SR and a lightbulb
in [Relativity]
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From: dk on 30 Dec 2009 10:30 On Dec 30, 9:32 am, "Inertial" <relativ...(a)rest.com> wrote: > "Greg Neill" <gneil...(a)MOVEsympatico.ca> wrote in message > > news:4b3b6199$0$29200$9a6e19ea(a)news.newshosting.com... > > > > > > > Inertial wrote: > >> "Cocoon" <wy45e...(a)hushmail.com> wrote in message > >>news:4b8be11a-d45c-453e-84fb-b8dbd3eb6cbb(a)r5g2000yqb.googlegroups.com.... > >>> On Dec 30, 4:25 am, "Inertial" <relativ...(a)rest.com> wrote: > >>>> "dk" <dakalami...(a)sci.ccny.cuny.edu> wrote in message > > >>> [snip imbecility] > > >>>> No .. that would be nonsense. > > >>>> What happens is that the two set of wires do not connect at the same > > time > >>>> in > >>>> S' and do not disconnect at the same time in S'. If the bulb is to > >>>> light, > >>>> they would need to both stay connected long enough for a current to > > flow. > > >>> so, you need thick connectors, > >>> this is what you say, right? > > >> Thick enough to make a contact long enough. That's if there is any > >> chance > >> for the bulb to flash. > > >> Of course, there's not enough info to know whether the bulb will flash.. > > But > >> probably not if the wires are passing so fast that the length contraction > > is > >> noticeable. There would need to be a large surface area for them to > > remain > >> in contact long enough as they slide past each other. > > >> My guess is that there is no flash in either frame at any relatively fast > >> speed for the two frame to be move wrt each other. > > > The OP did not consider the fact that the speed of the > > electric field in a conductor is quite a bit less less > > than c. > > It depends on the conductor, of course. I suppose around 75% the speed of > light would be typical. Good conductors can get above 90%. > > > If the connection points are small and the light > > bulb wires moving at near c, there will be insufficient > > time for the field to traverse the wire to make the > > circuit and light the bulb in either frame. > > Yeup. > > And, of course, whether or not it lights up is not frame dependent. Either > it does, or it doesn't.- Hide quoted text - > > - Show quoted text - Thanks to all who responded and for their opinions. The original set- up is too simple. It does seem crucial that the points x1 and x2 should actually be finite segments: Then, the lightbulb device endpoints could have enough time in contact with the segments so that the potential difference can be transmitted across the distance L. So it seems that, in frame S, at least a time L/c is reguired for the circuit to complete. The segments have to be long enough, in S, so that the lightbulb device endpoints remain on them for at least an L/c interval. The question now is: Does this required time delay, in S, which would cause the lightbulb to flash, make the S' observer's explanation physically valid?
From: dlzc on 30 Dec 2009 12:20 Dear dk: On Dec 30, 8:30 am, dk <dakalami...(a)sci.ccny.cuny.edu> wrote: .... > Thanks to all who responded and for their > opinions. The original set-up is too > simple. Simple is good. I found the lack of description to be its only drawback. > It does seem crucial that the points x1 > and x2 should actually be finite segments: Points are not segments. x1 to x2 is (or could be) one segment. > Then, the lightbulb device endpoints > could have enough time in contact with > the segments so that the potential > difference can be transmitted across the > distance L. The problem is "simultaneity". You assume that the two ends appear to make contact at the same instant. Whereas this would never be observed. > So it seems that, in frame S, at least > a time L/c is reguired for the circuit > to complete. Current flows are on the order of 0.1c, and inductance of wiring will delay onset of current flow by a good bit. > The segments have to be long enough, > in S, so that the lightbulb device > endpoints remain on them for at least > an L/c interval. Better to stick with the barn-pole paradox. > The question now is: Does this required > time delay, in S, which would cause the > lightbulb to flash, make the S' observer's > explanation