A constant speed of light in all reference frames? Surely you can't be serious.
in [Relativity]
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From: Bruce Richmond on 6 Mar 2010 01:15 On Mar 5, 12:12 am, "Inertial" <relativ...(a)rest.com> wrote: > "Bruce Richmond" <bsr3...(a)my-deja.com> wrote in message > > news:7806715d-93d2-49ff-ad67-6dac8ea64d8c(a)e7g2000yqf.googlegroups.com... > > > > > > > On Mar 4, 10:48 am, PD <thedraperfam...(a)gmail.com> wrote: > >> 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. > > > Do you mean like this one? > > >http://mysite.verizon.net/cephalobus_alienus/papers/Gagnon_et_al_1988... > > > The author is kind enough to point out problems in some similar > > experiments, while failing to notice any in his own. > > > For example, has he made any assumption about contraction of his > > equipment in the direction of motion? Tom Roberts has written posts > > in this group showing where some of these experiments are in effect > > two way measurements. > > >> > 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. > > > Provide a link to an experiment and I'll take a look. > > >> > > 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. > > > You are reading more into that than what I wrote. I am not choosing > > LET over SR. They use the same math > > Yes > > > and I consider them two > > interpertations of the same thing. > > Not at all. Very different as far as how they explain reality > > LET has and required a fixed (theoretically undetectable) aether in a fixed > absolute frame. > SR does not specify nor require anything about an aether > > LET has objects physically compressed due to absolute motion thru the aether > SR has no absolute motion, so objects are not affected by such motion > > LET has processes physically slowed due to absolute motion thru the aether > SR has no absolute motion, so processes are not affected by such motion > > LET has a side-effect of the speed of light being measured as the same in > all frames of reference, due to measuring with compressed rulers and slowed > clocks, even though its only really has that speed relative to the aether, > SR has no absolute compression and slowing, and the speed of light really is > c > > LET has a side-effect of an appearance of the lorentz transforms holding on > measured values, due to measuring with compressed rulers and slowed clocks. > SR has no absolute compression and slowing, so the lorentz transform hold Read what I actually wrote, not what you think I wrote. I wrote, "I consider them two interpertations of the same thing." The events are the same. The predictions are the same. The interpertation of why things appear the way they do is different. > > The LET interpertation had the > > advantage, for me, of showing how c + or - v could end up being > > measured c in all frames. > > In SR there is no c+v or c-v, because there is no fixed absolute aether > frame in which light really travels at c. There most certainly is a c+v and c-v in SR. They are called closing speed. And one of the most difficult things for a new student to understand is why unlike anything else EM waves have the same speed in all frames. I will probably screw up how I put this but IMO it is because we made it that way. Nature does what it wants to, but we still have some choice in how we write the equations that describe what nature is doing. Say you have a cannon that launches a projectile using a spring. Given the strength of the spring, how far it is compressed, the weight of the projectile and the inclination of the barrel, you could calculate the trajectory of the projectile. Put the cannon on a flatbed of a moving train and it would be easiest to calculate the trajectory relative to the train, and then add the velocity of the train to get the position of the projectile relative to the ground at any given instant. But it is possible to work things out directly from the FoR of the ground, so long as you are consistant. For example, the spring may only expand a foot in the barrel of the cannon, but in doing so it pushes the projectilie six feet relative to the ground. When we make a calculation from the track FoR that involves the train we use the closing speed of c+v and get a correct answer. There is nothing stopping a rider on the train from using the same track coordinates and the same c+v to get the same answer. It just makes things a whole lot easier if he uses coordinates from his rest frame. Maxwell had found that the speed of light always seemed to be c, as measured using clocks synchronized in the rest frame the measurement was made in. I don't know if he was aware of