the Twin paradox; but it doesn't harm to stress that simple fact. IMO, one sentence suffices.
 * OTOH, I don't recall a Twin paradox example "where no one accelerates and there is no change of rest frames, and one twin will age less according to SR" - remember that for it to be categorized as "Twin paradox", they must meet again at the same point. Harald88 21:35, 22 May 2006 (UTC)


 * No, my point was that it is not relevent which twin accelerates. The twin who views the distance travelled as "length contracted" will end up aging less, as seen in my example below, where the accelerating twin ages more.Alan Hill 23:22, 22 May 2006 (UTC).


 * OK, how about this example: We will specify the distance travelled in the frame of the twin on the space ship. The ship is towing a buoy behind on a rigid steel rod which is 10 light years long measured at rest. The ship leaves earth at 0.866c and will turn around when the twin on earth sees the buoy reach earth. He will, of course, have to be familiar with SR to figure out when to turn around. The rod will be 5 light years long as seen by the twin on earth. From the twin on the ship's point of view, he will turn around after 11.5 years, total round trip time is 23 years. From the twin on earth's point of view, he will see the buoy arrive after 5.75 years, total time passed for him when ship returns is 11.5 years.Alan Hill 23:17, 22 May 2006 (UTC).


 * Why do you think the traveler would need to be familiar with SR? He sees the Earth pass him at 0.866 lt-yr/yr and he wants to turn around when the Earth is 10 lt-yr behind him. Galileo could have told him to wait 10/0.866 yr. But while the stay-at-home sees the buoy pass him after 5.75 yr, in his rest frame the traveler doesn't turn over until after 23.1 yr. —wwoods 08:44, 24 May 2006 (UTC)


 * OK, maybe he doesn't need to be familiar with SR, he just needs to be smarter than a rock. No argument here. But I don't quite understand the last part of your last sentence. Alan Hill 10:22, 24 May 2006 (UTC).
 * See below. —wwoods 19:45, 24 May 2006 (UTC)


 * That's elaborate. I'll look at it more closely later when I have time. I just didn't understand what "traveler doesn't turn over" meant, and what "his rest frame" refered to in the last sentence. Alan Hill 00:48, 25 May 2006 (UTC).


 * I notice here, just like in the more common version, the twins will disagree about when the ship turned around, and how far apart they were at the time. And the turnaround point was specified as a certain distance as measured in the frame of the twin on the ship. Also notice that, the twin on earth is actually present at the turnaround point in this example, instead of the other way around. It looks to me like this example has the opposite result, even though I haven't changed which twin accelerated. But I switched around the real source of the asymmetry.Alan Hill 23:17, 22 May 2006 (UTC).


 * The Twin or Clock paradox is about two clocks very near to each other at rest in an inertial frame, whereby one moves away and returns. That's not what you present here. To remove confusion: which article do you refer to? Harald88 20:17, 23 May 2006 (UTC)


 * My example above is specifically designed to be different then the Twins Paradox, in that the accelerated twin in my example ages more than the unaccelerated twin. I just wanted to illustrate that the fact that, in my example, the twin who accelerates is the twin who ages more is a coincidence. And analogously, in the Twins Paradox, the fact that the twin who ages less is the one who accelerated is also a coincidence. Yet the article (Wiki on Twins Paradox) claims that it is important which twin accelerated. This article stresses that the acceleration of one twin is the reason for the asymmetry that causes the differential aging of the twins. Obviously, the fact that the distance between the earth and the ship is specified in one frame, and "length contracted" only in the other frame is the real source of the asymmetry, which results in differential aging of the twins. Alan Hill 23:40, 23 May 2006 (UTC).


 * I meant: material from which source do you use here? And only the Twin paraodox should be discussed in the article Twin paradox, it's already long enough as it is and not yet fully finished.
 * BTW, I've never read the claim that definitions by people can cause a clock to lag behind on another clock at the same point in space. Harald88 20:13, 24 May 2006 (UTC)


 * I agree that I should not have edited the actual Twin Paradox Article. I did not read the entire Wikipedia policy. I only read the part that said to not be afraid to edit, be bold, and not worry about it, because you can't hurt anything. And I agree that already published source material should be used in the article. Of course there is plenty of source material resolving the Twins Paradox, while referring to the acceleration of the ship's twin as only incidental, for example the Scientific American article at http://sciam.com/print_version.cfm?articleID=000BA7D8-2FB2-1E6D-A98A809EC5880105. And I only used a different thought experiment as an example, for the purpose of illustrating an aspect of asymmetry of the Twins Paradox that is not mentioned in the article. And referring to your second statement, I have never heard such a claim either. Alan Hill 09:52, 28 May 2006 (UTC).


 * I quote: "The asymmetry in the paradox is that the traveler leaves the earth’s reference frame and comes back, whereas the homebody never leaves the earth." It is physically impossible to "change reference frame" in the sense meant here without changing speed. Thus that article doesn't seem to add anything to this article. And we already emphasize that it's the change of speed that matters (but not the relative speed between the twins!), and that acceleration forces has nothing to do with it directly:
 * "It is to be noted, however, that time dilatation has no relationship whatsoever to the amount, direction, or duration of acceleration. Even the time dilatation of particles in the Fermilab ring is determined only by their speed, in spite of the huge accelerations they undergo."
 * It appears that you suggest to improve that clarification. Harald88 10:25, 28 May 2006 (UTC)


 * Also, if we were to assume, just for the sake of argument, that in the Twins Paradox, the ship did not change reference frames, and the earth (along with the distant star system) changed reference frames instead, the earth would speed away from the ship until the distant star system reached the ship, then the earth (and the distant star system) would change direction and earth would return to the ship. The twin on the ship would still age less. Yes, do the math, if the earth is assumed to change reference frames instead of the ship, the twin on the ship would still age less, as long as all the other assumptions are the same. ie, the distance between the earth and the distant star system is specified in earth's frame, and the turnaround point is when the ship and the star system meet. Alan Hill 00:04, 24 May 2006 (UTC).


