[GoC (OP)]

So what are you trying to say by bringing that into this discussion? If the coin is stationary and some observers see it as elliptical either because they're looking at it from an angle that makes it look elliptical or because they're moving past it at a high speed that makes it appear length-contracted, those observers are not seeing the true shape of the coin.

All views are equally valid by observed position. You try to diss relativity by using a strict interpretation of valid.

Movement of the sun and the galaxy will lead to changes in contraction at any point on the Earth's surface as the Earth rotates unless it's at the poles, but the sun isn't guaranteed to have moved unless we wait millions of years. We only have to wait a few weeks or months to guarantee that the Earth has moved though, which is why it's the Earth's orbit round the sun that's most important as it guarantees that the rate at which clocks at sea level cannot be ticking at the same rate as each other other than on average over a full rotation of the Earth.If a planet could rotate at such a speed that a point on its surface moved at 0.866c relative to the centre and if that planet could remain spherical, it would take twice as much cable to stretch round the equator than to make a loop round over the poles. If in addition to that the planet is moving along at 0.866c on the same plane as the equator, on one side of the planet the equatorial cable will be uncontracted while on the opposite side it will be contracted three and a half times as much as the average contraction on the loop (and the surface of the Earth will have the same contraction acting on it in the same places). A clock sitting at any point on the equatorial loop will likewise vary in its ticking rate, sometimes ticking twice as often as the average and at other times ticking three and a half times slower than average. But if you analyse it from the frame of reference in which the planet is stationary, you won't detect any of that variation at all.

Ok you either do not know the limits of relativity or you are stuck on 0.887. Since one direction of spin would allow ~1.7c lets look at the relativistic limit of spin and speed. At 0.5c speed through space and rotation of 0.5c the one direction would be c and the other direction at rest. So the forward spin the light would be relative to the spin and not move to an observer that could not observe anyway. The electron cycle using a physical clock likewise could not cycle. So no time would be recorded. In the opposite direction relative light is at rest and is moving relative 2c. c in one direction and c in the opposite direction relative is 2c. c being constant in any direction. So you have ticking in the opposite direction. Ok the physical object has zero length forward and a physical length backwards. I am not to keen on physical contraction. Explain your position on this.

[David Cooper]

All views are equally valid by observed position. You try to diss relativity by using a strict interpretation of valid.

They are not all equally valid when it comes to determining the true shape of the coin. I'm not dissing relativity - I'm the one who's looked at it most carefully and who has disproved all the models that can be labelled as SR while identifying modified models which are still potentially viable. All the viable ones depend on a preferred frame in one way or another, and that dictates that there is a real shape to the coin which is either circular or elliptical (and not both at once).

Ok you either do not know the limits of relativity or you are stuck on 0.887. Since one direction of spin would allow ~1.7c lets look at the relativistic limit of spin and speed. At 0.5c speed through space and rotation of 0.5c the one direction would be c and the other direction at rest. So the forward spin the light would be relative to the spin and not move to an observer that could not observe anyway. The electron cycle using a physical clock likewise could not cycle. So no time would be recorded. In the opposite direction relative light is at rest and is moving relative 2c. c in one direction and c in the opposite direction relative is 2c. c being constant in any direction. So you have ticking in the opposite direction. Ok the physical object has zero length forward and a physical length backwards. I am not to keen on physical contraction. Explain your position on this.

Again you have demonstrated a severe lack of understanding of relativity by tripping over one of the basics. I keep using 0.866c because it's convenient and saves using new figures each time just for the sake of it. That speed is the best one to use because it neatly leads to length contraction to 1/2 of the rest length, clocks ticking half as often, and it illustrates a key point about the correct addition of velocities never exceeding c. 0.866c + 0.866c = 0.99c once you factor in the effects of relativistic mass. If a stationary planet revolves such that a point on its equator is moving at 0.866c and you then move the planet so that it is travelling through space at 0.866c, it takes twice as long to complete each rotation as it did when it was at rest, the material at one point where it's moving through space fastest is moving at 0.99c and the material at the opposite point is (for a moment) not moving at all. There is a bunching up of material in the hemisphere that's moving forwards and a spreading out of material on the opposite side of the planet (which means that more of the material of the planet is on the faster moving side than the slower moving side at any given time). The contraction varies and keeps changing for any given part of the planet away from the axis, and this causes extreme warping. And yet, for an observer on the planet, no warping is measured at all (other than the length contraction caused by rotation which leads to the circumference round the equator being measured as twice as long as the circumference passing through the poles even though they measure that the planet is spherical in shape).

I found a couple of images via another forum which illustrate this warping of a rotating planet or disc that's either stationary or moving at high speed through space, so hopefully they'll work here too.

