A constant speed of light in all reference frames? Surely you can't be serious.
in [Relativity]
|
From: Ste on 10 Mar 2010 10:31 On 9 Mar, 23:41, "Inertial" <relativ...(a)rest.com> wrote: > "Ste" <ste_ro...(a)hotmail.com> wrote in message > > news:e37617e7-52f9-4fbd-a740-bac32eb220dd(a)o3g2000yqb.googlegroups.com... > > > On 9 Mar, 05:34, "Peter Webb" <webbfam...(a)DIESPAMDIEoptusnet.com.au> > > wrote: > >> "Ste" <ste_ro...(a)hotmail.com> wrote in message > > >> Did you look at the diagrams on the Wikipedia page on the twins paradox > >> as I > >> suggested? > > >> This shows *exactly* what the moving and stationary clocks see as > >> happening > >> at all stages of the thought experiment. > > > This isn't the twins paradox, > > http://en.wikipedia.org/wiki/Twin_paradox > > Of course it is the twins paradox. Do you even know what the twins paradox > is ? Lets see what the web page says > > "In physics, the twin paradox is a thought experiment in special relativity, > in which a twin makes a journey into space in a high-speed rocket and > returns home to find he has aged less than his identical twin who stayed on > Earth. This result appears puzzling because each twin sees the other twin as > traveling, and so, according to the theory of special relativity, > paradoxically each should find the other to have aged more slowly. How the > seeming contradiction is resolved, and how the absolute effect (one twin > really aging less) can result from a relative motion, can be explained > within the standard framework of special relativity. The effect has been > verified experimentally using precise measurements of clocks flown in > airplanes.[1][2]" I repeat myself again, the scenario we have here is *not* the twins paradox. > > so it would be strange to find the > > answer to my question there. Also, I've read that page in the past, > > and I don't recall it having relevant detail. > > Clearly you are either lying about reading it, or you didn't understand it. No, perhaps you didn't understand. As I say, this is *not* the twins paradox, because in the twins paradox only *one* twin leaves Earth.
From: PD on 10 Mar 2010 10:50 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. > 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: Ste on 10 Mar 2010 10:59 On 9 Mar, 20:03, PD <thedraperfam...(a)gmail.com> wrote: > On Mar 9, 1:25 pm, Ste <ste_ro...(a)hotmail.com> wrote: > > > > > > > On 9 Mar, 17:20, PD <thedraperfam...(a)gmail.com> wrote: > > > > On Mar 9, 11:07 am, Ste <ste_ro...(a)hotmail.com> wrote: > > > > > What I haven't found compelling is the argument that falsificationism > > > > is the hallmark of science as against non-science or religion. What is > > > > quite clear from the judgment is that it was that court's view that it > > > > is naturalism that is the hallmark of science. Indeed to quote the > > > > judge: "This rigorous attachment to natural explanations is an > > > > essential attribute to > > > > science by definition and by convention." > > > > Where "natural" is distinguished from "supernatural", this being said > > > at least ... oh, never mind, I lost count. > > > > You've had numerous people from the scientific field flatly averring > > > that falsification and experimental test IS the hallmark of science, > > > and yet you find it less than compelling. This perhaps goes back to > > > the issue that you believe what you want to believe, and you choose > > > your experts according to whether they hold the same belief. And this > > > IS a hallmark of religious thinking. > > > But this case was *your* quoted authority Paul. I didn't choose it, > > you did! > > I made no statement about it being an authoritative declaration. I think we both accept that this case is not an authoritative declaration. I think you're taking it too seriously Paul. > What > I said is that the definition is acknowledged (and it is) in a > statement intended for layfolk outside the scientific field, which I > took this ruling to be. Your return comment was that this is in fact > not a statement intended for layfolk at all, and there are nuances in > how to read a legal judgment, wherein it is not sufficient to actually > read the statement in the section about how intelligent design and > creationism are distinguished from science, but instead one must count > instances of words. I didn't say that at all Paul. I said there is a strong emphasis in that judgment on distinguishing ID from science, on account of the fact that science is naturalistic, and ID is not. This was felicitous in light of the discussion we had been having previously, where I was contending that the essence of science is naturalism, and that in practice it amounts to a sort of naturalistic faith, and you rejected this analysis. However I did not say "there are nuances in how to read a legal judgment", and nor did I say "one must count instances of words". > Moreover, one should -- in the context of a legal > opinion -- ignore the explicit identification of "methodological > naturalism" with the scientific method and the explicit contrast of > naturalism against creationism's supernaturalism, and feel free to > interpret naturalism however the hell one wants, including one's > favorite philosophical connotation, though that connotation is > unmentioned entirely in the judgment. In