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Post by mrsonde on Sept 6, 2012 14:16:30 GMT 1
My usual board is in maintenance mode, so I thought I'd bring this fascinating argument over here: see if there's any more agreement on a science board! As Eric Laithwaite eloquently demonstrated 40 years ago, a spinning mass apparently loses weight - or there is a force acting in opposition to the Earth's gravitational attraction; whatever way you want to express it. The Physics establishment assert, without any evidence that I'm able to find - certainly not adduced by Laithwaite's detractors - that this force is given by Newton's laws of motion, or at least by a "manipulation" of them as applied to 3D angular momentum. The standard ploy of presenting a chain of equations is presented to support this contention; the equally standard tactic of not bothering to explicate these equations in terms of logic is also employed. That is, if you can't follow the self-evident conclusions of such simple mathematics, you're not worth arguing with, or you simply can't understand what is obvious, because you can't add up. The fact that Laithwaite was one of our most respected and lauded and successful physicists - or electrical engineers, if you want to get pedantic about it, as they dismissively do of course - who understood electrodynamics and gyroscopic motion probably better than anyone else in the world is blithely forgotten. So: can anyone give a coherent logical explanation of how and why gravitational mass is apparently reduced in a spinning body? Given that this is supposedly a basic deduction from Newtonian laws of motion, and prsents no problem whatsoever, it should be a simple matter of a googled reference to where it must be mentioned in every A-Level Physics text, I'd have thought. The description, at least. A full explanation might perhaps require a degree-level text - but, again, these should be equally ubiquitous. Here's Laithwaite reproducing his original Royal Institution demonstration: And here's the standard "rebuttal", including the standard tactics of the scientific establishment when affronted of demeaning misattributions, dismissive failure to engage in the relevant point, and patent inability to construct a meaningful English sentence: www2.eng.cam.ac.uk/~hemh/gyroscopes/newtoncircular.html
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Post by striker16 on Sept 6, 2012 17:07:24 GMT 1
I do not know but is not mass nowadays considered to be equivalent to energy, in which case the faster something is spinning the more mass it acquires. This is shown by Einstein's ideas about never being able to reach the speed of light due to the amount of mass generated.
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Post by mak2 on Sept 6, 2012 20:27:53 GMT 1
There is saying, originally by David Merman, that is well known among physicists. "Shut up and calculate!"
It is the most reliable way of getting the right answer to complicated problems.
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Post by mrsonde on Sept 7, 2012 2:09:01 GMT 1
I do not know but is not mass nowadays considered to be equivalent to energy, in which case the faster something is spinning the more mass it acquires. This is shown by Einstein's ideas about never being able to reach the speed of light due to the amount of mass generated. Ermmm...ultimately I'm sure this has some relevance, but for the moment the issue at contention is that the phenomenon demonstrated is or is not accounted for by Newton's laws of motion. Apart from that - the standard Newtonian explanation of the behaviour of a spinning body would say that the additional energy given to a mass by spinning it is translated into angular momentum, resulting in a force at right angles to its direction of spin, the centrifugal force, and again, another inertial momentum at right angles to both, resulting in a precession (which is why Laithwaite is guided in a circle.) And as far as my education, and subsequent googling, goes: that's all he wrote. No mention of a force in contradictinction to gravitational attraction.
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Post by marchesarosa on Sept 7, 2012 2:12:17 GMT 1
Hi, welcome back, Mr Sonde!
Off to bed now. Will see you later.
Toodle-oo.