[Le Repteux]

And yet, for an observer on the planet, no warping is measured at all (other than the length contraction caused by rotation which leads to the circumference round the equator being measured as twice as long as the circumference passing through the poles even though they measure that the planet is spherical in shape).

I understand why the distance at the equator would be contracted, but I don't understand why it would be observable. If we would use a rope to measure the two distances for instance, it would contract when we would measure the equator, and stretch when we would measure the distance between the poles, so there would be no way to observe the difference.

[GoC (OP)]

Let's say there cable from NY to SF and you are sitting on the moon. There is a mirror on the SF side to return light. There is an event in NY an observer is able to view that moves to SF and the observer is able to watch the photon progress With his measuring stick on the moon. He measures the distance with his measuring stick. Taking the same position of termination and returned event the observer measures the returning light. His measurement is longer on the return trip. The cable did not change but the distance light traveled in each direction did.

[Le Repteux]

The time light takes to make the roundtrip is observable, it has lead to the time dilation effect, but contraction is not. Things really live longer when they move, and they should contract too in their direction of motion, but that contraction is supposedly unobservable from any viewpoint.

[GoC (OP)]

On the Earth if you move East to West timing increases and so does reactions such as your cell rate of decline. You age faster in that direction because you are slowing down. If you go West to East reactions slow because you are moving faster. Definitely imperceptible.

[Le Repteux]

It would be observable if the earth was rotating at .866c though, and contraction should still be unobservable.

[David Cooper]

I understand why the distance at the equator would be contracted, but I don't understand why it would be observable. If we would use a rope to measure the two distances for instance, it would contract when we would measure the equator, and stretch when we would measure the distance between the poles, so there would be no way to observe the difference.

If you start with a non-rotating disc and then spin it such that the edge is moving round at 0.866c, that edge will contract to half its rest length, so the disc will split and leave lots of gaps in it - the same amount of gap as there is remaining edge. If you manufacture the disc while it's rotating though, it needn't have the split as you can put twice as much material into the construction of the edge, but if you slow the disc down it will buckle as there will be too much material there for slower rotation speeds. A planet rotating with its edge doing 0.866c at the equator would (if it was possible for it to hold together with such a ridiculous rotation speed) rearrange its material to take up the extra space available, and that would shrink its size a fair amount in the process, but the end result would be that a measuring tape which stretches all the way round the equator when it's hovering over the planet and not rotating with it would only stretch half way round the equator if it was rotating with the planet. If the planet is somehow held in a spherical shape, that same measuring tape would stretch right round the planet over the poles whether it's rotating with the planet or not. Inhabitants of such a strange world would know that it takes them twice as long to go round their world on the equator than via both poles. If this planet is a small rock that they can drill holes through, they could have one pass through the centre which would enable them to measure the diameter with the same tape, at which point they'd see that the pole-to-pole hole distance is equal to the over-the-poles circumference distance divided by pi. If they drill another hole from the equator to an opposite point on the equator and measure that with their tape, it will give them the same answer, so they will be able to determine that that their planet is spherical despite the equator length being measured as two times pi times the diameter, and if they get off the planet and stop rotating with it, they'll see that it is indeed spherical, and they'll see the length contraction acting on its surface (most severely at the equator).

Let's say there cable from NY to SF and you are sitting on the moon. There is a mirror on the SF side to return light. There is an event in NY an observer is able to view that moves to SF and the observer is able to watch the photon progress With his measuring stick on the moon. He measures the distance with his measuring stick. Taking the same position of termination and returned event the observer measures the returning light. His measurement is longer on the return trip. The cable did not change but the distance light traveled in each direction did.

That's right, and any contraction of the cable is unimportant in this case as it makes no difference to how far the light has to travel to complete the trip.

The time light takes to make the roundtrip is observable, it has lead to the time dilation effect, but contraction is not. Things really live longer when they move, and they should contract too in their direction of motion, but that contraction is supposedly unobservable from any viewpoint.

The contraction is fully observable to any well-positioned uncontracted observers, but as none of them know which observers are uncontracted, if the contracted ones think they're uncontracted, they'll see the uncontracted ones as contracted instead.

On the Earth if you move East to West timing increases and so does reactions such as your cell rate of decline. You age faster in that direction because you are slowing down. If you go West to East reactions slow because you are moving faster. Definitely imperceptible.

That's all correct.

It would be observable if the earth was rotating at .866c though, and contraction should still be unobservable.

The contraction is only unobservable to the people who are standing on the contracted surface and who have the same contraction applying to them. If you hover over the planet and don't rotate with it, the contraction will then be visible to you.