 * You're confusing 'reference frame' with 'rest frame'. There are a zillion frames of reference, but rest frames are convenient because by definition somebody's velocity and spatial position is zero, and drops out of the calculations. There is a frame of reference in which the Earth (well you know what I mean, the Solar System) is at rest throughout this adventure. There is no such frame for the ship if it goes out and comes back. That's the asymmetry. A change of rest frame == a change of velocity, which for a physical object implies an acceleration. —wwoods 08:44, 24 May 2006 (UTC)


 * OK, I'll put it another way. Let's say then that I falsly assume that the ship stays at rest, because I wrongly disregard acceleration, and I falsly assume that the earth (along with the distant star system) accelerated, turned around, and decelerated so the earth returned to the ship. I still have the ship's twin aging less. I only make these false assumptions to show that you do not need to consider which twin turned around or accelerated to conclude that the ship's twin aged less. Alan Hill 09:57, 24 May 2006 (UTC).


 * Please note that just because I make false assumptions to illustrate a point, that does not mean that I don't know my assumptions are wrong. I just say this to try to ward off comments claiming that I am wrong about my assumptions. Alan Hill 10:10, 24 May 2006 (UTC).


 * Explanation moved so as not to interrupt flow of discussion. I'm handicapped by the lack of a blackboard, but here goes:
 * The Earth's rest frame has coordinates x and t. The ship's rest frame has coordinates x' and t'. Here's a diagram of space-time as seem in the latter frame. The former is harder with ASCII art, but you can draw it yourself, using the Lorentz transform:
 * x = &gamma;( x' + &beta;t')
 * t = &gamma;(&beta;x' +  t')

_                     .   |\ t       ^ t'. O: ( 0, 0  ) &rarr; (  0 ,  0  ) \       |            .   A: (-10, 0  ) &rarr; (-20  ,-17.3) D---F. B: (-10, 8.7) &rarr; ( -5,  0  ) \.    |            .   C: (-10,10  ) &rarr; ( -2.7,  2.7) C \. |           .   D: (-10,11.5) &rarr; (  0 ,  5.8) \ . |            .   E: (  0, 2.9) &rarr; (  5 ,  5.8) B  \  .|. F: ( 0,11.5) &rarr; ( 20 , 23.1) . \  E. . \ |           .            .\|            .    --A---O > x'. .         .                  .        .                   _| x.


 * OD is the worldline of Earth, and the t axis.
 * OEF is the worldline of the ship, and the t' axis.
 * ABCD is the worldline of the buoy.
 * OC is the lightcone of O.
 * AO is the position of the buoy--ship
 * at the time the ship passes Earth, in the rest frame of the ship.
 * BO is the position of the buoy--ship
 * at the time the ship passes Earth, in the rest frame of the Earth.
 * DF is the position of the buoy--ship
 * at the time the buoy passes Earth, in the rest frame of the ship.
 * DE is the position of the buoy--ship
 * at the time the buoy passes Earth, in the rest frame of the Earth.


 * —wwoods 19:45, 24 May 2006 (UTC)

impossible
quote from the article: "The ship's crew calculate how long the trip will take them. They realize that the distant star system and the earth are moving relative to the ship at speed v during the trip. Therefore, the distance between the earth and the star system will be shortened (by the length contraction) to εd = 0.5d = 2.23 light years, for both the outward and return journeys. Each half of the journey takes 2.23 / v = 2.57 years, and the round trip takes 2×2.57 = 5.14 years. The crew arrives home having aged 5.14 years, just as those on Earth expected." Light takes 8.90 years for a round trip, they would be exceeding light speed! The contraction is only perceived by the crew because their clocks are running slower. -phyti jun 6 2006


 * If I understand well, it sounds as if the crew shortens the distance by going faster, while that is of course impossible. Is that what you mean? Harald88 06:26, 8 June 2006 (UTC)
 * I now corrected that. Harald88 21:55, 9 June 2006 (UTC)


 * Eh? But it's true; the universe of the traveler is squashed. The stay-at-home says the traveler thinks the time is only 2.6 years because his clock's running slow. The traveler says the stay-at-home thinks the distance is 4.5 ltyr because his ruler is contracted.
 * —wwoods 07:50, 10 June 2006 (UTC)


 * That's what the traveller will measure. Few people would think that they can actually shrink the universe by changing their own state of motion, but phyti appears to have understood it that way! It's of course impossible for the traveller to induce by his change of motion a contraction of the ruler of the stay-at-home. Harald88 08:29, 10 June 2006 (UTC)


 * Few would, but some do! It is strange: distance at rest is the rest distance. When you reach speed of light (what is impossible, for good reasons), the distances shrink to zero, you are everywhere in the same, ever lasting moment and you will meet all people. So, at speed of light, the remaining rest of the distance is zero. At least in direction of movement. To avoid collisions: keep your lane alone!ErNa 17:54, 10 June 2006 (UTC)


 * [[Image:Lorentz transform of world line.gif|left]] E pur se mouve. The contraction is due to the relative motion of the two observers. If the traveller has caused that relative motion by accelerating away from the stay-at-home, then he's caused the effect. —wwoods 01:15, 11 June 2006 (UTC)


 * He can cause an effect for himself of course, there is nothing "impossible" about that. Anyway, IMO the current phrasing avoids phyti's objection. Harald88 10:39, 11 June 2006 (UTC)

my mistake but
if a force is applied to a rod 10 light yrs. long, it would require 10 yrs @ c to propagate to the other end before the whole thing could be in motion. You have to add 40 yrs for two accelerations and two decelerations. Phyti 05:09, 9 June 2006 (UTC)


 * In fact we should do little more than represent what the literature provides. From which publication was that example taken? Harald88 21:57, 9 June 2006 (UTC)

the rod
from Alan's previous example, but I don't think it really matters because there is so much confusion about this subject from the reader's point of view.Phyti 00:12, 10 June 2006 (UTC)


