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 International Skeptics Forum Split Thread: Pendular Motion (And Relativity)

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 4th September 2018, 07:04 AM #361 Dave Rogers Bandaged ice that stampedes inexpensively through a scribbled morning waving necessary ankles     Join Date: Jan 2007 Location: Cair Paravel, according to XKCD Posts: 28,485 Originally Posted by SDG We have a problem here. No, in fact, we don't. Originally Posted by SDG Different radius, different rotational kinetic energy, different average acceleration even though the center of the ball has the same acceleration. So? When an object of finite size moves in a curved path, its acceleration varies from point to point according to the local path curvature and local velocity of that point. Therefore, different parts of the ball will experience different centripetal forces, in accordance with Newton's second law. The result is that the force and acceleration of the centre of mass are more difficult to calculate than those for a point mass. "More difficult to calculate" does not equate to "In violation of Newton's second law." Originally Posted by SDG My take on this issue is E_ball = m_ball c^2. If the E_ball is bigger because it has bigger rotational kinetic energy then m_ball has to be bigger, right? We take two photons, make them spin and we have mass particles, so what's the big deal. https://en.wikipedia.org/wiki/Pair_production ... but I see why this idea does not fly by many. All this is completely irrelevant to the problem you're dicsussing. When you behave like this people are less inclined to take you seriously. Originally Posted by SDG Dave's take on the issue is to keep the mass the same and we have different average acceleration. Wrong. My take on the issue is that, if you treat the ball as an extended object for the purpose of calculating its acceleration, then you must also treat it as an extended object for the purpose of calculating its acceleration. Originally Posted by SDG Then we have an issue A > r \omega. We 'break' the calculus and the textbooks. Either way we look at it, ... THIS IS A BIG PROBLEM! No, it isn't. All that you're showing is that the true value of the average acceleration as calculated for an extended object is different to the approximate result for acceleration drived from treating it as a point mass. This is a fully expected observation. Dave __________________ Me: So what you're saying is that, if the load carrying ability of the lower structure is reduced to the point where it can no longer support the load above it, it will collapse without a jolt, right? Tony Szamboti: That is right Last edited by Dave Rogers; 4th September 2018 at 07:08 AM.
 4th September 2018, 07:20 AM #362 tusenfem Master Poster     Join Date: May 2008 Posts: 2,458 What on earth does this weird discussion about different radii and forces and whathaveyounots to do with the original problem of the impossible determination of linear motion by a rotating wheel in a train? __________________ 20 minutes into the future This message is bra-bra-brought to you by z-z-z-zik zak And-And-And I'm going to be back with you - on Network 23 after these real-real-real-really exciting messages (Max Headroom) follow me on twitter: @tusenfem, or follow Rosetta Plasma Consortium: @Rosetta_RPC
 4th September 2018, 07:40 AM #363 Dave Rogers Bandaged ice that stampedes inexpensively through a scribbled morning waving necessary ankles     Join Date: Jan 2007 Location: Cair Paravel, according to XKCD Posts: 28,485 Originally Posted by tusenfem What on earth does this weird discussion about different radii and forces and whathaveyounots to do with the original problem of the impossible determination of linear motion by a rotating wheel in a train? SDG is trying to demonstrate that he has a counter-argument to Einsteinian relativity; the exact nature of the argument is secondary to its existence, which is the only thing he cares about because it would make him cleverer than Einstein. What he doesn't seem to understand is that he is arguing against not only Einsteinian, but Galilean, relativity, and hence all of classical mechanics; and, in fact, against mathematics, in that he seems to believe that he can construct two internally consistent mathematical descriptions of the same scenario, from the same starting assumptions, that are nevertheless mutually inconsistent. All the detail is simply a smokescreen to cover the fact that he doesn't have any in-depth understanding of what he's talking about. Dave __________________ Me: So what you're saying is that, if the load carrying ability of the lower structure is reduced to the point where it can no longer support the load above it, it will collapse without a jolt, right? Tony Szamboti: That is right
 4th September 2018, 09:35 AM #364 MRC_Hans Penultimate Amazing     Join Date: Aug 2002 Posts: 21,711 Originally Posted by SDG Right, so they will report the accelerations at that point. https://i.imgur.com/efIXNNZ.png Yes, that was what I said. Quote: The accelerations have different magnitude and different direction for the r=1m and r=100m. This leads to different tensions in the ball. Each atom has a different tension at different radius. Yes, as I said, some of the force is redistributed within the ball. So what? Do you think you are the first person to discover this? Quote: Each ball has its own angular momentum. These are different at different radii. Yes. What about it? Quote: If you had one of these https://i.imgur.com/OXsBIpg.png in your hands then you know how real is the angular momentum and how it affects the systems. Of course it is real. Quote: If we go the last photon then the balls will 'change' the shape differently based on the different tensions at different radii. This is the basis for my claim that the forces are not equal at different radii. Your claim is elementary. It is mundane knowledge. Quote: We could create 'a ball' from smaller balls connected by springs and observe the different responses. SDG Yes we could. What has all this to do with relativity? You know, by the term "claim" we usually understand something new, or at least something contested. It makes no sense to "claim" that the sky is blue or that water is wet. Everybody knows that. Hans __________________ If you love life, you must accept the traces it leaves. Last edited by MRC_Hans; 4th September 2018 at 10:10 AM.
