Known physics defeated by simple puzzle?
in [Relativity]
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From: nuny on 14 Feb 2010 18:38 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: ^ | > 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. If the latter, neither detector registers a hit *until the setup reaches a constant velocity*. Mark L. Fergerson
From: Inertial on 14 Feb 2010 18:46 "Inertial" <relatively(a)rest.com> wrote in message news:4b787dc6$0$27879$c3e8da3(a)news.astraweb.com... > > "Ste" <ste_rose0(a)hotmail.com> wrote in message > news:929ce032-2892-4258-a004-fe497de345ee(a)k41g2000yqm.googlegroups.com... > > Oh dear .. another armchair physicist trying to show physics is wrong > based on his own lack of understanding > >> No takers for this simple question then? > > Eh? You only just asked it. > >> Consider this setup: >> >> S1 D2 >> >> >> D1 S2 > > Fine > >> 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. > > Fine > >> 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. > >> 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, > > They don't receive them at all. Gees. Oops.. misread your example. Somehow saw diagram as showing the beams going left-to-right and right-to-left >> or does one receive its signal before the other? And are the signals >> identical, or do they suffer from Doppler shifting, etc? Also now not sure whether you mean upward out of the page, or upward within the page. That also affects whether the acceleration would tear apart the device or not.
From: Inertial on 14 Feb 2010 18:55 "nuny(a)bid.nes" <alien8752(a)gmail.com> wrote in message news:05d6a5e5-9996-4a4b-8bf9-a3c93108da51(a)x10g2000prk.googlegroups.com... > 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: > > ^ > | > >> 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. 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. 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. > If the latter, neither detector registers a hit *until the setup > reaches a constant velocity*. Yeup.
From: dlzc on 14 Feb 2010 22:04 Dear Ste: On Feb 14, 12:42 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. How did you propose to do that? Matter cannot do this, with the acceleration profile you are about to describe. > 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. What are they supposed to do with this information? > 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. Matter cannot do this. > 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. > 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. David A. Smith
From: nuny on 14 Feb 2010 22:08
On Feb 14, 3:55 pm, "Inertial" <relativ...(a)rest.com> wrote: > "n...(a)bid.nes" <alien8...(a)gmail.com> wrote in message > > news:05d6a5e5-9996-4a4b-8bf9-a3c93108da51(a)x10g2000prk.googlegroups.com... > > > > > 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. Sorry, my question should have read: > > By "upwards", do you mean within the page along the direction > > parallel to a line drawn from D1 to S1 (S2 to D2), i. e. that way: > > > > ^ > > | > > > > ...or out of the screen towards me? > > >> 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. 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, That would be correct if light velocity depended on the velocity of the emitter, but it doesn't. Light is always observed to travel at c no matter the relative state of motion of detector and emitter. When an emitter/detector don't move WRT each other, but are accelerated as a unit, they see Doppler shift during acceleration and deceleration. When they are moving at a *constant velocity* the signal is seen at it's at rest wavelength. The device is an accelerometer, not a speedometer. If it were, it would demonstrate the existence of an absolute frame of reference. I suspect that's the OPs point. If it is, I suggest he build the apparatus and see; it isn't complicated. No matter how he yanks it around (hundreds, even thousands of gs of *nondestructive* acceleration is not hard to achieve with small, well-built electronics) I predict he will not observe a timing change with acceleration. I would be very interested if he did. > 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. That's because if the acceleration is fast enough the light simply misses the detector; in the first case the light has nowhere to go *but* the detector. It's still an "accelerometer" of sorts, but go-no go rather than analog. > 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. I was being generous and assuming the emitters were triggered by, and the detectors compared by, mechanisms equidistant from both, tied to the frame holding everything together. The signal paths from the trigger to the emitters, and the path from the detectors to the comparator, *and* the timing signal from the trigger, must be the same lengths (or suitable delays introduced to make their signal travel times identical). Notice the frame, being made of matter (since there isn't anything else to work with) is held together by electron-mediated bonds, which can't respond faster than disturbances in their mutual electromagnetic field can travel, IOW light speed. This is essentially the same "puzzle" the OP posed. If lightspeed bonds independent of velocity can't hold the structure together there's no puzzle. > > If the latter, neither detector registers a hit *until the setup > > reaches a constant velocity*. > > Yeup. Mark L. Fergerson |