Speed of Time
in [Relativity]
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From: Inertial on 28 Dec 2009 07:38 "Ste" <ste_rose0(a)hotmail.com> wrote in message news:8bb8d8a0-6050-4b64-b129-8f86ca7b32e2(a)e27g2000yqd.googlegroups.com... > On 28 Dec, 11:03, "Dirk Van de moortel" > <dirkvandemoor...(a)nospAm.hotmail.com> wrote: >> Ste <ste_ro...(a)hotmail.com> wrote in message >> >> a35de26f-5383-4b5f-86b5-0c0c3b43b...(a)26g2000yqo.googlegroups.com >> >> >> >> >> >> > On 27 Dec, 11:19, "Dirk Van de moortel" >> > <dirkvandemoor...(a)nospAm.hotmail.com> wrote: >> >> Ste <ste_ro...(a)hotmail.com> wrote in message >> >> >> 82a2de5c-1a2e-48e4-a7e4-76287acb8...(a)j19g2000yqk.googlegroups.com >> >> >>> On 26 Dec, 23:32, "Dirk Van de moortel" >> >>> <dirkvandemoor...(a)nospAm.hotmail.com> wrote: >> >>>> Ste <ste_ro...(a)hotmail.com> wrote in message >> >> >>>> c6d4ea67-9711-4b79-b35f-7bc54e086...(a)n35g2000yqm.googlegroups.com >> >> >>>>> On 26 Dec, 00:30, "Androcles" <Headmas...(a)Hogwarts.physics_q> >> >>>>> wrote: >> >> >>>>>> You should read Dork's twin paradox analysis. He can >> >>>>>> pick up the origin of frame of reference and move it, >> >>>>>> so if you go from London to New York you can do it >> >>>>>> twice without ever going from New York to London. >> >> >>>>>> He says >> >>>>>> quote/ >> >>>>>> "We use 3 inertial reference frames. >> >>>>>> S: The frame of the "stay at home" twin. >> >>>>>> S': The frame of the "outbound part of the trip". >> >>>>>> S": The frame of the "inbound part of the trip". >> >>>>>>http://users.telenet.be/vdmoortel/dirk/Physics/TwinsEvents.html >> >> >>>>>> So if T = 5 years and v = 0.8c, then the stay at home twin will >> >>>>>> have aged 10 years while his travelling twin sister will have aged >> >>>>>> 6 years. >> >>>>>> /unquote >> >> >>>>> I'm afraid I don't understand how he arrives at that conclusion. I >> >> >>>> You see how I arrived at it by looking at >> >>>>http://users.telenet.be/vdmoortel/dirk/Physics/TwinsEvents.html >> >>>> If there is anything unclear about it, let me know - perhaps I >> >>>> can explain. >> >>>> Or if there's a mistake, I can correct it. >> >> >>> There is indeed a mistake. >> >> >> I assume you understood everything about it, so, in which >> >> line do you find the first mistake? >> >> > The mistake is with this "changing frame of reference" business. It's >> > not the frame of reference that changes, the time-lag is on account of >> > the fact that the astronaut accelerates more than the Earth, within a >> > reference frame that encompasses the Earth, the astronaut, and the >> > whole journey. >> >> Sure, if you like, you can use equations where no more >> than the proper accelerations of both twins are used: >> See for instance >> http://arxiv.org/PS_cache/physics/pdf/0411/0411233v1.pdf >> and >> http://en.wikipedia.org/wiki/Twin_paradox#Difference_in_elapsed_times... >> >> In this case however, a simplified *calculation* can be used, >> with simple Lorentz transformations in simple inertial >> reference frames. >> In order to be able to use the transformations, we use >> three of them. (Of course we ignore the fact that the stay >> at home twin is not *really* inertial, since he is on the >> surface of a rotating planet. It can be shown however >> that the effect of this can be ignored, and of course we >> can just as well put the stay at home twin somewhere >> freely floating in space). >> >> The twin who takes the trip can't possible stay in one >> inertial reference frame, but in order to make the >> calculations, we can use two different inertial frames >> to model the trip in the most simplified case. >> If you look at the PDF (1st paragraph of section A), >> you will find a way to use the "proper-acceleration-way" >> to model the simplified situation. It gives the same >> result as the two-frame-jump way. >> Don't you agree? > > Let me be clear I didn't actually disagree with your model within its > own mathematical terms. What I disagree with is the approach which you > say is mathemetically more simple and yet is in fact less intuitive. > The fact that this supposed paradox has not been laid to bed yet > surely proves that's it's in want of a simple explanation. its been laid to bed for many many decades. > And indeed the explanation does seem to be simple: It is > the astronaut > accelerates more. That's part of it .. but you can eliminate acceleration and still get the effect. So its nto a good answer. > If the universe *had* accelerated around the > astronaut, It doesn't > then the astronaut would end up *older* than his twin - but > in fact, a simple accelerometer *proves* that the universe did not in > fact accelerate around the astronaut - the astronaut accelerated > around the universe, and that is why the astronaut returns to Earth > younger. The more general answer is that the travelling twin changed which inertial frame of reference it was at rest in. As I've said, you can modify the scenario to remove any acceleration and still get the effect. So acceleration of an object is not itself the answer.
