# Anti-Antigravity Demonstration

This page discusses the May 10, 2011 Fun Physics Facts for the Family Demonstration...

• In the first demonstration (Feb 15, 2011) we examined the principle of Conservation of Angular Momentum, and showed how a body will spin in the same orientation unless some external force is applied. Here is a link to the wiki page for this demonstration: FPF-01 Astronaut: Turn Around? .
• In the second demonstration (Mar 15, 2011) we studied the gyroscope, the embodiment of angular momentum, and discussed a simple Newton's Law explanation (here is a link to the wiki page discussing Newton's Laws: FPF Newton's Laws ) for its intriguing behaviors, such as precessional motion. Here is a link to the wiki page for this demonstration: FPF-02 Mystical, Mythical, Magical Gyroscope .
• In the third demonstration (Apr 12, 2011) we continued the examination of the properties of gyroscopes and show how a very clever trick can be employed to produce a compass that always points to the true North direction and always works at all locations and in all vessels. Here is a link to the wiki page for this demonstration: FPF-03 The Most Marvelous Mechanical Machine .
• In the fourth demonstration (May 10, 2011) we yet again continue the study of the magical behaviors of the gyroscope, only this time since we now understand the mechanism underlying these mystical behaviors we endeavor to dispel some of the mythical behaviors attributed to gyroscopes. In particular, a famous British engineer by the name of Eric Laithwaite claimed antigravity capabilities for gyroscopes leading to a plethora of similar claims, and we will debunk these claims. Here is a link to the wiki page for this demonstration: FPF-04 Anti-Antigravity: Eric Laithwaite .

• ## Anti-Antigravity and Eric Laithwaite: May 10, 2011

Eric R. Laithwaite ... is the inventor of the Linear Induction Motor. An electric motor has a rotor with magnets surrounded by a set of electric coils in a circular shape. Alternating the polarity of the current through the coils alternates the signs of the magnetic fields surrounding the rotor. By careful timing of the changing polarity, the rotor can be made to spin. Eric Laithwaite's idea was to take the electric motor, split the coils surrounding the rotor down the middle, and unroll the coils so that they are in a straight line instead of in the shape of a circle. The "rotor" then "spins" in a straight line instead, that is, the "rotor" now moves in a straight line along a track instead of rotating. This is the essence of the linear induction motor.
The following video is an clip from around minute 53 of the James Bond film, The Spy Who Loved Me, showing Q (Desmond Llewelyn) demonstrating a "magnetic river". A metal tray with magnets is suspended above a track of electromagnets by magnetic force and then propelled down the track via the linear induction motor mechanism. You have to understand that this Albert Broccoli film is from 1977, really before, or at the very beginnings of, computer graphics being employed routinely in movies. No, this clip was not produced by computer graphics, it shows a real physical levitation and propulsion system. In fact, this track was made by Eric Laithwaite, and it was "dressed up" a bit for the film by adding a cosmetic box around the electromagnets of the linear track.
Here is the short video clip of Laithwaite's "magnetic river": (Laithwaite-SpyWhoLovedMe_MAGLEV-1080p.mov). [This video includes about a 10 second excerpt from the James Bond movie and thus I cannot upload it to YouTube. In the setting of classroom education, however, I will show this short clip since he shows Eric Laithwaite's "magnetic river".]
Description of the video: In this film clip, Q demonstrates magnetic levitation and the linear induction motor by levitating a metal tray above a track of electromagnets. When the tray is released, it zooms down the track off the end and decapitates a mannikin. This is a real apparatus, built by Eric Laithwaite. It is not computer graphics.
Before we get started, let's perform a quick thought experiment that will help us in our thinking about Professor Laithwaite's subsequent experiments and claims...

## Preliminary Gedankenexperiment:

Let's say the we have a platform scale that measures weights in stones (1 stone = 14 pounds). In the following Figure, Part A shows the scientist standing on the scale. His weight is 10 stone. [The stone is an older British weight measurement equal to 14 avoirdupois pounds. Interestingly, the plural of stone is stones, thus you would ask How many stones do you weigh?' But the plural of the stone unit is stone, thus you answer I weigh 10 stone', not I weigh 10 stones'.] In Part B, a medicine ball is shown to weigh 1 stone.