 * Please express yourself more clearly. Harald88 07:17, 10 June 2006 (UTC)

for clarity
From a previous post by 'Alan Hill may 22 2006' who proposed a rod 10 light yrs long attached to his space ship. He did not consider the physics of the trip. The acceleration forces are not instantaneous, but would require 10 years to transmit to the other end of the rod (inertia). With two accelerations and two decelerations, he has to add 40 yrs to the trip(earth time). The second point from (Alan's Alternate Resolution with non-accelerating twins) a quote: "The ship's crew calculate how long the trip will take them. They realize that the distant star system and the earth are moving relative to the ship at speed v during the trip. Therefore, the distance between the earth and the star system will be shortened (by the length contraction) to εd = 0.5d = 2.23 light years, for both the outward and return journeys. Each half of the journey takes 2.23 / v = 2.57 years, and the round trip takes 2×2.57 = 5.14 years. The crew arrives home having aged 5.14 years, just as those on Earth expected." The amount of energy used to accelerate the ship if applied to the earth would obviously not produce an equivalent result in the opposite direction even by classical standards of momentum conservation, therefore the ship's speed has changed and not the speed of the earth. We can always have the ship make an orbit to start at the earth with a uniform speed and stay within SR. One thing left out of all the discussions is, the time dilation is not the result of the relative speed of the ship to the earth, it's the relative speed of the ship to light. The ship contracts according to the Lorentz theory, which the earth twin observes. The twin on the ship is subject to time dilation because of his speed, but he is not aware of this because his brain and all the elements of his body and every particle on the ship that depends on internal light signals is effected the same way. It's the same state as the contracted length of the ship, his ruler contracts also therefore he can't detect any change. Obviously his motion is not going to change the size of the universe, but the effect of the time dilation makes his unit of time longer than on the earth. He arrives at locations with a known distance earlier than expected (by his clock). His conclusion, things are shrinking in his direction of motion. This is the difference between actual and perceived contraction. The reference "by length contraction" in the above quote usually will refer to the Lorentz factor but as shown is time dilation. There are two different principles at work. Hopefully this is clear enough. Phyti 01:41, 11 June 2006 (UTC)

Edits by 87.217.89.114
, aka the Jazztel triple play services anon from Spain, made some changes which made a rather bad article worse: ---CH 23:32, 13 June 2006 (UTC)
 * 1) "(In GR the word gravitational is used frecuently to speak about fictitious forces)" This is very misleading.
 * 2) "With this effect in mind we can explain the point of view of the travelling twing. When he starts accelerating towards his brother he will see a fictious field, and the whole universe will be free-falling in this field, including the brother at home." This is nonsense.

Would somebody like to justify this statement from the page, " the laws of physics are invariant from one frame to another, whether the frames are accelerating or not" Martin Hogbin 21:59, 5 July 2006 (UTC)


 * I find that sentence rather obscure. Perhaps the author tried to say that in GRT the laws of nature are valid for inertial frames and accelerating frames alike? Harald88 18:18, 6 July 2006 (UTC)


 * It's not just obscure, it's plain wrong. When we physicists speak of 'fictitious forces' we speak of mathematical terms in the expression of total forces on a system (derived from that system's Hamiltonian) that has units of force but which does not derive strictly from interactions with any of the four primary fields (electromagnetic, weak nuclear, strong nuclear, or gravity).  A perfect case is centrifugal 'force' which is a 'fictitious force' because it is an apparent affect stemming from the tendency of objects in uniform motion to remain in uniform motion, and it occurs as an expression dependent upon angular momentum ( F = mass*$$\omega$$ x($$\omega$$ x r).  It has units of force but it is inertial, and not dependent upon any of the four fundamental fields.  I use this example to illustrate that nothing about a gravitational field is 'fictitious' because it is derived from a fundamental field, unlike the centrifugal 'force' from from my example here.  And the invariance of physical law statement is misleading because gravitational fields are fundamental fields.  This individual, however well-meaning, basically doesn't understand the principles s/he is discussing and this material is rightly removed from the article. Astrobayes 17:34, 21 August 2006 (UTC)

Good faith agreement
I have to agree with the article when it states that "this occurs because of faulty assumptions". Obviously there has to be a faulty assumption somewhere. Unfortunately the faulty assumption has not been correctly identified. It is in fact
 * 2AB/(t'A-tA) = c,

significant because in relativity, light travels from A to A in time t'A-tA, which is of course a faulty assumption. That it is indeed an assumption is stated in the English translation of Einstein's paper, "Zur Elektrodynamik bewegter Körper", where the translation reads : "In agreement with experience we further assume the quantity 2AB/(t'A-tA) = c, to be a universal constant--the velocity of light in empty space. Certainly no mathematician would identify himself with a reversal of direction and call that "velocity", not even a schoolboy. (First posted to http://groups.google.co.uk/group/sci.physics.relativity/msg/4674b29449f08fb0?hl=en Wed, Mar 17 1999 9:00 am when Schaefer, a major wikipedia editor and proponent of Einstein's relativity, was a USEnet correspondent and should have been aware of it.) Der alte Hexenmeister 21:39, 11 July 2006 (UTC)


 * I'm afraid that your own WP:OR isn't a valid source for information in Wikipedia. Harald88 22:11, 11 July 2006 (UTC)


 * Velocity is a vector expressing the speed of a mass, as well as its direction. To reverse a direction is an acceleration because the velocity is changing, and this is a simple physics 101 statement.  The pejorative "schoolboy" comment above is unfortunate because any "schoolboy" (or girl) of physics learns within the first week or two that a change in direction is an acceleration, so your comment is out of place. This entire concept of acceleration coming from a speed or direction change is what allows us to exploit angular momentum to stabilize satellites.  I would be interested to see any physics textbook you can cite that does not call a change of direction of a moving object an acceleration.  You can bet such a text isn't used in any university physics course. Astrobayes 17:43, 21 August 2006 (UTC)

Conflicting and/or ambiguous information
From the article:
 * 1) The twin paradox, sometimes called the "clock paradox", stems from Paul Langevin's 1911 thought experiment.
 * 2) In 1911, Langevin discussed the evolution of the concepts of space and time in physics and presented the principal aspects of special relativity.
 * 3) The usual resolution of the paradox as presented in physics text books ignores its origin (it only surfaced with general relativity, see above)


 * General relativity was not written in 1911, how could Paul Langevin's paradox have surfaced with general relativity?

Der alte Hexenmeister 22:04, 11 July 2006 (UTC)


 * As explained in the article, it wasn't regarded paradoxical in 1911 when Langevin discussed the example of differently aging people. And as the article also points out, neither was it considered paradoxical when Einstein presented the basic calculation with clocks in 1905. Perhaps another clarifying sentence is needed in the article to spell it out? Harald88 22:17, 11 July 2006 (UTC)

A paradox is a paradox, whether it was written in 1911 or last week. It is clear Paul Langevin considered it a paradox, or he would not have written it.

