michel123456

Contraction goes away. But time dilation don't?

Emphasis mine. The diagram is about light. And the angle represents speed, as you stated, which is C. (in orange color on the diagram)

My advice: 1.never begin a paper apologizing for any kind of ignorance. 2.don't begin introducing yourself and the history of your life. Insert at the end an extremally small curriculum (one or 2 lines) starting with your PhD in the subject or Nobel prize in the subject. Nationality & born date are crucial (after the age of 35 your chance of succeeding diminishes expantionaly). If you don't have the required qualities, don't introduce yourself at all. Mystery is better than refutal. 3. Put the elements you admit first, and go to "what if" after. Never put more than one "what if" in one paper, or you die. 4. Make sure the reader don't stop exactly there. 5. Make a looong list of references, avoiding self-reference, publications from the 80's or older & publications from Esquire magazine. I am sure other Members here will give you some other valuable advices. ___________________ Ah. Make sure you haven't discovered a theory from the 3rd century BC. It happens to me all the time. Google & Wikipedia are of great help. I agree and applause. But don't take that for granted. I have a bad experience when discussing with people who don't think that way.(not here)

Good move.

During the return phase of the travel, did the twin expand? (I mean return to its original size)

Emphasis mine. Thanks I may do that. Is there a simple way to download entire threads & organize these in my PC? I have a bad experience with another Forum that closed for a long time. I thought I lost everything. Thanks to Idontknowwhy the Forum reestablished connection after a few months & I had to rely on my (bad) memory to extract the interesting stuff. Fortunately there was not much. For the moment I have put all confidence in the reliability of this Forum but since there is a lot of interesting conversations arising I would like to save some of it.

During the part of the travel when he contracted, did time dilated?

I think my diagram ressembles a spacetime diagram: space on abscissa & time on ordinate. How could I state differently equations (2) and (3) in Minkowskian space?

During the travel, did the twin contract?

watched topics are not listed under "my content". Usually I try to reply constructively in interesting threads, but when no one respond they get harder to find. For some peculiar reason I had lost this specific one. There should be some utility that could help each user to organize threads & posts (sorting by preferences, by stars, by colors, alphabetic list or subjects or specific words or other). Maybe this utility exists and I am not aware of it.

So time has accumulated the gap. But the gap in spatial dimension has disappeared, it remains only as a measurement (the velocity). Do we have to conclude that time & space have a different behaviour? And that " the natural human tendancy to think in terms of space and time as distinct" is correct.

One could make the remarkthat it is not a matter of agreement (although I agree with you). It is a matter of calculations. What do the maths tell? -or is it too much off topic?-

Even the 3D picture is deformed. Here is my point of vue: If you take a cube, and look at it from a distance, you will never see it as it "really" is. You cannot observe a cube and see simultaneously its 6 faces as squares. Even with mirrors, I doubt you can do that. What you can do is take a measure and represent on a sheet of paper the 6 faces as different schemes, and say: that's a cube. or you can use 3D virtual representation and make a computerized representation of the 3D cube, and look at "as in reality" hence deformed by perspective. In other words, even without counting the effects of time & motion, what we are used to see as reality is not Reality. When a physicist try to approach what the cube "is", the dimensions of its sides are not enough. He must know of what material it is made of, what color, what density, and going into the material the physicist inquiry has almost no end. What the physicist gathers from its search are all measurements. And most of the time, the sum of those measurements hardly correspond to any macroscopic "reality" of the cube. Many physicists do not care at all about what all those measurements put together may "mean" for the layman. Physicists care that all those measurements do not conflict each other , that measurements in cube A can be reproduced in cube B, and that those measurements can be done in any other cube. So, when the layman will ask the physicist "explain me the reality of this cube?" the scientist will explain about relativistic distances of the sides, of particles jiggeling producing its color or internal temperature or wathever, going into deep mathematical constructs that show the tremendous amount of energy hidden in the cube's mass but say about nothing to the layman. If you get annoyed and propulse the cube into space, the scientist gets terribly excited and procedes into explanations including length contraction and time dilation. You can also take the cube and put it in your coffee.

Isn'it a wonderful property for an object standing at rest? Doesn't that mean that "at rest" has unique properties compared to all other observers? I may need your point in some other thread. What is the reason that make you conclude that in this thought experiment time "behaves" differently than space and has separated effects? If "contraction only applies between two reference frames in relative motion", in which I agree, why is it different for time? Or, to put the same question otherwise, if time dilation produces a gap in the age of the twins, why length contraction produces no effect at all? Isn't there some contradiction with your very logical statement (in which I agree) that : "Confusion arises from the natural human tendancy to think in terms of space and time as distinct. They are not distinct. They are not invariant. They are coordinate-dependent."

