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Everything posted by Eise

  1. Wow! Another physics Nobel price winner I have seen in real life. Martinus Veltman (lectures at the University of Utrecht) Gerard 't Hooft (speech about entropy) Brian Josephson (but he was a speaker in a seminar where he defended his funny ideas about paranormal phenomena. Meh... ) And now Roger Penrose (but there he was defending his funny ideas about consciousness, microtubules, and quantum gravity (Orchestrated objective reduction)) I had a small chat with him, and he was very open to my critique. Not dogmatic at all. And he is a kind of eccentric, academic Englishman, all in the very positive sense. Being taught by him must be real fun!
  2. I stand corrected. But I made another error, so again: In the FOR of B: E and X travel a distance of 0.6Lh It takes them 45 minutes I already answered that: And the observer is in the same FOR as E and X. Don't you see that E and X are standing still in Janus' first animation? That means the virtual observer is in the same FOR as E and X.
  3. However, that is what is shown in animation 1. Look at B's clock. No again. B is not in the same frame of reference as Earth, X and the 'virtual observer'. These 3 are in the same FOR. B is not. With other words, this your problem 1: So to extend on Swansont's reaction above: In the FOR of E and X (and the observer): B travels a distance of 1Lh It takes B 1:15h to get from E to X. In the FOR of B: B travels a distance of 0.6c It takes him 45 minutes No, this is physically perfectly possible. Imagine the observer at my spacestation (see above, it stands still in the FOR of E, and X)), making a movie of what happens. Janus' animation shows exactly what the clocks will look like. Yes, both. The speed of B in the FOR of E and X is 0.8c. I think you have here problem 2: relativity has nothing to do with delay of signals. In what you really observe delay plays a role. But not in what actually happens. When relativity would be based on signal delays, your argument would make sense. But relativity is not based on signal delay. It does not describe what you see, but what actually happens. So:
  4. Like is shown clearly in Janus' animations? Just look again... Yep. So Michael, do you want to go to the simplest example, with the clear additional advantage that we have precise measurements? In case we can clear up the muon experiment, then we can go back to your thought experiment.
  5. Again mixing up what is really the case, and what observers observe. Let's first do the clock synchronisation between Earth and planet X: a space station, standing still (so being in the same FOR as Earth and X)exactly in the middle of Earth and X sees that the readings of both clocks are the same. He sends his finding to both Earth and X, who now know that their clocks are really synchronised. This is what Janus' animation shows: both clocks show the same time. However from that it follows that Earth observes X's clock one hour behind, and of course X sees earth's clock one hour behind. But they know that this is just signal delay, so they know their clocks still are synchronised. a. When it is 12:00h it is 12:00h at X. As shown in Janus' diagram. b. When T starts, it will take an hour before X sees it. But he knows of the time delay, so he knows T started at 12:00 on both Earth's and X's clock. As depicted in Janus' animation. Nowhere, because it is not there. Remember? I said: And you reacted: Janus' first animation is from the FOR of Earth and X (and my added space station). As per definition of a FOR Earth and X do not move, so there is nothing length contracted. Only T's clock is moving, so it is length contracted. This is insulting. I don't know ho much time Janus needs for make such an animation, but slowly I getting the idea that all our efforts are useless. You just stick to your wrong intuitions. What weird effect? PLEASE STOP using ambiguous phrases! If you believe in your intuitions, you believe that relativity is wrong. That is of course what I try to find out, but maybe Michael would show us where his mental block lies. Until now I see two mental blocks, but mentioning them seems not to help: he is not able to relate his measurements of time and distance to one single FOR he is not able to make the difference between what observers actually observe, and what they conclude Every suggestion we make to clarify the situation (e.g. my suggestion to use log books instead of remote readings (which introduce signal delays that even confuse Michael more), my suggestion to explain the same phenomena with muons, and last but not least Janus' unambiguous animations) is pushed aside, because Micheal thinks he has a clear view of the situation.
  6. OMG...! What 'it'? Which scenario? This is even less clear! My guess what your 'argument is pointing at': the missile travelling from planet X to Earth (With T as static guest...). From the Earth's FOR it takes 1:15h. (60Lminutes/0.8c) T travels a contracted distance, 0.6 x 1 lh = 36 Lminutes. As he is traveling with 0.8c, this takes him 0:45 according his own clock. Where is this wrong according you? Please always mention in your reactions: your scenario (you are introducing new one after new one, only to feed your intuition to find yet another counter argument...) which event or process are you looking at? According to which FOR's measurements? Looking at the clock and ruler of the other FOR or its own FOR? I do not agree. Your imprecise remarks show that you do not really think through our answers, and this is insulting to the effort Janus, Bufofrog, Swansont, md<somenumberhere>, Markus, and who more. We are all trying to be as precise as possible, and you come with some vague counter argument, shot from the hip. Tell us e.g. what is wrong with Janus' animations? If nothing, where do you differ in our interpretations of them? And why do you refuse again and again to take real examples, where we have empirical measurements?