I'm not discussing the merits (or lack of) relativity here, I'm discussing point of view, in particular, the parodox of the twin paradox being a paradox in 1911 when it wasn't a paradox until after GR was written.


 * General relativity was not written in 1911, how could Paul Langevin's paradox have surfaced with general relativity?

Der alte Hexenmeister 08:14, 12 July 2006 (UTC)\


 * I can only advice you to read the article. Harald88 22:16, 12 July 2006 (UTC)

____

The separation distance
The distant star group is an irrelevance which only serves to encourage the illusion that the Space distance between Earth and the ship is somehow connected with Earth and the star group and is therefore moving relative to the ship such that this distance is subject to length contraction from the point of view of the ship. In the simplest from of the twins paradox the star group need not and should not exist. Only Earth and the ship need exist. A measure of the separation distance can be undertaken by a radar pulse reflected from the other object where the transit time at the speed of light then converts to the separation distance for each party. As the speed of light is equal for either party ( according to SR) then both parties will measure the separation distance to be the same. Instead the article states that the separation distance is considered by the ship to be one half of that considered by Earth.

R F Norgan 1pm GMT 21 AUGUST 2006


 * Yes, in the article the 'separation distance' d is defined as the distance according to the Earth frame between the event of departure of the ship and the event of its turnarond. In order for this distance to be comparable with the distance as measured by the ship, an object (the distant star group) is introduced that is present at the turnaround event and that keeps the same distance to the Earth. The reason for this is that when the ship wants to measure the distance to the Earth at the return event (for instance by means of radar), it must do so by considering two events: at some point(s) of the outbound trip, it had to send a signal back to Earth and a signal to the "Earth-place" of the ship's return event, such that the two reflection events are ship-simultaneous, and therefore not Earth-simultaneous. So in order to keep the predefined distance d, this must be a constant proper distance according to Earth, which can be used to define the object. This ensures that we can use the Lorentz transformation equation $$\Delta x = \gamma (\Delta x' + v \Delta t')\,$$ where $$\Delta t' = 0\,$$ (and of course $$\Delta x = d\,$$), resulting in $$\Delta x' = \Delta x / \gamma\,$$
 * DVdm 13:47, 21 August 2006 (UTC)


 * I dont quite understand what you are getting at here. The maximum distance to reversal can be determined by both parties by continuous distance measurement and then taking the maximum amount. Any difficulties in making this measurement should never be allowed to compromise the whole experiment by determining that the separation distance should be seen as different from Earth as from the ship.With only two neccessary parties, Earth and the ship, observations are reciprocal and equal.Assuming simulateity of measurement both parties will measure the separation distance to be the same. By taking only the maximum distance measurement I believe that this overcomes the simultaneity problem.But if a simultaneity problem remains then so be it.
 * R F Norgan 2.30pm, 21 August 2006


 * You objected to the concept of the "distant star system", so I explained how you can rationalize its relevance. AFAIK in the original twin paradox a ship travels from Earth to some "place" and then returns. The "separation distance" is given - or can be calculated by multiplying the given ship's speed with the given Earth-time of the half trip. This given distance then defines an object that can, in the most natural and straightforward way, be used as a radar target by the ship to measure its distance. Likewise the Earth can be used. With the results of these measurements the ship can calculate how it perceives the distance covered during the trip, and, with the known result, meaningfully compare it with what the Earth has found.
 * DVdm 14:48, 21 August 2006 (UTC)


 * Again I do not understand your logic. You are saying that it is preferable to determine a distance by timing a matter object over that distance at a 'known' velocity rather than employing a light pulse at a velocity which is always known as a Universal constant. Whatever is your point.
 * R F Norgan 4pm GMT 21 August 2006


 * Of course I am not saying "that it is preferable to determine a distance by timing a matter object over that distance at a 'known' velocity". I have no idea where you get the idea that I would say that. And indeed, you don't seem to understand the logic. I am trying to help you understand why your initial claim that "the distant star group is an irrelevance", is wrong. In the numeric example of the article the initial definition of the trip and the introduction of the variable d together fix an object (at rest w.r.t. the Earth) that can be used by the ship to measure something (namely the half trip distance according to the ship) and find that it is half of d.
 * DVdm 16:51, 21 August 2006 (UTC)


 * As the separation distance can be measured by a light ray there is no need for a third object. For one thing the Twins Paradox describes only two objects. In my opinion you are introducing a third object so as to create a privileged frame where none exists. A privileged frame destroys the whole TP experiment.
 * R F Norgan 8pm GMT 21August 2006


 * The object is at rest in the Earth's rest frame, which is defined in the setup of the TP, so this does not introduce another frame, and certainly no "priviliged frame". So your opinion about what I am doing is wrong. I am trying to help you understand the situation of the numeric example in the article.
 * DVdm 20:20, 21 August 2006 (UTC)


 * I have no objection to you introducing an unneccesary third object so long as you do not employ it to justify a privileged frame. But the main point is this. It is not neccessary to know the degree of time dilation which requires knowledge of the distance. it is only neccessary that the ship knows that it has travelled further in between the two meetings with Earth than has Earth. From the point of view of the ship it is he who thinks that Earth has made the greater journey and consequently suffered time dilation. The final reading shows the opposite. The paradox is therefore of sign and not of degree.
 * R F Norgan 9am GMT 22 August 2006


 * I do not introduce "an unneccessary new object" and indeed, as I just said, I do not justify a privileged frame. I carefully explained the function of the object. Too bad if you still don't get it. If you haven't understood it by now, then I don't think I can help. I have no idea what you mean with your "main point". I suggest you have a look at the page I recommended and carefully express your main point in terms of the events that are used. If you are not capable or prepared to do that, I'm afraid I have to cut it short here.
 * DVdm 09:21, 22 August 2006 (UTC)