From: Androcles on 28 Dec 2009 07:31 "Henry Wilson DSc" <..@..> wrote in message news:drsgj5h5ms4tqlc813k98a6uih0bonc5qo(a)4ax.com... > On Sun, 27 Dec 2009 18:38:34 -0800, George Hammond <Nowhere1(a)notspam.com> > wrote: > >>On Sun, 27 Dec 2009 21:30:17 GMT, ..@..(Henry Wilson DSc) >>wrote: >> >> >>> >>> Selling something that doesn't exist is a serious crime....unless >>> it's called god. >>> >>> >>[Hammond] >> Fact of the matter is that God exists, and the hard >>scientific proof has been published in the peer-reviewed >>literature, by me in 2003. >>http://webspace.webring.com/people/eg/george_hammond/Hammond5s1.html >> Selling something that doesn't exist is a serious >>crime.... unless it is called atheism, in which case it is >>only a harmless misdemeanor. > > Oh, hello George...glad to see you read my messages occasionally... > > Did you read about my birthday? Responding to Hammond is a capital offence punishable by plonking, but in your case I'll grant clemency. I'll make a note... Jeezuus H. Wilson's birthday - 25/12/0000.
From: Dirk Van de moortel on 28 Dec 2009 07:44 Ste <ste_rose0(a)hotmail.com> wrote in message 8bb8d8a0-6050-4b64-b129-8f86ca7b32e2(a)e27g2000yqd.googlegroups.com > On 28 Dec, 11:03, "Dirk Van de moortel" > <dirkvandemoor...(a)nospAm.hotmail.com> wrote: >> Ste <ste_ro...(a)hotmail.com> wrote in message >> >> a35de26f-5383-4b5f-86b5-0c0c3b43b...(a)26g2000yqo.googlegroups.com >> >> >> >> >> >>> On 27 Dec, 11:19, "Dirk Van de moortel" >>> <dirkvandemoor...(a)nospAm.hotmail.com> wrote: >>>> Ste <ste_ro...(a)hotmail.com> wrote in message >> >>>> 82a2de5c-1a2e-48e4-a7e4-76287acb8...(a)j19g2000yqk.googlegroups.com >> >>>>> On 26 Dec, 23:32, "Dirk Van de moortel" >>>>> <dirkvandemoor...(a)nospAm.hotmail.com> wrote: >>>>>> Ste <ste_ro...(a)hotmail.com> wrote in message >> >>>>>> c6d4ea67-9711-4b79-b35f-7bc54e086...(a)n35g2000yqm.googlegroups.com >> >>>>>>> On 26 Dec, 00:30, "Androcles" <Headmas...(a)Hogwarts.physics_q> wrote: >> >>>>>>>> You should read Dork's twin paradox analysis. He can >>>>>>>> pick up the origin of frame of reference and move it, >>>>>>>> so if you go from London to New York you can do it >>>>>>>> twice without ever going from New York to London. >> >>>>>>>> He says >>>>>>>> quote/ >>>>>>>> "We use 3 inertial reference frames. >>>>>>>> S: The frame of the "stay at home" twin. >>>>>>>> S': The frame of the "outbound part of the trip". >>>>>>>> S": The frame of the "inbound part of the trip". >>>>>>>> http://users.telenet.be/vdmoortel/dirk/Physics/TwinsEvents.html >> >>>>>>>> So if T = 5 years and v = 0.8c, then the stay at home twin will >>>>>>>> have aged 10 years while his travelling twin sister will have aged >>>>>>>> 6 years. >>>>>>>> /unquote >> >>>>>>> I'm afraid I don't understand how he arrives at that conclusion. I >> >>>>>> You see how I arrived at it by looking at >>>>>> http://users.telenet.be/vdmoortel/dirk/Physics/TwinsEvents.html >>>>>> If there is anything unclear about it, let me know - perhaps I >>>>>> can explain. >>>>>> Or if there's a mistake, I can correct it. >> >>>>> There is indeed a mistake. >> >>>> I assume you understood everything about it, so, in which >>>> line do you find the first mistake? >> >>> The mistake is with this "changing frame of reference" business. It's >>> not the frame of reference that changes, the time-lag is on account of >>> the fact that the astronaut accelerates more than the Earth, within a >>> reference frame that encompasses the Earth, the astronaut, and the >>> whole journey. >> >> Sure, if you like, you can use equations where no more >> than the proper accelerations of both twins are used: >> See for instance >> http://arxiv.org/PS_cache/physics/pdf/0411/0411233v1.pdf >> and >> http://en.wikipedia.org/wiki/Twin_paradox#Difference_in_elapsed_times... >> >> In this case however, a simplified *calculation* can be used, >> with simple Lorentz transformations in simple inertial >> reference frames. >> In order to be able to use the transformations, we use >> three of them. (Of course we ignore the fact that the stay >> at home twin is not *really* inertial, since he is on the >> surface of a rotating planet. It can be shown however >> that the effect of this can be ignored, and of course we >> can just as well put the stay at home twin somewhere >> freely floating in space). >> >> The twin who takes the trip can't possible stay in one >> inertial reference frame, but in order to make the >> calculations, we can use two different inertial frames >> to model the trip in the most simplified case. >> If you look at the PDF (1st paragraph of section A), >> you will find a