 4th September 2018, 12:23 PM #365 JeanTate Master Poster   Join Date: Nov 2014 Posts: 2,306 Originally Posted by Dave Rogers SDG is trying to demonstrate that he has a counter-argument to Einsteinian relativity; the exact nature of the argument is secondary to its existence, which is the only thing he cares about because it would make him cleverer than Einstein. What he doesn't seem to understand is that he is arguing against not only Einsteinian, but Galilean, relativity, and hence all of classical mechanics; and, in fact, against mathematics, in that he seems to believe that he can construct two internally consistent mathematical descriptions of the same scenario, from the same starting assumptions, that are nevertheless mutually inconsistent. All the detail is simply a smokescreen to cover the fact that he doesn't have any in-depth understanding of what he's talking about. Dave Thanks for this summary. I stopped trying to follow what's in this thread quite some time ago, having concluded that if indeed the claim is some sort of internal inconsistency in (special) relativity, it should be much easier to demonstrate it than what was being posted. Also, I have found it strange that, in support of the (hard to grasp) claim, there is a complete absence of anything which could become an actual, physical experiment ... you know, test the ideas by how well they match what the universe actually does ...
 5th September 2018, 06:34 AM #366 SDG Thinker   Join Date: Jul 2018 Posts: 240 Originally Posted by Dave Rogers SDG is trying to demonstrate that he has a counter-argument to Einsteinian relativity; the exact nature of the argument is secondary to its existence, which is the only thing he cares about because it would make him cleverer than Einstein. What he doesn't seem to understand is that he is arguing against not only Einsteinian, but Galilean, relativity, and hence all of classical mechanics; and, in fact, against mathematics, in that he seems to believe that he can construct two internally consistent mathematical descriptions of the same scenario, from the same starting assumptions, that are nevertheless mutually inconsistent. All the detail is simply a smokescreen to cover the fact that he doesn't have any in-depth understanding of what he's talking about. Dave Dave, Here are some questions very tightly linked to all this discussion. We spin the wheel/balls firmly attached to the ground to 465m/s tangential velocity at the equator. The Earth equatorial rotation velocity is 465m/s. We have an ideal cycloid in the non rotating Earth reference frame. What gravitational accelerations will be reported by accelerometers attached to the center of the ball in the z-direction towards the center of the Earth at the top T and the bottom B of the cycloid? We speed up the wheel/balls to 7.67km/s. What accelerations will be reported now? We place the wheel/balls on the International Space Station that is flying at 7.67km/s through space and the wheel/balls spinning at 7.67km/s. What accelerations in the z-direction will be reported now? Now the ISS flies at 7.67km/s in the intergalactic space and the wheel/balls are spinning at 7.67km/s. What accelerations in the z-direction will be reported now? SDG
 5th September 2018, 07:06 AM #367 MRC_Hans Penultimate Amazing     Join Date: Aug 2002 Posts: 21,711 Originally Posted by SDG Dave, Here are some questions very tightly linked to all this discussion. We spin the wheel/balls firmly attached to the ground to 465m/s tangential velocity at the equator. The Earth equatorial rotation velocity is 465m/s. We have an ideal cycloid in the non rotating Earth reference frame. What gravitational accelerations will be reported by accelerometers attached to the center of the ball in the z-direction towards the center of the Earth at the top T and the bottom B of the cycloid? We speed up the wheel/balls to 7.67km/s. What accelerations will be reported now? We place the wheel/balls on the International Space Station that is flying at 7.67km/s through space and the wheel/balls spinning at 7.67km/s. What accelerations in the z-direction will be reported now? Now the ISS flies at 7.67km/s in the intergalactic space and the wheel/balls are spinning at 7.67km/s. What accelerations in the z-direction will be reported now? SDG That's funny ... when I asked about the influence from Earth's movement some time ago, you claimed it would be negligible. However, none of the motions you mention are linear, so that makes it rather more complex. But go ahead, calculate it. Hans __________________ If you love life, you must accept the traces it leaves.