  7. No. I know I said it took 1:15h, but I made very clear that this is from the FOR of Earth, X and T (standing still at Earth). Sentences like the above say nothing, unless you say both what event or process, and according to which FOR. Why can't you stop these imprecise way of speaking. You are just confusing everybody, and most of all yourself. STOP IT! Again you use this ambiguous 'seen'. If you do not stop this, i.e., if you keep intentionally vague, I will ask this thread to be closed. So let's repeat it again: the missile travels 1:15h according the FOR of Earth, X, and T in your example above the missile travels 1Lh according the FOR of Earth, X, and T in your example above. the missile travels 0:45h according the its own FOR (i.e. its own clock) the missile travels 0.6Lh according the its own FOR (i.e. its own odometer)* Exactly the same holds when Planet X travels to Earth (replace 'missile' with 'Planet X' in the above 4 lines). Except that you use 'observe' again: T observes Planet X to arrive 0:15h after it observes Planet X starting to move. But because of signal delay, T rightly concludes that the trip took 1:15h. But nobody ever said that the trip takes 0:45h from the FOR of Earth and Planet X!!! (except you..) The '0:45' appears in two (equivalent) ways: It is the trip time that T measures on his own clock. For T, he travels only 0.6Lh. It is according the FOR of Earth and Planet X the time dilation of T: according Earth's own clock, the trip took 1:15h. But reading the logbook of T, it turns out that T took only 0:45h, i.e. according T's clock. As for the FOR of Earth the distance is still 1Lh, Earth can only conclude that T's clock was slower. I am wondering how you are thinking. Are you really trying to understand what we write (or animate!!), or do you throw a potential counter example against every step you simply do not understand? I proposed several times that you concentrate on real scenarios, i.e. scenarios where we really have measurements. It is an empirical fact that many muons that are created in the upper atmosphere reach the earth's surface. But the halftime of the muons is too short to reach the earth's surface, even if they would travel at near light velocity. Or take muons in an accelerator: where given their half life they could maybe not even make one complete turn through the synchrotron, it is measured that it runs about 30 times through it. This is real stuff, not relativity applied to a science fiction scenario. *So Earth, X, and T on one side, and the missile on the other side, agree about their relative velocity: From Earth, X, and T: 60 LMinutes / 75 minutes = 0.8c From the missile: (0.6 x 60 LMinutes)/45 minutes = 0.8c. "Exactly as it should be."
  8. Without saying what is time dilated and what is length contracted, and for whom this is a very imprecise remark. Nothing follows from it. No, of course not. T travels in the direction of X, so he will see it coming closer immediately. Again you are mixing up what actually occurs, and what any observer sees. Signal delay has nothing to do with relativity. You only need to take signal delay in account when you want to calculate what the observers actually see. Let's change the scenario a little: Earth, T and X register their time readings and measured distances in a logbook. After T returns at earth, they can compare their logbooks. Or T can stay at X and send the data from his logbook to Earth, and the other way round. In this way we can leave out effects of time delay. Sigh... Why don't you let T travel back from X to Earth? And your 'as seen' is again ambiguous. Let first try my 'logbook approach'. So the missile has its logbook too. And it shows that the trip took 45 minutes for the missile. The missile also registered the time of X's clock, and Earth's clock when it arrives, and sees that according to these (synchronised) clocks, his trip took 1 hour and 15 minutes, exactly 1Lh/0.8c, what is expected from the Earth's and X's FOR. When you actually mean 'observes' with 'seen': Earth will only see that the missile started from X after one hour, the time light takes to reach Earth. But then, oh shock, the missile arrives only 15 minutes later. So it looks as if the missile took only 15 minutes. But the earth observer is not so stupid. He knows that he got the signal of the missile's start after 1 hour. So he concludes that the trip took 1 hour and 15 minutes. So it all fits. This I would have missed. One can see that you have relativity in your blood. With me it is only in the top of my head, and it sometimes costs me an awful lot of thinking.