[Le Repteux]

If you start with a non-rotating disc and then spin it such that the edge is moving round at 0.866c, that edge will contract to half its rest length, so the disc will split and leave lots of gaps in it - the same amount of gap as there is remaining edge.

It means that contraction is observable even if we are rotating with the disc. Relativists use to say that contraction is not physical, so I thought it was unobservable. What do they say when you present that mind experiment?

[David Cooper]

If you start with a non-rotating disc and then spin it such that the edge is moving round at 0.866c, that edge will contract to half its rest length, so the disc will split and leave lots of gaps in it - the same amount of gap as there is remaining edge.

It means that contraction is observable even if we are rotating with the disc. Relativists use to say that contraction is not physical, so I thought it was unobservable. What do they say when you present that mind experiment?

You hear a lot of irrational nonsense from people on the establishment side on this point, but they are able to get away with it to a large extent because it's impossible to turn the thought experiments into practical real experiments - the centrifugal "force" would tear a rotating disc to pieces before you could see the effects of the length contraction acting on its edge. It is therefore only reason that can be used to explore this through thought experiments, and the establishment isn't good at reasoning - they claim they're doing it and that they're doing it properly, but they actually make a mockery of it. The edge cannot fill the whole space though if it is spinning as it has to display length contraction to stationary observers - they will measure it as taking up half the space and they will have to measure something else taking up the other half. They can close in the space between two non-rotating discs and use those to measure which part of the rotating disc is in between them at each point around the edge, all taking photos of the adjacent rotating disc (no time delay for the photons to go from rotating disc to sensors), with the cameras' clocks all synchronised for the rest frame of the non-rotating discs. The top SR people probably do recognise that this is the case, but for every one of those there are tens of thousands of "fanboys" who think they understand SR but don't. They are misled by the "ladder paradox" into thinking that ladder that's longer than a garage isn't really short enough to fit into it but is made to appear to fit inside it with both the doors closed for a moment because the doors aren't really closed at the same time, but in the absolute frame, the doors really can be closed at the same time with the ladder fitting inside. If the garage is moving and the ladder is stationary, it's then that the doors are closed at different times, and the ladder (which is twice the length of the garage when they're co-moving with each other) will at that moment be four times the length of the garage. But the truth of physical length contraction is revealed by a disc with eight ladders moving past it on tangents at 0.866c, each on a path angled at 45 degrees to the nearest two other ladders. If they all pass the disc at the same moment, they can momentarily form a ring around the disc in which each is touching the ladder in front and the one behind at the same moment. If they were co-moving with the disc, you could not fit them into that space as they'd all be twice as long.

If you go to my ref-frame camera program ( http://www.magicschoolbook.com/science/ref-frame-camera.htm ) and load the fourth set of example objects (you have to type "d" into the dialog box after clicking the first button), you'll see a blue ring with eight red or yellow boxes round its edge, though only the corners of the boxes are shown. Type the S key to unfreeze the action (or to freeze it if it's already moving) - the boxes are moving past the disc at 0.866c. Press the D key to change the direction if they move too far away from the disc. Some of the number keys are pre-programmed to select different reference frames, so type 2 to select the reference frame of the red box at the bottom, or 3 to select the red one on the right-hand side - you can then see them at their full uncontracted length while all the other objects display the length contraction that applies to them for that frame. Type 1 to return to the disc's reference frame - all eight boxes are contracted to half their rest length for this frame. If these boxes were not moving relative to the disc, each would be touching its two closest neighbours. Because they're moving at a speed that contracts them to half their rest length though, you could fit 16 of them round the disc instead of eight, and if you hooked them all together at that moment, they would rotate round the disc for as long as you like without getting in each other's way - this also works regardless of which frame might be the absolute frame of reference, so they will still fit in that space without needing any tricks to do with the timing of doors being closed or open like with the ladder paradox. Sixteen boxes definitively must fit in the space of eight if they're moving round the disc at 0.866c.

[GoC (OP)]

David


   You are using circular logic all based on your model of contraction strictly based on clocks ticking at the same rate in any orientation. Yours is only one model that cannot be verified except through math. Math does not prove a theory is correct. Math only proves a theory is not correct.

   The ladder paradox is based on simultaneity of relativity showing the signal to get to the doors affect the synchronicity of the doors being closed at the same time. While it's useful to show simultaneity of relativity it does not prove contraction. The design of contraction eliminates a testable measurement. Your model passes the hurdle of math but math does not prove your model.

[Le Repteux]

If you go to my ref-frame camera program ( http://www.magicschoolbook.com/science/ref-frame-camera.htm ) and load the fourth set of example objects (you have to type "d" into the dialog box after clicking the first button), you'll see a blue ring with eight red or yellow boxes round its edge, though only the corners of the boxes are shown.

