A constant speed of light in all reference frames? Surely you can't be serious.
in [Relativity]
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From: PD on 11 Mar 2010 10:18 On Mar 11, 7:37 am, "Peter Webb" <webbfam...(a)DIESPAMDIEoptusnet.com.au> wrote: > "Ste" <ste_ro...(a)hotmail.com> wrote in message > > news:860a5e85-6231-4eeb-a3a8-f2b25ced173b(a)x12g2000yqx.googlegroups.com... > > > > > On 11 Mar, 01:58, "Peter Webb" <webbfam...(a)DIESPAMDIEoptusnet.com.au> > > wrote: > >> "Ste" <ste_ro...(a)hotmail.com> wrote in message > > >> > except for the fairly > >> > obvious explanation that it is the reference clock which is undergoing > >> > a "real" slowdown. > > >> Or, that you have no idea of what SR predicts, and have completely and > >> falsely assumed that observers see clocks jump ahead when turnaround > >> occurs. > > > I'm merely going off what "experts" here say happens. I didn't say > > there is a "leap ahead". Paul Draper (if I remember correctly) said > > there is a "leap ahead". Now perhaps I misunderstood, but that is what > > was said. > > Perhaps that was what he said. > > But now you know. > > No leap ahead. http://scope.joemirando.net/faqs/Relativity/SR/TwinParadox/twin_gap.html This and the supporting links give some of the context here.
From: PD on 11 Mar 2010 10:47 On Mar 10, 7:12 pm, Bruce Richmond <bsr3...(a)my-deja.com> wrote: > On Mar 10, 10:50 am, PD <thedraperfam...(a)gmail.com> wrote: > > > On Mar 9, 7:58 pm, Bruce Richmond <bsr3...(a)my-deja.com> wrote: > > > > On Mar 9, 9:31 am, PD <thedraperfam...(a)gmail.com> wrote: > > > > > On Mar 8, 11:53 pm, Bruce Richmond <bsr3...(a)my-deja.com> wrote: > > > > > > On Mar 8, 1:58 am, "Inertial" <relativ...(a)rest.com> wrote: > > > > > > > "Bruce Richmond" <bsr3...(a)my-deja.com> wrote in message > > > > > > >news:29fd9f7d-c9b4-41e6-b33a-585c3e0e7acf(a)q23g2000yqd.googlegroups.com... > > > > > > > > On Mar 7, 9:48 pm, "Inertial" <relativ...(a)rest.com> wrote: > > > > > > >> "Bruce Richmond" <bsr3...(a)my-deja.com> wrote in message > > > > > > > >>news:1c6a2640-39f5-4ea4-9c85-127e71f4e6a2(a)33g2000yqj.googlegroups.com... > > > > > > > >> > On Mar 7, 6:58 pm, "Inertial" <relativ...(a)rest.com> wrote: > > > > > > >> >> "Peter Webb" <webbfam...(a)DIESPAMDIEoptusnet.com.au> wrote in message > > > > > > > >> >>news:4b943853$0$11336$afc38c87(a)news.optusnet.com.au... > > > > > > > >> >> > "Inertial" <relativ...(a)rest.com> wrote in message > > > > > > >> >> >news:4b942bcf$0$27789$c3e8da3(a)news.astraweb.com... > > > > > > >> >> >> "Peter Webb" <webbfam...(a)DIESPAMDIEoptusnet.com.au> wrote in > > > > > > >> >> >> message > > > > > > >> >> >>news:4b93bf73$0$28464$afc38c87(a)news.optusnet.com.au... > > > > > > > >> >> >>>>> 1) your statement: "For clarity, both effects are purely > > > > > > >> >> >>>>> observational - SR presumes (ideal) clock mechanisms are > > > > > > >> >> >>>>> completely > > > > > > >> >> >>>>> unaffected by a clock's motion." -- I agree the physical > > > > > > >> >> >>>>> mechanism > > > > > > >> >> >>>>> of > > > > > > >> >> >>>>> the clock is unaffected, but this is a really misleading > > > > > > >> >> >>>>> statement, > > > > > > >> >> >>>>> since the amount of proper time that the clock consumes is > > > > > > >> >> >>>>> affected > > > > > > >> >> >>>>> by > > > > > > >> >> >>>>> its motion. Are you trying to say > > > > > > > >> >> >>>> I was "trying to say" exactly what I did say. If you didn't find > > > > > > >> >> >>>> it > > > > > > >> >> >>>> clear enough, try this: relative slow-downs/speed-ups observed in > > > > > > >> >> >>>> the > > > > > > >> >> >>>> readings of SR's ideal clocks aren't due to changes in the tick > > > > > > >> >> >>>> mechanisms of those clocks. > > > > > > > >> >> >>> I still don't find it clear, as it begs the question - it says > > > > > > >> >> >>> what > > > > > > >> >> >>> doesn't cause the change, not what does cause the change. > > > > > > > >> >> >>> The standard SR answer is much more direct - the clocks slow down > > > > > > >> >> >>> due > > > > > > >> >> >>> to > > > > > > >> >> >>> relativistic time dilatation from them being in different > > > > > > >> >> >>> reference > > > > > > >> >> >>> frames. > > > > > > > >> >> >>> Is that standard position of SR also your position? Or is your > > > > > > >> >> >>> somehow > > > > > > >> >> >>> different? > > > > > > > >> >> >> SR says that the difference in clock sync (clock settings) cause > > > > > > >> >> >> the > > > > > > >> >> >> measurement of length to be contracted and measurement of clock > > > > > > >> >> >> ticking > > > > > > >> >> >> rates to be dilated. > > > > > > > >> >> > More or less. > > > > > > > >> >> That's what it is :) > > > > > > > >> >> > But I asked you about *your* position, not SR's position. > > > > > > > >> >> My position is SR's position > > > > > > > >> >> > Do you agree that that the clocks slow down due to relativistic time > > > > > > >> >> > dilation, as predicted by SR, or not? > > > > > > > >> >> They are measured as slower, just as a rod is measured as shorter. > > > > > > >> >> This > > > > > > >> >> is > > > > > > >> >> due to the difference in simultaneity. They don't slow down because a > > > > > > >> >> moving observer is looking at them any more than a rod shrinks because > > > > > > >> >> a > > > > > > >> >> relatively moving observer is looking at it. > > > > > > > >> >> Here's a little example you might follow .. with time differences > > > > > > >> >> exagerated > > > > > > >> >> for clarity > > > > > > > >> >> Here are six clocks, in tow rows (S and S'), all ticking at the > > > > > > >> >> correct > > > > > > >> >> rate, but set with different times... > > > > > > > >> >> S' 10:30 11:00=A 11:30 <--v > > > > > > >> >> S 11:30=C 11:00=B 10:30 -->v > > > > > > > >> >> Clocks B sees the A is synchronized with it. > > > > > > > >> >> Now .. the clocks are moving in opposite directions so after an hour > > > > > > >> >> we > > > > > > >> >> have > > > > > > > >> >> S' 11:30 12:00=A 12:30 > > > > > > >> >> S 12:30=C 12:00=B 11:30 > > > > > > > >> >> Clock A has moved away from clock B .. but another clock (C) in S can > > > > > > >> >> see > > > > > > >> >> the time on it. Clock C sees that clock A is half an hour slow (A > > > > > > >> >> shows > > > > > > >> >> 12:00 when C shows 12:30). So according to the clocks in S, clock A > > > > > > >> >> is > > > > > > >> >> ticking slower. We also note that clock B now sees a *different* S' > > > > > > >> >> clock > > > > > > >> >> next to it as being fast (it shows 12:30 when B shows 12:00) > > > > > > > >> >> If you look at the same scenario but from the point of view of the > > > > > > >> >> other > > > > > > >> >> row > > > > > > >> >> of clocks, you get symmetric results. > > > > > > > >> >> This is how clock synch affects measured ticking rates for moving > > > > > > >> >> clocks > > > > > > >> >> in > > > > > > >> >> SR. Even though the clocks themselves do NOT change their intrinsic > > > > > > >> >> ticking > > > > > > >> >> rates.- Hide quoted text - > > > > > > > >> > Looks good, but let's take it one step further. The observer with > > > > > > >> > clock A jumps to frame S" which is traveling in the same direction as > > > > > > >> > S relative to S' but at twice the velocity. > > > > > > > >> > S" 1:00 12:00=A 11:00 -->2v > > > > > > >> > S' 11:30 12:00=A 12:30 <--v > > > > > > >> > S 12:30=C 12:00=B 11:30 -->v > > > > > > > >> > Clocks A and B continue to tick at there same intrinsic ticking rate > > > > > > >> > and an hour later A has overtaken B. > > > > > > > >> > S" 2:00 1:00=A 12:00 -->2v > > > > > > >> > S' 12:30 1:00=A 1:30 <--v > > > > > > >> > S 1:30=C 1:00=B 12:30 -->v > > > > > > > >> > The above provides the same situation as the twins paradox.. Clock A > > > > > > >> > left clock B and returned. So why doesn't clock A show less time > > > > > > >> > elapsed than B? (Note the clocks in S" are further out of sync than > > > > > > >> > those in S due to the higher velocity.) > > > > > > > >> The three clock situation cannot be so easily drawn .. bit like trying to > > > > > > >> drawing a three dimensional figure in 2d :) This sort of diagram only > > > > > > >> really works for a single pair of clocks looking from a third frame in > > > > > > >> which > > > > > > >> they move with the same speed. Things are trickier when there is frame > > > > > > >> jumping going on :):)- Hide quoted text - > > > > > > > >> - Show quoted text - > > > > > > > > The question still remains, if there is no change in the tick rate of > > > > > > > the clock, how can clock A have fewer ticks recorded when it is > > > > > > > brought back to clock B? > > > > > > > Look at the Lorentz transforms to see. Its all due to clock synch.