If the scientist holds the medicine ball, the scale reads 11 stone (Part C), obviously the sum of the two weights. Let's consider what happens when the scientist tosses the ball into the air, as illustrated in Part D. Once the ball is airborne, the scale reads 10 stone, the weight of the scientist (if the scientist is stationary, it can't read any more than 10 stone, the scientist's weight). After the scientist catches the ball, the situation returns to Part C and the scale reads 11 stone once again.

If we consider the time progression of the scale reading, we would see that the scale reading is initially 11 stone while the scientist is holding the medicine ball. When the scientist tosses the ball, the scale reading momentarily increases beyond 11 stone because the scientist must apply a force to accelerate the ball upwards. This is shown as the "toss" in the Figure below. Once the ball leaves the scientist's hands, however, the scale reading reverts to 10 stone, the weight of the scientist. When the ball returns to Earth and the scientist catches it, the scale reading momentarily increases beyond 11 stone as the scientist applies a force on the ball to decelerate it. Once the ball and scientist are stationary, the scale reading reverts to the 11 stone total weight once again.

This is the behavior of the scale (somewhat idealized) that we would expect if we were to actually perform this Gedankenexperiment. Before the scientist tosses the ball, the scale reads 11 stone as labelled with C' , during the toss the scale reads greater than 11 stone, when the medicine ball is airborne the scale reads 10 stone as labelled with D' , during the catch the scale reads greater than 11 stone, and after the catch the scale once again reads 11 stone and is labelled with C' .

This makes physical sense, doesn't it?

## Antigravity:

Numerous arguments for antigravity and free energy have been presented over the past two centuries, really since the very beginning of what we have surmised that energy even means. Here is an argument perpetrated by a famous engineer, the inventor of the linear induction motor (i.e., MAGLEV trains), to his Queen and the Royal Institution at the famous annual Christmas Lectures. It even received an US Patent. See if you can determine if it is real or not...

The Mystical, Magical, Mythical Gyroscope: Eric Laithwaite

Eric R. Laithwaite, Engineering Professor at Imperial College London, invented the linear induction motor (essentially by unrolling the windings of a rotary electric motor) in the 1960s and was instrumental in the early days of the MAGLEV (MAGnetic LEVitation) trains. After the British government canceled its funding of the MAGLEV project, Professor Laithwaite became interested in gyroscopes. In 1974 he was invited by Sir George Porter from the second oldest continuously running scientific research society, the Royal Institution of Great Britain (founded in 1799), to give their annual invited lecture before a distinguished audience of scientists and the Queen. Since the inception of these RIGB lectures, this particular discourse remains the only one that the Royal Institution never published in its Proceedings. During this private lecture, the Professor performed numerous demonstrations of the gyroscope and its behaviors, making some fantastic claims along the way. The private RIGB lectures are always followed by public lectures in front of an audience of young students; these are called the Christmas Lectures. During Laithwaite's subsequent public Christmas Lecture before an audience of children, Professor Laithwaite performed the following demonstration. He had an 18 lbf gyroscope wheel mounted upon a 6 lbf three foot long bar. He asked a young boy to try and lift the non-spinning gyroscope and hold it in horizontal position by holding onto the end of the roughly 3 ft handle. Of course, the boy could not do so because of the weight of the gyroscope and the requisite torque needed to raise the gyroscope horizontally using only the end of the handle bar. After the gyroscope was spun up to about 2,000 rpm, another young boy was able to hold the gyroscope in a horizontal position. Professor Laithwaite implied that somehow the gyroscope was avoiding gravity; he even went so far as to say that Newton had gotten it wrong, that Newton's Laws only applied to things in linear motion and not to objects that were rotating. So, who was right, Sir Isaac Newton, a favorite son of the British, or Professor Laithwaite, a distinguished engineer and a professor at a respected British university?