 5th September 2018, 07:07 AM #368 Dave Rogers Bandaged ice that stampedes inexpensively through a scribbled morning waving necessary ankles     Join Date: Jan 2007 Location: Cair Paravel, according to XKCD Posts: 28,485 Originally Posted by SDG Dave, Here are some questions very tightly linked to all this discussion. It would help if your questions made sense. Originally Posted by SDG We spin the wheel/balls firmly attached to the ground to 465m/s tangential velocity at the equator. Doesn't make sense. Try to describe your scenario clearly enough that it's comprehensible. What is moving at 465m/s? Are you describing spins of individual wheels or motion in a circle? If the former, what is a spin of "465m/s tangential velocity at the equator" supposed to mean, and if the latter, given the wheels/balls are "firmly attached to the ground," how are we spinning them and relative to what? Originally Posted by SDG The Earth equatorial rotation velocity is 465m/s. We have an ideal cycloid in the non rotating Earth reference frame. What gravitational accelerations will be reported by accelerometers attached to the center of the ball in the z-direction towards the center of the Earth at the top T and the bottom B of the cycloid? Accelerometers do not measure "gravitational accelerations," they measure actual accelerations. Originally Posted by SDG We speed up the wheel/balls to 7.67km/s. What accelerations will be reported now? What do you mean by "speed up the wheel/ball to 7.67km/s," given that you haven't clearly explained what the ball was doing in the first place? Originally Posted by SDG We place the wheel/balls on the International Space Station that is flying at 7.67km/s through space and the wheel/balls spinning at 7.67km/s. What accelerations in the z-direction will be reported now? 7.67km/s is not a rate of spin. Your question makes no sense. Originally Posted by SDG Now the ISS flies at 7.67km/s in the intergalactic space and the wheel/balls are spinning at 7.67km/s. What accelerations in the z-direction will be reported now? SDG 7.67km/s is not a rate of spin. Your question makes no sense. If you can't formulate a coherent question, it's not surprising that your answers look like nonsense. Dave __________________ Me: So what you're saying is that, if the load carrying ability of the lower structure is reduced to the point where it can no longer support the load above it, it will collapse without a jolt, right? Tony Szamboti: That is right
 5th September 2018, 07:46 AM #369 MRC_Hans Penultimate Amazing     Join Date: Aug 2002 Posts: 21,711 Originally Posted by Dave Rogers Accelerometers do not measure "gravitational accelerations," they measure actual accelerations. [nitpick] That would depend on the type of accelerometer. Some types will measure steady forces (e.g. gravity) too. [/nitpick] Hans __________________ If you love life, you must accept the traces it leaves.
 5th September 2018, 07:52 AM #370 Dr.Sid Graduate Poster   Join Date: Sep 2009 Location: Olomouc, Czech Republic Posts: 1,737 IMHO all accelerometer must measure gravity, they just can adjust for it, if their orientation is known. It's impossible to distinguish between gravity and other source of acceleration.
 5th September 2018, 08:53 AM #371 MRC_Hans Penultimate Amazing     Join Date: Aug 2002 Posts: 21,711 Originally Posted by Dr.Sid IMHO all accelerometer must measure gravity, they just can adjust for it, if their orientation is known. It's impossible to distinguish between gravity and other source of acceleration. Yes, agreed. But, let's cut to the chase here: On a horizontally rotating structure, rotating at a constant rate, an accelerometer will measure a value determined by the formula in this page: http://www.calctool.org/CALC/phys/newtonian/centrifugal This is true no matter where it is mounted on the structure, and the direction of the force will be exactly radial (away from the center). Any constant linear displacement of the rotating structure will not affect this. If the structure is something like mentioned earlier (balls on spokes), the forces acting on different parts of the balls will be redistributed inside the ball to act radially on the point where the spoke is attached. It might be possible to measure these internal forces, but it will be much easier to calculate them by triangulation. Any constant linear displacement of the rotating structure will not affect this. The cycloid observed from an external frame, in case of a linear displacement of the rotating structure, is merely an observational illusion and does not affect any forces acting on the parts of the rotating structure. .... Yes, I think that covers it. Hans __________________ If you love life, you must accept the traces it leaves.