- Hide quoted text - > > > > > > > - Show quoted text - > > > > > > You are going to give yourself a head cold with all that arm waving. > > > > > You are saying the tick rate doesn't change, yet SR says that the > > > > > returning twin's clock will show less elapsed time. You don't see any > > > > > conflict there? > > > > > No, there is no conflict. When you say that the tick rate does not > > > > change, this is a LOCAL statement. What it means is that a process > > > > measured locally with this clock will still have the same duration. > > > > That is not what we were discussing. I agree that the clock continues > > > to tick at a rate of one second per proper second in the rest frame of > > > the clock. The question was whether the slowed tick rate measured in > > > the frame of the stay at home twin is real, or an illusion due to the > > > clock sync proceedure, as length contraction is. > > > I don't know that length contraction IS an illusion. Length is > > *defined* operationally by relying on simultaneity, and so the REAL > > length according to that definition is of course frame-dependent, > > because simultaneity is frame-dependent. > > > > If it is an illusion > > > the accumulated time on the two clocks should be the same when they > > > are brought back together. The way Inertial described it, it came > > > across as an illusion caused purely by clock sync. > > > > I hate discussing what is "real". In a sense length contraction is > > > real because the pole will fit into the barn. > > > Absolutely. If I have a clear understanding of what "simultaneous" > > means in a given reference frame, and I close the barn doors > > simultaneously with the pole between them, and there are no marks on > > the doors where the pole hit either one of them, then I can't think of > > any sensible meaning of "fit" that would hold these circumstances to > > be true and yet the pole does not fit in the barn in this frame. And > > since the pole fits, I cannot think of any sensible meaning of > > "shorter" where the pole would fit in the barn and yet be not shorter > > than the barn. > > Careful here. I don't see how you can claim that the rod really is > shorter but that the clock didn't really slow down. I didn't say that. The length of the rod depends on simultaneity, and simultaneity is frame-dependent. The pole fits in the barn in the barn frame because the doors are shut simultaneously *in the barn frame*. But in the pole frame, the doors are not shut simultaneously at all. So did the pole "really" fit in the barn? Yes, according to the definition of "fit" that makes sense -- but clearly this is a frame-dependent conclusion. > The fact that the > rod has different measured lengths at the same time tells me that the > measured length is a matter of perception, which can be distorted. No, not perception. If it were perception, then there would be a sensible way to measure the length of the rod that would dispense with this frame-dependence. However, there is no sensible way to define length that gets around this frame dependence. The *only* sensible way to define length happens to rely on simultaneity, and therefore is intrinsically a frame-dependent quantity, because simultaneity is frame-dependent. This is not an illusion. It is just how length is physically defined. This should not worry you too much. Velocity is another very real physical parameter which is frame dependent, and it just takes a moment's thought to understand why it is frame-dependent and get over it. > But the fact that the returned clock has less elapsed time tells me > that it isn't just how I looked at it. If we are to agree that length > contraction and time dialation are real I'm good with that. But don't > then tell me that the clock didn't slow down. It doesn't slow down for the measuring of local phenomena. If it slowed down in some local sense, then muons as measured locally by this clock would not have a half-life of 2.2 microseconds but something longer. But they don't. I do understand what your frustration is. In the twin puzzle, when the two clocks are brought to rest relative to each other, they have different readings, and so the slow-down is in this sense "real", where there is no such persistence of length difference in the barn- and-pole puzzle, and so it seems less "real". Part of the issue here is that you're not really measuring the same kinds of thing in the two cases. In the twin puzzle, the clock is measuring a "proper time" of the whole trip through two different paths in spacetime. In the barn- and-pole puzzle, you'd have to be measuring the "proper length" of some path through two different paths in spacetime, and the way it is posed that's not what you're measuring at all. Part of the issue here is making oversimplified statements. One example is thinking that "relative motion produces slowing of a clock". Well, the twin puzzle is *designed* to dispel that oversimplification by reminding you that the Earth twin is moving relative to the traveling twin, but it did not lead to a slowing of the Earth twin's clock at all, did it? Another example is thinking that "reality of length contraction or time dilation should be indicated by persistence of the effect, and that any instance of motion should produce this persistence if it is real." That simply is not the case, and the comparison of the twin puzzle and the barn and pole puzzle should dispel that oversimplification. > It slowed in our frame > but the traveling twin couldn't detect it because he used the > coordinates of his new frame of reference to measure it.