A constant speed of light in all reference frames? Surely you can't be serious.
in [Relativity]
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From: mpc755 on 14 Feb 2010 12:45 On Feb 14, 12:49 am, mpc755 <mpc...(a)gmail.com> wrote: > On Feb 13, 8:29 am, Ste <ste_ro...(a)hotmail.com> wrote: > > > > > I've been absolutely racking my brain (to the point of getting a > > headache) for the last few days about this issue, and it's clear that > > the speed of light (where light is either considered in the form of a > > ballistic photon, or a wave-cycle) cannot, physically, be constant in > > all relative frames, and at the same time be constant when travelling > > between two objects in two different frames. It's a physical and > > logical impossibility. > > > It's also clear that velocities cannot be additive (in the form of > > speed of bullet+speed of gun), and nor can they be subtractive > > relative to a background medium (in the form of speed of propagation > > in medium-speed of source). > > > Take an illustration: > > > A C > > B > > > Where A and B are atoms that pass infinitely close to each other. In > > the illustration, A and B are separated from C by a distance L. A and > > C are stationary relative to each other. B is moving, and approaching > > C at a speed S. A pulse is emitted from both A and B simultaneously > > towards C, at the point when A and B are equidistant from C. > > > Now, clearly, if velocities were additive, then light from B would > > reach C much quicker than light from A. We don't see that, so we can > > dismiss that immediately. > > > Next, if velocities were subtractive, like sound, well that seems like > > a compelling explanation for what we see, which is that light from > > both A and B travel towards C at the same speed. But the presence of > > an absolute medium seems to fall down when one considers that, to be > > consistent with observation, the speed of propagation orthogonal to > > the direction of travel must be the same as the speed in the direction > > of travel. > > > A speed (i.e. a mesure of distance traversed within a period of time) > > cannot possibly be measured constant in all directions within a frame, > > *and* constant between frames, where the frames themselves are moving > > at a speed relative to each other. So how the hell does one reconcile > > this physically? > > Light propagates at 'c' with respect to the aether. > > Think of the train and the embankment in Einstein's train gedanken to > be filled with water. Consider the water to be at rest with respect to > the embankment. Consider the clocks on the train to consist of paddles > for the second hand. > > Let's have three Observers on the embankment all standing at M and > they synchronize their clocks. Now, have two of the Observers walk to > A and B from M. As two of the Observers walk towards A and B they are > walking through the water. This increases the water pressure on the > paddle and their clocks 'tick' slower than the Observer at M. Once the > Observers get to A and B they stop and now their clocks 'tick' at the > same rate as the clock at M, even though if you could see the time on > all three clocks simultaneously the clocks at A and B would be > slightly behind the clock at M. > > There are three Observers on the train at M'. Since the train is > moving through the water the clocks on the train are already 'ticking' > slower than the clocks on the embankment due to the increase the water > pressure the clocks are under because the clocks are moving relative > to the water while the clocks on the embankment are at rest with > respect to the water. > > The three Observers on the train synchronize their clocks. Two of the > Observers start walking towards A' and B'. The Observer walking > towards B' will have his clock 'tick' the slowest as they walk because > their clock not only has to deal with the train moving through the > water but their clock also has to deal with the additional rate at > which the clock is moving relative to the water because the Observer > walking towards B' is walking against the flow of the water. The > Observer walking towards A' is walking with the flow of water and > their clock will actually tick faster than the clock which remains at > M'. > > Lightning strikes occur at A/A' and B/B'. The water propagates through > the water at rest with respect to the embankment. The light from the > lightning strikes arrives at M simultaneously. This correlates with > the time on the clocks at A and B. > > The light from the lightning strikes at B/B' arrives at M' and then > the light from the lightning strikes at A/A' arrives at M'. Now, if > the Observers on the train do not know their state with respect to the > water they will conclude the lightning strike at B/B' occurred