 5th September 2018, 10:18 AM #372 jadebox Graduate Poster     Join Date: Sep 2004 Location: USA Posts: 1,444 Originally Posted by MRC_Hans [nitpick] That would depend on the type of accelerometer. Some types will measure steady forces (e.g. gravity) too. [/nitpick] Not really. Accelerometers measure acceleration, not force. And, they can only record proper acceleration (which is kind of like saying that they can only sense acceleration that they can sense). For example, ignoring drag, if you tossed an accelerometer into the air it would record no acceleration once it left your hand even though it is still affected by gravity and follows a ballistic trajectory. It is only when it reaches the ground that it will record approximately 9.80 m/s/s of acceleration away from the center of the earth (because it is now being prevented from following a ballistic trajectory in free fall). In free fall, all parts of the accelerometer are being acclerated at the same rate. So, it can't sense the acceleration. It is only when something external pushes it that it records acceleration. So, an acclerometer cannot directly record the force of gravity or the acceleration due to gravity. It can, however, record the acceleration caused by the earth pushing against it to prevent it from free falling. This relates somewhat to SDG's scenario in that the accelerometer in free fall is not able to sense gravity and the apparatus on the train is unaffected by the constant linear motion of the train. His balls aren't going to be able to sense the motion of the train no matter how much he fiddles with them. Last edited by jadebox; 5th September 2018 at 10:21 AM.
 5th September 2018, 11:28 AM #373 MRC_Hans Penultimate Amazing     Join Date: Aug 2002 Posts: 21,711 Most accelerometers are indirect instruments, that is, they essentially sense how much a given mass can deflect a given force (nearly always in the form of a spring). Such accelerometers cannot detect the force they are under in free fall. However, there exists types that are direct. They detect the acceleration of a released mass. But they still cannot detect the acceleration force under free fall. This is because the acceleration force under free fall is unknowable according to relativity. Hans __________________ If you love life, you must accept the traces it leaves.
 5th September 2018, 12:21 PM #374 theprestige Penultimate Amazing   Join Date: Aug 2007 Posts: 31,651 Originally Posted by jadebox His balls aren't going to be able to sense the motion of the train no matter how much he fiddles with them. Indeed, the whole exercise has a masturbatory quality to it.
 6th September 2018, 08:12 AM #375 SDG Thinker   Join Date: Jul 2018 Posts: 240 Originally Posted by MRC_Hans That's funny ... when I asked about the influence from Earth's movement some time ago, you claimed it would be negligible. However, none of the motions you mention are linear, so that makes it rather more complex. But go ahead, calculate it. Hans I still stand by my original claim. The gravitational acceleration effect is negligible when the tangential velocity at he wheel edge caused by rotation is much less then the Earth's tangent velocity caused by the Earth rotation. Nevertheless if we analyze presented scenarios then the gravitational acceleration has to be considered. The calculation of the instantaneous acceleration is not that complicated. This is from the same book that I quoted before - page 10: How do we calculate the delta between the rotating and non-rotating Earth? The Earth equatorial radius: 6378100m The Earth equatorial rotation tangential velocity: 1674.4km/h -> 465m/s The non rotating g at the equator: 9.814m/s^2 The centrifugal acceleration caused by the rotation: v^2/r = 465^2/6378100=0.0339m/s^2 The rotating gravitational acceleration g is: 9.814-0.0399=9.781m/s^2 This result is in line with the above presented plot. Now if we spin the wheel to the 465m/s tangential velocity then the accelerometer at the bottom of the cycloid is going to report 9.814m/s^2 acceleration because the bottom point B has 0m/s velocity in the non-rotating Earth reference frame. The point at the top of the cycloid T has velocity 930m/s in the non-rotating Earth reference frame. The accelerometer at the top: - the centrifugal acceleration a_cf = v^2/r = 930^2/6378100 = 0.1356m/s^2 - the gravitational acceleration g = 9.814-0.1356 = 9.678 m/s^2 Is there any issue with the proposed solution of the instantaneous acceleration? I would like to get an agreement before I continue with the calculation of the other rotations. SDG
 6th September 2018, 08:22 AM #376 Dave Rogers Bandaged ice that stampedes inexpensively through a scribbled morning waving necessary ankles     Join Date: Jan 2007 Location: Cair Paravel, according to XKCD Posts: 28,485 Originally Posted by SDG I would like to get an agreement before I continue with the calculation of the other rotations. If your aim is primarily to bog down the discussion in minutiae, you seem to have hit on a very effective strategy here: describe a scenario in sufficiently unclear terms, ideally with enough internal contradictions, that nobody can divine exactly what it is that you mean, then demand universal agreement on the conclusions you derive from your scenario before proceeding. As I've said before, it's a pointless and childish game that I decline to play. Dave __________________ Me: So what you're saying is that, if the load carrying ability of the lower structure is reduced to the point where it can no longer support the load above it, it will collapse without a jolt, right? Tony Szamboti: That is right