RoS or not, but it certainly made the writing of his equations easier to keep the speed of light a constant. > > Given that was possible I no longer had any > > problem accepting the second postulate. Eventually I became aware > > that the second postulate wasn't so much an assumption as a > > stipulation. We will consider the speed of light to be our standard. > > No .. it is an observed fact. Not a stipulation It was an observed fact in part because of the proceedures used to observe it. As I have said before, light behaved differently than anything else and it wasn't clear how it could do so. > > Recently I have been going back and re-reading some of the books I > > have bought over the years to see if I can come to grips with some of > > the modern interpertations of SR. After thinking about it for awhile > > I have realized that my objections about the changing definition of c > > were petty/anal. > > :) Always a good conclusion to reach .. it shows you really are thinking > and learning and advancing. Reading Bondi he gave a good explaination for why time is considered a fourth dimension and how rotations fit in. I wont say any more at this point because I would probably screw it up. Sometimes it is easier to understand things than it is to express the ideas to others. Then again, it could be because I don't really understand it that well yet. > > An analogy would be that there used to be 24 hours > > in a day, 60 minutes in an hour, and 60 seconds in a minute. Now we > > have defined a second as so many transitions of an atom, and can > > measure the variation in the length of a day. The new way is better. > > That it is not in perfect agreement with the old doesn't change much. > > There was nothing sacred about the old. So yes, an old dog can be > > taught new tricks :) > > > Bruce > > And several points up my estimation ladder for doing so and admitting it > :):)- Hide quoted text - > > - Show quoted text -
From: Bruce Richmond on 6 Mar 2010 01:20 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 :)~
From: Jerry on 6 Mar 2010 05:21 On Mar 5, 10:43 pm, Bruce Richmond <bsr3...(a)my-deja.com> wrote: > On Mar 5, 12:08 am, Jerry <Cephalobus_alie...(a)comcast.net> wrote: > > On Mar 4, 10:33 pm, Bruce Richmond <bsr3...(a)my-deja.com> wrote: > > > The author is kind enough to point out problems in some similar > > > experiments, while failing to notice any in his own. > > > > For example, has he made any assumption about contraction of his > > > equipment in the direction of motion? Tom Roberts has written posts > > > in this group showing where some of these experiments are in effect > > > two way measurements. > > > Do you understand the principle of Gagnon's experiment? Do you > > understand the inverse relationship between group velocity and > > phase velocity that exists in a wave guide? Do you understand > > that length contraction would be a second order phenomenon, while > > Gagnon's experiment should be sensitive to first order, assuming > > an anisotropy exists? Do you understand that Gagnon's experiment > > is a true one-clock measurement of OWLS anisotropy? Do you > > understand the difference between an attempt to detect OWLS > > anisotropy versus an attempt to perform a one way light speed > > measurement? > > I know what OWLS is, and I know what assume means. > > > On the negative side, I probably know a lot more about defects > > in Gagnon's experiment than you have ever dreamed of. Gagnon > > drove the wave guides near cutoff. What does that imply about > > heating? Take a good look at the test theory that they used to > > analyze their results. Do you notice something about its internal > > consistency in terms of an important criterion that I shall not > > name, but which you ought to be aware of? Is the fact that the > > test theory does not meet this standard of internal consistency > > important in their analysis? Can you guess what this problem is? > > Can you guess why I consider Gagnon et al. to be an important > > experiment, despite some problems in analysis? > > > Start with the basics. I've given you important clues. How does > > Gagnon et al's xperiment work? > > I haven't looked it over that closely but off hand I would say it is a > gussied up MMX. No, their experiment was very different from MMX. http://mysite.verizon.net/cephalobus_alienus/papers/Gagnon_et_al_1988.pdf There is a reciprocal relationship between group velocity and phase velocity in a waveguide. Depending on the frequency, a typical waveguide transmits microwave signals at 70% of the speed of light. However, the phase velocity would be 140% of the speed of light (the product of group velocity and phase velocity is c^2). Gagnon et al. used two parallel waveguides with different cutoff frequencies, one close to the oscillator frequency, the other widely different from the oscillator frequency. At the cutoff frequency, the wavelength in an ideal waveguide would become infinite,and there would no longitudinal position dependence for the electrical phase of the wave along the waveguide. At the far end of the waveguides, Gagnon et al. situated a phase comparator. The signal was injected at one end of the two waveguides. The phase difference was measured at the other end of the two waveguides. Here is an ascii art representation of their setup: --------------------------------------------------- --------------------------------------------------- @ > =================================================== The top parallel set of hyphens represents the first waveguide. The equal signs represents the second waveguide. The @ represents the oscillator at one end. The > represent the phase comparator at the other end. In the first waveguide (operating at close to cutoff frequency), the phase of the RF exiting the waveguide would be essentially identical to the phase of the RF entering the waveguide. In the second waveguide, variation in OWLS would alter the phase of the RF exiting the waveguide as a first-order effect. So DEPENDING ON THE THEORY BEING TESTED, the setup should be highly sensitive to anisotropies in the one way speed of light (OWLS). if you wish to measure OWLS, you need synced clocks at different points. The hidden assumption in most measurements of OWLS is that the synchronization procedure for the clocks either involves two-way signaling (as for instance in Einstein synchronization), or can be shown to be equivalent to the Einstein sync procedure. Gagnon et al. didn't measure OWLS. Rather, they measured DELTA OWLS. That's a -very- different measurement, and hence they were able to use a single clock. If Tim Lincecum simultaneously throws a baseball and a paper airplane to you against the wind, you do not need a clock synchronized to Lincecum's watch to determine that they arrive at your location at different times. Gagnon et al. "threw" two continuous RF beams simultaneously in the same direction, one, like the baseball, relatively insensitive to any hypothetical aether wind, the other, like the paper airplane, sensitive to a classical aether wind. There are no hidden assumptions concerning clock synchronization in their experiment. They did make assumptions, however, about their "test theory" that turn out to have been unwarranted. Gagnon et al. believed that their setup was capable of distinguishing between between LET and SR. In other words, they believed their experiment capable of detecting a LORENTZIAN aether wind. This turns out to have been wrong. Despite defects in their test theory that led them to erroneous conclusions concerning their ability to distinguish between LET and SR, the experiment of Gagnon et al. is important because it represents a true one-clock measurement of OWLS anisotropy. Jerry
From: Ste on 6 Mar 2010 06:12 On 5 Mar, 14:46, mpalenik <markpale...(a)gmail.com> wrote: > On Mar 5, 3:55 am, Ste <ste_ro...(a)hotmail.com> wrote: > > > So what you're saying (and I had recognised this problem before you > > said it) is that it is the "original" position of emission that > > matters? > > > And the "original" position changes depending on the frame (i.e. in > > the source frame, the source does not move, whereas in the receiver > > frame, the sources are constantly moving from their "original" > > positions)? > > Right. The sources send out one pulse at one particular point in > time. The only thing that matters is where they were located when > they sent out that pulse. That location is the "source" of the pulse. Ok. But one observation I would make first is that, I presume, from the source inertial frame, both the rising and falling edges of the wave have the same origin. However, in the receiver inertial frame, the rising edge does not have the same origin as the falling edge - so there is a lack of symmetry between what is being described in these inertial frames. Secondly, we talk of the sources being in a "particular place" when the pulse is emitted, and yet by your own argument they are not in a "particular place" at all - in one frame, the sources are in the same place at all times, and in the other frame, the sources are never in the same place for more than an instant. So is it really meaningful to talk of the "place of origin" of the source as a well-defined, single point in space and time?