I already had a glance at this simulation but I didn't understand it and it didn't seem to work properly. I load object D, I change the reference frame number, and nothing changes. To get a change, I have to change its speed. You said that the boxes were all moving at .866c with regard to the boxes at rest in the middle, so I understand that we can chose another reference frame than this one, which means that we can consider that one of the moving box is at rest, but why should we consider that it moves at other speeds than those two ones? And why can't we get a change when we change the reference frame without changing the speed?

[guest4091]

David Cooper;
The coin has a diameter of 1 unit length. The coin has the diameter oriented along x, the direction of motion. A and B each have an identical coin. B passes A at speed v. A measures the B-coin x diameter as 1/γ. B measures the A-coin x diameter as 1/γ. Are their measurements correct? Yes. One may be length contracted via em field deformation, and the other via time dilation for the observer. It may even be a combination of both. Since perception is reality confined to the mind of the observer, both are real or true, and based on laws of universal behavior. Perception does not alter the object being observed. SR is also a theory of perception, which is why it's so observer dependent.

[Le Repteux]

David

   You are using circular logic all based on your model of contraction strictly based on clocks ticking at the same rate in any orientation. Yours is only one model that cannot be verified except through math. Math does not prove a theory is correct. Math only proves a theory is not correct.

   The ladder paradox is based on simultaneity of relativity showing the signal to get to the doors affect the synchronicity of the doors being closed at the same time. While it's useful to show simultaneity of relativity it does not prove contraction. The design of contraction eliminates a testable measurement. Your model passes the hurdle of math but math does not prove your model.

Its the only model that could explain the twins paradox in a way that I could understand, and of course the MM experiment. I'm seventy, so it took 50 years before somebody comes with an understandable solution. Either I'm hard to convince, either nobody had the right way to explain relativity. I'm bad at maths because I forgot about them a lot, so its not the maths that convinced me even if I know they are part of David's simulations, it's the simulations themselves. How come you're not convinced yet? I didn't even believe in the relativity principle before I saw them and you do. Do you have a hidden goal? One that you cannot explicitly show otherwise people would think you are crazy? We're all crazy anyway so why bother. :0)

[David Cooper]

You are using circular logic all based on your model of contraction strictly based on clocks ticking at the same rate in any orientation. Yours is only one model that cannot be verified except through math. Math does not prove a theory is correct. Math only proves a theory is not correct.

There is no circularity in the logic. Particle accelerators show how much energy goes into a particle and how its speed is controlled in such a way that it can never go faster than c, and you see all that energy come back out when it collides head-on with another particle. The way relativistic mass builds up forces length contraction. The null result of the MMX shows too that length contraction is real. Maths proves that theories that don't have length contraction are not correct.

The ladder paradox is based on simultaneity of relativity showing the signal to get to the doors affect the synchronicity of the doors being closed at the same time. While it's useful to show simultaneity of relativity it does not prove contraction. The design of contraction eliminates a testable measurement. Your model passes the hurdle of math but math does not prove your model.

I mentioned the ladder paradox because it illustrates why some people learn the wrong lessons from it and end up thinking there is no length contraction. I am not using it as proof of length contraction, but to show how easy it is for people to end up being mislead by good education.

[David Cooper]

I already had a glance at this simulation but I didn't understand it and it didn't seem to work properly. I load object D, I change the reference frame number, and nothing changes.

It may be that some of the functionality doesn't work on more recent browsers, but I have no way to test that. Do the letter keys S and D function in the way I described or is that broken too?

You said that the boxes were all moving at .866c with regard to the boxes at rest in the middle, so I understand that we can chose another reference frame than this one, which means that we can consider that one of the moving box is at rest, but why should we consider that it moves at other speeds than those two ones? And why can't we get a change when we change the reference frame without changing the speed?

The initial frame shows all objects with their actual speeds and the actual length contractions acting on them. When you change to a different frame, you see the "God view" for the new frame instead (which shows a distorted version of reality, but which also looks just as real and which for observers co-moving with it behaves exactly as if it is the absolute frame). You can set it to display an infinite number of different frames, and each box can be made to appear to have any speed you like by selecting a frame that is moving at that speed relative to it. Changing the frame is done by typing in the speed of the new frame relative to the absolute frame, so you can't change frame without changing that speed, but the view continues to track the blue disc no matter which frame you select.