 6th September 2018, 08:48 AM #377 SDG Thinker   Join Date: Jul 2018 Posts: 240 Originally Posted by Dave Rogers If your aim is primarily to bog down the discussion in minutiae, you seem to have hit on a very effective strategy here: describe a scenario in sufficiently unclear terms, ideally with enough internal contradictions, that nobody can divine exactly what it is that you mean, then demand universal agreement on the conclusions you derive from your scenario before proceeding. As I've said before, it's a pointless and childish game that I decline to play. Dave Dave, I want to discuss Einstein relativity. The above post is about a wheel (as originally described) put in the concrete block on the Earth surface at the equator. The wheel axle points to the center of the Earth. We spin the wheel so the accelerometers at the center of the balls have tangential velocity 465m/s in regards to the non-rotating reference frame at the center of the wheel/axle. This is essentially the ground reference frame. The Earth equatorial rotation tangential velocity is 465m/s in regards to the non-rotating Earth reference frame at the center of the Earth. Now the accelerometers follow ideal cycloid trajectory in the non-rotating Earth center reference frame. The accelerometers have 0m/s velocity at the bottom of the cycloid B and they have 930m/s tangential velocity at the top of the cycloid T in the non-rotating Earth center reference frame. I hope this helps at the moment. SDG
 6th September 2018, 08:52 AM #378 theprestige Penultimate Amazing   Join Date: Aug 2007 Posts: 31,651 Originally Posted by Dave Rogers If your aim is primarily to bog down the discussion in minutiae, you seem to have hit on a very effective strategy here: describe a scenario in sufficiently unclear terms, ideally with enough internal contradictions, that nobody can divine exactly what it is that you mean, then demand universal agreement on the conclusions you derive from your scenario before proceeding. As I've said before, it's a pointless and childish game that I decline to play. Zeno's Gish Gallop. Avoid unwanted progress by slicing the question ever finer, and manufacturing disagreement about each paper-thin slice in turn. It was one of Jabba's principal techniques for over five years. I think it's clear this thread is on track* to go at least five years without any real progress. *See what I did there? Last edited by theprestige; 6th September 2018 at 08:54 AM.
 6th September 2018, 09:02 AM #379 JeanTate Master Poster   Join Date: Nov 2014 Posts: 2,306 Originally Posted by SDG Dave, I want to discuss Einstein relativity. The above post is about a wheel (as originally described) put in the concrete block on the Earth surface at the equator. The wheel axle points to the center of the Earth. We spin the wheel so the accelerometers at the center of the balls have tangential velocity 465m/s in regards to the non-rotating reference frame at the center of the wheel/axle. This is essentially the ground reference frame. The Earth equatorial rotation tangential velocity is 465m/s in regards to the non-rotating Earth reference frame at the center of the Earth. Now the accelerometers follow ideal cycloid trajectory in the non-rotating Earth center reference frame. The accelerometers have 0m/s velocity at the bottom of the cycloid B and they have 930m/s tangential velocity at the top of the cycloid T in the non-rotating Earth center reference frame. I hope this helps at the moment. SDG (my bold) SDG, you have now introduced the real world, with all its non-ideal aspects. If you insist on using the real world for your thought experiment, I have lots of questions of clarification for you (e.g. how do you know that "The wheel axle points to the center of the Earth"?), clarifications that are essential in order to even begin to address your claims. So, please confirm that your claim has now left the ideal world and entered the real. If you wish to remain in an ideal world, please re-state your claims, making it explicit that it is not the real world.
 6th September 2018, 10:17 AM #381 MRC_Hans Penultimate Amazing     Join Date: Aug 2002 Posts: 21,711 Originally Posted by SDG Dave, I want to discuss Einstein relativity. The above post is about a wheel (as originally described) put in the concrete block on the Earth surface at the equator. The wheel axle points to the center of the Earth. We spin the wheel so the accelerometers at the center of the balls have tangential velocity 465m/s in regards to the non-rotating reference frame at the center of the wheel/axle. This is essentially the ground reference frame. The Earth equatorial rotation tangential velocity is 465m/s in regards to the non-rotating Earth reference frame at the center of the Earth. Now the accelerometers follow ideal cycloid trajectory in the non-rotating Earth center reference frame. The accelerometers have 0m/s velocity at the bottom of the cycloid B and they have 930m/s tangential velocity at the top of the cycloid T in the non-rotating Earth center reference frame. I hope this helps at the moment. SDG You keep revising your model, but you have been told repeatedly (and you have ignored it repeatedly): The cycloid is illusory. While it can be observed from an outside reference frame, it has no influence on the moving frame. It does not matter if you imagine a train, the Earth, someone on a bicycle, or in a spaceship: A linear movement has no influence inside the moving reference frame. Live with it. Oh, and btw, the Earth is not a linear movement frame. It is circular, and certain effects WILL be detectable inside a frame moving with the surface of Earth. Hans __________________ If you love life, you must accept the traces it leaves.