> > But with length > > > contraction there is no accumulated length to inspect when the pole is > > > brought to rest. > > > This is true. The twin puzzle is a different animal that the barn-pole > > paradox. In the twin puzzle, there is no symmetry in terms of inertial > > motion. One twin is DEFINITELY not residing wholly in one inertial > > reference frame, and that is a frame-independent observation. > > > > I can see that the measured slowing of the clock is > > > due to the rotation of the time coordinates when it changed frames, > > > but that doesn't make it any less real. > > > > > For example, if the half-life of a muon that is slow in frame A and is > > > > measured with a clock at rest in A is 2.2 us, then if you make the > > > > same measurement of the half-life of a muon that is slow in frame B > > > > and is measured with a clock at rest in B, clock B will still show the > > > > half-life to be 2.2 us. In this sense, we say that the clock tick rate > > > > has not changed, because measurements of local phenomena are > > > > unchanged. > > > > Yes, but again you are measuring locally, more or less in the rest > > > frame of the muon. We know that if we measure the half life of a fast > > > moving muon it is longer, as if its personal clock was ticking slower.. > > > > > However, this does NOT mean that the tick rate of clock B will agree > > > > with the clock rate of all other clocks, nor that it will read the > > > > durations of nonlocal processes to be the same. > > > > > Do you see the distinction? > > > > If we set up a light clock with a vertical bouncing beam, and have it > > > send a flash back to the stay at home twin every time the beam hits > > > the top, we can tell just how fast the clock is ticking. The signal > > > will be doppler shifted, but the total count is what it is. None of > > > the flashes drifted off and avoided detection. I am not claiming this > > > slowing is due to motion wrt an ether. It is due to the finite speed > > > of light and how we define/construct the coordinate systems. > > > The last sentence is right, but how we define/construct the coordinate > > systems is constrained by the structure of spacetime (and this in fact > > produces the finite speed of light). That is, there is no way to > > define/construct a coordinate system in our spacetime such that these > > effects go away. (You are free to try.) > > > PD > > > > Bruce > >
From: glird on 11 Mar 2010 10:58 On Feb 27, 10:38 pm, glird <gl...(a)aol.com> wrote: > << If physicists understood the equations in segment 3 of Einstein's 1905 STR paper, they would KNOW the following things: 1. Einstein never did accurately derive the LTE. 2. He neither understood his own OR Poincare's equations. 3. Neither has any physicist then or now. (If they did, they would know _and publicize_ the fact that the value of (delta tau)/(delta t) imposed by his EQUATIONS disagrees with that required by the LTE!) Lest you think I am being too critical of physicists, thus indirectly of physics as well, I will now tell you WHY they don't understand the equations: ... CALCULUS IS A BLINDFOLD over the eyes of physicists and mathematicians. Therefore, dear physicists, it isn't your fault that you don't understand E's high-school-level mathematics. ... Since it is obvious that no physicist would agree with me on this, here is a challenge for you: In the next sentence, answer the first two questions and then answer, if you can, the third and most significant one. In his equation tau = a(t - vx'/{c^2 - v^2}), where did the "a" come from and what does it signify; and IF it IS "a function phi{v) at present unknown" WHAT is its value if, as he later said, "phi(v) = 1"? > Although there were another 300 postings on this thread, NOBODY has answered this challenge. The reason is obvious: It's because I was right. glird
From: Dono. on 11 Mar 2010 11:02 On Mar 11, 7:58 am, glird <gl...(a)aol.com> wrote: > snip< Back to slurring Einstein, Lebau?
