SR and a lightbulb
in [Relativity]
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From: dlzc on 8 Jan 2010 09:55 Dear Darwin123: On Jan 7, 5:35 pm, Darwin123 <drosen0...(a)yahoo.com> wrote: > On Dec 29 2009, 10:17 pm,dlzc<dl...(a)cox.net> wrote:> On Dec 29, 7:46 pm, dk <dakalami...(a)sci.ccny.cuny.edu> wrote: > > > > I should have mentioned that it is assumed > > > that the wires on the lightbulb device are > > > insulated and only at their endpoints is the > > > conductor exposed so as to make contact with > > > x1 and x2 in frame S. > > > Draw a diagram. How are the wires oriented > > wrt the x axis? > > > Next, wires have inductance. Only in a > > fantasy world does the light "flash". > > I would like to add: > "Wires have an inductance. therefore the signal > traveling from switch to light bulb has to move > slower than the speed of light. you have to > include the propagation time of the electric > power once the circuit is complete. Most of the > signal upon completing the circuit will actually > move slower than the speed of light. Plus the > fact that the filament needs time to heat. > To facilitate the discussion, assume that > the signal moves from switch to light bulb at > the speed of light, and that the light bulb > heats up "instantly." Also include the propagation > time of the light from bulb to observers." Remove the bulb, and replace it with an LED. Still no way to get the signal to flow as close to c as to be convincing. If it lights, it lights for all frames. David A. Smith
From: train on 8 Jan 2010 10:19 On Jan 8, 5:49 am, "Inertial" <relativ...(a)rest.com> wrote: > "train" <gehan.ameresek...(a)gmail.com> wrote in message > > news:7c9ad0f4-b028-4949-9a3f-305fc195c68c(a)e37g2000yqn.googlegroups.com... > > > > > > > On Jan 8, 4:13 am, eric gisse <jowr.pi.nos...(a)gmail.com> wrote: > >> ..@..(Henry Wilson DSc) wrote: > >> > On Thu, 7 Jan 2010 12:55:33 -0800 (PST), PD <thedraperfam...(a)gmail.com> > >> > wrote: > > >> >>On Jan 7, 2:41 pm, ..@..(Henry Wilson DSc) wrote: > >> >>> On Thu, 7 Jan 2010 06:54:28 -0800 (PST), PD > >> >>> <thedraperfam...(a)gmail.com> > >> >>> wrote: > >> >>> >On Jan 6, 6:29 pm, ..@..(Henry Wilson DSc) wrote: > > >> >>> >This has nothing to do with what humans see. This is a matter of > >> >>> >whether the barn door strikes the pole or not, which can be recorded > >> >>> >with or without humans present. > > >> >>> >Now: At the time when the front of the pole hits the back wall of > >> >>> >the > >> >>> >barn, what happens to the back end of the pole AT THAT INSTANT? > > >> >>> At any particular instant...or if time diesn't even exist ...the two > >> >>> ends of the pole are separated by the same absolute spatial interval. > > >> >>I'll be a little more precise: At the instant when the motion of the > >> >>front of the pole stops as it hits the back wall of the barn, what > >> >>happens to the motion of the back of the pole? > > >> > It stops instantly as well. Reality doesn't rely on what humans see. > > >> Really? Instantly? > > >> [...] > > > We this is indeed the point. Can anything travel faster than light? > > When the pole hits the back of the barn door and stops instantly, > > Which means its a pretty tough barn door :) > > > the > > impact has to be transmitted through the pole atom by atom. Can this > > happen faster than the speed of light? In classical mechanics yes > > It usually happens at what is usually called the speed of sound for that > material .. the speed that such compression 'information' is transmitted > through the material. > > If this immovable barn door is trying to travel through the rod (from the > moment of collision) at faster than the speed of sound in that rod, it will > cause catastrophic damage to the rod, as its back end tries to plough on > forwards and compress the rod faster than it can handle. > > This effect is the same in principle whether SR or classical mechanics. > > > In SRT if you follow it, you will have two effects The instant the > > pole stops, > > You mean the instant the front end of it stops. In the pole frame, the back > end is blissfully unaware that its front end has crashed into a carelessly > closed barn door. > > > the length contraction disappears, atom by atom along the > > length of the pole > > Yes .. as those atoms get slowed down > > > at the speed of light. > > Well. it all depends on what happens to the various bits of the rod. Its > certainly not going to be good for it. Certainly the information (in SR) > cannot get to the back end of the rod FASTER than the speed of light. it > would probably get there at the maximum of the speed of sound in that > material, and the speed of the barn wrt the rod (ie either the compression > wave thru the rod gets to the back of the rod first, or the barn door itself > does :)) > > > as the stopping of the pole also takes place at the speed of light > > atom by atom. > > The pole will then pop right out of the front of the Barn Door. > > More likely it will compress and shatter under the stress. We're assuming a > very strong barn door here. > > > All > > this for the farmer watching the pole fly through the barn door at > > close to the speed of light. > > Life is pretty dull on a farm .. you need al lthe entertainment you can get. Well well, so reality for the rod is now limited by the speed of sound. A fine pickle we have here. Anyway Inertial you're cool. What if the barn doors are electrified? Then will the speed of electricity pass through the rod faster than sound? But I digress. I would like to know what you think of the question - is the light bulb on only when you see it is on or before? It is important and relevant. T
From: PD on 8 Jan 2010 12:29 On Jan 7, 3:42 pm, ..@..(Henry Wilson DSc) wrote: > On Thu, 7 Jan 2010 12:55:33 -0800 (PST), PD <thedraperfam...(a)gmail.com> wrote: > >On Jan 7, 2:41 pm, ..@..(Henry Wilson DSc) wrote: > >> On Thu, 7 Jan 2010 06:54:28 -0800 (PST), PD <thedraperfam...(a)gmail.com> wrote: > > >> >No, relativity does NOT say that. The OP thought that relativity says > >> >that, but he was incorrect. His error was precisely the one I just > >> >pointed out. > > >> You only pointed out that humans perceive a distorted view of reality because > >> of their reliance on light, which travels at a finite speed. > > >I pointed out that there was no internal contradiction in relativity, > >which you claimed there was, and which the OP thought was there too, > >both of you erroneously. > > there is no internal contradiction in much of Earth centrism either...or 'flat > Earthism'.... > But you said there WAS an internal contradiction in relativity and this example pointed it out. And that was wrong. But instead of admitting that your claim of internal contradiction was wrong, you say SR is wrong anyway.