Here is the RIGB video of Professor Laithwaite demonstrating the antigravity effects of a rotor, see if you can help explain how this works without the need for antigravity: (Laithwaite-Xmas_18lb-1080p.mov). [Because this video includes a short excerpt from the RIGB video and it is not clear who owns copyright on the RIGB video, I will not upload this video to YouTube. Rather, in a classroom educational setting, I will show this short video clip so that we can learn how to best argue against such claims of antigravity.]

Description of the video's experiment: This video shows a small boy, Dennis, who is strapped to a platform that can be rotated by a crank. An 18 pound rotor on a 3 foot handle weighing an additional 6 pounds is handed to another boy who is asked to hold the rotor horizontal with his hands only at the end of the handle. The boy obviously cannot generate enough torque with his hands to do so. The rotor is then spun up to speed and the handle handed to Dennis. Professor Laithwaite then turns the crank to spin the platform on which Dennis is strapped. Dennis is able to hold up the rotor in a horizontal direction with his hands only at the end of the 3 foot handle. Professor Laithwaite then claims that the rotor has lost weight, otherwise Dennis would not be able to hold it up.

Puzzler: What was Professor Laithwaite's error, and can you explain his demonstration with the 18 lbf gyroscope without violating Newton's Laws?

[By the way, Professor Laithwaite's Christmas Lecture at the RIGB was taped by either by the RIGB or the BBC and has been made available online at www.gyroscopes.org. The Christmas Lecture videos are unattributed as to their source (I assume they are copyrighted by the RIGB). The BBC also made a 30 minute special documentary entitled "Heretic". It is quite interesting to watch each of the Professor's experiments and then figure out how to argue against each of his contentions. The question is, was there something more sinister in the Professor's demonstrations?]

Also it should be noted that, in 1975, Professor Laithwaite was not considered to be a "crank". He had been awarded a PhD in engineering, was a Professor of Heavy Electrical Engineering at the Imperial College London, and he had won numerous international honors for his engineering accomplishments.

Hint: Recall the qualitative explanation of the behavior of a gyroscope.

Solution: The solution to this portion is provided after the following "Short Video Clip from the BBC Heretic Documentary" and the "Simple Experiment" topics...

## Short Video Clip from the BBC "Heretic" Documentary:

Before we answer the above Puzzler, let's consider another argument given by Eric Laithwaite. The 1994 BBC film documentary, written and produced by Tony Edwards and narrated by Rosemary Hartill, was entitled "Heretic". The film raised the question as to whether there was anything real to Eric Laithwaite's claims of antigravity. It made analogy to Galileo who was branded a heretic for espousing the Copernican heliocentric system. Was Laithwaite also being unjustly branded a heretic without cause? Perhaps Laithwaite really had invented something that produced antigravity!?!

Let's examine a short clip from this BBC documentary (minutes 22:50 - 25:01): (Laithwaite-Heretic_GyroWeightLoss-1080p.mov). [Since this video includes a short, roughly 2 minute, excerpt from the BBC Heretic documentary, I will not upload this video to YouTube. Rather, in a classroom educational setting, I will show this video clip so that we can learn how to argue against Laithwaite-like claims of antigravity for gyroscopes.]

[Note that this film is not available on the BBC website. This clip is an excerpt taken from the 28 minute video located on the www.gyroscope.org website. The video on this website is very poor quality; this website also does not document how it was obtained. The original film was copyrighted by the BBC.]

Description of the video's experiment: Notice that in this clip Eric Laithwaite is shown standing on a scale lifting a 50 pound rotor and axle. The spinning rotor swings up and over Laithwaite's head, and a plot of the scale reading is recorded. Laithwaite describes what the graph illustrates, that the weight seemed to get lighter as the rotor swings up and over his head... Is this gyroscopic antigravity?
Eric Laithwaite claims that it is! He claims that he has now demonstrated what he set out to show, that gyroscopic action can produce an antigravity effect.