prior > to the lightning strike at A/A'. This matches to what the clocks at B' > and A' say occurred. The reason for this is because when the clock was > walked to B' it was under additional water pressure and 'ticked' > slower than the clock walked to A'. Let's use some numbers to try and > make this less confusing. The three Observers on the train synchronize > their clocks to be 12:00:00. Let's say it takes them one minute, as > determined by an outside observer, to walk to A' and B'. Because the > clock being walked to B' is under additional water pressure, when the > Observer gets to B', their clock will read 12:00:59. The clock being > walked to A', since it is under less water pressure and ticks faster, > will read 12:01:01. Now, if the lightning strikes take place at this > moment and the light from B/B' reaches M' and then the light from A/A' > reaches M' all three Observers agree the lightning strike at B/B' > occurred prior to the lightning strike at A/A' because the clock at B/ > B' read 12:00:59 and the clock at A/A' read 12:01:01 at the time of > the lightning strikes. > > Now, here's the kicker. If the Observers on the train know they are > moving relative to water at rest with respect to the embankment, the > Observers on the train will be able to factor in the trains motion > relative to the water and calculate back and determine the lightning > strikes were in fact, simultaneous with respect to the water and > conclude the lightning strikes were simultaneous, in nature. When the Observers arrive at A and B their clocks will be slightly behind the clock at M because the clocks moved relative to the aether at rest with respect to the embankment. Lets say the clock at M reads 12:01:00 and the clocks at A and B read 12:01:00.5. The Observers at A and B, using SR, know their clocks ticked slower than the clock at M and factoring this in the Observers at A and B reset their clocks accordingly to 12:01:00. If you could see all three clocks simultaneously all three will be the same time. When the Observers arrive at A' and B' they also factor in the SR calculations based up their motion relative to the clock at M'. When the Observers arrive at A' and B' their clocks stated the time as 12:01:01.5 and 12:00:59.5, respectively. If the Observers at A' and B' assume the aether is at rest with respect to the train they will conclude their clocks 'ticked' slower than the clock at M' as they walked towards A' and B' and moved relative to the train. As stated in the previous post this is not actually the case. The Observers at A' and B' reset their clocks to 12:01:01 and 12:00:59, respectively. If you could see the clocks at A', M', and B' simultaneously the clocks would read 12:01:01, 12:01:00, and 12:00:59, respectively. It is easy to understand how lightning strikes on the embankment arrive at the 'correct' times regardless if there are lightning strike at A and B which arrive at M or a single lightning strike at M which arrives at A and B. It is not as straight forward when discussing the lightning strikes on the train. Let's first assume the Observers on the train do not realize they are moving relative to the water. Lightning strikes at A/ A' and B/B' determined to be simultaneous by the Observer at M on the embankment will occur at A' at 12:01:01 and at B' at 12:00:59. The train is moving relative to the water the light waves propagate through. The light from B' is flowing with the water relative to the train and the light from A' is flowing against the water relative to the train. The light from B' will arrive prior to the light from A'. When the three Observers on the train discuss when the lightning strikes occurred, they are all in agreement the lightning strike at B' occurred prior to the lightning strike at A'. If there is a single lightning strike at M' at 12:01:01. The light waves propagating towards B' are propagating against the flow of water relative to the train and the light waves propagating towards A' are propagating with the flow of water relative to the train. Let's assume it takes two seconds for the light waves to reach B' and one second for the light waves to reach A'. When the light waves reach the Observers at A' and B' both of their clocks read 12:01:02. When the three Observers discuss when the lightning strike occurred at M', they are all in agreement the lightning strike at M' occurred at 12:01:01. Now, again for the kicker. If the Observers on the train know they are moving relative to the water the light waves propagate through and factor this in when determining when the lightning strikes occurred in nature, the Observers on the train, and in fact any Observer in any frame of reference, will all arrive at the same conclusion as to when the lightning strikes occurred in nature.