The impossibility of an sr explanation of the twins paradox
From the point of view of the non-reversing clock A there is no paradox in what he predicts of the time keeping of clock B and what he observes at the return of clock B to A. The paradox lies entirely with what clock B predicts of A and what he observes at reunion. According to the equal and reciprocal predictions of two clocks both A and B predict the same time dilation in the other clock both when receding and approaching at the same velocity. Therefore B predicts that A will be slow by dV/c^2 at reunion where-as he actually finds A FAST by that amount. For there to be no paradox the difference of 2dV/c^2 must arise in the time keeping of clock B at some point. Where can that point be. I suggest that it can only be at the reversal point. In fact exactly that effect does occur at that point in the observation of clock A by clock B. It is a resynchronisation effect due to the change in relative velocity. So is that the solution to the paradox. Unfortunately not as this synchronisation effect is a function of separation distance which starts and finishes at zero. So over the whole experiment this effect has zero effect. If no source can be found to give rise to a correction factor of +2dV/c^2 then the paradox remains. I do not believe that that source will be found and hence SR does not predict the observation in this experiment and a new theory must be found that does. R F Norgan 3pm 21 August 2006


 * Perhaps it might be a good idea for you to first have a look at the paradox in term of events. It is well known that many errors are made when people try to apply the concepts of time dilation and length contraction in order to understand what's going on. I don't know whether this is appropriate, but you can have a look at, for instance Twins, Events and Transformations.
 * DVdm 15:01, 21 August 2006 (UTC)


 * Your suggestion might be a good one if there was a need. That need only arises if I have made a mistake in my assessment so far. You have not pointed one out.
 * Any attempt to create an assymmetry in the postions of the two clocks during the constant velocity parts of their journey is in truth an attempt to create a privileged frame, a sort of pseudo Aether, for the Earth clock. If you want an Aether then it is best to start with an Aether and employ an Aether theory.
 * R F Norgan 5.30pm GMT 21 August 2006


 * I think that this remark and your phrase "SR does not predict the observation in this experiment and a new theory must be found that does", does not really belong on the discussion page of this article. Have a look at the guidelines how to use talk pages: discuss the article, not the subject.
 * You can use your private talk page for a subject like this. I'm sure you will find someone to talk this through.
 * DVdm 21:11, 21 August 2006 (UTC)


 * You are saying that I can say that any one explanation of the TP is incorrect but I cannot say that logic requires ALL explanations to be incorrect.


 * No, that is not what I am saying. You obviously are not capable of paraphrasing what I am saying, so you can stop doing that. (DVdm 09:23, 22 August 2006 (UTC))


 * I think a preferable response from you would be to prove my logic wrong by showing a source of the factor +2dV/c^2 in an SR explanation.


 * I have no idea what you mean with "showing a source of the factor +2dV/c^2 in an SR explanation". AFAICS that 'factor' is not in the article. I only see factors gamma and 1/gamma. (DVdm 09:23, 22 August 2006 (UTC))


 * The overall requirement of Wikipedia is to give a correct explanation. If the correct explanation of the Twins Paradox is that it IS a paradox for SR then that must be Wikipedias explanation. I do not see that it is Wikipedias duty to support any one particular theory regardless of the truth.
 * R F Norgan 9am GMT 22 august 2006


 * Have a look at Neutral point of view, specially the bulletted list in the section Neutral point of view. I think you will have to look for another forum to express your opinions and -i.m.o. severe- misunderstandings about special relativity. I recommend the newsgroup sci.physics.relativity on Usenet.
 * DVdm 09:23, 22 August 2006 (UTC)


 * It is preferable that you point out any errors that I may have made rather than accuse me of severe misunderstandings with no evidence. It gives the impression that you are trying to smear my comments rather than counter them.
 * R F Norgan 10am GMT 22 August 2006


 * Yes, it is quite clear and I fully understand that this is what you find preferable, but that is of no concern on this article talk page in the Wikipedia. You will understand this if/when you really take some time to carefully read the policies and guidelines. If you are looking for sparring partners to (1) counter your comments, to (2) provide evidence of your misunderstandings, and most important to (3) help you formulate your thoughts in an understandable way, Usenet is a very good place. This is definitely not such a place.
 * DVdm 10:37, 22 August 2006 (UTC)


 * This is a discussion page. I have pointed out that the article is incorrect to state that one clock considers the separation distance to be different from the other clock. I have accused the article of creating a privileged frame which is contrary to SR. So far you have not countered my criticism. I suggest you do so rather than attempt to deny me the right to make that point.
 * R F Norgan 11am GMT 22 August 2006


 * In the context of the article I have carefully explained how the separation distance is defined, how both observers can measure it, and how the results are related - all this definitely without "creating a privileged frame". As I said, if you still don't understand it, I'm afraid I cannot help you. Perhaps indeed a sparring partner is not what you need at this point. Perhaps you first need some kind of introduction to special relativity. I suggest "Spacetime Physics" by Taylor and Wheeler and "General Relativity from A to B" by Robert Geroch
 * DVdm 11:34, 22 August 2006 (UTC)


 * The article considers that the separation distance is length contracted for clock B and yet not for clock A. There is absolutely no doubt that A is therefore in a privileged frame for this to occur. This fact cannot be denied. I would appreciate if you would cease attempting to rubbish my argument by implying that I do not understand Relativity.I have studied it for 25 years.
 * R F Norgan 12.30 pm GMT 22 August 2006


 * I have reviewed the section 'The separation distance' and did some counting. For the 6th time: The distance is defined as the distance to an object that is at rest in the frame of the Earth which is the first frame that is mentioned ("Consider a space ship going from Earth..."). I'm sorry to disappoint you, but that does not "create a privileged frame". It merely requires you to imagine an object that is at rest in an already existing frame. When the distance between the Earth and this object, at rest in this non-privileged frame, is measured by observers at rest in the ship's frame, they find that this distance is half the distance as measured in the Earth's frame. The Earth only differs from the ship in the sense that the Earth remains at rest in one inertial frame, whereas the ship does not. Either it must accelerate, decelerate, accelerate and decelerate, or it must jump from an 'outgoing' inertial frame to an 'incoming' inertial frame. That does not "create a privileged frame", it just shows the difference between Earth and ship, and that is the essence of the situation. Failing to understand that, is what creates the paradox. I think that my ways of explaining that no "privileged frame is introduced by the article" are exhausted.
 * I'm sorry, but I don't see how the number of years that you have studied special relativity should be related to your understanding of its basics. So perhaps indeed you don't need a sparring partner and perhaps you also don't need the books I recommended. Perhaps you need another hobby?
 * DVdm 12:45, 22 August 2006 (UTC)


