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 6 Mar 2010 10:03 Then why did Einstein say that M' is runshing toward the light front from the front (c+v) and receding away from the light front from the rear (c-v)?? ____________________________ If you want to know why the expressions c+v and c-v appear in Einstein's 1905 paper, it is because from the viewpoint of some inertial reference frame then an object moving at v is moving with a relative velocity of v+c to a light ray travelling in the opposite direction, and similarly for c-v. A simpler example: We fire two photons in opposite directions. After 1 second, they are 2 light seconds apart, their relative velocity is 2c, measured in the frame which fired the photons. HTH
From: Ste on 6 Mar 2010 11:49 On 6 Mar, 12:47, "Peter Webb" <webbfam...(a)DIESPAMDIEoptusnet.com.au> wrote: > > 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? > > _________________________ > They know that the operations were not symmetric. Only one clock remained in > the same inertial reference frame throughout. The other two clocks spent > different amounts of time in at least 3 different inertial reference frames. > Everybody can see this is true, and so nobody expects that the clocks will > remain synchronised. Yes, but the important question here is whether they agree *after* the effects of acceleration are taken into account. I mean, if we said that each travelling clock slows by 2% when moving away from the start point at a certain speed, then by rights both travelling clocks should slow equally. Yes? And yet, the assertion seems to be that each clock will consider itself correct, while holding that the other clock has slowed by, what, 4%?
From: Ste on 6 Mar 2010 11:56 On 6 Mar, 12:56, "Peter Webb" <webbfam...(a)DIESPAMDIEoptusnet.com.au> wrote: > > It's quite different from the disputes that arose over words like > "physical" and "material", where each side seems to battle childishly > over whose idiosyncratic understanding of the word will prevail, when > the time could be better used getting on with the substantive argument. > > ________________________________ > "Physical" and "material" are words that you introduced that have no real > meaning in physics. Impulse, on the other hand, has a very specific meaning > in this context; it is integral of Force over time (=Momentum, cf Force over > distance which is Energy). Use words like that correctly and you might start > understanding SR, because instead of discussing the interpretation of > English words you are actually discussing physics. As I say, I accept that words like "acceleration" and "impulse" do have precise meanings, and for that very reason I'm happy to use them.
From: Y.Porat on 6 Mar 2010 12:15 On Mar 5, 3:31 am, "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 ------------------ psychopath -----------------------------
From: G. L. Bradford on 6 Mar 2010 12:45
"waldofj" <waldofj(a)verizon.net> wrote in message news:91cf20f2-735c-4ba2-b961-e0337f9d257f(a)q23g2000yqd.googlegroups.com... >> > 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. >> >> Then why did Einstein say that M' is runshing toward the light front >> from the front (c+v) and receding away from the light front from the >> rear (c-v)?? >> >> Ken Seto > that is from the point of view of the observer on the ground and it's > called closing speed (c + v) and separating speed (c - v). > Why is that so difficult to understand? ===================== In both going away and closing, 'c' always forces the view that the traveler is located, positioned, somewhere between the real-time traveler and the real-time observer. A false position always apparently closer in space than the real, always apparently earlier in time than the real, always apparently slower in velocity than the real. In going away not only does the real-time space traveler distance itself from the observer, but distances itself from what will be apparent to the observer. Distancing itself from what is apparent to the observer (distancing itself from the virtual of itself being observed by the observer). An expansion. At apparently one light second's distance from the observer, the real-time traveler will be one light second plus one second in distance from the observer. At apparently ten light seconds in distance from the observer, the real-time traveler will be ten light seconds plus ten seconds in distance from the observer. And so on, gaining distance in both space and time (at once) from both the observer and the virtual of itself being carried by the speed of light to the observer. In closing, not only does the (unobserved) real traveler close upon the observer, but closes upon the apparent traveler (only apparent to the observer) situated between them until it closes up to the virtual of itself and a merger of the real traveler and the apparent traveler occurs [dead at the observer in the merged frame of all three]. A contraction. At apparently ten light seconds from the observer (apparent coordinate position) the real-time -older- traveler will be ten light seconds plus ten seconds in distance from the observer. At apparently one light second from the observer the real-time -older- traveler will be one light second plus one second from the observer....and closing fast upon that light-time -younger- virtual of itself -- apparently gaining in age ever more quickly -- being observed; closing fast upon the light-time -younger- virtual of the observer -- also apparently gaining in age ever more quickly -- it is observing; closing fast upon the (unobserved) -older- real-time observer. At [apparently] one light micro-second from the observer, as pointed out above WHETHER IN CLOSING OR OPENING DISTANCE, the real-time traveler will be one light micro-second plus one micro-second in [actual] distance from the observer. At [apparently] one light year from the observer, as pointed out above WHETHER IN CLOSING OR OPENING DISTANCE, the real-time traveler will be one light year plus one year in [actual] distance from the observer. Thus in either direction, contracting or expanding distance in space-time, the unobserved -faster- real always gains on the observed -slower- apparent [always] located between itself and the observer. Yet!.....in closing to any observer....it, the light speed carried -younger- apparent, or -younger- virtual version, of the -older- traveler, did get there "between" reals (getting there first! only -- and always -- to be tied by the real at the finish line: every finish line)! GLB ====================== |