 6th September 2018, 12:10 PM #382 Elagabalus Illuminator   Join Date: Dec 2013 Posts: 3,843 Originally Posted by SDG Dave, I want to discuss Einstein relativity. The above post is about a wheel (as originally described) put in the concrete block on the Earth surface at the equator. The wheel axle points to the center of the Earth. We spin the wheel so the accelerometers at the center of the balls have tangential velocity 465m/s in regards to the non-rotating reference frame at the center of the wheel/axle. This is essentially the ground reference frame. The Earth equatorial rotation tangential velocity is 465m/s in regards to the non-rotating Earth reference frame at the center of the Earth. Now the accelerometers follow ideal cycloid trajectory in the non-rotating Earth center reference frame. The accelerometers have 0m/s velocity at the bottom of the cycloid B and they have 930m/s tangential velocity at the top of the cycloid T in the non-rotating Earth center reference frame. I hope this helps at the moment. SDG Perhaps send Jaroslav J. Kopernicky over here so we can hear it straight from the hoses mouth. I noticed his original experiment was this: Quote: Jaroslav Kopernicky’s comments Inertial Tendencies of the Massive Body Following the Path of the Cycloid. Inertia, accordingly to Newton’s views, appears inherent and independent for every single particle. This assumption raises an importance of the behavior – inertial changes – of the body having mass, moving on the cycloid path. One of early examples was the toy carousel equipped with two pendulums positioned diagonally on the carousel. When the rotating carousel moves in the plane of rotation, pendulums of equal length and weight fly in different levels; One advancing with the movement of the carousel flies higher, while one moving momentarily in the opposite direction flies lower. Each pendulum moves on its own cycloid path. When carousel rotates stationary, pendulums fly at the same level. The mercury switch replacing the pendulum makes an intermittent (On – Off) connection when the rotating carousel moves. But when carousel rotates stationary – not moving laterally – the switch keeps only one position. This phenomenon provides possibilities of indication and measurements of the uniform movement, its speed and direction. It also has potential to indicate and explain observations in astronomy (zone convenient for life) and geology (tides, prediction of earthquakes, etc). This Jano Onderco’s analysis and connected experiments are welcomed contributions to the further understanding of the phenomenon. Jaroslav J. Kopernicky January 16th, 2014 http://theelectromagneticnatureofthi...al-relativity/ I managed to dig up a few more things. Apparently he's invented some kind of Mobiloscope: An Independent Indicator of Movement. http://www.watertorch.com/pacead/PACENewsIndex.pdf page 9. And a listing in The Worldwide List of Alternative Theories and Critics.
 15th September 2018, 06:56 AM #383 MRC_Hans Penultimate Amazing     Join Date: Aug 2002 Posts: 21,711 Well, seems Relativity withstood yet another assault. Hans __________________ If you love life, you must accept the traces it leaves.
 16th September 2018, 07:22 PM #384 Little 10 Toes Graduate Poster     Join Date: Nov 2006 Posts: 1,918 I'm sorry, but how many thought experiments are going on now? __________________ I'm an "intellectual giant, with access to wilkipedia [sic]" "I believe in some ways; communicating with afterlife is easier than communicating with me." -Tim4848 who said he would no longer post here, twice in fact, but he did.
 17th September 2018, 12:10 AM #385 MRC_Hans Penultimate Amazing     Join Date: Aug 2002 Posts: 21,711 I think we had aroud four basic scenarios, all based on various combinations of linar and circular motion. I think the OP has now either given up or left greener pastures. Hansý __________________ If you love life, you must accept the traces it leaves.
 17th September 2018, 07:15 AM #386 SDG Thinker   Join Date: Jul 2018 Posts: 240 Originally Posted by MRC_Hans Well, seems Relativity withstood yet another assault. Hans Right I am busy next 4-5 weeks. I'll come back then, SDG
 17th September 2018, 12:30 PM #387 theprestige Penultimate Amazing   Join Date: Aug 2007 Posts: 31,651 Originally Posted by SDG Right I am busy next 4-5 weeks. I'll come back then, SDG Is your motion in and out of this thread cycloid? Does the observation of your departure and return allow us to determine whether the thread is making forward progress?
 4th October 2018, 05:51 PM #388 Little 10 Toes Graduate Poster     Join Date: Nov 2006 Posts: 1,918 Originally Posted by SDG Right I am busy next 4-5 weeks. I'll come back then, SDG So when you said that you would back in 4-5 weeks, I take it you meant that you'll come back to this topic. Right? __________________ I'm an "intellectual giant, with access to wilkipedia [sic]" "I believe in some ways; communicating with afterlife is easier than communicating with me." -Tim4848 who said he would no longer post here, twice in fact, but he did.
