A constant speed of light in all reference frames? Surely you can't be serious.
in [Relativity]
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From: Inertial on 4 Mar 2010 07:16 "Ste" <ste_rose0(a)hotmail.com> wrote in message news:3ba45de3-bdb9-4693-b15a-d58d0f4d929f(a)t23g2000yqt.googlegroups.com... > On 3 Mar, 22:59, PD <thedraperfam...(a)gmail.com> wrote: >> On Mar 3, 11:52 am, Ste <ste_ro...(a)hotmail.com> wrote: >> >> > On 3 Mar, 12:30, "Peter Webb" <webbfam...(a)DIESPAMDIEoptusnet.com.au> >> > wrote: >> >> > > "Ste" <ste_ro...(a)hotmail.com> wrote in message >> >> > > >> You say you are here to learn about SR. >> >> > > > I am here to learn more about the *conceptual basis* of SR. >> >> > > Minkowksi space time? >> >> > No. >> >> How about just spacetime, then, for which there is both a conceptual >> description and a mathematical description? > > No. I would go as far as saying I don't want another word said about > spacetime as a means of answering any of my questions. Tough .. it is an intergral part of SR. You don't get to decide what is SR and what isn't > If an > explanation falls back on appealing to the truth of even a single > equation, Who said anything about equations? > then the explanation is defective as an answer to my > questions. No .. it is YOU who are defective, by refusing to listen to valid explanations because you refuse to learn enough math to understand them. You're truly an arrogant ignorant idiot. The worst kind there is. >> > > >> Do you believe SR is true? >> >> > > > I accept it's mathematical form has some obvious truth, yes. >> >> > > Do you believe that it correctly predicts the results of every >> > > experiment >> > > that it claims to? That clocks run slower, >> >> > No. In SR, clocks *appear* to run slower as you are increasing your >> > distance from the clock. The effect is entirely apparent in SR. >> >> That's not the extent of what SR claims. Muons in a circulating ring >> exhibit time dilation, though they are not receding from the clock at >> all, for example. > > What they exhibit is a longer half-life. Yes > But I'm not sure that a > single variable, time, has been isolated here. Firstly, there is > constant acceleration if the particle is in a ring (and it seems > unarguable that acceleration causes some kind of real change in > behaviour at an atomic level). Careful there might be some math involved there. > Secondly, were an observer travelling along with the muon, he may also > report an increased half-life, as against if he and the muon were > stationary relative to the ring - possibly because the cause of decay, > which is assumed to be random, is actually influenced by the fact that > the environment (as perceived by the muon) is spinning at relativistic > speeds. > > There is certainly a need to account for this behaviour, but I am not > sure it is accounted for by time dilation as opposed to the physical > reality that the muon really is decaying slower. There is other experimental evidence. >> > > and 80 foot ladders can fit through 40 feet barns, >> >> > It remains slightly unclear, but I'm inclined to say no, although it >> > can certainly be made to appear to happen in certain circumstances. >> >> I would be cautious about inclinations. It is pretty easy to make the >> distinction between "appears to" and "does". For example, if I hold >> the doors of the barn open to admit the pole, and at a carefully >> chosen moment, briefly close both barn doors simultaneously and then >> open them again, in such a way that I can verify that the both ends of >> the pole had entered the barn before I closed both doors, then I can >> be pretty sure that the pole was wholly in the barn. I can also then >> check whether there were any strike marks on the barn doors where the >> pole would have struck them. If there are none, then this pretty well >> unambiguously tells you the pole WAS inside the barn, not just >> appeared to be inside the barn. If you think those events (no marks on >> the barn doors, both doors closed simultaneously after entry of the >> pole) can be observed while still maintaining the pole does not fit in >> the barn, you'll have to explain to me how this is. > > This door-marking test is nice in principle, and I agree that the > results would be conclusive. However I fear it is not a test that is > implementable in practice with real materials. It is impractical. But a 'real' contraction (not just some illusion) is what SR predicts. I'd explain how, but you don't want to know >> > > and that the speed of light is measured the same in >> > > every intertial frame of reference and this speed is independent of >> > > the >> > > speed of the emitter, receiver, and underlying medium