From: Ste on 6 Mar 2010 06:41
On 5 Mar, 16:02, PD <thedraperfam...(a)gmail.com> wrote: > On Mar 5, 2:55 am, Ste <ste_ro...(a)hotmail.com> wrote: > > > > > > > On 4 Mar, 18:12, PD <thedraperfam...(a)gmail.com> wrote: > > > > On Mar 4, 12:04 pm, Ste <ste_ro...(a)hotmail.com> wrote: > > > > > On 4 Mar, 17:46, PD <thedraperfam...(a)gmail.com> wrote: > > > > > > On Mar 4, 11:17 am, Ste <ste_ro...(a)hotmail.com> wrote: > > > > > > > On 4 Mar, 16:49, mpalenik <markpale...(a)gmail.com> wrote: > > > > > > > > On Mar 4, 11:45 am, Ste <ste_ro...(a)hotmail.com> wrote: > > > > > > > > > On 4 Mar, 16:32, mpalenik <markpale...(a)gmail.com> wrote: > > > > > > > > > > On Mar 4, 11:28 am, Ste <ste_ro...(a)hotmail.com> wrote: > > > > > > > > > > > On 4 Mar, 16:20, mpalenik <markpale...(a)gmail.com> wrote: > > > > > > > > > > > > On Mar 4, 10:31 am, Ste <ste_ro...(a)hotmail.com> wrote: > > > > > > > > > > > > > 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. > > > > > > > > > > > > Yes, that is correct. Both will report a slow down.. And in fact, > > > > > > > > > > > which ever one breaks the inertial frame to match speed with the other > > > > > > > > > > > is the one that will be "wrong". This is still within the realm of > > > > > > > > > > > SR, not GR. > > > > > > > > > > > What if they both "break the inertial frame"? > > > > > > > > > > Then whichever frame they both accelerate into will be the one that > > > > > > > > > has measured the "correct" time dilation. > > > > > > > > > So in other words, the clocks will register the same time, but will > > > > > > > > have slowed in some "absolute sense"? > > > > > > > > Yes--assuming they both accelerated by the same amount (that is to > > > > > > > say, assuming they both broke the inertial frame in a symmetric way). > > > > > > > Otherwise, they will register different times. > > > > > > > Agreed. > > > > > > > So let's explore an extension of this scenario. Let's say you have two > > > > > > clocks, and you accelerate both of them up to a common speed, and > > > > > > after they have travelled a certain distance, you turn them around and > > > > > > return them to the starting point. The only difference is that one > > > > > > clock goes a certain distance, and the other clock goes twice that > > > > > > distance, but they *both* have the same acceleration profile - the > > > > > > only difference is that one clock spends more time travelling on > > > > > > inertia. > > > > > > > Obviously, one clock will return to the starting point earlier than > > > > > > the other. But when both have returned, are their times still in > > > > > > agreement with each other, or have they changed? > > > > > > Agreement. Both of them will agree, but will be showing a time earlier > > > > > than a third clock that was left behind at the starting point. > > > > > Oh dear. Mark contends otherwise. > > > > Right. I misunderstood. He's right. I was wrong. > > > Ok. So what you're (both) saying is that time dilation (in SR) is a > > simple function of speed and distance, so that the quicker you travel > > the more time dilates, and the further you travel the more time > > dilates? And, to boot, you're saying that it's only *relative* > > distance and speed that counts (i.e. there is no absolute measure of > > movement in space)? > > The time dilation *factor* (by what factor is the clock moving more > slowly) is a simple function of relative speed. The difference in the > time *elapsed* between the two clocks is also a function of the > relative distance. > > This should make perfect sense to you. If a clock is running 2% > slower, then it is running 2% slower regardless of distance. But if, > as a result of running 2% slower, it falls behind 6 minutes after > running a certain amount of time, then it will fall behind 12 minutes > after running for twice as long. Agreed. The question now is, if we agree that both clocks suffer time dilation in this way, then when they return to the start point, how do they each reconcile the fact that (after accounting for the effects of acceleration) it ought to be the other clock which is slow, when in fact one clock (the one that went furthest from the start point) will be slower than the other? And a third clock, left at the start point, will be running ahead of both? |