way to use the "proper-acceleration-way" >> to model the simplified situation. It gives the same >> result as the two-frame-jump way. >> Don't you agree? > > Let me be clear I didn't actually disagree with your model within its > own mathematical terms. What I disagree with is the approach which you > say is mathemetically more simple and yet is in fact less intuitive. Yes, perhaps, to some. But intuition is rather personal and not really measurable. > The fact that this supposed paradox has not been laid to bed yet > surely proves that's it's in want of a simple explanation. "Simple" for one person can be "complicated" or even "downright impossible" for other people. > > And indeed the explanation does seem to be simple: the astronaut > accelerates more. If the universe *had* accelerated around the > astronaut, then the astronaut would end up *older* than his twin - but > in fact, a simple accelerometer *proves* that the universe did not in > fact accelerate around the astronaut - the astronaut accelerated > around the universe, and that is why the astronaut returns to Earth > younger. I don't agree with your usage of "why". I don't see physics as a provider of answers to the "why"-question. I leave that to the philopsophers and theologists. Phrases like "If the universe *had* accelerated" are meaningless to me. The age difference can be calculated with relative velocities and it can be calculated with proper acceleratins. The results are the same. There it ends for me. Dirk Vdm
From: Inertial on 28 Dec 2009 07:48 "Ste" <ste_rose0(a)hotmail.com> wrote in message news:a6faf893-f8b5-4d81-8392-1267de08fa95(a)d20g2000yqh.googlegroups.com... > On 28 Dec, 12:26, "Inertial" <relativ...(a)rest.com> wrote: >> "Ste" <ste_ro...(a)hotmail.com> wrote in message >> >> news:b10fc983-4174-4006-8d32-59ab590a3497(a)k19g2000yqc.googlegroups.com... >> >> >> >> >> >> > On 28 Dec, 05:59, "Inertial" <relativ...(a)rest.com> wrote: >> >> "Ste" <ste_ro...(a)hotmail.com> wrote in message >> >> >>news:55e687f7-b47e-4325-aedc-9584f0234270(a)b2g2000yqi.googlegroups.com... >> >> >> > On 28 Dec, 03:55, "Inertial" <relativ...(a)rest.com> wrote: >> >> >> "Androcles" <Headmas...(a)Hogwarts.physics_q> wrote in message >> >> >> >> >> People are so bitter here! >> >> >> >> > It's not a question of emotion, it's a question of teaching >> >> >> > arrogant >> >> >> > lunatics like you the basics. You forgot to adjust the speed of >> >> >> > lunacy. >> >> >> >> Androcles described himself nicely .. an arrogant lunatic. Though >> >> >> he >> >> >> forgot >> >> >> to add "blatant liar" to his self-description >> >> >> > Indeed. Why is this place so feral? >> >> >> Crackpots who have enormous egos, usually accompanied by a hatred for >> >> Einstein. >> >> >> Usually they are fail physics students who, rather than accept that >> >> they >> >> failed physics, think physics must be wrong, and become convinced of >> >> that >> >> fact. >> >> >> Others think they are intelligent and yet they have not achieved the >> >> fame >> >> the Einstein has (usually for good reason) and so therefore Einstein >> >> must >> >> be >> >> some sort of con artist or charlatan .. and so therefore SR (as it was >> >> something einstein was involved in) must (by association) be wrong. >> >> > So which did you say you were? >> >> None of the above >> >> >> Of course, all physicists must be part of a cult or conspiracy to keep >> >> this >> >> 'truth' hidden. Anyone who disagrees with them if obviously one of >> >> the >> >> runts of the Einsteinian religion. >> >> > I actually think Einstein was on the right track. If he was wrong at >> > all, then he wasn't that wrong. >> >> Indeed .. though he was wrong about some things (particularly later in >> life) >> .. he was, after all, only human. >> >> >> In order to maintain these delusions, they deny the existence of all >> >> the >> >> experiments that support SR, except those that also happen to not >> >> refute >> >> their particular pet theory. They will make ridiculous claims about >> >> what >> >> they mistakenly think SR says in order to 'prove' it wrong (and >> >> instead >> >> show >> >> why it is they failed physics) and go on a character assassination >> >> vendetta >> >> against Einstein. >> >> > I claim to have solved the paradox within the terms of SR. >> >> Its already been solved for a century. > > Indeed. So why does it persist (if only amongst non-physicists)? You just answered it .. because they are non-physicist and haven't (bothered to) learn about the solution. Or they are student physicists who are just learning about it, or do not yet understand SR to apply it