 * I would prefer if you relied upon the force of your arguments rather than on your insults. The fact is that you are considering the space between the two clocks to have different significance to one clock than to the other. This is a simple point which you are doing your best to ignore. It is a disappointment that I have to keep reminding you of that point. If you attempt to apply the article explanation to the three clock model of the TP where all three clocks are non-accelerating then the difficulty may become clearer to you.
 * R F Norgan 2pm GMT 22 August 2006


 * Perhaps one last attempt...
 * You and I are floating next to each other in space. Our clocks are synchronized. With a short powerful boost of your thrusters in some direction you depart from me. I notice that you fly away during some time T (as seen on my clock). After that time you give another short boost in the oppostite direction, so you come to a stop w.r.t. me. There and then you carefully dump your waste and then return to me with two more boosts, so we end up floating next to each other again. When we compare our clocks, yours will show less elasped time: I say you were away for a time 2T and you say you were away for a time 2T/gamma. While you are out, I monitor your distance and I notice that at your turnaround event, i.e. after a time T on my clock, your distance was d. The waste that you dropped at the turnaround has speed zero w.r.t. me, so it remains at rest w.r.t. me at a distance d. While you return, you can measure the distance to me and the distance to your waste. When you do that, you must of course make sure that you measure those distances at the same time, so you must arrange for your radar signals to bounce off me and off the waste simultaneously according to you. You find that the distance between me and your waste is d/gamma. Now you can also imagine that an object was already present where you dropped your waste. You can also imagine that this object happened to be at rest with respect to me (at distance d, according to me), so you could have measured the distance between me and the object even before you turned around, and I could have done the same. I find a distance d, and you find a distance d/gamma. No "privileged frame" anywhere near and not "considering the space between the two clocks to have different significance to one clock than to the other".
 * Mind you, these are not arguments. This is how special relativity works and it seems that you fail to understand it, which I find a bit remarkable considering your claim of 25 years of study.
 * DVdm 14:09, 22 August 2006 (UTC)


 * The ship clock will NOT measure the separation distance as d/gamma. The fact that there happens to be one object in front and one behind both moving at the same velocity does not cause length contraction of the intervening Space. The ship sees these two objects moving thru its OWN IRF. The ship will see the Earth contracted but not the intervening Space. Our argument is who 'owns' the intervening Space I say that it is both ship and Earth.The returning ship will see one object approaching and the other receding and expects time dilation relative to the ships clock in both objects. The actual distance is not material. I strongly suggest you examine the three clock version of the TP using your arguments.
 * R F Norgan 3.30pm GMT 22 August 2006


 * As said, it was a last attempt. I have given you everything you need to get rid of your confusion. Good luck.
 * DVdm 14:58, 22 August 2006 (UTC)


 * You think i am confused, I think you are confused. I am happy to continue the conversation but I think not on this site. My email is rfn@btconnect.com. I hope you will take me up.
 * R F Norgan 11am 23 Aug 2006


 * Ha, so you are the author of EINSTEIN WAS WRONG - (SEE THE $10,000 CHALLENGE) - THE AETHER EXISTS and THE TWINS PARADOX - THE EXPERIMENT WHICH PROVES EINSTEIN WRONG
 * That immediately explains why you seem incapable of recognizing your elementary mistakes. It would require you to admit to yourself that you wasted 25 years of study *and* it would cost you a fortune. No, you are right about one thing: this site most definitely is not the place for you. If you really want to be "taken up" and if you can stand the heat, you know my recommendation.
 * I think I owe the Wiki community an apology for having engaged in this. I should have had less confidence in this contributor's motives.
 * DVdm 12:30, 23 August 2006 (UTC)


 * Yes,but does that automatically make me wrong. Furthermore i have not mentioned alternative theories. My offer to you remains open.With or without the $10000.
 * R F Norgan 3.30pm GMT 23 August 2006

Further questions re the article
I have already explained that the Twins Paradox is no paradox for the Earth based clock, only for the ship clock. There is therefore no point in considering the Earth clocks observations from Earth’s frame. Instead the paradox must be considered from the frame of the ship, through which the speed of light is isotropic at a constant velocity ‘c’. Neither of the Minkowski diagrams view the problem from that point of view. Also the Doppler effect has no relevance to the paradox. The observer of pulses emitted by a clock or frequency source which emits a stream of pulses throughout a journey between two separated meetings with the observer will of necessity always receive exactly the same number of pulses as were emitted. Thus the final readings of the two clocks are unaffected by Doppler effects. R F Norgan 12.30 pm GMT 24 August 2006


 * I don't see any question here. Just like in your previous two sections I only see a number of (i.m.o. confused) statements showing your (i.m.o.) lack of understanding of the subject. You might look at how a dictionary defines "paradox", for instance . There is no such thing as "a paradox for the ship clock but not for the Earth". A paradox is a seemingly contradictory statement about a situation. It is well known that the twin paradox arises when one fails to aknowledge that one frame remains inertial whereas the other does not. The article does not state that "the final readings of the two clocks are affacted by Doppler effects". It shows how the Doppler effect can help understand the lack of symmetry between the two frames.
 * Again you are trying to discuss your personal view of the subject, rather than the article. You might consider changing the title of this section into "Further assertions re the subject and my understanding of it", and then, following the guidelines of the Wikipedia, abandon it.
 * DVdm 14:57, 24 August 2006 (UTC)


 * I do not understand your motivation for stating that I am not discussing the article. I am referring to the Minkowski diagrams within it and the use of the Doppler effect which is particular to the article.
 * R F Norgan 12.30 pm GMT 25 August 2006

