A constant speed of light in all reference frames? Surely you can't be serious.
in [Relativity]
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From: Peter Webb on 5 Mar 2010 05:25 Aren't you that crank who says he believes SR is true, except for the bits about simultaneity, time dilation, length contraction and c being the same in every inertial reference frame? Learned anything yet?
From: Y.Porat on 5 Mar 2010 06:08 On Mar 4, 7:44 pm, PD <thedraperfam...(a)gmail.com> wrote: > On Mar 4, 11:09 am, Ste <ste_ro...(a)hotmail.com> wrote: > > > > > On 4 Mar, 16:48, mpalenik <markpale...(a)gmail.com> wrote: > > > > On Mar 4, 10:19 am, Ste <ste_ro...(a)hotmail.com> wrote: > > > > > 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. > > > > The problem is your use of the term "total acceleration". If by total > > > acceleration, you mean integral(a dt), then yes, you are correct. > > > However, there is already a word for integral(a dt) -- it's called > > > "the change in velocity". The term "total acceleration" isn't > > > actually defined. Acceleration is defined, velocity is defined, > > > deltav is defined. But "total acceleration is not". > > > Essentially, I'm defining "total acceleration" as something akin to > > total force, so that even though the force may be small, if it > > continues for a long time then the total force will be the same as if > > a large force was applied for a short period of time. In this way, if > > the application of force is what is causing either part or the whole > > of the time dilation effect, then it is the final speed that counts, > > not how quickly the object reached that speed. > > Indeed. This should tell you that it is not the details of the > acceleration that matter. > The overly simplistic statement would be, "Yes, you see that is why > SR's effects are based on speed, not on acceleration." > > In fact, there is a speed time dilation effect on GPS satellites, > which are going around in a circular path at constant speed, relative > to earth clocks, and accounting for this is crucial to their proper > operation. This is the same speed dilation effect, though different > size, as seen in muons in a circulating ring. (Since, by the way, the > GPS satellites are certainly not inside a magnetic ring but still > experience time dilation properly calculated by SR, this is another > good way to be sure that the magnetic ring is not what's responsible > for the time dilation of the muons.) > > Regarding something I alluded to earlier, though, what really matters > is how straight the path through spacetime is. We're used to thinking > that the shortest path through space is the straight one (and that's > right), but the straightest path through spacetime yields the LONGEST > duration. Any change in motion (such as an acceleration) introduces a > kink in this path (something that can be illustrated visually very > easily) and so lowers the duration. Why this is, has to do with the > structure of spacetime and we could discuss that. But this is perhaps > the most intuitive way (once these concepts are explained) to > understand why the traveling twin returns younger. > > > > > > Also, you could just be dealing with a system where the velocity > > > started out high and you never measured any acceleration. > > > Indeed. ---------------------- (:-) to mix **biologic process** with inorganic physics is ridiculous!!! (i said it in a big understatement ...(:-) Y.Porat -----------------------
From: Inertial on 5 Mar 2010 05:51 "Ste" <ste_rose0(a)hotmail.com> wrote in message news:b7a59ca3-e362-4a7d-868e-261fd2c33b40(a)d2g2000yqa.googlegroups.com... > On 4 Mar, 18:17, mpalenik <markpale...(a)gmail.com> wrote: >> On Mar 4, 1:12 pm, Ste <ste_ro...(a)hotmail.com> wrote: >> >> >> >> >> >> > On 4 Mar, 17:20, mpalenik <markpale...(a)gmail.com> wrote: >> >> > > On Mar 4, 12:02 pm, Ste <ste_ro...(a)hotmail.com> wrote: >> >> > > > On 4 Mar, 16:29, 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. >> >> > > > > I don't know what happened to this thread, or why google >> > > > > registers >> > > > > several different copies of this thread, each with only a few >> > > > > messages >> > > > > in it, but I'm going to describe the thought experiment I posted >> > > > > before in greater detail. >> >> > > > > In order for the ^ to receive the pulse of light from both >> > > > > emitters at >> > > > > the same time and half way between the two emitters, the light >> > > > > must be >> > > > > emitted BEFORE the ^ is half way between the two emitters. >> >> > > > Indeed. >> >> > > > > From the stationary frame, the two emitters emit light at the >> > > > > same >> > > > > time and the ^ moves vertically until it is half way between the >> > > > > two >> > > > > of them, when it receives both pulses. >> >> > > > Ok. >> >> > > > > But from the moving frame, the ^ sees the emitters emit light >> > > > > when it >> > > > > is not half way between them, and then it sees the emitters move >> > > > > until >> > > > > he