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Post by mrsonde on Sept 7, 2012 2:19:40 GMT 1
There is saying, originally by David Merman, that is well known among physicists. "Shut up and calculate!" It is the most reliable way of getting the right answer to complicated problems. Calculate what? Where, for example, in that sequence of equations purportedly rebutting Laithwaite is there any term relating to an upward force acting against the gravitational attraction of the Earth? In the "external forces" term? How and why does this change? And this is asserted to be an uncomplicated problem. The behaviour of Laithwate's wheel is said to be a perfectly expected and explicable consequence of Newton's second law. Never mind that Laithwaite continued throughout the remaining 30 years of his professional life to insist that this law has no application to this phenomenon. You'd have thought that during those 30 years, given such a supposedly simple problem of basic mathematics, someone - one of his legion of dismissive detractors, a colleague, a friend - would have said: "Look, Eric, here's the solution to your so-called overlooked problem, something everybody knows, including your first-year students, that's so simple it doesn't even require a page of text to lay out, but for some reason you've weirdly forgotten about, so do dear fellow stop making such a complete and utter ass of yourself? You're the foremost professor of engineering in this country if not the world and yet you persist in this woeful misunderstanding of a basic law of physics that's three centuries old and even someone who can't write intelligible English can explain with a few mathematical equations! Get a grip man!"
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Post by mrsonde on Sept 7, 2012 2:21:02 GMT 1
Hi Marchesa, nice to see you.
Not there you won't.
Pip pip.
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Post by striker16 on Sept 7, 2012 9:30:59 GMT 1
Here's Laithwaite reproducing his original Royal Institution demonstration: Yep, now I have seen the demo. it does appear that a fast spinning wheel defies the earth's gravity and effectively becomes as light as a feather! This must be due to the wheel's angular momentum so why hasn't this principle been used in anti-gravity devices? Or has it?
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Post by mrsonde on Sept 7, 2012 15:25:37 GMT 1
Yep, now I have seen the demo. it does appear that a fast spinning wheel defies the earth's gravity and effectively becomes as light as a feather! This must be due to the wheel's angular momentum so why hasn't this principle been used in anti-gravity devices? Or has it? Well, let's hear what this "principle" is supposed to be first. How does an apparently "anti-gravitational" effect arise from angular momentum? At the moment, until I'm persuaded otherwise (by reference to standard physics texts dealing with angular momentum), I don't believe the equations dealing with angular momentum have anything to say about the gravitational attraction of external bodies whatsoever. Where in Newton's laws of motion, or in the equations of angular momentum that are derived from them, is there any term relating to a variable measure of G (and hence the measurable inertial mass of the body undergoing such motion)? There is no such reference as far as I'm aware. How is this variability calculated? Why and how does it arise? Now, you may be right that to understand these questions requires a relativistic notion of gravity. Presumably such an understanding would make use of notions of curved space-time, the equivalence of acceleration and a gravitational field, and so on. This may be so. But the fact is that none of Laithwaite's detractors have ever made this case. They argue instead that the classical Newtonian notions of space, time, gravity, momentum etc. are all quite adequte to account for this phenomenon. Laithwaite is dismissed as an ignorant crank for even raising the issue as a problem. So, what I'm looking for is mak2 or StA or Eamonn, or whoever might still be around from the Physics community, to present a coherent logically explicated defence of this standard "consensus" view. I'd like to see mak2 present his calculation, for example - it should apparently be fairly straightforward. A simple problem in classical physics. All the equations are well known and old hat - nothing more complicated than standard algebra and basic arithmetic. The parameters are given and simple: a 13" wheel of 40lb mass spinning at 2,500 rpm. Enter these quantities into the relevant equations please, and thus calculate according to that simple equation of known classical physics how an old man is able to lift this weight with his little finger. What weight does he experience it as, and why?
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Post by mrsonde on Sept 7, 2012 15:45:44 GMT 1
Incidentally - sort of - you may be interested in how this question arose in debate. It was referred to in a discussion initially about the theory of dark matter, and dark energy - what observational evidence is there for this extravagant theory, why was it proposed, why is it now the generally accepted consensus view, etc. Most of the evidence derives either directly - historically - or indirectly (later inferences about other highly theory-laden observations - grvitational lensing, for example) from measurements of the orbital velocities of spinning galaxies, or clusters of galaxies. Spinning mass, at various scales. Primarily using this classical understanding of angular momentum, it was determined that there's a "missing mass" problem - stars and galaxies are moving too quickly according to calculations using this theoretical toolkit, given the observed mass estimated from the radiation emitted from it. The Milky Way needs to have ten times or so more mass than we can observe, for example.