of >> > > transmission? >> >> > Yes. I think I've been able to reconcile this partially, but only >> > vaguely and within a definitely non-standard conceptual framework, and >> > it is forced to completely dispense with any corpuscular form of >> > matter, and instead relies wholly on fields. Unfortunately it's >> > probably the sort of thing that physicists spend their lives thinking >> > about and never quite put their finger on. >> >> Aha. I hope you did not sprain your wrist while hand-waving. > > Lol. > > > >> > > If you believe all of those things, then you are saying more than "SR >> > > has >> > > some obvious truths in its mathematical form" you are saying it is an >> > > accurate portrayal of reality - ie, what happens when you conduct >> > > those >> > > experiments, what physically and actually happens, is exactly as >> > > predicted >> > > by Relativity. >> >> > I think we all agree that SR portrays reality, but none of us seem to >> > be able to agree on what kind of reality it portrays. >> >> Do you believe there is more than one kind of reality? Namely, do you >> believe there is a reality that matches your expectations for the >> orderliness of that reality, and another reality that does not >> necessarily meet those expectations? > > I'm a materialist (i.e. realist). You can't be a materialist and > believe in more than one kind of reality. You are deliberately ignorant. >> > > If, on the other hand, you do not believe in the twin "paradox" >> > > actually >> > > happening, you don't believe in SR. >> >> > We resolved the twins paradox months ago. The astronaut twin undergoes >> > asymmetrical acceleration, and that is why he returns younger. >> >> Yes, but that is still very much the prediction of SR. > > I didn't realise SR could cope with acceleration. I thought that was > what GR was required for? There is a lot you do not know and do not realize. And it will stay that way. >> > > If you do believe the predictions of SR >> > > that one twin is older, then you believe that time dilation is more >> > > than >> > > some mathematical fiction, its what actually happens in the real >> > > world. >> >> > On the contrary. The involvement of acceleration, which is the domain >> > of GR, makes me wonder why this is held to be a paradox in SR at all. >> >> This is incorrect. SR can handle acceleration just fine. What matters >> here, and what marks the difference between the twins, is the >> straightness of the path (a special term called "worldline" in >> physics) in spacetime. Straighter paths consume longer "proper >> time" (another specialized term in physics). > > Yes, and off we go into la-la land again. > > (I know exactly what you're describing, but it is the most obtuse way > of describing the essential physical reality.) You wouldn't know .. you are deliberately ignorant. >> > And yes, the acceleration causes real effects for the astronaut twin. >> >> Yes indeed, and it is remarkable that the effects are precisely in the >> quantity that is predicted by SR. > > I need some clarification Paul. My understanding is that SR does not > deal with acceleration You've been corrected several times already .. how many times do you need to be told before it sinks into your thick skull >- one must "reanchor" the frame of reference > each time velocity changes. Now is that correct or not? > > > > >> > > You seem to agree they are "mathematical truths". Do you also agree >> > > those >> > > equations correctly predict the outcomes of real world experiments, >> > > which >> > > means they are far more than simply "mathematical truths"? >> >> > The question is of interpreting the mathematical predictions. As I say >> > above, there is a difference between what is real and what is merely >> > apparent. >> >> See above regarding the pole and the barn. In terms of the >> observations given, you'll have to explain to me how the pole would >> have really NOT fit into the barn (but only apparently) and been >> consistent with the observations noted. > > Ok. We have an observer standing by a door of the barn. We call this > the near door. The other door is the distant door. Now, we close the > distant door, and then reopen it. Then we send the ladder in (at > relativistic speeds). The observer watches the ladder go in. Then we > close the near door behind the ladder. The propagation delays from the > distant door mean that, according to the observer standing by the near > door, the doors are closing simultaneously, but in fact the distant > door had closed and reopened before the ladder had even entered the > barn. Hence the ladder fits apparently, but not really. Nope. That's not what happens at all. Again . you are deliberately ignorant. Or a liar.
