Known physics defeated by simple puzzle?
in [Relativity]
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From: Inertial on 15 Feb 2010 06:42 "Ste" <ste_rose0(a)hotmail.com> wrote in message news:a67515b4-7c2f-4b65-97fc-690c10066f3a(a)f15g2000yqe.googlegroups.com... > On 14 Feb, 21:15, William Hughes <wpihug...(a)hotmail.com> wrote: >> On Feb 14, 3:42 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? >> >> What's more think of running with a long pole, fast enough >> so it is foreshortened enough to fit in a barn. An observer >> on the roof closes the in door and opens the out door >> simultaneously. But you see the barn foreshortened, not the >> pole ... >> >> Those who do not study the FAQ are condemned to repeat >> it. > > Let's forget the pole and barn paradox because it introduced too much > argument. Only amongst those with no idea > This setup is simple, It is more complicated than the pole and barn. But certainly does not 'defeat known physics' !! > in that it involves a setup that undergoes a > straightforward translation along a single dimension, No .. it involves a non-constant acceleration > except that one > detector moves towards the source (as it was before the translation), > and the other moves away.
From: Inertial on 15 Feb 2010 06:44 "Ste" <ste_rose0(a)hotmail.com> wrote in message news:3556f6e8-f893-4f80-a335-6b18eaf40321(a)q29g2000yqn.googlegroups.com... > 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? Those who understand it .. yes >> 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 - What delays? > so that I know instantly the state of > everything in the universe. You don't need to know it instantly .. you can know it an analyse it some time after the fact. > 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. So really we have four inertial observers now.
From: Ste on 15 Feb 2010 07:11 On 15 Feb, 07:35, Owen Jacobson <angrybald...(a)gmail.com> wrote: > Subject: Known physics defeated by simple puzzle? > > If you're serious about actually learning something about physics, as > opposed to being serious about winding people up, don't take this > approach. It discourages others from taking you seriously. I dare say it is the preconceptions of many of those here that prevent them taking any questioning seriously. It's often like being surrounded by a bunch of ideological crackpots. > We already > have enough "physics is wrong!" threads kicking around. As I say, I don't think it is wrong. Relativity clearly works - or at least to a sufficiently precise approximation. The point is that no one seems to be able to explain some of its more esoteric assumptions in physical terms - such as the constant speed of light no matter what the velocity of the observer. > If you don't understand what modern physical theories (in this case, > relativity) predict for a given experiment, that's fine, and asking > about it is not unwise; however, presupposing that they offer no > prediction or that the prediction is illogical or inconsistent is only > going to make you look foolish to the people who could help you > understand. I'm not saying physics offers no predictions or that it is illogical. But my honest apprehension of most people here is that they don't understand relativity, except in the rote mathematical terms by which they learned it.
From: Peter Webb on 15 Feb 2010 07:38 I think you have tried to re-tell a much more interesting and well known "paradox" of GR in your own words, but missed the point (because you didn't really understand it). Disclaimer: I am no expert on GR, which is a billion times more mathemtically sophisticated than SR. Whilst I am confident of what I say about SR, much less so on GR. The light pulses will reach the detectors at different times. Indeed, to jump to the endpoint you might want to hear, experimenters would measure the light going up and down as having two different velocities; the acceleration is equivalent to a gravitational field and light slows in a gravitational field. I note that by definition this is not an inertial frame of reference, so SR has nothing to say about it, its a GR thought experiment. Of couse, if you don't understand Minkowski space time in SR, you have no chance whatsoever of getting any real understanding of GR. Sorry.
From: Inertial on 15 Feb 2010 07:24
"Ste" <ste_rose0(a)hotmail.com> wrote in message news:f3b13712-7e39-4005-ad5d-d0ce7f04e40f(a)k19g2000yqc.googlegroups.com... > On 15 Feb, 07:35, Owen Jacobson <angrybald...(a)gmail.com> wrote: >> Subject: Known physics defeated by simple puzzle? >> >> If you're serious about actually learning something about physics, as >> opposed to being serious about winding people up, don't take this >> approach. It discourages others from taking you seriously. > > I dare say it is the preconceptions of many of those here that prevent > them taking any questioning seriously. It's often like being > surrounded by a bunch of ideological crackpots. > >> We already >> have enough "physics is wrong!" threads kicking around. > > As I say, I don't think it is wrong. Relativity clearly works - or at > least to a sufficiently precise approximation. The point is that no > one seems to be able to explain some of its more esoteric assumptions > in physical terms - such as the constant speed of light no matter what > the velocity of the observer. No . .we can explain it .. but you refuse to learn the terminology that physics uses >> If you don't understand what modern physical theories (in this case, >> relativity) predict for a given experiment, that's fine, and asking >> about it is not unwise; however, presupposing that they offer no >> prediction or that the prediction is illogical or inconsistent is only >> going to make you look foolish to the people who could help you >> understand. > > I'm not saying physics offers no predictions or that it is illogical. > But my honest apprehension of most people here is that they don't > understand relativity, except in the rote mathematical terms by which > they learned it. Just because it is expressed mathematically, that dose not mean it doesn't have a meaning and can only be rote learned .. quite the opposite. The math makes the meanings and logic very precise and unambiguous. That is why it is the preferred 'language' of physics. |