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From: train on 10 Jun 2010 19:38 SNIPPED > > >> "Any ray of light moves in the ``stationary'' system of co-ordinates > >> with the determined velocity c, whether the ray be emitted by a > >> stationary or by a moving body." > > >> Harald > > > OK let me parse that sentence > > >> "Any ray of light moves > > > `ray of light` is that not inexact since a ray of light consists of a > > visible stream of photons ie ray of sunlight? Maybe he met the tip of > > the ray of light? > > Yes > OK fine > > in the ``stationary'' system of co-ordinates > > > why the inverted commas? > > Because there is no absolute stationary system. Just any system we declare > as our stationary one > > > Why stationary why not say `observer` or > > `target` system of coordinates? Stationary wrt to what? OK > > The observer. If you know what is meant .. why are you making such an issue > of it? Because I am in a discussion group :) > > >> with the determined velocity c, > > > OK > > > whether the ray be emitted by a > > > the ray of light again > > Derrr > > >> stationary or by a moving body." > > > sounds a lot like Personal Ether Theory to me PET Theory > > No. Nothing like one at all > > > it goes something like this- > > > `each observer is floating in a virtual personal ether that extends to > > infinity and which entrains, entraps, restricts and otherwise > > constrains all photons to travel at c relative to that observer` > > That is nothing like whateinsteinsaid .. other than the 'c' part AE did not say this, but for purposes of visualizaton and clarity I use the PET , that is, imagine an ether stationary wrt to you the observer and you will get the right answers. It is only imaginary, nothing to be afraid of. > > >butnote talking about the behavior of light within a coordinate > > system - coordinate box I call it - does not say anything about the > > behaviour between coordinate systems or reference box as I call it - > > That is why that relationship is then derived from the postulates > > > unless you take the additional step of saying that light emitted in > > another reference box will travel at c in your reference box > > Which is exactly what he says > > > - why is > > he saying this? > > Because it is the basis of the theory. What a silly question > > > Is it the principle of equivalence? > > Yes .. when you include a speed of light as being c as one of the laws. > no I think as the next post says it is not the principle of equivalence that gives rise to the SRT but the first and second postulate, however my reading of AE is that he was giving too much emphasis to the equivalence principle, this has troubled me. *They suggest rather that, as has already been shown to the first order of small quantities, the same laws of electrodynamics and optics will be valid for all frames of reference for which the equations of mechanics hold good* http://www.fourmilab.ch/etexts/einstein/specrel/www/ > > I will describe > > how the principle of equivalence has been wrongly applied here . > > No, you won't
From: train on 10 Jun 2010 19:48 On Jun 10, 8:53 pm, harald <h...(a)swissonline.ch> wrote: > On Jun 10, 1:58 am, train <gehan.ameresek...(a)gmail.com> wrote: > > > > > > > On Jun 8, 9:03 pm, harald <h...(a)swissonline.ch> wrote: > [..] > > > > Tis strange. I always thought that saying light propagates at a rate > > > > of c without giving any stipulation relative to what it was measured > > > > against was strange. This confirms that there is no basis for speed > > > > relative to empty space. I cannot accept this definition. > > > > > An astronaut floats in space, at what velocity is he moving? > > > >Einsteinborrowed that phrasing from common language as used by > > > Maxwell and Lorentz. In order to give it operational meaning for the > > > purpose of the theory, he redefined the light postulate as follows: > > > > "Any ray of light moves in the ``stationary'' system of co-ordinates > > > with the determined velocity c, whether the ray be emitted by a > > > stationary or by a moving body." > > > > Harald > > > OK let me parse that sentence > > > > "Any ray of light moves > > > `ray of light` is that not inexact since a ray of light consists of a > > visible stream of photons ie ray of sunlight? Maybe he met the tip of > > the ray of light? > > Nobody can see photons flying; what we can see is the scattering of > light on particles. In other words, we can only directly see light > that falls on our eyes, and our eye does not tell us if it was a > photon, ray, or wave. > > Einsteinmight have been clearer if he stated "light wave",butmost > people concerned understand how light speed can be measured. OK BTW this group is becoming really good. Like old