 5th October 2018, 12:32 AM #389 MRC_Hans Penultimate Amazing     Join Date: Aug 2002 Posts: 21,711 Well, but why, really. Is there anything left worth discussing? Hans __________________ If you love life, you must accept the traces it leaves.
 5th October 2018, 04:57 AM #390 SDG Thinker   Join Date: Jul 2018 Posts: 240 Here is a question based on this text from Engineering Mechanics Volume 2 Dynamics Seventh Edition by J. L. Meriam and L. G. Kraige page 244: We know that the rotational effect 0.0339m/s^2 is real. Is the orbit effect 0.00593m/s^2 real as well? Is there a delta of approximately 0.01186m/s^2 between the noon and the midnight at the equator due to the orbit velocity? Not only that but how come this orbit component is even considered here???? The GR says there is no force acting on a body in a free fall and the Earth is for sure in a free fall around the Sun therefore the orbit acceleration 'does not exist'. Right?
 5th October 2018, 05:24 AM #391 jadebox Graduate Poster     Join Date: Sep 2004 Location: USA Posts: 1,444 Originally Posted by SDG We know that the rotational effect 0.0339m/s^2 is real. Is the orbit effect 0.00593m/s^2 real as well? [snip] The GR says there is no force acting on a body in a free fall and the Earth is for sure in a free fall around the Sun therefore the orbit acceleration 'does not exist'. Right? What you call "orbit acceleration" is the acceleration due to gravity at the distance the earth orbits the sun. In General Relativity gravity is not considered a force. Instead it acts to bend spacetime. Edit: I snipped the middle part because it wasn't clear. But, now I think you are referring to the Tidal Force, which really isn't a force either in GR. It can be detected because the acceleration due to gravity really does change based on distance. But, there is no equivalence with your train analogy where the accleration is either zero or constant. Last edited by jadebox; 5th October 2018 at 05:49 AM.
 5th October 2018, 07:10 AM #392 Dave Rogers Bandaged ice that stampedes inexpensively through a scribbled morning waving necessary ankles     Join Date: Jan 2007 Location: Cair Paravel, according to XKCD Posts: 28,485 Originally Posted by SDG Not only that but how come this orbit component is even considered here???? The GR says there is no force acting on a body in a free fall and the Earth is for sure in a free fall around the Sun therefore the orbit acceleration 'does not exist'. Right? Wrong. This is not a description of the GR interpretation of motion; it's a description of the Newtonian interpretation of motion, a reasonable approximation for engineering purposes in which gravity is a force giving rise to an acceleration. Dave __________________ Me: So what you're saying is that, if the load carrying ability of the lower structure is reduced to the point where it can no longer support the load above it, it will collapse without a jolt, right? Tony Szamboti: That is right
 5th October 2018, 09:37 AM #393 MRC_Hans Penultimate Amazing     Join Date: Aug 2002 Posts: 21,711 Originally Posted by SDG The GR says there is no force acting on a body in a free fall and the Earth is for sure in a free fall around the Sun therefore the orbit acceleration 'does not exist'. Right? Wrong. GR says nothing of the kind. An orbiting object is in free fall, but is under the influence of a centripetal force. Hans __________________ If you love life, you must accept the traces it leaves.
 5th October 2018, 11:28 AM #394 SDG Thinker   Join Date: Jul 2018 Posts: 240 Originally Posted by MRC_Hans Wrong. GR says nothing of the kind. An orbiting object is in free fall, but is under the influence of a centripetal force. Hans Does GR allow to measure the centripetal force without any outside signal? If we are in a room on the equator, we do not see outside, we measure the gravitational acceleration g and we see 24 hours period in g values, then we know the Earth is moving through space. If we have the same setup and the Earth is in the intergalactic space then we are not going to measure the 24 hours period. The Earth is not influenced by the centripetal force. We can detect gravity without external signal. SDG
 5th October 2018, 12:28 PM #395 MRC_Hans Penultimate Amazing     Join Date: Aug 2002 Posts: 21,711 Originally Posted by SDG Does GR allow to measure the centripetal force without any outside signal? The question makes no sense. The centripetal force IS an outside signal. Quote: If we are in a room on the equator, we do not see outside, we measure the gravitational acceleration g and we see 24 hours period in g values, then we know the Earth is moving through space. You make no sense. The gravity of the sun IS an outside signal, and of course we can detect it. Quote: If we have the same setup and the Earth is in the intergalactic space then we are not going to measure the 24 hours period. The Earth is not influenced by the centripetal force. We can detect gravity without external signal. And, you make no sense. If there is no centripetal force, there is no external gravity. An object in orbit does not "sense" the centripetal force, because it causes a constant acceleration that causes a circular (really elliptical) movement. There is however, an effect that allows us to detect the circular movement, namely the Coriolis effect. Hans __________________ If you love life, you must accept the traces it leaves.