From: JT on 14 Feb 2010 13:33 On 14 Feb, 14:34, mpc755 <mpc...(a)gmail.com> wrote: > On Feb 14, 1:31 am, "Peter Webb" > > > > > > <webbfam...(a)DIESPAMDIEoptusnet.com.au> wrote: > > "mpc755" <mpc...(a)gmail.com> wrote in message > > >news:49c69202-f525-4bba-bfa0-09b662433837(a)s33g2000prm.googlegroups.com.... > > On Feb 14, 1:12 am, "Peter Webb" > > > <webbfam...(a)DIESPAMDIEoptusnet.com.au> wrote: > > > Now, here's the kicker. If the Observers on the train know they are > > > moving relative to water at rest with respect to the embankment, the > > > Observers on the train will be able to factor in the trains motion > > > relative to the water and calculate back and determine the lightning > > > strikes were in fact, simultaneous with respect to the water > > > > _______________________________________ > > > Yes. > > > > and conclude the lightning strikes were simultaneous, in nature. > > > > __________________________________________ > > > No. Nowhere in the 200 lines that preceded this do you show that reference > > > frame of the water is the reference frame of "nature". It doesn't even > > > make > > > any sense. > > > Light propagates at a constant speed with respect to the state of the > > medium in which it exists. > > > __________________________________________ > > No. > > > The Observers on the train know their state > > with respect to the state of the water and are able to conclude > > correctly the lightning strikes at A/A' and B/B' were simultaneous, in > > nature. > > > ________________________________ > > If by "in nature", you mean the "in the frame of reference of the earth > > considered as an inertial frame", then yes. If "in nature" means something > > else, perhaps you should explain exactly what "in nature" is supposed to > > mean. > > As long as any Observer is able to factor in their state with respect > to the state of the medium in which the light propagates being at rest > then the Observer is able to conclude when the lightning strikes > occurred in nature. Well units is comparisson measurments that is agreed upon, if observer B,C,D,E,F is travelling different velocities but at moment X all is aligned parallell in fron of A and all agree on length of object A the distance to A then you deal with a *UNIT* Iif B,C,D,E,F all have different distance and length of A they do not deal with units they deal with ECDT=Einstein compressed diamond turds. In SR every *inertial frame*=set have it's own flavour of meters can be banana, cucumber or pretty much any extension you can think of. Those different flavoured units make the barn and the pole paradox a joke, actually they make it into turdjuggling. JT > > If an infinite number of Observers in an infinite number of frames of > reference all exist in the same medium in which the light waves > propagate and all of the Observers are able to determine their state > with respect to the state of the medium the light waves propagate > through being at rest all of the Observers will arrive at the same > conclusion as to when the lightning strikes occurred in nature. > > Even if the Observers themselves do not exist in the same medium in > which the light waves propagate, as long as every one of the infinite > Observers are able to factor in the light waves propagating through > the medium at rest, all of the Observers will arrive as to when the > lightning strikes occurred in the medium, in nature. All of the > Observers will arrive at the same conclusion as to when the lightning > strikes occurred. If an infinite number of Observers all arrive at the > same conclusion as to when the lightning strikes occurred then the > infinite number of Observers have determined when the lightning > strikes occurred in nature.- Dölj citerad text - > > - Visa citerad text -
From: Ste on 14 Feb 2010 14:03 On 14 Feb, 05:27, Tom Roberts <tjroberts...(a)sbcglobal.net> wrote: > Ste wrote: > > I've been absolutely racking my brain (to the point of getting a > > headache) for the last few days about this issue, and it's clear that > > the speed of light (where light is either considered in the form of a > > ballistic photon, or a wave-cycle) cannot, physically, be constant in > > all relative frames, and at the same time be constant when travelling > > between two objects in two different frames. It's a physical and > > logical impossibility. > > Not true. You are making implicit assumptions that are not valid in the world we > inhabit. > > At base, this is GEOMETRY, not any properties of light itself. And the only way > to understand it is to study SR and its underlying geometry, Minkowski spacetime. > > The primary invalid assumption you make appears to me to be Euclidean geometry. > But you also implicitly assume that speeds add like vectors; they don't. > > Indeed, even this is wrong: "I mean the alternatives are that > a object's velocity must cause either an increase or a decrease > in the speed of light in a particular direction relative to > something." > > One does not "reconcile this physically", one reconciles it GEOMETRICALLY.. > > Speaking VERY LOOSELY, one could say that there are "grooves" > in spacetime that go in every direction at every point, with > the speed of light. And light "just happens" to always travel > in these grooves. The actual geometry is MUCH more interesting, > but as I keep saying, you must STUDY this -- your "20 questions" > approach on the internet is woefully inadequate. > > Tom Roberts I'm afraid you're easily satisifed Tom. As I say, I'm not really interested in learning geometry, or talking about completely hypothetical "grooves in spacetime". I want simple answers to what seem to me to be simple physical questions. As I said on a previous occasion, few here seem to be able to break out of the notion that something exists independent of observation. I want an explanation where, essentially, information travels instantaneously, but from which I can derive the effects that any particular observer would observe. It matters not that information does not, really, travel instantaneously. The point is that I want an explanation where it *does*, and I can then add on a layer of observer effects to reconcile it with real observation.