wine. > > > in the ``stationary'' system of co-ordinates > > > why the inverted commas? Why stationary why not say `observer` or > > `target` system of coordinates? Stationary wrt to what? > > He already explained that: "take a system of co-ordinates in which the > equations of Newtonian mechanics hold good" and "call it the > ``stationary system''", in order to "distinguish this system of co- > ordinates verbally from others which will be introduced hereafter". > > OK but the inverted commas give unnecessary hope to anti relativists > > > > with the determined velocity c, > > > OK > > > whether the ray be emitted by a > > > the ray of light again > > > > stationary or by a moving body." > > > sounds a lot like Personal Ether Theory to me PET Theory > > > it goes something like this- > > > `each observer is floating in a virtual personal ether that extends to > > infinity and which entrains, entraps, restricts and otherwise > > constrains all photons to travel at c relative to that observer` > > No. That postulate is compatible with a stationary ether model OK thanks that is all I meant, entrainment happens at moment of emission. (it > even stems from the use of that model by Lorentz),butit is *not* > compatible with entrained ether models (just think about it: the speed > of light as measured in the solar system would then not be c near the > earth). And it has been argued - despiteEinstein'ssuggestion to the > contrary - that his light postulate is only compatible with stationary > ether models. > > >butnote talking about the behavior of light within a coordinate > > system - coordinate box I call it - does not say anything about the > > behaviour between coordinate systems > > That is exact, and even the central issue of SRT. As he put it: the > [light postulate] is only apparently irreconcilable with the > [relativity postulate]. > Well sure if you take time to flow like water and space to contract you can squeeze the theory in, but is it self consistent? I think the twin paradox demonstrates that it is not. > > or reference box as I call it - > > unless you take the additional step of saying that light emitted in > > another reference box will travel at c in your reference box - why is > > he saying this? > > ????! Light is not "emitted in a reference box", and the light > postulate already states that light that is emitted from a moving body > (according to your system) will be measured to travel at c with your > coordinate system and clocks. That is not an additional step, as it > had already been stated. Yes there is a subtle step - say there at two labs A and B, A has a source and target stationary wrt itself, so has B. Inside A and B scientists measure the velocity of light to be c and c respectively. If the labs A and B are moving wrt each other, it cannot be assumed that the light emitted in lab A , when measured by lab B , will be measured at c, unless you stipulate that the speed of light will be always measured at c anywhere. But I think you answered this when you said the equivalence principle is not involved. > > > Is it the principle of equivalence? > > No, the second postulate states that the speed of light is not > affected by the speed of the emitting system, and will still travel at > c according to your measurements. That is the light postulate. > > > I will describe > > how the principle of equivalence has been wrongly applied here . > > It is not applied in SRT. OK Harald we agree. But do you realize what I said that AE incorrectly cites the equivalence principle as a basis for SRT or have I misread the Great Scientist? > > Harald
From: train on 10 Jun 2010 19:59 On Jun 10, 10:41 pm, "Androcles" <Headmas...(a)Hogwarts.physics_z> wrote: > "harald" <h...(a)swissonline.ch> wrote in message > > news:c043d370-515b-4992-a1f0-4483cf995871(a)i31g2000yqm.googlegroups.com... > > Nobody can see photons flying; what we can see is the scattering of > light on particles. In other words, we can only directly see light > that falls on our eyes, and our eye does not tell us if it was a > photon, ray, or wave. > > =============================================== > Or what its speed is. We get that from it's emission colour and its observed > colour. > > Professor C.A.Doppler had it work out, > f' = f *(c+v)/c > cf' = f *(c+v) > cf'/f = c+v > cf'/f - c = v > v = c(f'/f-1) > > Whether the car comes to the radar gun or the radar gun goes to the car, > the relative speed is v. Hence Doppler radar and a speeding ticket for > travelling at speed v. > The speed of light relative toEinstein's > superfluous aether = > superfluous empty space = > superfluous stationary frame of reference = > superfluous inertial frame = > superfluous absolute frame = > is non sequitur, > the speed