[David Cooper]

The coin has a diameter of 1 unit length. The coin has the diameter oriented along x, the direction of motion. A and B each have an identical coin. B passes A at speed v. A measures the B-coin x diameter as 1/γ. B measures the A-coin x diameter as 1/γ. Are their measurements correct? Yes. One may be length contracted via em field deformation, and the other via time dilation for the observer. It may even be a combination of both. Since perception is reality confined to the mind of the observer, both are real or true, and based on laws of universal behavior. Perception does not alter the object being observed. SR is also a theory of perception, which is why it's so observer dependent.

There is an absolute reality underlying everything which is not turned into ambiguous slodge by the perceptions of monkeys looking at coins. The nature of that reality is either logical or magical, and if it's the former, the coin cannot both be circular in that reality and elliptical at the same time. The only SR models that can free themselves of an absolute frame of reference are ones which depend on magic instead of logic for their functionality because one of them destroys causality, another has event-meshing failures and something equivalent to a preferred frame, and the third has events magically unhappen and rehappen every time the universe changes frame to prove to itself that it isn't running everything by the same frame all the time (so that it can claim not to have an absolute frame). You can take your pick, but I'm not impressed by theories that rely on magic for their functionality.

[David Cooper]

And I'm still waiting for someone (anyone in the world, or an intelligent being from outer space - I'm not fussy on that score) to show me a model of SR that can do what it claims on the tin without breaking its own rules and without it doing magical things like having events unhappen and rehappen as the model changes the frame it's using to generate events as it generates the future out of the past. You'd think there would be a demonstration model out there for everyone to admire, but no - they don't have one! The best they've got is the static block where their maths works beautifully for running imaginary physics in a pre-built block in which nothing actually moves or changes at all, but how does their model build that block in the first place without using different physics? The answer is that they can't do it - all they can do is bury their heads in the sand and go on asserting that their model can do what it manifestly cannot do.

[Le Repteux]

It may be that some of the functionality doesn't work on more recent browsers, but I have no way to test that. Do the letter keys S and D function in the way I described or is that broken too?

S and D keys do function. I think it's me that doesn't.

The initial frame shows all objects with their actual speeds and the actual length contractions acting on them. When you change to a different frame, you see the "God view" for the new frame instead (which shows a distorted version of reality, but which also looks just as real and which for observers co-moving with it behaves exactly as if it is the absolute frame). You can set it to display an infinite number of different frames, and each box can be made to appear to have any speed you like by selecting a frame that is moving at that speed relative to it. Changing the frame is done by typing in the speed of the new frame relative to the absolute frame, so you can't change frame without changing that speed, but the view continues to track the blue disc no matter which frame you select.

I think I get it. When we give a speed to a frame, it can move in any direction, not only in the one it has with regard to the blue boxes when they are considered at rest. If we give a speed to the right to a frame for instance, all the system should be considered to move to the right while the red boxes are still considered moving at a tangent to the blue ones. In this case, I think that the simulation would be a lot easier to understand if the whole system would already be traveling to the right on the screen before we hit the S key. That's what you simulation of the MMx does.

[David Cooper]

S and D keys do function. I think it's me that doesn't.

Do the number keys not work though? If your keyboard is set up for French, don't use a shift key with them: use &, é, ", etc. instead and see if that helps.

When we give a speed to a frame, it can move in any direction, not only in the one it has with regard to the blue boxes when they are considered at rest. If we give a speed to the right to a frame for instance, all the system should be considered to move to the right while the red boxes are still considered moving at a tangent to the blue ones.

If you select a frame that's moving to the right, that would make the blue disc move to the left but it doesn't because we then track it to keep it on the screen - this is done so that we can see the events play out there for longer than a short time. If everyone had a wall-sized display with 20,000 pixels from one side to the other I would have programmed it differently and not bothered to track it.

In this case, I think that the simulation would be a lot easier to understand if the whole system would already be traveling to the right on the screen before we hit the S key. That's what you simulation of the MMx does.

I wrote it to track objects that are stationary in the absolute frame and to let you change the frame of reference to see how they warp while still looking at them, and to show the effect of the changes on other objects that are moving through the absolute frame. I could modify it to track other objects. I'd like to put clocks into it too so that you'd be able to see one of the big effects of changing frame in the LET model - that would show clearly that it shows some objects further in the future than others while showing others back in the past and making them look simultaneous. This effect leads to the action happening faster as you go to more extreme frames, not because things are fundamentally happening any faster, but because it's projecting into the future at a faster rate. For example, if you set it to a frame that's moving to the right, the left of the screen shows the objects there as they were in the past while the right of the screen shows objects as they will be in the future. Change to a frame moving the opposite way and that all reverses, which means that events on the right unhappen while a whole stack of events on the left that hadn't happened suddenly have happened.