Known physics defeated by simple puzzle?
in [Relativity]
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From: Ste on 6 Apr 2010 11:39 On 6 Apr, 16:28, PD <thedraperfam...(a)gmail.com> wrote: > On Apr 5, 6:41 pm, Ste <ste_ro...(a)hotmail.com> wrote: > > > > > > > On 5 Apr, 22:10, PD <thedraperfam...(a)gmail.com> wrote: > > > > On Apr 5, 3:47 pm, Ste <ste_ro...(a)hotmail.com> wrote: > > > > > I'm happy to make concessions, but I have to be able to ask questions > > > > and get meaningful answers. The ladder in the barn is a prime example. > > > > I'm told "the ladder contracts to fit in the barn". > > > > It contracts to fit the barn in the rest frame of the barn, which is > > > why the ladder makes no marks on the barn doors when the doors are > > > shut at the same time. In the rest frame of the ladder, the ladder > > > does not contract and indeed does not fit inside the barn at all. In > > > the rest frame of the ladder, the reason why there are no marks on the > > > barn doors when they are shut is that they were not shut at the same > > > time in this frame. > > > This logic is easily defeated Paul, because if we contracted the > > ladder's length *just* enough so that it marked the door in the barn > > frame (in other words, the ladder has contracted just enough to manage > > an interference fit with both doors shut), then this cannot be > > accounted for in the ladder frame (because, in the ladder frame, if > > the ladder is *even larger* relative to the barn than when it started, > > then the ladder could not possibly mark the doors in the same way). > > I'm not sure what the fuss is. The observation is that the doors are > shut and open without striking the pole, and this is true in both > reference frames examined (as well as any other inertial reference > frame). The account in the ladder frame is, however, not because the > ladder fits inside the barn. It is exactly as I described above. Why > is this difficult? It isn't difficult for me. I can explain it, in its entirety, in terms of a "visual effect" and the careful timing of the doors. It's other people here who keep insisting that it is not a visual effect, and hence the fuss.
From: PD on 6 Apr 2010 11:42 On Apr 5, 7:15 pm, Ste <ste_ro...(a)hotmail.com> wrote: > On 5 Apr, 22:57, PD <thedraperfam...(a)gmail.com> wrote: > > > On Apr 5, 4:29 pm, Ste <ste_ro...(a)hotmail.com> wrote: > > > > I do not see how this can work, > > > unless the clocks themselves fall out of synchronisation (and hence > > > are not actually measuring the same periods of time as each other). > > > The clocks' synchronization can be (and is) checked both before and > > after the operations described above and verified to still hold, so > > your supposition of what must have happened is ruled out. > > Not necessarily. If both slowed in the middle of the operation, then > they would still be synchronised with each at the end, but it would > utterly confound any calculation about simultaneity, unless you also > knew by how much the other clock had slowed and when. > > To give you an example, if I have two clocks stationary relative to > each other and ten light-seconds apart, and I suddenly slow both > clocks to half-speed (in other words, ticking once for every two > previous ticks), then according to each clock, the other one speeds up > to double speed, Why does the other speed up to double speed, when it is also identically slowed? > because for a period of 10 seconds (the time it takes > for the change of rate to propagate), there is only one "local" tick > for every 2 "received" ticks. And at the end there is a similar and compensating two local ticks for every one received ticks. Furthermore, recall that there is no TIMING that is done by any clock during the signal propagation at all. The only decision that has to be made is whether the signals are received at the receiver at the same time or at different times. This is not something that is done with the need of a clock. When you look with your eyes at two flashes of light, you do not need to refer to a clock to decide whether the flashes were received at the same time or at different times. You can see it with your plain eyes. If you want to use electronics, you do it with a coincidence counter, not with a clock. The only other bit of information you need is whether the signal propagation time is identical. Again for this, you do not need a clock. You need a measuring stick to measure the distance of flight of the signals, and you need an independent measurement of the velocity of the signal. The velocity measurement can be done at leisure, either before the entire experiment or after or both. The only presumption that is made is that the speed of the signal propagation did not happen to change during the one time you were receiving signals from the two events. Since signal propagation speed is governed by constant laws of nature and are not subject to random whim, this is a justifiable presumption -- especially since you can repeat that speed measurement any number of times at random moments and confirm that the speed never varies. Again, there is NO CLOCK needed to determine simultaneity. > > If you did a simplistic correction for propagation delays, then > according to this model, the other clock will have actually *leaped > ahead* in time. Let's use some concrete times. The clocks are 10 light > seconds apart, and stationary. We set them both going from 00:00. > Obviously this setup is entirely symmetrical, so I'll simply talk > about the "local" clock, and the "distant" clock. I use the word > "really" to describe what the clock shows for a local observer, and I > use the word "apparently" to describe what that clock actually shows > for a distant observer. > > At 00:11 local, the distant clock apparently reads 00:01. We let them > go until it's 00:20 local, and apparently 00:10 distant. At that > point, I slow them both down (obviously, I'm pretending to play God > here, but if you need a specific explanation for how I slow them down, > let's just say I programmed their circuitry in advance to both slow > down when they displayed 00:20 local). > > So, with the clocks running at half speed, it is now 00:21 local, and > 00:12 distant. By 00:25 local, the distant clock apparently shows > 00:20. Reasoning that it takes 10 local seconds for that information > to reach us, that means the distant clock "really" reads 00:30. > > Except it doesn't. > > The distant clock really reads 00:25, the same as the local clock - > they were never out of real synchronisation for even a moment. > > Now, would you say that this explanation appears to suffice for at > least *some* of what is observed in SR? > > > I want to > > emphasize that this is observational reality, even if you are stymied > > to explain how it can be, given your presently held concept sets about > > how nature works. > > I think the explanation I've just given in the paragraph above > suffices. I'm not stymied by it. I'm just not blown away by it - the > effects seem quite straightforward to me, but every time I offer that > explanation, posters here say the explanation is inadequate and faulty.