From: PD on 8 Jan 2010 12:37 On Jan 7, 3:42 pm, ..@..(Henry Wilson DSc) wrote: > On Thu, 7 Jan 2010 12:55:33 -0800 (PST), PD <thedraperfam...(a)gmail.com> wrote: > > >I'll be a little more precise: At the instant when the motion of the > >front of the pole stops as it hits the back wall of the barn, what > >happens to the motion of the back of the pole? > > It stops instantly as well. Reality doesn't rely on what humans see. > I am SO happy that you gave this response. This gives me the chance to ask you a few questions. 1. You claim that the back end stops instantly, but that this is a reality we cannot see. If you cannot see it, how do you know that it happens? What method of truth checking are you using to determine the truth value of the claim that the back end stops instantly. (PLEASE PLEASE PLEASE tell me that you rely on common sense for this.) 2. Since science uses observation to check the truth of claims, but you believe that reality is not revealed by observation, is it your claim that science is in general a waste of time, since that is not how reality is determined? If so, then why diddle around on sci.*.*, if you believe that the whole business of how science works is just bogus to begin with? (PLEASE PLEASE PLEASE tell me that what you do is science and what scientists do is not science.) 3. By what physical process does the back end of the rod become aware that the front end of the rod has stopped, at the very instant that the front end of the rod stops? What signal travels at infinite speed from the front of the rod to the back of the rod to inform the back of the rod that it should stop? And by what fundamental interaction does this signal travel at infinite speed? (PLEASE PLEASE PLEASE tell me it's the Wilson Infinite Communication Speed Interaction [WICSI] that you believe that people should be investigating.)
From: eric gisse on 8 Jan 2010 13:16
PD wrote: > On Jan 7, 3:42 pm, ..@..(Henry Wilson DSc) wrote: >> On Thu, 7 Jan 2010 12:55:33 -0800 (PST), PD <thedraperfam...(a)gmail.com> >> wrote: >> >> >I'll be a little more precise: At the instant when the motion of the >> >front of the pole stops as it hits the back wall of the barn, what >> >happens to the motion of the back of the pole? >> >> It stops instantly as well. Reality doesn't rely on what humans see. >> > > I am SO happy that you gave this response. This gives me the chance to > ask you a few questions. I, too, have been enjoying Henri's responses as of late. It is so entertaining when he engages me and reveals his thought processes. > > 1. You claim that the back end stops instantly, but that this is a > reality we cannot see. If you cannot see it, how do you know that it > happens? What method of truth checking are you using to determine the > truth value of the claim that the back end stops instantly. (PLEASE > PLEASE PLEASE tell me that you rely on common sense for this.) I have often opined about how it is odd that he knows such things with such absolute certainty even though he can't show me how he knows it to be true. Like how he 'knows' that "equal time intervals" are a law of physics, even though he can't demonstrate why this is the case or show me where it is written in a physics textbook that it is a law of physics. > > 2. Since science uses observation to check the truth of claims, but > you believe that reality is not revealed by observation, is it your > claim that science is in general a waste of time, since that is not > how reality is determined? If so, then why diddle around on sci.*.*, > if you believe that the whole business of how science works is just > bogus to begin with? (PLEASE PLEASE PLEASE tell me that what you do is > science and what scientists do is not science.) Sorry Paul, but Henri has explained this one to me. "No, but they are so stupid I'm laughing my bloody head off at their posts. Haven't laughed so much in years." Henri knows he is not doing science, as Henri can't be bothered to do simple things like publish his work (which he has talked about doing for a decade) or make concrete, falsifiable predictions with his theory (which he wants me to do FOR HIM). But rather he enjoys the game of laughing at what people like you and me tell him, which is fine with me since that goes both ways. > > 3. By what physical process does the back end of the rod become aware > that the front end of the rod has stopped, at the very instant that > the front end of the rod stops? What signal travels at infinite speed > from the front of the rod to the back of the rod to inform the back of > the rod that it should stop? And by what fundamental interaction does > this signal travel at infinite speed? (PLEASE PLEASE PLEASE tell me > it's the Wilson Infinite Communication Speed Interaction [WICSI] that > you believe that people should be investigating.) I'm sure he'll have a fancy one-lined rejoinder about how you are dumb / it is obvious / etc. Do me a favor, and make it a point to frequently ask him what textbook on the subject he has read. It is amusing to see him respond with non-answers like "[...]", "many", or some random insult which shows he never has read a single book on the subject or it has been so many years that he can't even remember. |