physically valid? All interpretations are physcially valid, and self consistent. The various "conundrums" come about by making "frame jumps". Using rest frame lengths for moving objects, rather than lengths measured in your frame, for example. If the lamp lights in one frame, it lights in all frames. It may be red or blue shifted (depending on observer position or speed), but it'll light (or not) for all observers. http://math.ucr.edu/home/baez/physics/ http://math.ucr.edu/home/baez/physics/Relativity/SR/barn_pole.html http://math.ucr.edu/home/baez/physics/Relativity/SR/spaceship_puzzle.html http://math.ucr.edu/home/baez/physics/Relativity/SR/penrose.html http://math.ucr.edu/home/baez/physics/Relativity/SR/Spaceship/spaceship.html David A. Smith
From: Inertial on 30 Dec 2009 19:02 "dk" <dakalamidas(a)sci.ccny.cuny.edu> wrote in message news:33aa0ee1-a61e-445a-ba02-ef8367510985(a)r24g2000yqd.googlegroups.com... > On Dec 30, 9:32 am, "Inertial" <relativ...(a)rest.com> wrote: >> "Greg Neill" <gneil...(a)MOVEsympatico.ca> wrote in message >> >> news:4b3b6199$0$29200$9a6e19ea(a)news.newshosting.com... >> >> >> >> >> >> > Inertial wrote: >> >> "Cocoon" <wy45e...(a)hushmail.com> wrote in message >> >>news:4b8be11a-d45c-453e-84fb-b8dbd3eb6cbb(a)r5g2000yqb.googlegroups.com... >> >>> On Dec 30, 4:25 am, "Inertial" <relativ...(a)rest.com> wrote: >> >>>> "dk" <dakalami...(a)sci.ccny.cuny.edu> wrote in message >> >> >>> [snip imbecility] >> >> >>>> No .. that would be nonsense. >> >> >>>> What happens is that the two set of wires do not connect at the same >> > time >> >>>> in >> >>>> S' and do not disconnect at the same time in S'. If the bulb is to >> >>>> light, >> >>>> they would need to both stay connected long enough for a current to >> > flow. >> >> >>> so, you need thick connectors, >> >>> this is what you say, right? >> >> >> Thick enough to make a contact long enough. That's if there is any >> >> chance >> >> for the bulb to flash. >> >> >> Of course, there's not enough info to know whether the bulb will >> >> flash. >> > But >> >> probably not if the wires are passing so fast that the length >> >> contraction >> > is >> >> noticeable. There would need to be a large surface area for them to >> > remain >> >> in contact long enough as they slide past each other. >> >> >> My guess is that there is no flash in either frame at any relatively >> >> fast >> >> speed for the two frame to be move wrt each other. >> >> > The OP did not consider the fact that the speed of the >> > electric field in a conductor is quite a bit less less >> > than c. >> >> It depends on the conductor, of course. I suppose around 75% the speed >> of >> light would be typical. Good conductors can get above 90%. >> >> > If the connection points are small and the light >> > bulb wires moving at near c, there will be insufficient >> > time for the field to traverse the wire to make the >> > circuit and light the bulb in either frame. >> >> Yeup. >> >> And, of course, whether or not it lights up is not frame dependent. >> Either >> it does, or it doesn't.- Hide quoted text - >> >> - Show quoted text - > > Thanks to all who responded and for their opinions. The original set- > up is too simple. It does seem crucial that the points x1 and x2 > should actually be finite segments: Then, the lightbulb device > endpoints could have enough time in contact with the segments so that > the potential difference can be transmitted across the distance L. So > it seems that, in frame S, at least a time L/c is reguired for the > circuit to complete. The segments have to be long enough, in S, so > that the lightbulb device endpoints remain on them for at least an L/c > interval. The question now is: Does this required time delay, in S, > which would cause the lightbulb to flash, make the S' observer's > explanation physically valid? If the flash occurs, it must occur in all frames .. and it won't occur unless it is 'physically valid'. The same laws of physics apply in all inertial frames. Of course, some laws are more complex for objects in motion as opposed to objects at rest in a given frame, which is why one usually does analysis in the rest frame of the experiment where possible.