is exactly half way between them. However, the speed of light >> > > > > is >> > > > > the same in all frames, and unaffected by the motion of the >> > > > > emitters. >> >> > > > > So the the emitter emit while one is closer to him than the >> > > > > other. >> > > > > The fact that they are moving does not affect the way light >> > > > > propagates. If the light signal from the closer one reaches him >> > > > > at >> > > > > the same time as the light signal from the farther one, that >> > > > > means the >> > > > > farther one must have emitted first. The fact that he is half >> > > > > way >> > > > > between the emitters at the end doesn't matter, because in his >> > > > > frame, >> > > > > it is the emitters that are moving, which does not affect the >> > > > > speed of >> > > > > light. >> >> > > > This seems implausible. You cannot possibly (that is, physically) >> > > > have >> > > > the situation you describe, in the way you describe it. The >> > > > receiver, >> > > > when it receives the pulse of light, cannot possibly be in more >> > > > than >> > > > one position relative to the two sources. >> >> > > It isn't. >> >> > > > It either receives when the >> > > > sources are equidistant, or it receives when one source is closer. >> >> > > The sources are equidistant. >> >> > > > It >> > > > cannot receive when it is equistant *and* when one source is >> > > > closer, >> > > > for that would be an obvious contradiction. >> >> > > What you don't understand is the fact that the sources were not >> > > equidistant when they emitted the pulse. >> >> > Indeed, but it's neither here nor there where the sources where at the >> > time of emission. >> >> Not in the rest frame. But it is in the moving frame. >> >> >> >> > The question is where the sources are at the time of reception, >> >> Not in the ^ frame. The fact that the sources have moved does not >> affect the way the light propagates. They could run over the moons of >> jupiter and back, and it wouldn't affect the way the light propagates. >> >> Lets say that you have two sets of emitters, A and B. One set is >> moving and the other set is not. If they both emit >> >> They both emit like this >> A B >> >> A B >> >> But the B set is moving like this >> >> A >> B >> >> A >> B >> >> The light from the A set and B set propagates exactly the same way. >> It doesn't matter that the B set has moved. > > 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? Of course .. because that is where the light was emitted. What happens to its emitter AFTER that makes no difference. The light is already 'out there' > 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)? Yeup
From: Inertial on 5 Mar 2010 05:55 "Ste" <ste_rose0(a)hotmail.com> wrote in message news:057b5351-82a4-4487-8501-6308451c921a(a)x22g2000yqx.googlegroups.com... > On 5 Mar, 01:31, "Inertial" <relativ...(a)rest.com> wrote: >> "Ste" <ste_ro...(a)hotmail.com> wrote in message >> >> news:8c0ae071-8d13-491b-92d0-cd2e2727af1a(a)u9g2000yqb.googlegroups.com... >> >> > 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. >> >> Then you were badly taught. >> >> a) if you start at speed 0.8c and acceleration at 0.00001 m/s/s .. then >> your >> speed is still large. you claimed small acceleration means small speed >> >> b) if you start at speed 0.0 and acceleration at 0.00001 m/s/s .. then >> your >> speed after a million years will be quite fast. Yet the acceleration was >> small and constant. >> >> You do realize that you cannot 'total' acceleration. and acceleration of >> 1m/s/s followed by an acceleration of 1m/s/s is still an acceleration of >> 1m/s/s > > In any event, we've resolved the meaning of "total acceleration" - > Mark suggests using the concept of "impulse" instead. You certainly are taking the long and painful route (for yourself and us) to learn the basics of physics. It would have helped if either: a) you came here asking questions in order to help you learn b) you understood enough of physics before making bold statements, mostly wrong, and criticizing science. Do you understand yet how time dilation and length contraction are both just 'side effects' (or consequences) of simultaneity not being absolute. I can give you a simple example of how length contraction and time dilation comes about simply from synchronizing clocks differently if you like.
From: Inertial on 5 Mar 2010 05:57
"BURT" <macromitch(a)yahoo.com> wrote in message news:aa1471c1-20e6-4d8f-9bf0-b66e16e89b9c(a)m35g2000prh.googlegroups.com... > On Mar 4, 9:12 pm, "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 >> >> > 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. >> >> > 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 >> >> > 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. >> >> > 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 - > > Space contraction leads to flat atoms which do not pass for physics. One reason why LET is not regarded as a good model. In SR there is no intrinsic change to atoms themselves. |