Known physics defeated by simple puzzle?
in [Relativity]
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From: Ste on 15 Feb 2010 06:26 On 14 Feb, 23:38, "n...(a)bid.nes" <alien8...(a)gmail.com> wrote: > On Feb 14, 11:42 am, Ste <ste_ro...(a)hotmail.com> wrote: > > > > > > > Consider this setup: > > > S1 D2 > > > D1 S2 > > > We've got sources S1 and S2, paired with detectors D1 and D2. They're > > all mechanically connected, so that a movement in one of them > > produces > > a movement in all the others - in other words, their relative > > distances are always maintained. Each source is transmitting a > > regular > > pulse of light to its counterpart detector (so S1 is transmitting to > > D1, etc.), and both sources are transmitting simultaneously with each > > other. > > > Now, we calculate that a pulse has just been emitted from both > > sources, and we suddenly accelerate the whole setup "upwards" (i.e. > > relative to how it's oriented on the page now) to near the speed of > > light, and we complete this acceleration before the signals reach > > either detector. > > By "upwards", do you mean within the page along the direction > parallel to a line drawn from D1 to S1 (S2 to D2), or out of the > screen towards me? i. e. that way: > > ^ > | Along the direction parallel to the line. *Not* out of the screen. > > Now, do both detectors *still* receive their signals simultaneously, > > or does one receive its signal before the other? And are the signals > > identical, or do they suffer from Doppler shifting, etc? > > If the former, both receive their signals simultaneously. Doppler > applies. They receive their signals simultaneously, even though they have moved from their original location?
From: Ste on 15 Feb 2010 06:31 On 14 Feb, 23:55, "Inertial" <relativ...(a)rest.com> wrote: > > >> Now, do both detectors *still* receive their signals simultaneously, > >> or does one receive its signal before the other? And are the signals > >> identical, or do they suffer from Doppler shifting, etc? > > > If the former, both receive their signals simultaneously. Doppler > > applies. > > I don't agree. Hell fire! Can anyone here agree on what relativity predicts? > As D1 is accelerating in the opposite direction to the > light, and D2 in the same direction as the light .. the light would hit D1 > first, for the same reason that light would not hit the detectors at all in > the case where the device was accelerating out of the page. This is my preconception also. > Mind you, during accelerating the notion of 'first' is not all that clear .. > according to which frame of reference are we talking? But the experiment > does claim that the acceleration starts after the pulses leave the sources > and stops before the light reaches either detector .. so that really gives > us a choice of two reasonable frames to consider for deciding which is first > .. the original rest frame and the final rest frame. Let us go further, then, and assume that there are *no* propagation delays for this information - so that I know instantly the state of everything in the universe. But to hedge, in case you don't like the idea of me playing God, then let us say there is an observer equidstant from each detector and always travelling at the same speed.
From: Ste on 15 Feb 2010 06:34 On 15 Feb, 03:04, dlzc <dl...(a)cox.net> wrote: > > > Now, do both detectors *still* receive their > > signals simultaneously, or does one receive > > its signal before the other? > > S2 should get its signal first. The path length is shorter, due to > the acceleration. Acceleration is not really part of SR, and your > imaginary setup isn't helping. Forget the imaginary setup. The purpose of my questions are to establish and distill out the essential truths that are captured in relativity. It doesn't matter that no real device in the Universe could conceivably carry out such an acceleration. > > And are the signals identical, or do they > > suffer from Doppler shifting, etc? > > Since they were emitted at rest, and detected in motion, they will be > relativistic Doppler shifted. In the imaginary Universe that this > apparatus survived in. Ok.
From: Inertial on 15 Feb 2010 06:38 "Ste" <ste_rose0(a)hotmail.com> wrote in message news:c1fdc6e6-5897-4b88-be94-da2cddc946fa(a)15g2000yqa.googlegroups.com... > On 14 Feb, 22:48, "Inertial" <relativ...(a)rest.com> wrote: >> >> > Now, we calculate that a pulse has just been emitted from both >> > sources, and we suddenly accelerate the whole setup "upwards" (i.e. >> > relative to how it's oriented on the page now) >> >> Do they all accelerate the same acceleration profile and tart >> accelerating >> at the same time? If so, it would rip the device apart. > > Forget about the acceleration profile or the physical nature of the > device. All it requires is that an acceleration initiates after > emission at the sources, and before reception at the detector. It can matter because it can materially change the device > The fact that it would be physically impossible to achieve this setup > is the same as how virtually every other gedanken is impossible to > achieve in practice (what with ladders being accelerated into garages > at near the speed of light, etc). They don't accelerate .. in most gedankens that objects have constant velocity. SR can handle acceleration, but not with the very simple formulas involved with uniform velocity.
From: Inertial on 15 Feb 2010 06:40
"Ste" <ste_rose0(a)hotmail.com> wrote in message news:5fa40134-f5d0-4d05-bae7-a1c287ecef6c(a)g19g2000yqe.googlegroups.com... > On 14 Feb, 20:13, Darwin123 <drosen0...(a)yahoo.com> wrote: >> On Feb 14, 2:42 pm, Ste <ste_ro...(a)hotmail.com> wrote: >> >> >> >> >> >> > No takers for this simple question then? >> >> > Consider this setup: >> >> > S1 D2 >> >> > D1 S2 >> >> > We've got sources S1 and S2, paired with detectors D1 and D2. They're >> > all mechanically connected, so that a movement in one of them >> > produces >> > a movement in all the others - in other words, their relative >> > distances are always maintained. Each source is transmitting a >> > regular >> > pulse of light to its counterpart detector (so S1 is transmitting to >> > D1, etc.), and both sources are transmitting simultaneously with each >> > other. >> >> > Now, we calculate that a pulse has just been emitted from both >> > sources, and we suddenly accelerate the whole setup "upwards" (i.e. >> > relative to how it's oriented on the page now) to near the speed of >> > light, and we complete this acceleration before the signals reach >> > either detector. >> >> > Now, do both detectors *still* receive their signals simultaneously, >> > or does one receive its signal before the other? And are the signals >> > identical, or do they suffer from Doppler shifting, etc? >> >> The answer to your problem is actually very easy. The signals >> won't reach either detector. The path of the pulses, in the >> accelerated reference frame, will be curved downward. So the pulses >> will fall below the the detectors. By the time the light reaches the >> detector plane, the light beams will have fallen below the level of >> the detectors. > > I can see there has been a misunderstanding. When I said "upwards", I > didn't mean "above the page in 3D", I meant "the top of the page in > 2D". In other words, "the heading of the page", so that D1 and S2 head > towards S1 and D2, and S1 and D2 head towards where I wrote "consider > this setup". > > > >> The rules are different for accelerated frames. The constancy >> of the speed of light is strictly valid only for inertial frames, >> meaning the detectors are not accelerating. So you can't present a >> problem with accelerated detectors, invoke the constancy of the speed >> of light, and then honestly claim that you found a paradox. > > I'm not necessarily claiming to have "found a paradox". I'm asking a > relatively straightforward question that if the setup moves while the > photon is in "mid-air", what is the outcome? You seem to think this puzzle defeats known physics. It gets nowhere near it. |