But if Physics' understanding of the interaction between mass, angular momentum, and gravity is apparently so inadequate that a simple answer can't be given to a simple query arising from a simple observation like this, the behaviour of a lump of iron spinning at a low speed on a lecture stage, how is one supposed to have any confidence they know what the hell they're talking about, calculating quantities like the total mass of the entire universe, or the mass of a cluster of galaxies billions of light-years away, based entirely on a highly theoretical manipulation of these mathematical equations to give its supposed speed of rotation and total mass ratio? Let's hear how a 40 lb weight apparently becomes a few ounces when it spins at 2,500 rpm first, please. Then it might be rational to give such exotic fancies as dark matter some sort of credence.
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Post by marchesarosa on Sept 7, 2012 18:47:50 GMT 1
Does the initial energy imparted to the revolving weight by the electric drill help it to counteract the force of gravity? Presumably, as the energy was used up the wheel would slow down and eventually descend to the ground and be just as "heavy" as before. Things that spin fast can occasionally "fly off" what they are attached with a life of their own. Laithwaite devised a means of keeping hold of his as it "flew off".
(I know, not very clever but I'm only a girl, you see.)
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Post by mrsonde on Sept 8, 2012 3:48:06 GMT 1
Does the energy imparted to the revolving weight by the electric drill help it to counteract the force of gravity? Well, that's the conundrum Marchesa, the point in dispute. Evidently there is apparently some counteraction to gravity going on, however you might wish to express that. The Physics establishment has argued, to the extent any coherent argument to Laithwaite's demonstration was ever made at all (it unfortunately all got tangled up with what at the time was a more widespread argument he was making, about gyroscopic motion in general not being covered by Newton's laws of motion - a position he more or less later retracted), that this effect is fully accounted for using Newton's laws and the standard equations for analysing angular momentum. But I fail to see how and where they do so, and so did Laithwaite, who'd studied and taught that basic corpus of classical physics all his life. Obviously the centrifugal force can not be counteracting the gravitational attraction of the Earth (which gives the wheel its weight), because that's directed to the centre of the Earth, and the centrifugal force is equally distributed around the wheel: any upward momentum is equally balanced out by the downward. Then there is a torque produced, as he changes the angle of the axis of spin vis-a-vis the Earth, resulting in him being guided to follow a circle. All this is described using the standard angular momentum equations - there are minor adjustments made in relativistic situations, but as I've said above these don't enter into the argument. But what is not described, as far as Laithwaite was concerned, was this evident counter-gravity effect. One possible explanation might be that somehow there is a momentum of the spinning body's particles that for some reason sum up to an upward direction - but where is that given in the equations? Why upward? If the spin imparted had been in the opposite sense, would this have made the weight heavier? Would it have had this opposite sign if, say, the experiment had been conducted in the Southern Hemisphere? Interesting questions, but none of this is described by Newtonian angular momentum - the idea that any form of motion could vary the measured gravitational attraction between two bodies would have struck Newton as absurd, a contradiction of his whole metaphysic. It's not a question of who's clever - except perhaps for those physicists who felt demeaned by Laithwaite's intrusion into what they claimed was their field of expertise. For Laithwaite it was rather a clear case of science having missed an important fact about the universe - he wanted to understand the mechanics of that observation, and found that the classical laws of motion failed to predict it. As far as I know no one had ever predicted this observation before Laithwaite, incidentally - you won't find it described or discussed in any way in any physics text prior to his demonstration to the Royal Institution; at least, I can't, and no one ever makes any reference to such a text. This observation is, I hope you agree, a very surprising fact: a very surprising fact about what must be the basic mechanical operations of the universe. Never specifically discussed before - or if it ever has been, it's gone entirely unnoticed. And yet the reaction to Laithwaite pointing out this hitherto unremarked fact was a torrent of dismissive criticism and demeaning insults: he was an over-the-hill maverick who didn't really understand physics, a disrespectful troublemaker trespassing in a field and trying to make his betters look foolish for his own grandisement. He found it hard to get published, he was no longer invited to key conferences, pressure was exerted on Imperial College to shuffle him off to a quiet corner, he later found for a long time doors to further research posts in this country firmly closed - all the usual tactics of a scientific establishment when their standing and comfortable certainties are challanged. Laithwaite's point was: nobody understands this. Your attempt at reaching for an explanation is therefore as good as anyone else's, and probably in the right direction, for all I can tell. The next stage would be to explain why the direction of this "flying off" of the wheel should be upwards: and why, when prevented from doing so by Laithwaite holding its shaft, it should manifest this restriction in an apparent loss of weight (instead of what might be intuitively expected, but which Laithwaite clearly states does not occur, a force pulling along the length of his arm.)