From: Inertial on 4 Mar 2010 07:19 "Ste" <ste_rose0(a)hotmail.com> wrote in message news:be65914d-1e32-4c41-a3a7-7037f34d53bb(a)c16g2000yqd.googlegroups.com... > On 4 Mar, 09:39, "Peter Webb" <webbfam...(a)DIESPAMDIEoptusnet.com.au> > wrote: >> "Ste" <ste_ro...(a)hotmail.com> wrote in message >> >> news:8984b4b4-92e9-466a-ad51-20e6b4e815bc(a)u9g2000yqb.googlegroups.com... >> On 3 Mar, 22:23, "Inertial" <relativ...(a)rest.com> wrote: >> >> >> >> >> >> > "Ste" <ste_ro...(a)hotmail.com> wrote in message >> >> >news:64d02f70-01e4-44a5-a5ab-41429bf37f71(a)q15g2000yqj.googlegroups.com... >> >> > > I'm sure I said something about the ludicrous assertions that some >> > > people here have made about the conceptual basis of SR. That is, >> > > assertions that verge on meaningless, like "rotation into time" as an >> > > explanation for length contraction. Or even observed time dilation >> > > (in >> > > SR) being "real" as opposed to merely a function of propagation >> > > delays. But none of this fundamentally challenges SR. >> >> > Time dilation isn't anything to do with propagation delays .. they do >> > NOT >> > cause time dilation. It IS real in that it has been measured >> > experimentally. >> >> > Your denial of reality is another trademark of a crackpot. >> >> I'm not denying it. I'm saying experiments that involve acceleration >> are the realm of GR (as I understand it), and that acceleration is the >> cause of "real" time dilation. We're talking about SR, and therefore >> we cannot be talking about any experiment that involves acceleration. >> >> ________________________________ >> It is true that you cannot devise an experiment whereby two clocks are >> together and then separated without at least one of them experiencing >> acceleration at some point; that unfortunately is a mathematical fact, >> not a >> physical one. > > No, it is a physical fact. It neither, as you can achieve such a synchronization without acceleration during the process .. but it involves two additional clocks to make the process work >> However, you can make the contribution of acceleration "vanishingly >> small", >> by designing thought experiments where the accelerations are very low and >> slow. Sending a rocket to another star is one such example. > > Not really, because if the total acceleration is small, then so is the > speed. That is a nonsense argument. Acceleration can be small and speeds very large. >> You now appear to be claiming that you *don't* believe the twins will be >> different ages due to simple time dilation in SR, which means you *don't* >> agree that SR is correct. >> >> So, yet again, like the uber-crank you are, you have completely changed >> your >> story. >> >> Yesterday you believed in the predictions of SR. Now you say you don't. >> >> Its called *inability to learn*. > > <yawn> Yeah .. yawn away .. and remain a fool
From: Inertial on 4 Mar 2010 07:33 "Peter Webb" <webbfamily(a)DIESPAMDIEoptusnet.com.au> wrote in message news:4b8f8d23$0$24251$afc38c87(a)news.optusnet.com.au... > > >>> I'm not denying it. I'm saying experiments that involve acceleration >>> are the realm of GR (as I understand it), and that acceleration is the >>> cause of "real" time dilation. We're talking about SR, and therefore >>> we cannot be talking about any experiment that involves acceleration. >>> >>> ________________________________ >>> It is true that you cannot devise an experiment whereby two clocks are >>> together and then separated without at least one of them experiencing >>> acceleration at some point; that unfortunately is a mathematical fact, >>> not a physical one. >> >> No .. you can do that without acceleration. But it involves multiple >> clocks. >> >> > > Well, I put it to you that acceleration is the second derivative of > position You can put that all you like :):) > .... > > There is one way you can get close. You could have clock circling the > earth in a plane, and flying past some reference clock fixed to the earth, > and compare times when they are close. If it is going in a circle, it is accelerating. > Unfortunately though it could be argued correctly that the flying clock is > actually accelerated more, because it circles the earth faster, > effectively the additional centrifugal force reduces the measured force of > g in the plane, and I suspect that the nett effect is the opposite to that > predicted by SR - a very slight increase in the rate at which time passes. > I could be wrong. > > However, I stress that these effects of GR are typically many