these instructions on how to > properly read legal judgments, I of course defer to you, and I thank > you for the patient instruction. Again, I was not giving "instruction on how to read legal judgments", and nor did I "ignore the explicit identification of "methodological naturalism" with the scientific method and the explicit contrast of naturalism against creationism's supernaturalism". I can't identify any reasonable basis for your saying this Paul. > > I agree that some sort of testability plays a part in science, but as > > I say I remain unconvinced that testability (as a practical rather > > than a notional proposition) defines science. > > I may be of the opinion that architecture is art, and that structural > integrity is not an essential distinction between the two. I might > even find some source that agrees with this. However, if I find that a > number of architects strenuously disagree with me, then I suppose I > would reconsider the fitness of my position. I really don't see your point Paul. Your argument seems to be that, as a scientist, you are in a position to speak authoritatively on the matter. Your argument is also that, as a scientist, you have a good feel for what other scientists views are. The problem is that I've never taken any knowledge merely on the weight of the authority behind it, and I don't intend to start now. I accept knowledge on account of the fact that I'm convinced by it personally, not on account of the fact that other people (even a majority of people, who may well be highly educated) are convinced by it. And I remain unconvinced by what you've argued so far.
From: Ste on 10 Mar 2010 11:17 On 9 Mar, 20:10, PD <thedraperfam...(a)gmail.com> wrote: > > As a passing metacomment about this discussion, I will only remark > that at a juncture were I had the opportunity to choose between > physics and philosophy as a career path, one of the reasons I did not > choose philosophy is that it seemed to be more about the dance than > about the truth. The implicit assumption seemed to be that the better > the dance, the more likely it would represent truth, and there was no > recourse to any more objective adjudicator (such as physics uses when > it checks how nature actually behaves) than the dancers themselves. > This, philosophy shares with the practice of law, which perhaps > accounts for their appeal to you. Many times during our conversations > here, I have gotten the impression that you are more interested in the > verbal dance than in what nature actually does and what we think we > know about that and why. I think the real problem is that there is, in fact, a philosophical difference between us with respect to science, and the contention is due to the fact that I won't accept the (clearly prevailing) philosophy that you hold. I can't really say much about your assessment of me other than that you are wholly wrong, and so wholly wrong that (having sat here for 20 minutes contemplating the issue) I wouldn't know where to start in countering it.
From: Ste on 10 Mar 2010 11:40
On 10 Mar, 01:09, "Peter Webb" <webbfam...(a)DIESPAMDIEoptusnet.com.au> wrote: > When we talk of the "turnaround", can we be a bit more specific about > what is happening? Also, bear in mind that *both* turnaround at the > same time. > > I also find it implausible that C could leap ahead of B. The more > plausible explanation, surely, is that B slows down dramatically > relative to C. So for example, if both clocks stopped moving (relative > to A) while at their farthest distance from each other, then for a > short time the other clock would appear to leap ahead (actually a > slowing of the reference clock), until the effects of each clock > stopping had actually propagated to the other clock, at which point > they would snap back into synchronisation again (propagation delays > disregarded). Yes? > > ____________________________________ > > No. > > As I keep saying to you - but you fail to understand (which is itself a > worry) - is that statements like "the clocks are synchronisation" are not > really meaningful, as whether they show the same time is a function of the > inertial reference frame in which the clocks are observed; it is not a > function of the underlying dynamics, it is an artifact of the co-ordinate > system you choose. I'm not yet convinced of this. > That is why you can only ask questions about what is observed to happen for > a specific observer. Of course, but that doesn't stop us reconciling the experience of specific observers in a logically and physically consistent way. > In answer to your question about "snapping back into synchronisation", apart > from the fact that it is meaningless, even if we reformulated this as a > question about observable quantities it is still wrong. When B and C become > relatively stationary, there is no sudden dramatic change to the clock to > the time they read on each others clocks; no jumps or discontinuities or > "snaps". No, the snap should happen when news of the turnaround has propagated to the other observer. There is simply no plausible explanation for why the distant clock would "leap ahead" of the reference clock (in terms of the absolute number of ticks elapsed), except for the fairly obvious explanation that it is the reference clock which is undergoing a "real" slowdown. |