of light relative to the emitter, c, is pertinent. > > Radar guns work just fine (by millions of experiments) proving > thatEinsteinwas a jerk, his calculation V = (c+v)/(1+v/c) = c is > nonsense and would not agree with radar gun experiments. > http://www.fourmilab.ch/etexts/einstein/specrel/www/figures/img76.gif Not sure how the radar gun invalidates SRT. In any case the difference cannot be that great and you still get your speeding ticket? `Radar guns are, in their most simple form, radio transmitters and receivers. They send out a radio signal, then receive the same signal back as it bounces off the objects. However, the radar frequency is different when it comes back, and from that difference the radar gun can calculate object speed. A radar beam is similar to a beam of light in that it spreads out as the distance from the signal origin increases. The signal then bounces off objects in the path of the beam and are reflected back to the gun. The gun uses the Doppler effect to calculate the speed of the object in the beam's path. Using a comparison of frequency shift between received images instead of the frequency shift between sent and received frequencies creates what is known as moving radar. Unless the radar system has a provision for converting own-vehicle-speed to an appropriate receiver frequency offset then the radar must be stationary to measure speed.` Wikipedia What if a radar gun was used on a moving train thought experiment -
From: train on 10 Jun 2010 20:16 On Jun 10, 10:41 pm, "Androcles" <Headmas...(a)Hogwarts.physics_z> wrote: > "harald" <h...(a)swissonline.ch> wrote in message > > news:c043d370-515b-4992-a1f0-4483cf995871(a)i31g2000yqm.googlegroups.com... > > Nobody can see photons flying; what we can see is the scattering of > light on particles. In other words, we can only directly see light > that falls on our eyes, and our eye does not tell us if it was a > photon, ray, or wave. > > =============================================== > Or what its speed is. We get that from it's emission colour and its observed > colour. > > Professor C.A.Doppler had it work out, > f' = f *(c+v)/c > cf' = f *(c+v) > cf'/f = c+v > cf'/f - c = v > v = c(f'/f-1) > > Whether the car comes to the radar gun or the radar gun goes to the car, > the relative speed is v. Hence Doppler radar and a speeding ticket for > travelling at speed v. > The speed of light relative toEinstein's > superfluous aether = > superfluous empty space = > superfluous stationary frame of reference = > superfluous inertial frame = > superfluous absolute frame = > is non sequitur, > the speed of light relative to the emitter, c, is pertinent. > > Radar guns work just fine (by millions of experiments) proving > thatEinsteinwas a jerk, his calculation V = (c+v)/(1+v/c) = c is > nonsense and would not agree with radar gun experiments. > http://www.fourmilab.ch/etexts/einstein/specrel/www/figures/img76.gif Ok, more of what AE said, from the 1905 paper " 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" If A and B are stationary srt each other why is this necessary, if A and B are not, why is this possible - if A and B are moving parallel towards each other then AB is not equal to BA. Right?
From: whoever on 10 Jun 2010 21:11
"train" <gehan.ameresekere(a)gmail.com> wrote in message news:533e1780-0c0e-4bac-86f6-577aa4a1cd6d(a)s4g2000prh.googlegroups.com... [snip] > Well sure if you take time to flow like water and space to contract > you can squeeze the theory in, but is it self consistent? I think the > twin paradox demonstrates that it is not. There is no paradox. It is not inconsistent .. it is perfectly self-consistent. Just surprising the first time you see it. [snip] > Yes there is a subtle step - say there at two labs A and B, A has a > source and target stationary wrt itself, so has B. Inside A and B > scientists measure the velocity of light to be c and c respectively. > If the labs A and B are moving wrt each other, it cannot be assumed > that the light emitted in lab A , when measured by lab B , will be > measured at c, unless you stipulate that the speed of light will be > always measured at c anywhere. It cannot be assumed, but it is fonud to be the cast experimentally the light speed does not depend on the speed of the source. The second postulate of SR is found to hold [snip] > OK Harald we agree. But do you realize what I said that AE incorrectly > cites the equivalence principle as a basis for SRT or have I misread > the Great Scientist? It is PART of the basis. If you cannot assume that the rules of physics apply the same in all (inertial) frames, then you cannot use those rules to derive SR from constant light speed. --- news://freenews.netfront.net/ - complaints: news(a)netfront.net --- |