From: PD on 6 Apr 2010 12:02 On Apr 6, 10:39 am, Ste <ste_ro...(a)hotmail.com> wrote: > On 6 Apr, 16:28, PD <thedraperfam...(a)gmail.com> wrote: > > > > > On Apr 5, 6:41 pm, Ste <ste_ro...(a)hotmail.com> wrote: > > > > On 5 Apr, 22:10, PD <thedraperfam...(a)gmail.com> wrote: > > > > > On Apr 5, 3:47 pm, Ste <ste_ro...(a)hotmail.com> wrote: > > > > > > I'm happy to make concessions, but I have to be able to ask questions > > > > > and get meaningful answers. The ladder in the barn is a prime example. > > > > > I'm told "the ladder contracts to fit in the barn". > > > > > It contracts to fit the barn in the rest frame of the barn, which is > > > > why the ladder makes no marks on the barn doors when the doors are > > > > shut at the same time. In the rest frame of the ladder, the ladder > > > > does not contract and indeed does not fit inside the barn at all. In > > > > the rest frame of the ladder, the reason why there are no marks on the > > > > barn doors when they are shut is that they were not shut at the same > > > > time in this frame. > > > > This logic is easily defeated Paul, because if we contracted the > > > ladder's length *just* enough so that it marked the door in the barn > > > frame (in other words, the ladder has contracted just enough to manage > > > an interference fit with both doors shut), then this cannot be > > > accounted for in the ladder frame (because, in the ladder frame, if > > > the ladder is *even larger* relative to the barn than when it started, > > > then the ladder could not possibly mark the doors in the same way). > > > I'm not sure what the fuss is. The observation is that the doors are > > shut and open without striking the pole, and this is true in both > > reference frames examined (as well as any other inertial reference > > frame). The account in the ladder frame is, however, not because the > > ladder fits inside the barn. It is exactly as I described above. Why > > is this difficult? > > It isn't difficult for me. I can explain it, in its entirety, in terms > of a "visual effect" and the careful timing of the doors. It's other > people here who keep insisting that it is not a visual effect, and > hence the fuss. I don't believe it's a "visual effect" at all. The doors are closed and opened by a common trigger, electronically. Is it your claim that the doors are "really" closed and opened simultaneously, but they only visually appear to close and open nonsimultaneously in the ladder frame? Then how does the 80 foot ladder fit into the 40 ft barn without the doors striking the ladder, if the doors are "really" closed simultaneously? PD
From: Sue... on 6 Apr 2010 12:21 On Apr 6, 11:39 am, Ste <ste_ro...(a)hotmail.com> wrote: > On 6 Apr, 16:28, PD <thedraperfam...(a)gmail.com> wrote: > > > > > On Apr 5, 6:41 pm, Ste <ste_ro...(a)hotmail.com> wrote: > > > > On 5 Apr, 22:10, PD <thedraperfam...(a)gmail.com> wrote: > > > > > On Apr 5, 3:47 pm, Ste <ste_ro...(a)hotmail.com> wrote: > > > > > > I'm happy to make concessions, but I have to be able to ask questions > > > > > and get meaningful answers. The ladder in the barn is a prime example. > > > > > I'm told "the ladder contracts to fit in the barn". > > > > > It contracts to fit the barn in the rest frame of the barn, which is > > > > why the ladder makes no marks on the barn doors when the doors are > > > > shut at the same time. In the rest frame of the ladder, the ladder > > > > does not contract and indeed does not fit inside the barn at all. In > > > > the rest frame of the ladder, the reason why there are no marks on the > > > > barn doors when they are shut is that they were not shut at the same > > > > time in this frame. > > > > This logic is easily defeated Paul, because if we contracted the > > > ladder's length *just* enough so that it marked the door in the barn > > > frame (in other words, the ladder has contracted just enough to manage > > > an interference fit with both doors shut), then this cannot be > > > accounted for in the ladder frame (because, in the ladder frame, if > > > the ladder is *even larger* relative to the barn than when it started, > > > then the ladder could not possibly mark the doors in the same way). > > > I'm not sure what the fuss is. The observation is that the doors are > > shut and open without striking the pole, and this is true in both > > reference frames examined (as well as any other inertial reference > > frame). The account in the ladder frame is, however, not because the > > ladder fits inside the barn. It is exactly as I described above. Why > > is this difficult? > > It isn't difficult for me. I can explain it, in its entirety, in terms > of a "visual effect" and the careful timing of the doors. It's other > people here who keep insisting that it is not a visual effect, and > hence the fuss. Nothing wrong with that. That is what Einstein does in the 1920 paper where the clock and rod is *judged* from the relatively moving frame. Einstein's 1905 presentation of special relativity was soon supplemented, in 1907, by Hermann Minkowski, who showed that the relations had a very natural interpretation[C 5] in terms of a unified four-dimensional "spacetime" in which absolute intervals are seen to be given by an extension of the Pythagorean theorem. (Already in 1906 Poincaré anticipated some of Minkowski's ideas, see the section "Lorentz-transformation").