The Sagnac Effect revisited
in [Relativity]
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From: Jonah Thomas on 20 Sep 2009 10:22 I've figured out a metaphor for this. Imagine that you have a big merry-go-round with plenty of room to walk on it, and you have the assistance of a well-trained marching band. First we will demonstrate the Sagnac Effect under a simple emissions theory. We have two band members march on the carousel in opposite directions. They each march at the same speed. They will each march halfway around the carousel until they are facing each other. Are they in step? When the carousel is not moving and when their steps are the same length, definitely. Now we start the carousel moving slowly. The marchers continue to march at the same pace. When they face each other it will be on the opposite side of the carousel but it won't be lined up with the place they started. The carousel will have moved, so that one of the marchers has actually gone farther than the other. Are they in step? Yes, of course. Now a slightly more sophisticated emission theory. The marchers march on the carousel at the same speed no matter how fast the carousel is turning. But they can change the size of their steps and the rate they step, provided the speed stays the same. So they will definitely reach the end point at the same time, but they may or may not be in step. It depends on how they change their stepsize. And how much do they do that? It depends on which emission theory you choose. You can get them as much out of step as you want, just pick the theory that gives you that amount. Is there anything different about the guys who march in different directions? Here's one difference -- The one who marches in the direction of rotation is pushing against the carousel and tending to slow it down. The one who walks against the direction of rotation is pushing against the carousel and tending to speed it up. The effect on the carousel cancels, but the effect on the marchers does not. The one walking against the rotation accelerates less. He gets to the same place using less effort. Now on to other theories. It can be argued that the marchers should not arrive at the same time. One would have to move faster than the other. If they actually travel at the same speed then one will arrive late. So we need a new measure for whether they are in step or not. Say instead of two marchers it's two files of marchers. They are still in step if the first marcher from one side is precisely late enough to be in step with the second person on the other side. And anywhere inbetween, if he arrives between people but he's precisely the right amount out of step, he counts as being in step. So, suppose the marchers have a drum to keep the beat. Then the guys marching with the rotation have to slow down so that people who aren't on the carousel will see them going the same speed as if there was no rotation, and the only way they can do that is to take smaller steps. Meanwhile the ones who march against the rotation have to take big steps. Or if they take the same size steps then the ones who march against the rotation have to step faster while the ones who march with it must step slower. They'd probably rather not have the drum to distract them in that case. Which do they do? Do they change the size or their steps or the speed of their steps, so they can undo the effect of the rotation? Or maybe a combination of both? It depends. If you want distant observers to see them as if the carousel isn't moving, then they should march to the same beat but adjust their step sizes. Then observers can see their steps aren't the same size but at least the marchers won't be bunched up on one side and spread out on the other, and they will be traveling at the same speed, and they'll all be in step. Is that everything to consider? No, they are a trained marching band. If you tell them to face the same direction while they march, they can keep facing forward relative to an outside observer even while they march sideways or backward. If you tell them to do that in a way that leaves them facing different directions, how do you count whether they are in step or not? If they are facing at right angles you don't count them as in step or out of step either one. They just don't count then. If they are facing at some other angle then they count some, but less. So what are the rules that they actually follow, that make them just the right amount out of step? I don't know. There are various ways it might go. But my guess is that whatever the rules are, they are some combination that lets the marchers all do the same amount of work. Because that's fair. We don't want the ones in one direction to get more tired than the ones in the other direction. And what does relativity say about it all? Relativity says that we want to measure them as all marching at the same speed regardless what they're actually doing and regardless what perspective we look at them from, so it gives us rules for how to adjust our clocks and yardsticks to get that result. Whatever solution presents itself, it can be expressed in the terms required by relativity.
From: Inertial on 20 Sep 2009 11:02 "Jonah Thomas" <jethomas5(a)gmail.com> wrote in message news:20090920102215.38d9495f.jethomas5(a)gmail.com... > I've figured out a metaphor for this. > > Imagine that you have a big merry-go-round with plenty of room to walk > on it, and you have the assistance of a well-trained marching band. OK :):) > First we will demonstrate the Sagnac Effect under a simple emissions > theory. We have two band members march on the carousel in opposite > directions. They each march at the same speed. They will each march > halfway around the carousel until they are facing each other. Are they > in step? When the carousel is not moving and when their steps are the > same length, definitely. Yes > Now we start the carousel moving slowly. The marchers continue to march > at the same pace. When they face each other it will be on the opposite > side of the carousel but it won't be lined up with the place they > started. The carousel will have moved, so that one of the marchers has > actually gone farther than the other. Are they in step? Yes, of course. Yes. That's your basic emission theory. Sagnac refutes it. > Now a slightly more sophisticated emission theory. The marchers march on > the carousel at the same speed no matter how fast the carousel is > turning. Relative to the ground or relative to the carousel? > But they can change the size of their steps and the rate they > step, provided the speed stays the same. Relative to the ground or relative to the carousel? > So they will definitely reach > the end point at the same time OK . so its relative to the carousel > but they may or may not be in step. So they are spontaneously changing their frequency. What