The opposite of yes. ------------------------- How is different from why. If you take into account that the original question was what, it may become clear that the question has no importance at all, and that at the end Mr Feynman choosed to answer anything he liked. 1st question: what is it the feeling? 2nd Q.: what is going on? 3rd Q. what does that mean? 4thQ. why are they doing that? 5th Q how are they doing that? Answer: excellent question, when you ask why etceatera...

Isaac Newton (about gravity). "It is inconceivable that inanimate brute matter should, without the mediation of something else which is not material, operate upon and affect other matter, without mutual contact, as it must do if gravitation in the sense of Epicurus be essential and inherent in it. And this is one reason why I desired you would not ascribe 'innate gravity' to me. That gravity should be innate, inherent, and essential to matter, so that one body may act upon another at a distance, through a vacuum, without the mediation of anything else, by and through which their action and force may be conveyed from one to another, is to me so great an absurdity, that I believe no man who has in philosophical matters a competent faculty of thinking can ever fall into it." I.Newton, 1692, 3rd letter to Bentley. (emphasis mine)

Doesn't that pose some ethics question? I am reading on the subject. Mrs Zeta seems to be a transhumanist extropianist immortalist. Very interesting. I'll need you some day...soon.

Stop. It does not seem logical at all. We seem to accept too easily the propagation of force from something to something else through thin air. If you refute action at a distance, you understand nothing. As I do. edited

So you can get information even from such kind of thread. Thank you Tony (& Colgate).

I never use the watch topic feature. I dont want notifications, only to be kept on a list, about like a favorite in Internet Explorer. (this has nothing to do with this thread, see moderator note below (edited by michel) -------------------------------- Since DrRocket seems to know a lot, he may be interested in an older thread of mine. It is about time "sensed by a clock that is co-moving", as we do when standing at rest. The thread was "Rod at rest" with an interesting (to me) dialogue with Swansont who disagreed. http://www.scienceforums.net/topic/53547-rod-at-rest/page__p__578834__fromsearch__1#entry578834

Only to keep it in my personnal list. Sometimes interesting (to me) threads are disappearing from the Today's Posts (my favorite) due a shower of uninteresting (to me) topics.

I will never agree on that. Call me stubborn. There is a common point of vue that states that measurements are identical to reality: if I propulse the one meter metal bar into space at close to light speed and somehow take it back, I will get a metal rod contracted one inch long and can go away with it in my pocket? No. IMO it is a wrong interpretation of the equations of Relativity. Not that the equations are wrong, but our understanding of it is incorrect. IMVHO of course. ------------------------------------------ Edit; Sorry I didn't notice the "The bars have not "changed" part. Maybe we do not disagree that much. ----------------------------------------- I will re-read your posts more quietly. O.K. I have no problem with that. Relativity describes accurately the measurements of both observers. O.K. It is a matter of the very nature of "space" and "time". No disagreement there. Agree again. Is that the stone where we hit? Sure. I am not arguing against it. There is an obvious misunderstanding, I ought to improve my wording as it seems. Here I agree somehow with Owls point of vue. There cannot be "for the alien" or "for anyone" Reality. You were the one who stated that reality is 4D and that in this 4D reality physics are invariant. Or are we lost in translation? What we may agree on is that neither we, neither the alien can have a look at this 4D Reality, and that we all look at deformed 3D+1D measurements. Sorry, but it is really the effect it makes on me. Maybe. I am working on it.

Non scientific findings show that coffee tastes awful if you brush your teeth first.

What is your question? That is certain. Now that you mention it, I guess in the "twin paradox", we always forget to mention that the traveler twin is not only younger but contracted too... (I can't believe I referred to the twins again, sorry for that).

In Pavillon de Breteuil near Paris there exists a metal bar made of platinum & iridium which is the prototype metre not in use after the sixties, but still there. That is Reality with a big R: the metal bar measures one metre long. Point. If some astronaut or alien moving, accelerating, rotating, measures this metre as shorter, IMHO it is only a matter of measurement. The metal bar in the Pavillon de Breteuil does not actually contract. It cannot contract a lot for the alien, a little bit for the astronaut, and at all for the visitor at rest. It just like stating 1=2=3. It is simply wrong.