From: Ste on 14 Feb 2010 14:09 On 13 Feb, 20:28, mpalenik <markpale...(a)gmail.com> wrote: > On Feb 13, 2:11 pm, Ste <ste_ro...(a)hotmail.com> wrote: > > > I'm afraid I do not accept that my "choice of mathematical coordinate > > system" is the explanation for this.- Hide quoted text - > > Think of it as your orientation in spacetime. For example, if you're > facing north, a natural coordinate system is that north is foward and > east is right. If you walk in a straight line, you'll end up going > north. > > Now, turn 45 degrees. A natural choice of coordinate system is > northeast is forward and southeast is right. If you walk forward, > you'll go northeast. > > Are you going to tell me that you won't accept that your natural > choice of coordinate systems is responsible for you ending up in > different places when you walk forward? It has to do with your > orientation, whether it's your orientation on the surface of the earth > or your orientation in spacetime--your orientation depends on what > happens when you move forward. Of course I accept that your orientation affects your direction. But there is nothing magic about perspective.
From: Ste on 14 Feb 2010 14:27
On 14 Feb, 05:56, "Peter Webb" <webbfam...(a)DIESPAMDIEoptusnet.com.au> wrote: > > The poster Ste: > > 1. Won't accept mathemetical descriptions of what is happening, because he > doesn't know enough mathematics to even follow the most simplistic > explanation of Minkowski space time (in terms of the Euclidean metric with > an imaginary axis). Indeed. > 2. Won't accept non-mathematical descriptions, as he variously says they are > analogies, they are not "physical", they don't prove anything or (as above) > he simply doesn't agree. I will accept non-mathematical descriptions, but they have to be something realistic. A "groove in space" is a meaningless physical concept. It's really just a reformulation of saying "an imaginary line in space", but couched in purportedly "non-mathematical" language. And if I didn't know any better I'd be asking questions like "what are the properties of this groove", "how does it come about", etc., when in fact an "imaginary line" is easy to deal with, because I recognise it's abstract non-physical nature, as a representation of a movement that some real object will make. > Your use of the word "grooves" was a istake, it will just confuse him more. > Next he will want to know how to see the grooves. What I think you are > alluding to is the "light cone" or "causality cone", and it would be better > if you had used a more standard explanation. Indeed, it would have, although I also have a distaste for the "light cone" concept, too. > > The actual geometry is MUCH more interesting, > > but as I keep saying, you must STUDY this -- your "20 questions" > > approach on the internet is woefully inadequate. > > > Tom Roberts > > Ste has been studying physics for a whole month now! > > If he knows: > > 1. Enough Euclidean geometry to understand Pythagoras's theorem, > 2. What an "imaginary number" is, and arithmetic over the complex numbers > 3. The Newtonian derivation of Energy and Momentum .... > > (all of which are taught at secondary school level) > > Then he can actually learn the rules of Minkowski space and how they map to > the formulas of SR for himself in a couple of days effort. > > There is no point trying to teach him this on a newsgroup; he needs to learn > it for himself. There are lots and lots of web pages that do that. Or he > could buy a book. The real problem I suspect is that he is too lazy to try. As I said, I'm not that interested in formulas. As you concede, with next to no effort, I could have formulas coming out of my ears. What you don't seem to realise is that I don't *want* a mathematical proof, I want a physical explanation. If you're not interested in a physical explanation (or don't even understand what I mean by the word), then fine, but at least acknowledge that I have quite different questions than you have, which calls for quite different answers, and the only nexus between the answers you have and the answers I want is that the answers I want can quite possibly be derived from the answers you have. |