Professor Laithwaite states in this video clip from the BBC documentary, "Of all of the critics that I showed lifting the big wheel, none of them ever tried explaining it to me." [Laithwaite make this statement immediately before he demonstrates the "weight loss" by the big wheel in the BBC "Heretic" documentary. I find it disingenuous that Professor Laithwaite made this statement since at the time of his 1974/5 Christmas lectures a number of physicists did attempt to explain to him, both in person and in print, why his antigravity ideas were nonsensical.]

Having learned how gyroscopes operate, let's see if we can explain these reputed antigravity effects for Professor Laithwaite.

Rebuttal Argument: With our understanding of the behavior and mechanism of the gyroscope (recall Newton's Law explanation of the gyroscope from the March 15, 2011 "The Mystical, Mythical, Magical Gyroscope" Demonstration (here is a link: FPF-02 Mystical, Mythical, Magical Gyroscope ), we can understand precisely what is happening in Laithwaite's experiment. Recall that one way of understanding the behavior of a gyroscope is to realize that the gyroscope acts like a "force mirror", reflecting an incoming force to yield an outgoing force oriented at 90 degrees to the incoming. An input force along one axis results in an output force along a perpendicular axis, in other words. As an example, recall the gyroscope supported by a string holding only one end of its horizontal axle. The other end is free. The force of gravity acting on the gyroscope pulls in the vertical direction, but after "reflection" the result is a horizontal precession of the gyroscope instead of a vertical falling. What would happen if the initial force applied to the spinning gyroscope is horizontal? Then after "reflection" the output force would be perpendicular to the input horizontal force, or, in other words, it would be vertical. The precession resulting from a horizontal thrust would be in a vertical plane.

If we now look closely at the video clip, you will notice that Eric Laithwaite at the start gives the rotor quite a hefty horizontal shove. The spinning rotor, of course, "reflects" this horizontal shove yielding a vertically directed force producing a precession in the vertical direction and causes the scale to initially increase its reading during the time interval of the horizontal shove. This vertical precession is viewed as a "lifting" of the gyroscope. And as the video clip shows, the weight measured by the scale fluctuated as the rotor performed its motion: first the weight went up, then it dropped, bottoming out at some value, then it increased once again to the maximum (as the Professor "catches" the gyroscope coming down stopping its precession) before dropping to its initial value. Laithwaite interpreted this chart to mean that the gyroscope was displaying an antigravity effect, but we see that it is nothing more than the graph drawn for our Gedankenexperiment described above, that is, Laithwaite's graph from the BBC documentary is simply a non-idealized version of the following plot.

Thus we see that we can understand Eric Laithwaite's experiment without invoking gyroscopic antigravity! In fact, our simple Newton's Law explanation for the actions of a gyroscope is enough to fully explain Laithwaite's mysterious "antigravity effect" and debunk his argument: the Professor's initial horizontal shove of the spinning rotor causes a precession in the vertical plane that the Professor claims is an antigravity effect while it is nothing more than normal precessional motion. In fact, at the end of the above video clip you will notice that Laithwaite and Dawson attempt to perform the gyroscope "lift" experiment in a "hands-off" fashion. But, once again, from a close examination of the video you will see Laithwaite quickly shove the housing holding the precessing spinning rotor horizontally with quite the force. This horizontal force that the Professor applies speeds up the precessional motion and is converted by the spinning rotor to a vertical force that produces the lift you see in the video. Once again, there is nothing miraculous about this behavior of a spinning rotor, it is all predicted by our simple Newton's Law explanation of the operation of a gyroscope (link: FPF-02 Mystical, Mythical, Magical Gyroscope ). Laithwaite, on the other hand, stated in print in a number of articles he published in the 1970s and 80s, and expressed verbally during his 1974/5 Christmas Lectures and the BBC documentary, that Newton's Laws were not applicable to rotary motion and that Newton's Laws had to be modified in order to explain gyroscopic action. This is not the case! Newton's Laws (link: FPF Newton's Laws ) are fully capable of explaining, both qualitatively and quantitatively, these remarkable behaviors of the gyroscope. The gyroscope is not mystical, mythical, nor magical. It is a classical object that obeys Newton's Laws, and these laws predict some rather amazing, perhaps even counterintuitive, properties and behaviors.