From: Inertial on 30 Dec 2009 19:14 "dlzc" <dlzc1(a)cox.net> wrote in message news:df430872-2aaf-4fa6-9376-17e56bd08460(a)a6g2000yqm.googlegroups.com... > Dear dk: > > On Dec 30, 8:30 am, dk <dakalami...(a)sci.ccny.cuny.edu> wrote: > ... >> Thanks to all who responded and for their >> opinions. The original set-up is too >> simple. > > Simple is good. I found the lack of description to be its only > drawback. > >> It does seem crucial that the points x1 >> and x2 should actually be finite segments: > > Points are not segments. x1 to x2 is (or could be) one segment. > >> Then, the lightbulb device endpoints >> could have enough time in contact with >> the segments so that the potential >> difference can be transmitted across the >> distance L. > > The problem is "simultaneity". You assume that the two ends appear to > make contact at the same instant. Whereas this would never be > observed. > >> So it seems that, in frame S, at least >> a time L/c is reguired for the circuit >> to complete. > > Current flows are on the order of 0.1c, and inductance of wiring will > delay onset of current flow by a good bit. The speed propagation of the EM in a good conductor (which we would assume we're dealing with) are around 60% to 95% of c. If you're talking about the speed of the random electrons movement in the conductor, that's a good deal less .. I think 0.1c is prob around the right magnitude .. and if no current is flowing, the net motion balances out. If you're talking about the electron drift speed (the net effect of overall motion of electrons in a conductor when current is applied) then that is VERY slow. A tortoise could beat electron drift and have time for a nap :):) >> The segments have to be long enough, >> in S, so that the lightbulb device >> endpoints remain on them for at least >> an L/c interval. > > Better to stick with the barn-pole paradox. > >> The question now is: Does this required >> time delay, in S, which would cause the >> lightbulb to flash, make the S' observer's >> explanation physically valid? > > All interpretations are physcially valid, and self consistent. The > various "conundrums" come about by making "frame jumps". Using rest > frame lengths for moving objects, rather than lengths measured in your > frame, for example. If the lamp lights in one frame, it lights in all > frames. It may be red or blue shifted (depending on observer position > or speed), but it'll light (or not) for all observers. > > http://math.ucr.edu/home/baez/physics/ > http://math.ucr.edu/home/baez/physics/Relativity/SR/barn_pole.html > http://math.ucr.edu/home/baez/physics/Relativity/SR/spaceship_puzzle.html > http://math.ucr.edu/home/baez/physics/Relativity/SR/penrose.html > http://math.ucr.edu/home/baez/physics/Relativity/SR/Spaceship/spaceship.html > > David A. Smith Yeup :):)
From: Inertial on 30 Dec 2009 21:44
"Henry Wilson DSc" <..@..> wrote in message news:501oj5p29jck2ut4pqqfe2mmvd9e5gc13m(a)4ax.com... > On Thu, 31 Dec 2009 11:15:52 +1100, "Inertial" <relatively(a)rest.com> > wrote: > >> >>"Henry Wilson DSc" <..@..> wrote in message >>news:gggnj5t78me1itgmorlsgiuthauvh117v8(a)4ax.com... >>> On Wed, 30 Dec 2009 21:06:41 +1100, "Inertial" <relatively(a)rest.com> >>> wrote: > > >>>> >>>>It is never the case that it lights according to one frame but not in >>>>another. >>> >>> It is. >> >>No >> >>> The bulb light ONLY in the frame that moves at v/2 >> >>No >> >>That is nonsense. Either a light bulb is lit, or it is not. >> >>>>>>> How does the >>>>>>> observer in S' explain the objective fact of the lightbulb flashing? >>>>>>> >>>>>>> thanks to all who might respond >>>>>>> dk >>>>> >>>>> good one, dk >>>> >>>>Yeup .. nice little excercise. >>> >>> It again demonstrates the stupidity and self contradiction of SR. >> >>No .. it demonstrates YOUR stupidity. > > hahahahhaha! The Einstein Hoax is becoming more apparent every day. No .. your stupidity is. Actually , no .. its been apparent for a long time. > Consider the battery at rest and the light plus wires moving at v. OK > Surrounding it are lots of differently moving observers. Fine. > Only the observer who moves at v/2 will see the flash. Wrong. > In the other observer > frames, it simply doesn't happen (according to Einstein, of course) Wrong .. SR and Einstein does not say that at all. > So now we have Einstein the magician. He can make things appear and > disappear > at will. Unfortunately he can't make your ignorance disappear. |