Dear Danci

Thank you for your answer, I understand Lorentz transformations well, but I need to know the different opinions about this conflict, which of course related to your paradox, but this time the answer is longer or shorter in addition to the interpretation.

Regards

Time is the same for A and B. Then let us assume that sandwich eating is a very regular activity and always takes one unit of time at rest. We can call this unit a yummy. One yummy passes on the plane while the sandwich is being eaten. Since a moving clock seems to run slower than a stationary one, observer C would observe the sandwich being eaten in a time of less than one yummy, in fact 1/gamma yummies, where gamma is the usual relativistic factor, 1/√(1-vv/cc). Observer C thinks the guy on the plane is eating too fast, at a rate of more than one sandwich/yummy. The guy on the plane thinks that C is stopping his timer before he's finished eating.

Given that the yummy in your problem is 5 minutes, and gamma≈1, the effect will be hard to detect, but experiments at higher velocities and over longer times show that it exists.

You might try doing the calculations yourself. They are simple and symmetric and you'll be able to see if I'm right or not. You shouldn't trust this just because I typed it out :-)  

Dear all;

Thank you for your participation.

Please, lets leave personal attacks and do science.  

There is an important ambiguity in the way you phrase your question, which needs to be underlined: you say observer B (redundant indeed, as so many have observed, but quite pleasant to have along) *sends a signal* to observer C. Now B will send a signal to C who is at rest. Assume, at the time A is starting his sandwich, C is very close to the airplane. Thus the  signal from B to C takes negligible time. But as A finishes his sandwich, the airplane has gone on and is now quite far. The signal from B to C will now take significantly longer. It is possible to correct for this, but it is quite messy. The best way is to introduce a new observer.

So B should send her signal to D, who happens then to be close to the airplane at that moment, but at rest, just as C. Since D and C are both at rest, they can synchronise their watches, and D can tell C when, according to him, A had finished his sandwich.This time difference is the one that is given by the Lorentz transformation. This is indeed longer, by a factor gamma, than the five minutes recorded by B.

Is there any contradiction to the symmetry one should expect? Indeed there is not: let us assume C starts eating a sandwich just as the plane passes overhead. After five minutes, C is done. Does A or B in the airplane measure a shorter or longer time? Again we have a problem, because when C is done eating, the airplane is quite far. We need another airplane which flies above C just when C is domne eating. If you then do the Lorentz transforms, you will find everything turns out to be consistent.

One now expects Valentin to come frothing at the mouth and saying this is all nonsense. It then becomes important to ask Valentin how he proves his claims by actual Lorentz transforms. He never doe: it is always all words, and wrong words at that.

Let anyone who cares, indeed go and look at the diagram and see whether he understands it. The claim that there are any Lorentz transform calculations in the diagram is, as usual, mendacious: there are lots of numbers, and lots of arrows. No computations are ever performed, and even though I asked Valentin several times, as anyone can check, to show any kind of Lorentz transforms leading to a contradiction, he never did: the ``contradictions'' always involved some convoluted verbiage, usually interlaced with insults.

Here is a somewhat extensive set of observations for those who might actually be interested in an answer to the question.

Dear Leyvraz and Danci

Thank you so much for the informations that you gave for this thread.

@Valentin: Once more, empty words. I have 4 events, and have computed all the events' coordinates, first in the A frame, then in the B frame. I used an LT from A to B. I can, of course, use the inverse LT, which is well-known, by elementary algebra, to be the LT corresponding to -v. Nothing new is obtained by this. If you can get soemthing interesting this way, please show it, using formulae.

Finally you say: ``There is a big difference between calculated *evaluations* and the actual observations.'' Indeed: the one has error bars, depends on observations etc... But in relativity, there is no particular issue about measurement, as there would be, for example, in quantum mechanics. All the quantities I compute are the positions that would be observed, and the times that would be measured in such a setup: I see no reason to change this claim, nor do I have any idea or where you drew that peculiar notion from.

You still do not show how to get a contradiction using your calculations. You also do not say where my calculations are wrong. Saying that starting from one frame makes the calculation asymmetrical is simply wrong. In any case, show how you start from B and get a different result. But do actually show your calculations, instead of using confusing verbal descriptions.

Finally you say: ``The calculations are made to estimate, to evaluate the times and positions in the other frame. The only validation comes when physically the calculations are compared with the recorded values.''. Of course that is true. For example, if you have a circle of radius 1 meter, you calculate the circumference to be about 6.28 meters, and you validate this by experiment. True. But there is no fundamental importance to this distinction. I claim the time measured by one of my clocks is calculate to  be this, and measurement will bear it out to appropriate accuracy.

Leyvraz> Here is a somewhat extensive set of observations

A very nice note (perhaps a bit repetitive at times, but that may very well be a necessity). I have only one comment, to the last paragraph of your note: The claim by Einstein that a clock at the equator will go slightly slower than a similar clock at the pole, may actually be one rare case where he was wrong. There is also a gravitational correction of opposite sign (since the equator is further away from the center than the pole). I have seen a remark that the equilibrium criterium for the shape of the earth is such that all clocks on its surface "ticks with the same rate". I think this must mean an ideal earth, without mountains and valleys  and similar non-equilibrium configurations.