From: jem on 11 Mar 2010 11:50
harald wrote: > On Mar 7, 1:09 am, Bruce Richmond <bsr3...(a)my-deja.com> wrote: >> On Mar 6, 7:26 am, "Peter Webb" <webbfam...(a)DIESPAMDIEoptusnet.com.au> >> wrote: >> >> >> >>> "Bruce Richmond" <bsr3...(a)my-deja.com> wrote in message >>> news:26e68f86-9827-4534-9390-31137fb9853e(a)q15g2000yqj.googlegroups.com... >>> On Mar 5, 1:04 am, "Peter Webb" <webbfam...(a)DIESPAMDIEoptusnet.com.au> >>> wrote: >>>>> You are reading more into that than what I wrote. I am not choosing >>>>> LET over SR. They use the same math >>>>> ================================================== >>>> Well, e = mc^2 is maths. It appears in SR, but not LET. >>>> So I guess you were wrong, and they don't use the same maths. >>> It can be derived using LET. SR wasn't the first place it showed up, >>> so it doesn't own it any more than LET does. >>> Others here say they use the same math, so I guess you are wrong :)~ >>> _________________________________ >>> You said that SR uses the same maths. >>> 1. e=mc^2 is maths >>> 2. It appears in SR >>> 3. It does not appear in LET >>> 4. Therefore the maths in LET is not the same as the maths in SR >>> Which part of this do you disagree with? >> Like I said, it can be derived from LET just as easily as SR. How >> many books on LET have you read? ;) > > :-)) I doubt that there ARE any books on "LET", which is based on > (erroneous) revisionist history. According to Lorentz and Einstein > there was Lorentz's electrodynamics theory of before 1904, and SRT > which is based on Lorentz 1904 and Einstein 1905 - see Einstein's 1907 > paper as well as the collection "The Principle of Relativity" by > Lorentz et al (funny enough, recently it was subtly changed it into > "Einstein et al!). > > [snip nice arguments against a non-existing "LET") > >>> Similarly, if Lorentz and the others had considered the relationships >>> between energy and momentum in the right way, they would have got e=mc^2. >>> They didn't. More to the point, Lorentz had no explanation of why the >>> various transforms worked, they were empirical and not theoretical in that >>> described the results of experiments, but provided no theoretical framework. >> Not sure what you mean by that. The Lorentz-FitzGerald contraction >> was proposed to explain experimental results, but there was definitely >> a theory about how it was arrived at. > > Correct. As a matter of fact, Lorentz predicted the correct equation > of electron acceleration in 1904, based on the PoR. > >> It's not like some oddball >> equation was picked out of the air to match the data points recorded >> in the MMX. He was aware that in order to measure the speed of light >> as c in all frames, which what experimental results showed, he had to >> use "local time" that was different from absolute time. And again he >> made a pretty good guess at what that "local time" had to be. > > In fact he was a bit inconsistent in that, and Poincare corrected > that. However, he first learned about that correction from reading > Einstein. > >> I do agree that in a way SR shows how LET arrives at it's results, but >> at the same time I see LET explaining how to get from a single >> absolute frame to the second postulate. SR doesn't attempt to explain >> that, it just postulates it. > > Indeed, that's also what Lorentz stressed. And in his introduction, > Einstein made no secret of the fact that the second postulate stems > from Maxwell's theory. However, Lorentz came to adopt the derivation > of Einstein as that approach is easier (simpler) for students. > >>> You can use LET to calculate time dilation, just as you can use Kepler to >>> calculate orbits. But that doesn't mean that Kepler's theories are the same >>> as Newton's, or that LET is the same as SR. >>> HTH >> I see your point, but it doesn't change the fact that the theories >> make the same predictions. > > The point can be made in different ways, giving inverse impressions. > For example: > You can use SRT without physical model SRT IS a physical model, Harald. A physical model is anything that can be used to infer the outcomes of real-world measurements. In particular, a mathematical theory becomes a physical theory/model when its logical inferences get interpreted as measurement predictions. to calculate time dilation, > just as you can use Kepler's theory to calculate orbits. But that > doesn't mean that Kepler's mathematical theory is the same as Newton's > theory (which includes a physical model), or that Einstein's principle > theory is the same as Lorentz's theory (which similarly includes a > physical model). > > Note: as the one includes the other, Langevin promoted SRT using > Minkowski mathematics but with Lorentz's physical model. > > Cheers, > Harald |