Known physics defeated by simple puzzle?
in [Relativity]
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From: Ste on 18 Feb 2010 09:25 On 17 Feb, 21:33, PD <thedraperfam...(a)gmail.com> wrote: > On Feb 17, 2:57 pm, Ste <ste_ro...(a)hotmail.com> wrote: > > > > > > > On 17 Feb, 15:53, PD <thedraperfam...(a)gmail.com> wrote: > > > > On Feb 17, 9:13 am, Ste <ste_ro...(a)hotmail.com> wrote: > > > > > > > > Translations in relativity--or in fact, even in pure mathematics--are > > > > > > > very different things than rotations, and picking the detector up and > > > > > > > putting it somewhere else without changing the speed is a pure > > > > > > > translation. You don't even need relativity in this scenario, where > > > > > > > everything is at rest with respect to everything else. > > > > > > > Yes, but we're going to get to the bit where relativity is required in > > > > > > a moment. > > > > > > > Now, let us suppose we have two source and two detectors again: > > > > > > > D1 D2 D3 > > > > > > > S1 S2 S3 > > > > > > > S1 and D1 are stationary in the frame, and do not move. D2 is also > > > > > > stationary in the frame. S2, S3, and D3 are all moving in the y+ > > > > > > direction (i.e. same as the previous scenario) at a constant speed > > > > > > (which is close to 'c'). Just to be sure we understand, the same setup > > > > > > a few moments back in time would have looked like this: > > > > > > > D1 D2 > > > > > > > D3 > > > > > > > S1 > > > > > > > S2 S3 > > > > > > > Now, when all sources come into line with each other (as per the first > > > > > > illustration above), a pulse is emitted towards the respective > > > > > > detectors. After emission, S2 would continue towards D2, but in > > > > > > reality we remove S2 from the picture before any collision (and we've > > > > > > already established that any transformation of the sources after > > > > > > emission has no effect on photons already emitted). > > > > > > > Now, based on the previous scenario, I presume that in SR, D3 receives > > > > > > its pulse long after D1. However, this time, does D2 receive its pulse > > > > > > at the same time as D1? > > > > Yes, and yes. > > > Ok. > > > Consider yet another setup: > > > D1 D3 > > > S1 D2 S2 D4 > > > In case it isn't clear, D1 and D2 are equidistant from S1, and D3 and > > D4 are equidistant from S2. > > > The S1 group (i.e. comprising S1, D1, and D2) are always stationary in > > the frame, and S1 is emitting a pulse towards both D1 and D2. > > Let's make this a little more concrete. Let's say that S1 and S2 > flash, emitting pulses that radiate in all directions, and that the > detectors intercept a portion of the light from those pulses. (If you > want, think of S1 and S2 as firecrackers.) No, because that needlessly complicates the matter. The important thing is establishing where a single photon would land. > > There is > > a similar setup for the S2 group, except that after the emission of > > the pulse, the S2 group moves in the y+ direction, so that S2 is now > > in the former place of D3 (again, the whole group accelerates rapidly, > > and is stationary again by time of detection). > > > Now, I assume D1 and D2 receive their signals simultaneously. But what > > of D3 and D4? By the previous answers, I presume D4 receives it's > > signal before D3? > > In this frame, yes. > Note, not in all inertial reference frames. :>) Indeed, but there are no other relevant frames here, because both the emission and the detection take place while all parts of the setup are stationary and in the same frame.