 5th October 2018, 12:58 PM #396 SDG Thinker   Join Date: Jul 2018 Posts: 240 Originally Posted by MRC_Hans The question makes no sense. The centripetal force IS an outside signal. You make no sense. The gravity of the sun IS an outside signal, and of course we can detect it. And, you make no sense. If there is no centripetal force, there is no external gravity. An object in orbit does not "sense" the centripetal force, because it causes a constant acceleration that causes a circular (really elliptical) movement. There is however, an effect that allows us to detect the circular movement, namely the Coriolis effect. Hans The reference system attached to the center of the Earth is by definition inertial regardless if it is 'falling' in the orbit around the Sun or the Earth is in the intergalactic space. If all inertial reference systems are equal then we should not be able to measure gravitational acceleration. If we can measure the gravitational acceleration then these two inertial reference systems are not equal. Does this make sense? SDG
 5th October 2018, 01:38 PM #397 SDG Thinker   Join Date: Jul 2018 Posts: 240 Quote: As an example: an inertial body moving along a geodesic through space can be trapped into an orbit around a large gravitational mass without ever experiencing acceleration. This is possible because spacetime is radically curved in close vicinity to a large gravitational mass. In such a situation the geodesic lines bend inward around the center of the mass and a free-floating (weightless) inertial body will simply follow those curved geodesics into an elliptical orbit. An accelerometer on-board would never record any acceleration. https://en.wikipedia.org/wiki/Equivalence_principle We are not suppose to measure any contribution from the Sun's gravity! The Earth is in a 'free-fall' in the orbit. SDG
 5th October 2018, 02:47 PM #398 Dr.Sid Graduate Poster   Join Date: Sep 2009 Location: Olomouc, Czech Republic Posts: 1,737 Accelerometer in free-fall doesn't register any acceleration .. I always thought it acts like that because all atoms of the accelerometer are accelerated at exact same speed. It's different than accelerometer on rocket, because there the case of the accelerometer is accelerated, but the insides are not, which create measurable forces inside, which are actually measured by the acccelerometer. Not sure how photons would behave in free fall though. If you send photon in the direction of acceleration, and capture it later .. you have increased your speed compared to the moment the photon was released. Photon obviously couldn't get any faster, but it should have increased energy .. but if free fall is inertial motion, the photon would keep same energy .. well .. now I'm confused. Edit: oh, I've just got it .. the photon will gain energy in the free fall, it will be gravity blue shifted. But as the rest of the free falling chamber accelerates away from the point where the photon was created, the chamber will perceive the photon as red shifted. The amount of the shift will perfectly cancel out and the photon will behave as if the chamber was standing still. Last edited by Dr.Sid; 5th October 2018 at 02:59 PM.
 5th October 2018, 03:11 PM #399 jadebox Graduate Poster     Join Date: Sep 2004 Location: USA Posts: 1,444 Originally Posted by SDG https://en.wikipedia.org/wiki/Equivalence_principle We are not suppose to measure any contribution from the Sun's gravity! The Earth is in a 'free-fall' in the orbit. SDG The earth is not a single point. And it is not alone as it falls around the sun. There is a point within the earth/moon system that is following a free fall trajectory. If you were also travelling along that exact path, you would not be able to measure any contribution from the sun's gravity. In other places, such as riding along on the rotating surface of the earth, you can only feel the indirect effects of deviating from that free fall trajectory, not any direct effect of the sun's gravity.
 5th October 2018, 04:49 PM #400 SDG Thinker   Join Date: Jul 2018 Posts: 240 Originally Posted by jadebox The earth is not a single point. And it is not alone as it falls around the sun. There is a point within the earth/moon system that is following a free fall trajectory. If you were also travelling along that exact path, you would not be able to measure any contribution from the sun's gravity. In other places, such as riding along on the rotating surface of the earth, you can only feel the indirect effects of deviating from that free fall trajectory, not any direct effect of the sun's gravity. Let's simplify the setup. The Sun is in the intergalactic space and the Earth orbits the Sun, nothing else far away. We can detect the Sun's gravity contribution to the gravitational acceleration on the surface of the Earth. The gravitational acceleration of the Earth that would be in the intergalactic space alone, without the Sun will be different though. The Earth inertial reference systems are not equal. SDG

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