correctly. Its a very useful (and well known) puzzle to use when teaching physics, of course. >> > The fact >> > is, the homebody does *not* accelerate as much as the astronaut, no >> > matter what reference frame you choose. >> >> Of course .. that's what *I* have been telling *you* .. and you've been >> arguing that the acceleration is the same. > > I was saying that relativity, or at least the interpretations that I'd > read, all said that all reference frames are equal. No .. they aren't. The inertial frames are equivalent in that if you perform an experiment at rest in one inertial frame, and then perform the same experiment at rest in another inertial frame, then you'll get the same results (because the laws of physics are the same in all inertial frames). That principle has been around for centuries. > And I know a guy > with a PhD who suggests to me that the paradox does not exist, because > the astronaut returns to Earth the same age as his homebody twin. Then he's wrong. Obviously he doesn't properly understand that particular are of physics. > So > clearly there is a lot of popular misconception about an issue that > should be incredibly simple to explain (and trust me, I'd trawled the > internet and couldn't find any easy and intuitive refutation of this > paradox). It doesn't need refuting, because it is not a paradox. There are many explanations of how it works, however (and so why it is not paradoxical, just surprising).
From: paparios on 28 Dec 2009 09:16
On 28 dic, 09:19, Ste <ste_ro...(a)hotmail.com> wrote: > On 28 Dec, 11:03, "Dirk Van de moortel" > Let me be clear I didn't actually disagree with your model within its > own mathematical terms. What I disagree with is the approach which you > say is mathemetically more simple and yet is in fact less intuitive. > The fact that this supposed paradox has not been laid to bed yet > surely proves that's it's in want of a simple explanation. > > And indeed the explanation does seem to be simple: the astronaut > accelerates more. If the universe *had* accelerated around the > astronaut, then the astronaut would end up *older* than his twin - but > in fact, a simple accelerometer *proves* that the universe did not in > fact accelerate around the astronaut - the astronaut accelerated > around the universe, and that is why the astronaut returns to Earth > younger. I always cite the clear and simple explanation of Landau and Lifshitz for this "symmetric" behavior, which goes like this: "Suppose some clocks are moving in uniform rectilinear motion, relative to an inertial system K. A reference frame K' linked to the latter is also inertial. Then from the point of view of an observer in the K system the clocks in the K' system fall behind. And conversely, from the point of view of the K' system, the clocks in K lag. To convince ourselves that there is no contradiction, let us note the following. In order to establish that the clocks in the K' system lag behind those in the K system, we must proceed in the following fashion. Suppose that at a certain moment the clock in K' passes by the clock in K, and at that moment the readings of the two clocks coincide. To compare the rates of the two clocks in K and K', we must once more compare the readings of the same moving clock in K' with the clocks in K. But now we compare this clock with different clocks in K with those past, which the clock in K' goes at this new time. Then we find that the clock in K' lags behind the clocks in K with which it is being compared. We see that to compare the rates of clocks in two reference frames we require several clocks in one frame and one in the other, and that therefore this process is not symmetric with respect to the two systems. The clock that appears to lag is always the one which is being compared with different clocks in the other system. If we have two clocks, one of which describes a closed path returning to the starting point (the position of the clock which remained at rest), then clearly the moving clock appears to lag relative to the one at rest. The converse reasoning, in which the moving clock would be considered to be at rest (and vice versa) is now impossible, since the clock describing a closed trajectory does not carry out a uniform rectilinear motion, so that a coordinate system linked to it will not be inertial. Since the laws of nature are the same only for inertial reference frames, the frames linked to the clock at rest (inertial frame) and to the moving clock (non-inertial) have different properties, and the argument which leads to the result that the clock at rest must lag is not valid." Miguel Rios |