From: PD on 18 Feb 2010 09:34 On Feb 18, 8:25 am, Ste <ste_ro...(a)hotmail.com> wrote: > On 17 Feb, 21:33, PD <thedraperfam...(a)gmail.com> wrote: > > > > > On Feb 17, 2:57 pm, Ste <ste_ro...(a)hotmail.com> wrote: > > > > On 17 Feb, 15:53, PD <thedraperfam...(a)gmail.com> wrote: > > > > > On Feb 17, 9:13 am, Ste <ste_ro...(a)hotmail.com> wrote: > > > > > > > > > Translations in relativity--or in fact, even in pure mathematics--are > > > > > > > > very different things than rotations, and picking the detector up and > > > > > > > > putting it somewhere else without changing the speed is a pure > > > > > > > > translation. You don't even need relativity in this scenario, where > > > > > > > > everything is at rest with respect to everything else. > > > > > > > > Yes, but we're going to get to the bit where relativity is required in > > > > > > > a moment. > > > > > > > > Now, let us suppose we have two source and two detectors again: > > > > > > > > D1 D2 D3 > > > > > > > > S1 S2 S3 > > > > > > > > S1 and D1 are stationary in the frame, and do not move. D2 is also > > > > > > > stationary in the frame. S2, S3, and D3 are all moving in the y+ > > > > > > > direction (i.e. same as the previous scenario) at a constant speed > > > > > > > (which is close to 'c'). Just to be sure we understand, the same setup > > > > > > > a few moments back in time would have looked like this: > > > > > > > > D1 D2 > > > > > > > > D3 > > > > > > > > S1 > > > > > > > > S2 S3 > > > > > > > > Now, when all sources come into line with each other (as per the first > > > > > > > illustration above), a pulse is emitted towards the respective > > > > > > > detectors. After emission, S2 would continue towards D2, but in > > > > > > > reality we remove S2 from the picture before any collision (and we've > > > > > > > already established that any transformation of the sources after > > > > > > > emission has no effect on photons already emitted). > > > > > > > > Now, based on the previous scenario, I presume that in SR, D3 receives > > > > > > > its pulse long after D1. However, this time, does D2 receive its pulse > > > > > > > at the same time as D1? > > > > > Yes, and yes. > > > > Ok. > > > > Consider yet another setup: > > > > D1 D3 > > > > S1 D2 S2 D4 > > > > In case it isn't clear, D1 and D2 are equidistant from S1, and D3 and > > > D4 are equidistant from S2. > > > > The S1 group (i.e. comprising S1, D1, and D2) are always stationary in > > > the frame, and S1 is emitting a pulse towards both D1 and D2. > > > Let's make this a little more concrete. Let's say that S1 and S2 > > flash, emitting pulses that radiate in all directions, and that the > > detectors intercept a portion of the light from those pulses. (If you > > want, think of S1 and S2 as firecrackers.) > > No, because that needlessly complicates the matter. The important > thing is establishing where a single photon would land. Yes, it complicates the matter because you haven't specified which photon. Do you mean the one that is aimed at the detector when fired but does not hit it because of the acceleration of the detector, or do you mean the one that is not aimed at the detector when fired but DOES hit it because of the acceleration of the detector? This is important, you see, because if you restrict the attention to one of those, you might get the (false) impression that the detector sees no light at all. > > > > There is > > > a similar setup for the S2 group, except that after the emission of > > > the pulse, the S2 group moves in the y+ direction, so that S2 is now > > > in the former place of D3 (again, the whole group accelerates rapidly, > > > and is stationary again by time of detection). > > > > Now, I assume D1 and D2 receive their signals simultaneously. But what > > > of D3 and D4? By the previous answers, I presume D4 receives it's > > > signal before D3? > > > In this frame, yes. > > Note, not in all inertial reference frames. :>) > > Indeed, but there are no other relevant frames here, because both the > emission and the detection take place while all parts of the setup are > stationary and in the same frame. That's not so. There is no more relevant frame than any other frame. The experiment takes place in all frames at once, and the experiment can be described in any of them. The description varies from frame to frame, but all are equally useful for examining the events.
From: Ste on 18 Feb 2010 12:24 On 18 Feb, 14:34, PD <thedraperfam...(a)gmail.com> wrote: > On Feb 18, 8:25 am, Ste <ste_ro...(a)hotmail.com> wrote: > > > > Let's make this a little more concrete. Let's say that S1 and S2 > > > flash, emitting pulses that radiate in all directions, and that the > > > detectors intercept a portion of the light from those pulses. (If you > > > want, think of S1 and S2 as firecrackers.) > > > No, because that needlessly complicates the matter. The important > > thing is establishing where a single photon would land. > > Yes, it complicates the matter because you haven't specified which > photon. Do you mean the one that is aimed at the detector when fired > but does not hit it because of the acceleration of the detector, or do > you mean the one that is not aimed at the detector when fired but DOES > hit it because of the acceleration of the detector? This is important, > you see, because if you restrict the attention to one of those, you > might get the (false) impression that the detector sees no light at > all. Well I'm assuming that the source emits one photon at a time. And of course I refer to the photon that is aimed at the detector when fired, but does *not* hit due to the acceleration of the detector. > > > > There is > > > > a similar setup for the S2 group, except that after the emission of > > > > the pulse, the S2 group moves in the y+ direction, so that S2 is now > > > > in the former place of D3 (again, the whole group accelerates rapidly, > > > > and is stationary again by time of detection). > > > > > Now, I assume D1 and D2 receive their signals simultaneously. But what > > > > of D3 and D4? By the previous answers, I presume D4 receives it's > > > > signal before D3? > > > > In this frame, yes. > > > Note, not in all inertial reference frames. :>) > > > Indeed, but there are no other relevant frames here, because both the > > emission and the detection take place while all parts of the setup are > > stationary and in the same frame. > > That's not so. There is no more relevant frame than any other frame. > The experiment takes place in all frames at once, and the experiment > can be described in any of them. The description varies from frame to > frame, but all are equally useful for examining the events. Perhaps. But I suppose we can move on to that later.