[B 24] The utility and naturalness of the representations by Einstein and Minkowski contributed to the rapid acceptance of special relativity, and to the corresponding loss of interest in Lorentz's ether theory.>> http://en.wikipedia.org/wiki/Lorentz_ether_theory#Special_relativity << the four-dimensional space-time continuum of the theory of relativity, in its most essential formal properties, shows a pronounced relationship to the three-dimensional continuum of Euclidean geometrical space. In order to give due prominence to this relationship, however, we must replace the usual time co-ordinate t by an imaginary magnitude sqrt(-1) ct proportional to it. Under these conditions, the natural laws satisfying the demands of the (special) theory of relativity assume mathematical forms, in which the time co-ordinate plays exactly the same rôle as the three space co-ordinates. >> http://www.bartleby.com/173/17.html Sue...
From: Ste on 6 Apr 2010 12:32
Btw I just wanted to post this again, and invite responses from anyone: On 6 Apr, 01:15, Ste <ste_ro...(a)hotmail.com> wrote: > On 5 Apr, 22:57, PD <thedraperfam...(a)gmail.com> wrote: > > > On Apr 5, 4:29 pm, Ste <ste_ro...(a)hotmail.com> wrote: > > > > I do not see how this can work, > > > unless the clocks themselves fall out of synchronisation (and hence > > > are not actually measuring the same periods of time as each other). > > > The clocks' synchronization can be (and is) checked both before and > > after the operations described above and verified to still hold, so > > your supposition of what must have happened is ruled out. > > Not necessarily. If both slowed in the middle of the operation, then > they would still be synchronised with each at the end, but it would > utterly confound any calculation about simultaneity, unless you also > knew by how much the other clock had slowed and when. > > To give you an example, if I have two clocks stationary relative to > each other and ten light-seconds apart, and I suddenly slow both > clocks to half-speed (in other words, ticking once for every two > previous ticks), then according to each clock, the other one speeds up > to double speed, because for a period of 10 seconds (the time it takes > for the change of rate to propagate), there is only one "local" tick > for every 2 "received" ticks. > > If you did a simplistic correction for propagation delays, then > according to this model, the other clock will have actually *leaped > ahead* in time. Let's use some concrete times. The clocks are 10 light > seconds apart, and stationary. We set them both going from 00:00. > Obviously this setup is entirely symmetrical, so I'll simply talk > about the "local" clock, and the "distant" clock. I use the word > "really" to describe what the clock shows for a local observer, and I > use the word "apparently" to describe what that clock actually shows > for a distant observer. > > At 00:11 local, the distant clock apparently reads 00:01. We let them > go until it's 00:20 local, and apparently 00:10 distant. At that > point, I slow them both down (obviously, I'm pretending to play God > here, but if you need a specific explanation for how I slow them down, > let's just say I programmed their circuitry in advance to both slow > down when they displayed 00:20 local). > > So, with the clocks running at half speed, it is now 00:21 local, and > 00:12 distant. By 00:25 local, the distant clock apparently shows > 00:20. Reasoning that it takes 10 local seconds for that information > to reach us, that means the distant clock "really" reads 00:30. > > Except it doesn't. > > The distant clock really reads 00:25, the same as the local clock - > they were never out of real synchronisation for even a moment. > > Now, would you say that this explanation appears to suffice for at > least *some* of what is observed in SR? > > > I want to > > emphasize that this is observational reality, even if you are stymied > > to explain how it can be, given your presently held concept sets about > > how nature works. > > I think the explanation I've just given in the paragraph above > suffices. I'm not stymied by it. I'm just not blown away by it - the > effects seem quite straightforward to me, but every time I offer that > explanation, posters here say the explanation is inadequate and faulty. |