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Post by marchesarosa on Sept 8, 2012 12:09:31 GMT 1
Rapidly spinning pieces of metal like lathes, for example, are usually anchored firmly to a very large lumps of concrete so they do not fly off into the air and injure people.
Is this spinning weight of Laithwaite's behaving any differently to a discus propelled into space and hovering there "weightless" until its initial energy is used up, or a conjuror's plate spinning "weightless" on top of a rod? I am just trying to think of equivalent examples of "weightlessness" in association with spin. But I cannot contribute to the debate further than that because I know nothing of all these Newtonian et al "laws" framing the understanding of the phenomenon.
One of the differences between my examples and Laithwaites is that he is using a very heavy weight with a very fast electrically induced spin and by means of a rod and ball bearings is able to keep it "tethered" in a situation when other similarly spinning objects would just fly off into space. Whether currently understood laws of motion do or do not account for this behaviour in a "tethered" spinning object I could not say. But it is certainly "magical" to observe the "trick" in action. My examples have the spinning object parallel to the earth's surface, whereas Laithwaite's object is at right angles to the earth so very counter-intuitive.
Am I right in thinking gravity is a centripetal force keeping stuff attached to our planet and and a centrifugal force is what throws stuff outwards from a spinning body?
Maybe Laithwaite's spinning lump of iron is creating it's own "gravity" which is in opposition to the Earth's gravity and the two forces are repelling each other forcing the smaller object "upwards"?
There, am I helping the discussion on or hindering it with my obtuseness? No scholarly articles have been consulted in the writing of this post!
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Post by striker16 on Sept 8, 2012 14:19:57 GMT 1
Surely, if this was a correct scientific principle, a practical working anti-gravity model would have been made and tested, which is why I'm a bit suspicious about the legitimacy of this idea. Perhaps the energy required to make this technology a practical reality is simply far too great?
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Post by mak2 on Sept 8, 2012 14:56:23 GMT 1
Try this experiment. Stand on some bathroom scales and move around. Your weight will apparently vary. In Prof. Laithwaite's demonstration, he moves the rotor about. Therefore, there is no reason to expect the apparent weight of the object to be the same as when it was at rest.
Newton's 2nd Law says that force is equal to rate of change of momentum. It is quite possible that the changing momentum of the rotor produces an upward force which makes the thing easier to lift.
Although the basic principles are simple.....Newton's Laws of Motion, the problem under consideration is complicated. The rotor can move in three dimensional space and it can also rotate about three axes.... six degrees of freedom. There are four forces acting, gravity, friction, aerodynamic force and the unknown and varying force applied by Laithwaite. I am sure that, if all these things could taken into account, the behaviour of the rotor would be found to be in accordance with Newtonian mechanics.
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