From: PD on 18 Feb 2010 13:40 On Feb 18, 11:24 am, Ste <ste_ro...(a)hotmail.com> wrote: > On 18 Feb, 14:34, PD <thedraperfam...(a)gmail.com> wrote: > > > > > On Feb 18, 8:25 am, Ste <ste_ro...(a)hotmail.com> wrote: > > > > > Let's make this a little more concrete. Let's say that S1 and S2 > > > > flash, emitting pulses that radiate in all directions, and that the > > > > detectors intercept a portion of the light from those pulses. (If you > > > > want, think of S1 and S2 as firecrackers.) > > > > No, because that needlessly complicates the matter. The important > > > thing is establishing where a single photon would land. > > > Yes, it complicates the matter because you haven't specified which > > photon. Do you mean the one that is aimed at the detector when fired > > but does not hit it because of the acceleration of the detector, or do > > you mean the one that is not aimed at the detector when fired but DOES > > hit it because of the acceleration of the detector? This is important, > > you see, because if you restrict the attention to one of those, you > > might get the (false) impression that the detector sees no light at > > all. > > Well I'm assuming that the source emits one photon at a time. And of > course I refer to the photon that is aimed at the detector when fired, > but does *not* hit due to the acceleration of the detector. Ah, ok, then I have no objection to your conclusion, although I have no idea what you hope to learn about relativity about such a scenario. > > > > > > > > There is > > > > > a similar setup for the S2 group, except that after the emission of > > > > > the pulse, the S2 group moves in the y+ direction, so that S2 is now > > > > > in the former place of D3 (again, the whole group accelerates rapidly, > > > > > and is stationary again by time of detection). > > > > > > Now, I assume D1 and D2 receive their signals simultaneously. But what > > > > > of D3 and D4? By the previous answers, I presume D4 receives it's > > > > > signal before D3? > > > > > In this frame, yes. > > > > Note, not in all inertial reference frames. :>) > > > > Indeed, but there are no other relevant frames here, because both the > > > emission and the detection take place while all parts of the setup are > > > stationary and in the same frame. > > > That's not so. There is no more relevant frame than any other frame. > > The experiment takes place in all frames at once, and the experiment > > can be described in any of them. The description varies from frame to > > frame, but all are equally useful for examining the events. > > Perhaps. But I suppose we can move on to that later.
From: Ste on 18 Feb 2010 16:19
On 18 Feb, 18:40, PD <thedraperfam...(a)gmail.com> wrote: > On Feb 18, 11:24 am, Ste <ste_ro...(a)hotmail.com> wrote: > > > > > > > On 18 Feb, 14:34, PD <thedraperfam...(a)gmail.com> wrote: > > > > On Feb 18, 8:25 am, Ste <ste_ro...(a)hotmail.com> wrote: > > > > > > Let's make this a little more concrete. Let's say that S1 and S2 > > > > > flash, emitting pulses that radiate in all directions, and that the > > > > > detectors intercept a portion of the light from those pulses. (If you > > > > > want, think of S1 and S2 as firecrackers.) > > > > > No, because that needlessly complicates the matter. The important > > > > thing is establishing where a single photon would land. > > > > Yes, it complicates the matter because you haven't specified which > > > photon. Do you mean the one that is aimed at the detector when fired > > > but does not hit it because of the acceleration of the detector, or do > > > you mean the one that is not aimed at the detector when fired but DOES > > > hit it because of the acceleration of the detector? This is important, > > > you see, because if you restrict the attention to one of those, you > > > might get the (false) impression that the detector sees no light at > > > all. > > > Well I'm assuming that the source emits one photon at a time. And of > > course I refer to the photon that is aimed at the detector when fired, > > but does *not* hit due to the acceleration of the detector. > > Ah, ok, then I have no objection to your conclusion, although I have > no idea what you hope to learn about relativity about such a scenario. I'm basically trying to figure out how light can possibly travel at a constant speed, or at least *appear* to do so, when measured from any frame. |