would cause them to do that .. what would make a one group of marchers take smaller faster stpes than the other (relative to the carousel)? In a case like Sagnac, we know the 'marchers' start out with the same step size and step rate, as they start out as one line of marchers and then get split. > It > depends on how they change their stepsize. And how much do they do that? > It depends on which emission theory you choose. You can get them as much > out of step as you want, just pick the theory that gives you that > amount. I don't think any of the emission theories have light spontaneously change frequency. > Is there anything different about the guys who march in different > directions? Here's one difference -- The one who marches in the > direction of rotation is pushing against the carousel and tending to > slow it down. The one who walks against the direction of rotation is > pushing against the carousel and tending to speed it up. The effect on > the carousel cancels, but the effect on the marchers does not. The one > walking against the rotation accelerates less. He gets to the same place > using less effort. Depending on who is looking at it .. but that is obvsious as the rate of rotation is different for the marchers. If the carousel is fast enough ,they can even appear to be marching backwrd to an observer on the ground. > Now on to other theories. It can be argued that the marchers should not > arrive at the same time. yes.. that should always result in a phase difference > One would have to move faster than the other. > If they actually travel at the same speed then one will arrive late. Relative to the ground or relative to the carousel? > So we need a new measure for whether they are in step or not. Say > instead of two marchers it's two files of marchers. They are still in > step if the first marcher from one side is precisely late enough to be > in step with the second person on the other side. And anywhere > inbetween, if he arrives between people but he's precisely the right > amount out of step, he counts as being in step. Eh? > So, suppose the marchers have a drum to keep the beat. Then the guys > marching with the rotation have to slow down so that people who aren't > on the carousel will see them going the same speed as if there was no > rotation, and the only way they can do that is to take smaller steps. > Meanwhile the ones who march against the rotation have to take big > steps. Why would the marchers care what the people on the ground see? > Or if they take the same size steps then the ones who march against the > rotation have to step faster while the ones who march with it must step > slower. They'd probably rather not have the drum to distract them in > that case. :):) > Which do they do? Do they change the size or their steps or the speed of > their steps, so they can undo the effect of the rotation? Or maybe a > combination of both? It depends. SR says a combination, btw. > If you want distant observers to see > them as if the carousel isn't moving, then they should march to the same > beat but adjust their step sizes. Then observers can see their steps > aren't the same size but at least the marchers won't be bunched up on > one side and spread out on the other, and they will be traveling at the > same speed, and they'll all be in step. > > Is that everything to consider? No, they are a trained marching band. If > you tell them to face the same direction while they march, they can keep > facing forward relative to an outside observer even while they march > sideways or backward. If you tell them to do that in a way that leaves > them facing different directions, how do you count whether they are in > step or not? If they are facing at right angles you don't count them as > in step or out of step either one. They just don't count then. If they > are facing at some other angle then they count some, but less. If they arrive at the same location, then they will bve facing the same way, so you can tell > So what are the rules that they actually follow, that make them just the > right amount out of step? I don't know. There are various ways it might > go. But my guess is that whatever the rules are, they are some > combination that lets the marchers all do the same amount of work. > Because that's fair. We don't want the ones in one direction to get more > tired than the ones in the other direction. > > And what does relativity say about it all? Relativity says that we want > to measure them as all marching at the same speed regardless what > they're actually doing and regardless what perspective we look at them > from, so it gives us rules for how to adjust our clocks and yardsticks > to get that result. No adjusting of clocks and yardsticks in SR. The closest that is to is LET, where the act of moving thru the aether causes rulers to shrink and proceses to slow down, and the time of separated clocks to go out of sync. > Whatever solution presents itself, it can be > expressed in the terms required by relativity. All the experiments done to show SR predictions are wrong have failed. Nature behaves as though SR is correct.
From: Androcles on 20 Sep 2009 11:42 "Jonah Thomas" <jethomas5(a)gmail.com> wrote in message news:20090920102215.38d9495f.jethomas5(a)gmail.com... > I've figured out a metaphor for this. > > Imagine that you have a big merry-go-round with plenty of room to walk > on it, and you have the assistance of a well-trained marching band. Doesn't work with Wilson. He says grandpa has to be on the merry-go-round, he can't stand at the side and watch when I told him only the kids ride merry-go-rounds. < obligatory rude snip of anything I won't bother reading>
From: Jonah Thomas on 20 Sep 2009 13:11 Albertito <albertito1992(a)gmail.com> wrote: > > The Sagnac effect is evidence that Special Relativity > is badly flawed and nonsensical! > http://sites.google.com/site/albertzotkin/sagnac-effect I don't see that but perhaps I will after I study your analysis. It looks to me like the Sagnac effect is independent of SR, that SR makes little difference, that the SR explanation is almost the same as one of the classical ones. But I might change my minds about that when I understand more about the Sagnac effect and about SR.
From: Jonah Thomas on 20 Sep 2009 13:12
"Androcles" <Headmaster(a)Hogwarts.physics_o> wrote: > "Jonah Thomas" <jethomas5(a)gmail.com> wrote > > I've figured out a metaphor for this. > > > > Imagine that you have a big merry-go-round with plenty of room to > > walk on it, and you have the assistance of a well-trained marching > > band. > > Doesn't work with Wilson. He says grandpa has to be on the > merry-go-round, he can't stand at the side and watch when I told him > only the kids ride merry-go-rounds. I see. I thought it was a good metaphor so I shouldn't be surprised that it isn't new. |