Now you may be worried about the apparent slowness of the motion of the rotor above Professor Laithwaite's head. Well, as we have already demonstrated in the Mystical, Mythical, Magical Gyroscope Demonstration (link: FPF-02 Mystical, Mythical, Magical Gyroscope ), the precession rate is inversely proportional to the rotor spin rate, and thus for a fast spinning rotor, the precession rate is quite slow. Thus, even though, as the Professor claims, the motion is slow and smooth, this does not mean that it is antigravity. Rather the precessional motion that the Professor claims to be antigravity is slow simply because the rotor spin rate is fast. The thing to notice in the video is the effort that Laithwaite puts into thrusting the spinning rotor horizontally to the side. The force from this effort is what produces the precessional motion that causes the rotor to slowly loop over the Professor's head. Recall from the Mystical, Mythical, Magical Gyroscope Demonstration that one way of viewing precessional motion is to think of the gyroscope as a type of "force mirror", it takes an input force along one direction and "reflects" it to an output force along a perpendicular direction. Laithwaite thrusts the 50 lb rotor in the horizontal plane but this horizontal force gets "reflected" into the vertical force causing the rotor's precession. This precessional force produces the drop in measured weight on the chart recorded. It is as if the Professor heaved the rotor vertically into the air, then the scale weight would have dropped just as in our Gedankenexperiment above, but because of the gyroscopic effect, the Professor did not have to heave the rotor vertically, he had to thrust it horizontally to achieve the same thing.
[I believe that Laithwaite is being deceptive in his demonstration. If you watch carefully, you will notice that he has to wind-up in order to swing the 50 pound rotor horizontally with enough force to have it swing up and over his head. He must have known that this force was what was causing the apparent easy overhead motion of the rotor, but instead he attributes it to antigravity effects and records the "weight loss" on a chart recorder.]

This gyroscopic action displayed in the BBC documentary is NOT antigravity!

## Simple Experiment:

Weighing the bicycle wheel on a spring balance yields a weight of 30N:

If we support the opposite side of the wheel's axle on the back of a chair, the balance weight drops by a factor of 2 to a value of 15N:

The spinning wheel, even though it appears that the opposite side of the axle is being supported by some mysterious force, still weighs 30N:
There is no weight loss due to the gyroscopic effect, in other words...
Here is a video (Gyroscope-No_Weight_Loss-1080p.mov) of the wheel weighings.
(YouTube encodes the video at a number of different resolutions.)

Description of the video's experiment: In this video clip a spring balance scale is employed to measure the weight of the bicycle wheel. When the wheel is not spinning it hangs vertically from the scale and weighs 30N. If we support the axle opposite to the balance scale on the back of a chair, the scale reading drops by a factor of 2 to 15N (the chair supports half of the weight and the scale supports the other half). When the wheel is spinning, it appears that some mysterious force is "holding up" the opposite side of the axle, but instead of the scale reading 15N it reads the full weight of 30N.

## Solution to the Initial Christmas Lecture Demonstration:

And now we return to discuss Professor Laithwaite's demonstration where a boy, Dennis, is shown to be capable of holding up a 24 lb spinning rotor holding onto only one end of its axle.

An 18 lbf weight at the end of a roughly 3 ft handle would require a simply colossal torque to be applied by the hands to keep the unspinning gyroscope horizontal, as shown in Figure. Professor Laithwaite specifically requests the first boy to keep his hands together at the end of the handle while he attempts to lift the gyroscope. In this case the boy’s hands must supply the torque countering the torque from the gyroscope’s weight. But the force from the gyroscope’s weight is about 36 in from the fulcrum about which the Professor is asking the boy to keep the gyroscope from rotating. The boy’s hands, on the other hand, are approximately only 3 in from the fulcrum. In order to get a rough-and-ready idea of the force that must be supplied by the first boy, we neglect the weight of the handle and concentrate just on the weight of the gyroscope rotor itself.

