A constant speed of light in all reference frames? Surely you can't be serious.
in [Relativity]
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From: Ste on 4 Mar 2010 10:31 On 4 Mar, 13:40, mpalenik <markpale...(a)gmail.com> wrote: > 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). Ok. So let us suppose that we take two clocks. Separate them by a certain distance, synchronise them when they are both stationary, and then accelerate them both towards each other (and just before they collide, we bring them stationary again). Are you seriously saying that both clocks report that the other clock has slowed down, even though they have both undergone symmetrical processes? Because there is obviously a contradiction there.
From: PD on 4 Mar 2010 10:48 On Mar 3, 10:59 pm, Bruce Richmond <bsr3...(a)my-deja.com> wrote: > On Mar 3, 11:21 am, PD <thedraperfam...(a)gmail.com> wrote: > > > > > On Mar 2, 8:12 pm, Bruce Richmond <bsr3...(a)my-deja.com> wrote: > > > > > It is not a function of finite propagation speeds, this we know, > > > > because we took into account the finite propagation speeds in our > > > > procedure for determining simultaneity/nonsimultaneity. Do you not > > > > remember that? > > > > I beg to differ. It is not a "mere" or "simple" function of finite > > > propagation speed, but it *is* a function of it IMO. RoS only took it > > > into account by allowing us to use different time coordinates in each > > > frame. If the speed of light was infinite there would be no RoS. > > > I disagree. All that is needed in relativity of simultaneity is a > > signal speed that can be VERIFIED to be the same from both events by > > either observer. > > Well you are going to have problems with that. There is no way to > *know* that the speed is the same both ways. Yes, there is. That's what isotropy experiments have determined. I'm surprised you weren't aware of this. > That is why Einstein > wrote, "But it is not possible without further assumption to compare, > in respect of time, an event at A with an event at B. We have so far > defined only an ``A time'' and a ``B time.'' We have not defined a > common ``time'' for A and B, for the latter cannot be defined at all > unless we establish by definition that the ``time'' required by light > to travel from A to B equals the ``time'' it requires to travel from B > to A." > > > Since the distance from the events to the observer is > > equal, as verifiable at any time by each observer, we learn from this > > that each observer KNOWS the propagation delays from each event to the > > observer are equal. This acknowledges the propagation delays > > completely, but simply allows for verification that they are the same. > > Assuming the speed of light is the same in both directions. Which is an experimentally confirmed fact. Done well after Einstein's comments on the matter, by the way. > > > > > Then the determination of simultaneity or nonsimultaneity of the > > original events is completely unambiguous: If the observer receives > > both signals at the same time, then (because the propagation delays > > are the same) the original events were simultaneous; if the observer > > receives both signals at different times, then (because the > > propagation delays are the same) the original events were > > nonsimultaneous. > > > Then the frame-dependence of simultaneity follows directly from the > > experimental *observation* that for the same pair of events, one > > observer correctly and unambiguously concludes the events were > > simultaneous, and the other observer correctly and unambiguously > > concludes the events were nonsimultaneous. > > > You've mentioned in the past that you found your disbelief in > > relativity stems from being unable to find a good, understandable > > explanation of it. I invite you to read back on this thread where I > > was trying to explain to Ste (who has a similar complaint) how this > > comes about. > > No need. Lorentz showed how all frames could measure the speed of > light to be c. That in effect confirms the second postulate, which is > the stumbling block for many. Well then, you are just *choosing* what you would like to believe. In this case, lodging a complaint against relativity that it is not well explained, when you are not interested in pursuing a better explanation, having settled on LET instead, is a bit on the disingenuous side. PD
From: PD on 4 Mar 2010 10:55 On Mar 4, 1:36 am, "Peter Webb" <webbfam...(a)DIESPAMDIEoptusnet.com.au> wrote: > In a book by Feynman I read an explaination how the difference in > coordinate system had no effect on mechanics. I forget where it was > at the moment but I do know it was a convincing argument. > > _____________________________________________ > > Yes, it is really important point; changing co-ordinate systems cannot > change the results of physical experiments. Or more importantly, DOES not, as seen in experiment. > It is important historically > because it led the theory of Gauge theories, and was key to developing GR.. > That the choice of x, y and z axis cannot affect physical experiments is a > statement that the Universe is isotropic; that you can choose the origin to > be anywhere reflects the fact that physical laws are location independent.. > These give rise to natural symmetry groups in equations, which constrain the > sorts of equations that can actually model physical processes. For example, > if you wrote out F = ma = gmM/r^2 in terms of x, y and z co-ordinates, if > x=a, y=b, x=c, t=t1 is a solution to some equation then so is x=b, y=a, z=c, > t=t1 for the rotated experiment, as the choice of axis is arbitrary. This is > not true of Maxwell, where (if I have got this right) switching two axis > changes the sign of the time term, x=b, y=a, z=c, t=-t1. It was generalising > this concept that led to GR; as I understand it (and I don't claim to > understand GR well), this is almost but not quite enough to determine the > equations of GR uniquely. > > This is all lovely, deep, profound stuff, but the practical reality is that > to actually use it, you have know something about group theory, and Lie > groups in particular. For the amateur physicist, this is well off in left > field, group theory AFAIK is not taught in secondary school, at least that I > recall.
From: PD on 4 Mar 2010 10:57 On Mar 4, 2:13 am, Ste <ste_ro...(a)hotmail.com> wrote: > 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), That is incorrect. > 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. And that is also incorrect.
From: PD on 4 Mar 2010 11:08
On Mar 4, 2:48 am, Ste <ste_ro...(a)hotmail.com> wrote: > On 3 Mar, 22:45, PD <thedraperfam...(a)gmail.com> wrote: > > > On Mar 3, 11:05 am, Ste <ste_ro...(a)hotmail.com> wrote: > > > > > However, as with most religions, there are a set of beliefs that one who is > > > > to be a member of a religion must hold to be true, whether or not there is > > > > any evidence or proof of those beliefs. > > > > Indeed. And the same is true of science! The "scientific method" is > > > about as correspondent with reality as the Bible. > > > :>) > > I'm sure you wrote that to just get a reaction. > > It is of course a rhetorical style, but that should not be confused > with a lack of sincerity. As far as I am concerned, there is no one > here (or elsewhere) who has been able to establish that science is > defined by falsificationism. Even you concede that string theorists > are pursuing their course of research on the basis of hope and belief > that the theory will in time become falsifiable. Yes, indeed, and knot-tying is defined by the production of knots in ropes. Of course, if you find a sailor who has just picked up a rope and has not yet produced a knot, perhaps you would quibble that he is not in the activity of knot-tying until the knot has been produced. > > Insofar as anyone has tried to articulate the features of "science" or > the "scientific method", counterexamples have abounded. As I've said, > it appears to me that the only means of demarcating science from > religion is naturalism, which good scientists hold axiomatically (at > least in respect of their field of study, if not generally). And here we disagree. > > > One might argue that the Bible and science deal with very different > > aspects of reality. > > In some respects perhaps, but then again not really. Religion has, at > one time or another, made claims in all areas that are now considered > the domain of scientific study. As far as I know, science makes no claims about miracles. |