I.e., there is no point spending extending holidays in Guayaquil for becoming younger than your twin!

@Kare: Indeed, I agree. However, saying he was ``wrong'' is perhaps a bit of an anachronism. His claim did not take into account an effect which was to be discovered later (by himself). In any case, I tried to clarify the issue, and failed, of course, to convince those who never would be.

Leyvraz> It is possible to correct for this, but it is quite messy.

I liked the way you made the problem precise: C starts her clock when she receives the first signal from B, and stops it when she receives the second signal. And the solution is not messy at all --- at least not compared to most of the other stuff written here :-). The answer is that C registers a time difference

T = sqrt[(1+v/c)/(1-v/c)] * 5 min

where v is the velocity of the plane. There are some approximations: (i) the earth is flat, (ii) the plane travels in the same height as C, (iii) the signal travels through the atmosphere with velocity c (not with pigeons).

PS. I certainly don't belong to the Einstein-was-wrong crowd; the reason I remember the gravity correction so well is that I once gave the twin-in-Ecuador problem to my class, forgetting about the gravity correction.

@Kare: again I agree. I guess I was trying to present things in such a way that one does not explicitly to make computations with the Lorentz transform except at the final stage: one should, hopefully, see that the issue is not trivial simply by realizing that, at some point, the relativity of simultaneity comes into play.

In particular, as I stated in my notes, I believe the easiest way of comparing the times shown by a clock at rest at the origin, and another one at distance L and moving, is to use a third clock at distance L at rest: these last two times can be compared easily. Danci, on the other hand, always thinks he can compare the two clocks directly, and always does it wrongly.

I did the whole calculation by sketching some lines on a sheet of paper while following a Tour de Ski competition, doing everything in the restframe of C. One only have to use (the Minkowski space version of) Pythagoras once. I was pleased with the simplicity of the answer. Strangely, very few on this thread seemed to be interested in a quantitative answer (including the questioner). How can one understand anything of physics without doing explicit calculations??

As I said before, I liked the way you demonstrated how the two travelers are equivalent, and how some observations are non-equivalent. I think a briefed down version of your note deserves to be published (if it hasn't appeared in the literature during the last decade or so), f.i. in Am. J. Phys. Did you try?

I think Dingle was a tragic figure. Here is this expert guy who has written books about relativity; after 30 years it dawns on him (or at least everyone else around) that he has not understood a shit of it. He probably never tried to do any calculations.

OK, just give me one. You have made a lot of statements of that kind, without ever substantiating them. If one were unkind, it could be misunderstood as bluster by someone who does not know what he is talking about.

I saw the methods, at least the first one. It is, of course, uncontrolled: to the extent that you accelerate the reference frames tha are initially at rest with each other, it is easy to show, within the framework of relativity, that the clocks will come out of synchronisation. So, of course, there is no *contradiction* within SRT. Of course, you may decide that you prefer the description of physics----essentially Galilean---that follows from your own postulates. I believe you will have severe difficulties both with the muon experiments and the highly accurate modern variants of Micheplson-Morley. 

As to judging you, far be it from me to do any such thing. It rather seems to me that you judge yourself, and quite correctly at that.

Dear Sadeem,

You are right to wonder what happens. According to Einstein and assuming A, B and C on one line, if B sends a lightwave with a wavelength that starts its period at the start of eating and ends its period when the eating stops, then this wave will get a shortening of length and a lengthening of tick rate at the wave's arrival at C. B would just have a delayed sight due to the distance, but the begin and end moments are equal as at A. Hence, C would moreover get a delayed information compared with A and B of different time lengths. So far according to Einstein.

However, as we shall see, Einstein's theory is plain wrong when you analyse it.

In his 1905 paper, the "kinematical part", he uses information exchanges by light between reference frames, and concludes that light is deformed. When light is used to measure time (frequency) or length (wavelength), or when the mass is deduced via E=mc² with an assumed c = constant, then one calculates what the deformed signal is, and with the speed of the frame, one can calculate back the emitted values of length and tick rate, and the deduced mass.

Then we always find a retarded clock tick rate and a shortened length deformation.

However, the result is valid for every frame, even mutually! Hence, each frame will say that the other lengths are shortened and the other clock tick rates are retarded.

This mutual result is only possible if the measurements are optical deformations, not real physical values inside the frames themselves.

Conclusion: relativity is just an optical deformation, nothing fundamentally physical or anything else, spites many claims made by the mainstream science.

Yet, it is disputable that c = constant at all times, and that the same signal would be running at c on Earth, on the planet Serpo, and on any place between-in, as seen from either planet, when one assumes that there is a method to communicate much faster than light in order to check that, like it would be the case with waves in the oceans, when checked by light.

In the second part of his 1905 paper, the "electrodynamical part", he applies the former, "kinematical" result to the electric and the magnetic field of one of Maxwell's equations.

However, the electric and the magnetic field are not observable with light as he did in the former, "kinematical" part, so, it is unapplicable here!!!

The electric and the magnetic field are entities by themselves and propagate by themselves, hit other charges and are a real force field. They are no observable field (by light) as supposed by Einstein!!!

So, his theory is nonsense!

Best regards,

Thierry De Mees