  9. Because it is T that is traveling with 0.8c in Earth's and X's FOR. It is traveling the contracted distance between Earth and X. There is also length contraction of T seen from Earth, but only for what is moving, i.e. T's rocket. It is shorter from the FOR of Earth and X. But Earth and X are not traveling from the exhaust and the frontside of the rocket in your scenario.
  10. No, no and no again. From FOR of the Earth there is no length contraction, but only time dilation on the clock of T From FOR of T, there is only length contraction of the distance Earth -> X, but no time dilation on his own clock The end result is the same: Earth and T agree that at the moment of arrival of T at X , the clock of T shows 45 minutes triptime. Trip time calculation of T: distance x gamma /speed = 60Lm x 0.6 / 0.8 = 45 minutes Trip time seen by Earth according Earth's clock: 60 Lm / 0.8 = 75 minutes. But during the trip, Earth sees the clock running slow according the same factor of 0.6: So, trip time as Earth can calculate for T: distance (60LM / 0.8) x 0.6 = 45 Minutes. And this is also what Earth sees on T's clock when it arrives at X.
  11. Sorry, you are still mixing FORs: According to Earth's clock, the trip of T to X takes 1Lh/0.8c = 75 Minutes. From earth one sees the moment of arriving of T at X and looks at its clock, it only shows 45 minutes. (Of course one sees this only 1 hour after arrival of T at X, but that is just signal delay.)
  12. You are mixing up two things; - in Earth's and X's FOR the distance between them simply does not change because some spaceship happens to travel from Earth to X. - However, T is moving in this FOR, and so its spaceship and everything on board is length contracted. Apply md65536's criteria: is it moving? no --> no length contraction (the distance between Earth and X is not moving!) yes --> that what is moving is length contracted (and time dilated) I would say: for the traveler the distance between Earth and X is length contracted. Just as the shadow of an object can be shorter as the object itself: it really is shorter. (a shadow is a projection of the object on the horizontal plane). Maybe (maybe...) it helps to see it that way. Two different inertial frames have different projections of events (and distances between events) on their respective time and space axes. But the observers agree on 'the real length' between two events , i.e. the distance as defined in Minkowskian spacetime.
  13. But why don't you say it the simplest way? The speed of T is 0.8c in the FOR of earth and planet X. There is no length contraction of the distance in the FOR of earth and X. Yes, in the FOR of Earth and X. What an observer from Earth sees is time dilation: the clock of T seems to run slow by a factor of 0.6. So the Earth's observer, using T's clock, T needs only 0.6 x 60 minutes = 36.66 minutes. According T however, the distance between Earth and X is length contracted 0.6 x 1Lh, and his own clock runs normally, so he does that distance in ... 0.6 x 1Lh x 60 minutes = 36.66 minutes. So both Earth's observer and T see the same: T's clock shows that the trip took 36.66 minutes*. But according to Earth's own clock it took 1 hour/(0.8c) = 1 hour and 15 minutes. * That it takes another hour before he actually sees T arrive a X plays no role. He can see T arrive at X, and that his clock shows 36.66 minutes 'trip time'.
  14. Which makes no sense at all. From the FOR of the earth, you just see T traveling with 0.8c. A ruler attached to T will be length contracted with a factor of 0.6, but the distance between Earth and planet X will still be 1 Lh because they are still in the same FOR. So after one hour, T has simply traveled 0.8Lh in the FOR of Earth and X.
  15. No, you are not, and the syndrome that Swanson, Markus, md65536, Janus, Bufofrog, and I have, is that we have a more than superficial knowledge of relativity. Let's assume, as you do, that Earth and planet X are in the same inertial frame. Two spaceships, T1 and T2 (Traveler) make up for planet X, 1 light hour away. T1 travels with 0.8c, and T2 with 0.6c. What is the distance from Earth to Planet X? When T1 arrives at Planet X how far did T1 travel from the view of Earth's and planet X's FOR? When T1 arrives at Planet X how far did T2 travel from the view of Earth's and planet X's FOR? So how far is planet X from Earth?
  16. Of course not, as md65536 explained. The earth sees the travelling clock running slower by a factor of 0.6. Further your diagrams 5 and 6 do not make sense. Spacetime diagrams should always be drawn from one single inertial frame. But the travelling clock changes its inertial frame. And the gap is an artifact of the physically not realisable instantaneous change of inertial frame. In reality it would be something like this: From here. You do not need to invoke General Relativity (we do not have curved spacetime), SR can handle this.
  17. No. You should know if you had read my posting: the distance to X is not the same for A and B. For A the distance to X is contracted. And now stop with this 'observing'. The changing signal delay only makes the example more complicated. Just assume that A and B are intelligent enough to account for the signal delay, OK?