A more detailed criticism of the article
In the Twins Paradox the paradox occurs because the predictions, based upon SR, by clock A of the reading of identical clock B of the time measured between two meetings of the two clocks agrees with actual observation, where-as the SR prediction of clock B of clock A between the same two meetings does not agree with observation. This situation appears so absurd to a layman that it is called a paradox. From a scientific point of view it is simply an example of the predictions of a theory not describing observation. The article makes the mistake of not concentrating on the observations and predictions of the ship clock where-in alone lies the paradox. In concerning itself with the observations and predictions of the Earth clock the article confuses its discussion of the  situation of the ship clock to its serious detriment. SR states that an IRF can be arbitrarily ‘attached’ to any non-accelerating object irrespective of whether it has previously accelerated or is about to accelerate. An IRF is a non-accelerating frame of three distance dimensions, which stretch to infinity in all directions, and a time dimension. Thus every point in Space ‘exists’ in an infinity of IRFs attached to an infinity of material bodies. Thus Space is not ‘owned’ by any particular IRF. As an example, a body A, which is surrounded by a host of other bodies all moving at the same velocity with respect A, still views the surrounding Space as ‘his’ IRF rather than he is moving through the IRF of the host of bodies. Thus the ship views Space as his IRF and Earth is moving through it. Thus according to SR the Earth clock is time dilated relative to the ship clock. Consequently, over both constant velocity periods out and back the ship expects the Earth clock to run relatively slow. Over these two periods the slowness is –TV^2/2c^2. In fact the observation is +TV^2/c^2. The difference between prediction and observation is therefore TV^2/c^2. The article in no way explains or discloses the source of this difference and therefore sheds no light upon the Twins Paradox which, in part, it was intended to do. R F Norgan 12am GMT 25 August 2006


 * Your opening line is a dead on arrival. Clocks do not make predictions of other clock's readings. So I agree that what you try to say in that first sentence is indeed absurd and we can cut the discussion short at this point. The article explains in a few ways how the twin paradox is caused by failing to recognize that one involved clock remains at rest in an inertial frame, while the other does not. The article shows how to avoid making this mistake. You clearly have not understood this.
 * You really first should try to understand the *very* basics of this (and of the theory itself), and I don't think that this is the place where you will learn it. In the 3 previous sections I pointed you (1) to your private Wiki-talk page, to (2) a website where the paradox is explained with events and transformations only, to (3) a specialized Usenet newsgroup, to (4) two excellent introductory text books to the subject, and to (5) another hobby. For your own sake, do consider taking this seriously. Good luck.
 * (DVdm 12:48, 25 August 2006 (UTC))


 * Yes it is pedantically true that clocks do not as such make predictions. I have assumed that each clock is accompanied by a human observer. NO body remains for ever in an IRF. In fact there is a strong argument that no body ever exists in an IRF for more than an infinitesimably short time. Hence the ship clock is in no way unusual. It is true that the shift from one IRF to the other is the significant event here but the article fails to explain how or why. I do feel that your continuing assumption that because we disagree you are the all knowing one and I need to go back to school, merely reflects upon your lack of scientific response to my criticisms.I have already given you the opportunity to discuss our differences outside of Wiki.
 * R F Norgan 11am GMT 28 August 2006


 * "Outside of Wiki" there are many places where you can discuss your differences with the rest of the world. See for instance my recommendation (3). I guess there is even a place inside of Wiki: see recommendation (1). Just put your views there and wait for someone to join in. But before you do that, I suggest you seriously consider my recommendations (2), if not (4), if not (5).
 * DVdm 12:02, 28 August 2006 (UTC)


 * Now you are trying to counter my scientific arguments by a vote by saying that the rest of the world disagrees with me. What do they know of this subject. There are also many instances of scientists believing in theories which later turned out to be wrong. You really are scraping the bottom of the barrel in order to oppose my comments. Why not try scientific argument for a change.
 * R F Norgan 10.30am GMT 29 August 2006


 * I am not trying to "counter your scientific arguments by a vote". I told you before: you obviously are not capable of paraphrasing what I am saying, so you can stop doing that. Other than that I'm afraid I'm out of recommendations.
 * DVdm 10:50, 29 August 2006 (UTC)


 * If you cannot or do not wish to counter my criticisms with scientific argument then, as I assume that you are the author of the article, you should withdraw it.
 * R F Norgan 10pm 30 August 2006


 * Since it became obvious that "scientific argument" bounces on you, it is clear that there is indeed no point for anyone to try that approach with (someone like) you. Since everything you have assumed until now was wrong, you can stop assuming as well, and I don't think that, apart from taking (5), further recommendations to you would be called for, relevant, or even appropriate, at least not from my part.
 * DVdm 09:54, 30 August 2006 (UTC)


 * As you have given NO scientific reply other than to repeat what is in the article you would not know if it 'bounces' off me or not. Everything you have said on these pages has been an attempt to avoid a scientific discussion.It appears that you believe that the theories of Einstein should be beyond criticism to the extent that criticism is to be ignored rather than answered.
 * R F Norgan 2.30pm GMT 30 August 2006

A different version of the Twins Paradox
Clock A is not accelerating. Clock B passes A at near zero distance at relative velocity V and continues on into Space. At this point both clocks are zeroed. B is accelerating at an infinitesimal small amount towards a point in Space such that B's path describes a huge circle. Eventually B returns to A where the two clocks are compared over zero distance. If it is considered that SR does not apply to B because of its acceleration then SR aplies to no body at all and particularly not to Earth. If on the other hand it is considered that SR does apply, then because both x and x' are zero at the end of the experiment it follows from the Lorenz Transforms that t = gamma.t' and t' = gamma.t. Thus no time dilation occured. I believe that this would be contrary to observation. Hence SR cannot explain the Twins Paradox. R F Norgan 2.30pm GMT 30 August 2006


 * Again, you are not discussing the article, but the subject. This is the fifth section you try to open, and since with this one you show again that your understanding of the subject is as good as zero, I'm afraid that no one will be able to help you. Do consider finding another hobby - for your own sake.
 * DVdm 15:51, 30 August 2006 (UTC)


 * You said exactly what I thought you would say. The article shows that the Twins Paradox is not a paradox for SR. By giving a simpler version of the TP and showing that it is indeed a parodox I am making a criticism of the article in that its conclusion is wrong. Frankly, your article is so full of errors (as I have pointed out) that I cannot see how you can have the cheek to keep it there. Your knowledge of the TP and its various versions does not seem to be extensive.
 * R F Norgan 1.00pm GMT 31 August 2006


 * I see that you have quite a few things to learn about the Wikipedia as well, but somehow I suspect that you are not going to do that either, so I will not bother trying to explain.
 * DVdm 14:21, 31 August 2006 (UTC)


 * The most important aspect for Wiki must surely be that the article info is correct. Unfortunately your article is incorrect in its conclusion that the TP is no paradox for SR. For that reason your article should not remain there.
 * R F Norgan 3.30pm GMT 31 August 2006