orders of > magnitude lower than those from SR, and it is obviously very hard to > design experiments which even show the GR effects, the SR ones are so > dominant, and now a standard part of engineering. Not in a GPS satellite .. the effects due to difference in gravitational potential (GR) outweigh the SR effects. > I am sure you are aware that GPS satellites have to compensate for both SR > and GR. It is interesting though that these are for vastly different > reasons. SR causes the effects you would expect on the accuracy of the > clocks, but GR's effect is mostly not through time dilation but rather > through directly affecting the orbit of the satellite. Regarding the clock sync issue ... A way to get separated clock sync without acceleration during the process. A---> C1 C C2 <---B Have two clocks (A and B) already in motion (before you start the sync process) moving in opposite directions at equal speeds and distances from a common point c, where they will pass each other When the meet, synchronise their clocks as they pass (no stopping) A---> C1 C C2 <---B As they continue on their way they each pass two other clocks, C1 and C2, and sync with those as they pass A---> C1 C C2 <---B Clocks C1 and C2 are now synchronized, effectively in the same way as slow clock movement. You only need acceleration if the two moving-apart clocks are initially at REST when they are synced together and if they come to REST when they reach the extremes. having them in motion already avoids the initial acceleration from rest, and using two additional clocks (C1 and C2) avoids deceleration when to come to rest.
From: mpalenik on 4 Mar 2010 08:40 On Mar 4, 3:12 am, Ste <ste_ro...(a)hotmail.com> wrote: > On 3 Mar, 20:01, mpalenik <markpale...(a)gmail.com> wrote: > > > On Mar 3, 12:52 pm, Ste <ste_ro...(a)hotmail.com> wrote: > > > > No. In SR, clocks *appear* to run slower as you are increasing your > > > distance from the clock. The effect is entirely apparent in SR. > > > You must just go through the entire thread and not pay any attention > > to what anybody says. Ever. > > > 1) What you've stated above is not an effect of SR. It is an effect > > of propagation delay, which was used to calculate c from the motion of > > the moons of jupiter hundreds of years ago. > > Ok. > > > 2) If you were to move TOWARD the clock, it would appear to run > > faster. But SR says nothing about whether you are moving toward or > > away from an object. > > <suspicious eyebrow raised> Ok. > > > 3) The amount that the clock would appear to slow down is DIFFERENT > > from the amount that SR predicts the clock *actually* slows down > > Really? I'm growing increasingly suspicious. In what way does SR > predict the "actual" slowdown, as opposed to the "apparent" slowdown? > And for example, if we racked up the value of 'c' to near infinity, > would SR still predict an "actual" slowdown, even though the > propagation delays would approach zero? With what you have described, I checked just to be sure, even though I was already pretty sure what the answer would be, the time you read moving away the clock would be: t2 = t - (x+vt)/c = t(1-v/c) - x and when you move toward the clock t2 = t + (x+vt)/c = t(1+v/c) + x so moving away from the clock: dt2/dt = 1-v/c and toward dt2/dt = 1-v/c Special relativity predicts that the moving clock will always slow down as dt2/dt = sqrt(1-v^2/c^2) What you *measure* is a combination of the actual slow down predicted by SR (sqrt(1-v^2/c^2) and whatever changes occur due to propagation delays (which depend on the direction of motion). > > > 3) This does not explain why atomic clocks on a jet register different > > times AFTER being brought to rest than do their counterparts which > > have been at rest the entire time--or why the difference in time that > > they register is exactly consistant with the predictions of > > relativity. > > Indeed, because SR doesn't deal with acceleration. SR deals with acceleration just fine. GR is only needed to describe gravity. I'll explain the thought experiment I posted later but I have to teach in less than an hour.
From: Ste on 4 Mar 2010 10:19
On 4 Mar, 12:19, "Inertial" <relativ...(a)rest.com> wrote: > "Ste" <ste_ro...(a)hotmail.com> wrote in message > > > Not really, because if the total acceleration is small, then so is the > > speed. > > That is a nonsense argument. Acceleration can be small and speeds very > large. When I went to school, you could not have a large change of speed with only a small amount of total acceleration. |