  18. 😄 Yes, maybe. You recognised what was in the back of my head when I wrote that...
  19. AFAIK, the real problem he wanted to solve is that Newtonian gravity does not fit to Special Relativity, especially that nothing can go faster than light. In Newtonian gravity, gravity is instantaneous. To say it a bit more technically: Newtonian gravity is not Lorentz invariant. @DEFinning: Just to tell you: on the day that somebody joins the forum, he can only post 5 times. So you reached the limit for today. From tomorrow on you can post again, and as much as you want.
  20. That is true. That objects with different mass accelerate exactly the same in a gravity field was already discovered by Galileo, and mathematically underpinned by Newton. Where Einstein went further is to wonder why mass has such totally different effects (inertia against forces, and the same attraction in a gravitational field). He realised (at least) two things (which are in fact just mirror phenomena, but it helps to spell them out): In a windowless laboratory, it is impossible to experimentally find out if you are put in a (homogeneous) gravitational field or suddenly accelerating if the same laboratory is in free fall in a (homogeneous) gravitational field, you can do no single experiment that shows you are accelerating From this he concluded that 'inertial mass' and 'gravitational mass' are exactly the same thing, and so are gravitation and acceleration. However, normally homogeneous gravity fields do not exist (only on small scales gravity fields can be approximated by homogeneous fields). To get the mathematics sound, Einstein had to use (difficult, even for him) techniques from differential geometry. And so he came to the conclusion that gravity can be described as spacetime curvature. In this way Einstein could explain the orbit of Mercury, which showed deviations from Newtonian gravity, and the bending of light in gravitational fields. And there followed many more discoveries and predictions which only make sense when using General Relativity. Phenomena that would not exist at all is Newtons theory would be correct.
  21. Sigh... First, I expect from you that you really explain to us how it is possible that muons reach the earth's surface. The (didactic) importance of that is either you see that you can't, in which case you know that your intuitions are wrong; or you think you can explain it, we see how you do it, and pinpoint precisely to the point where you make an error. Secondly, already said many times, you should start with the explanation why the twins did not age equally, and they agree on this difference. What observers see during the traveler's trip unnecessarily complicates the situation. But I know that for many people this is some kind of show stopper, so, look here in Wikipedia. Ask us questions if you do not understand it. And 'not understanding' is not the same as 'it is wrong'. Thirdly, just another try in the hope you will see the light: Say the traveler flies with 0.8c to the planet Solaris, 10 light years away, and to keep it simple, earth and Solaris are in the same frame of reference. Now for the traveler the distance, due to length contraction, is only 6 light years. Because the home stayer and the traveler agree on the speed of the traveler, that means that the traveler does the trip in 0.6 the time compared to the view from the earth. Moving back home of course the same. So the traveler grew 15 years older, the home stayer grew 25 years older. The asymmetry lies in the fact that the twins do not agree on the distance traveled. But because the twins agree on their different ages now, it means also that they do not agree on their time measurements. Taking that into account, the twins can be sure they live in the same reality: they agree on their age difference. And now, PLEASE, instead of throwing another conflicting intuition of yours at my post, work as carefully as you can through these points. If you get stuck with the muons, tell us where you are stuck. If you get stuck on the Wikipedia article, tell us exactly where, and why (no, not simply a conflict with your intuition, but where you cannot follow the logic of the explanations given). And tell us why you do not understand that the situation of the twins is not symmetric. Or simply refuse to understand relativity, but then say so honestly. In that case I would suggest to close the thread. So what it wanna be boy, trying to understand, or refusing to understand, yes or no?
  22. As others also notice: you are consistently avoiding to explain from your view why muons make it to the surface of the earth. It is time you take the challenge. Another remark (which might help you with the 'muon-challenge'): you assert that in the so called 'twin paradox', there is an asymmetry, because the effect of the time dilation stays (the traveler has not grown older so much as the home-stayer), but the length contraction has gone (the twins are still equally sized). Truth is that you comparison is wrong. After arriving back home the twin's clocks tick at the same rate, so the time dilation itself is gone, just as the length contraction. However this is not true during the travelling: the length contraction of the length of the trip for the traveler is real, and its 'mirror' for the home-stayer is the real time dilation. As space and time are relative, but spacetime is not, this is no problem at all. Important is that the twins agree on their observations when they are in the same FOR again: they agree that the traveling twin has not aged so much as the home-stayer twin. So they live in the same reality.
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