 * Wrong. It's explicitly stated that Wikipedia does not attempt to be "correct" in the sense that you mean, simply because people rarely agree on such things. Instead, the encyclopedia is meant to provide a verifiable overview of different opinions as found in the literature - which is a much more modest (realistic!) goal. To avoid an endless mess, no Original research as you propose is allowed. And this article, as most articles, consists of contributions by many editors. See also http://en.wikipedia.org/wiki/Wikipedia:List_of_policies Harald88 20:08, 31 August 2006 (UTC)


 * I have not proposed original research. If, as you say, Wiki's aim is to provide a verifiable overview of different opinions then where in the article are the opinions of those who believe that SR does not explain the TP. Why, for example, is there not a reference to H. Dingle and his work. Why is the Circling Clock Paradox and the Three Clock Paradox ( slightly different versions of the TP)not mentioned. The lengthy explanation in the article would have difficulty explaining these versions. The article makes no attempt to give different opinions.
 * R F Norgan 12am GMT 1 SEPT 2006


 * Then I must have overlooked the publication that you referred to. You may be right that one or two sentences about Dingle would be appropriate, but actually he is already referred to in "See also". The article does mention the opinion of for example Langevin, and why Einstein's GRT solution is not so popular nowadays. Perhaps you are disappointed that the article doesn't elaborate on such differing interpretations?
 * Note that this most famous paradox has a nearly endless stream of variants, comments and interpretations, and presentation of strong opinions would easily result in edit wars. As it stands, the article may have to be split up or contents moved to separate articles because it's already getting too long for Wikipedia standards. That would also be the place for variants of the paradox. Harald88 00:09, 2 September 2006 (UTC)


 * The main problem with the article is that it too greatly devoted to one explanation of the TP when probably hundreds of explanations exist. Furthermore it is easily shown that this particular explanation is logically incorrect. Any article on the TP should mention several opposing explanations and in less depth but should also point out the weaknesses in each. I would be happy to undertake such an article, but as an Aether man I feel it should be in conjunction with a Relativity man. But would a Relativity man be content to join with me.
 * R F Norgan 12.30 pm GMT2 SEP 2006


 * I'm afraid that you still don't understand how Wikipedia works, especially as several explanations of different aspects of it are presented, including "Aether". Thus, what "particular explanation" do you mean that according to you, the article "is devoted to", and which notable paper showed that that particular explanation "is logically incorrect"?
 * Apart of that, an overview page such as you propose might serve as a welcome appendix to this article (I guess that it will be, in the end, at least as long as this article). But it must reflect opinions in the literature. Harald88 12:46, 2 September 2006 (UTC)


 * ... the literature, which does of course not include Norgan's pages EINSTEIN WAS WRONG - (SEE THE $10,000 CHALLENGE) - THE AETHER EXISTS and THE TWINS PARADOX - THE EXPERIMENT WHICH PROVES EINSTEIN WRONG
 * DVdm 12:48, 3 September 2006 (UTC)
 * Right - see WP:V. Harald88 20:50, 3 September 2006 (UTC)


 * Einstein's 1905 paper shows that the main explanation in the article is logically incorrect. The paper encapsulates the Principle of Special Relativity which states that the laws of physics are the same for all observers. Thus this is equally true for the ship as for the Earth. The article takes the the Earth frame to be a privileged frame.
 * If DVdm is so sure of his postion but makes no attempt to earn $10,000 from it.
 * R F Norgan 12.20pm GMT 4 SEP 2006


 * I already explained the difference between the Earth frame and the ship's frame(s). Since you didn't understand it the first four times, you will almost certainly fail to understand it the fifth time, and so I do not intend to explain it again - in yet another way. That obviously is also the reason why I will never claim the $10,000 that I earned.
 * What anyone thinks does not seem to have much influence on you, but for the record, I think that it is really time for you to find another -more appropriate- market for your misunderstandings. See my previous recommendations.
 * DVdm 13:50, 4 September 2006 (UTC)


 * There is no difference between the Earth frame and the ship frame. Einsteins 1905 paper states that the laws of physics are the same for all IRFs. This is the fundamental error in the article in that it violates SR. Furthermore a large percentage of the article is devoted to the Doppler effect which has nothing to do with the the difference in the readings of the two clocks at return. The article should be removed as it is badly in error.
 * R F Norgan 4.10pm GMT 8 SEP 2006


 * Concerning your statement "There is no difference between the Earth frame and the ship frame": The difference between the frames has been explained in many ways (the Doppler effect being one of them) in the article itself, and, personnaly addressed to you, in the previous sections. Actually, that is the entire rationale behind the twin paradox. The fact that you (hopefully honestly) don't understand this after all the explanations given, demonstrates that you honestly should seek another hobby. Trust me.
 * DVdm 19:39, 8 September 2006 (UTC)


 * It would be pleasant if you would cut out the insults. It was obvious that i meant that there is no difference to an observer at rest in that frame in respect to the laws of physics. The TP is not concerned with the distance travelled. It is concerned with the relative time-keeping between two meetings of two clocks. It is also beyond argument that each clock will observe ( and predict) the other clock to be running slow throughout the two constant velocity parts of the TP. SR needs to reconcile this with the final observation of the ship that the Earth clock has run fast. The article comes no where near to achieving that.
 * R F Norgan 4.30pm GMT 18 SEPT.2006


 * You have no idea what you are talking about. Don't take this as an insult. Take it as a piece of friendly advice. Trust me.
 * DVdm 16:21, 18 September 2006 (UTC)


 * It is an insult for you to assume that you know more about the Twins Paradox than I do. I have given you the opportunity to discuss the subject by email in a scientific manner and you have refused my offer and instead 'argue' with insults.
 * R F Norgan 10.51 am GMT 28 Sep 2006


 * Since you lack the most basic understanding of the subject of special relativity, you really are not qualified to judge other people's perception of your lack of understanding. Trust me, there are no insults, arguments or assumptions, neither explicit nor implicit. There are documented facts in this section and in the four previous sections you opened. Furthermore, I repeat, this is not a place to invite people to have discussions by email, nor is it a place to make offers. I'm sorry if that conflicts with your agenda.
 * DVdm 11:56, 28 September 2006 (UTC)