In order to hold the unspinning gyroscope in a horizontal static position, the forces acting on the gyroscope must cancel. Specifically, this means that the vertical force of gravity acting on the rotor, F_G_CM , must be counterbalanced by the two forces stemming from the boy’s hands, the upwards pull F_H_u and the downwards push F_H_d . Written as an equation, in order to balance the vertical forces we must have

0 = F_H_u − F_H_d − F_G_CM

where we have taken all three forces as positive and then employed + or − signs to indicate the directions up or down, respectively. Thus

F_G_CM = F_H_u − F_H_d

This means that for the boy, his pull upwards with one hand must be 18 lbf greater than his push downwards with his other hand. At the same time, the torques generated by all three of these forces must also sum to zero, otherwise the gyroscope will not be static. Thus we must also have a net zero torque, or

0 = F_H_u(3 in) + F_H_d(3 in) − F_G_CM(36 in)

where again the directions of the torques are indicated by signs. Solving the zero net vertical forces equation for F_H_d and substituting this into the zero net torques equation, we find

F_H_d = F_H_u − F_G_CM

and then

0 = F_H_u(3in) + (F_H_u − F_G_CM)(3in) − F_G_CM(36in)

= 2F_H_u(3in) − F_G_CM(3in+36in)

Solving this last expression for F_H_u we find

F_H_u = F_G_CM(39in)/2(3in) = (13/2)F_G_CM

And substituting 18 lbf for F_G_CM we find

F_H_u = (13/2)(18 lbf ) = 117 lbf

and

F_H_d = 117−18 = 99 lbf

Consequently, the boy would have to supply roughly 117 pounds of upwards force with one hand while supplying 99 pounds of downwards force with the other hand in order to neutralize the torque caused by the rotor’s weight and keep the gyroscope held level in a horizontal plane. Since the young boy was incapable of supplying such large forces with his hands, he was not able to hold the gyroscope in a level position. (Note: If we had taken into account the weight of the handle bar, then the required hand forces would be even greater than those listed above.)

Of course the small boy was unable to supply such large hand forces to counteract the torque from the weighty gyroscope. An adult would even have a difficult time of it.

But the Professor continues with his demonstration, strapping another boy to a swiveling platform, spins up the gyroscope to speed, and hands it to the boy suggesting to him that he hold his arms close to his body. The boy “miraculously” (but only miraculous to someone not understanding the physics) holds the gyroscope out horizontally. How is this possible? (above are a photograph and a video of a gyroscope performing a similar feat of supporting itself on a long handle.)

Well, from our simple argument based upon Newton’s Laws we interpret the falling of a mass element of the spinning rotor produced by the torque stemming from the weight of the gyroscope to be canceled a moment later after a rotation of 180 degrees by a similar falling motion but which is now oriented in the opposite direction. This cancels the rotation of the gyroscope in the vertical plane, what we would calling a “falling” motion. The only motion that is not canceled is the motion after a 90 degree rotation, and this motion leads directly to the precession of the gyroscope around its support. See the solution on the webpage:

for a detailed discussion of this argument. Essentially, the boy only had to support the weight of the gyroscope and handle, a total of 24 lbf, in the vertical direction. The boy did not have to supply the torque countering the rotor’s weight since the action of the gyroscope was already supplying this counter torque. Note that the Professor tells the boy to hold his arms close to his body, this is because it is much easier to hold up a 24lbf weight when it is close to the body than when it is held out away from the body. I think this comment by the Professor is most telling; he wouldn’t have told the boy to hold it close to his body if he really believed that the gyroscope was somehow avoiding gravity, rather the Professor knew that the boy had to hold up the entire 24 lbf weight of the gyroscope in his hands, and the boy would be better able to carry this weight if he held his hands close to his body. But the Professor alludes to this gyroscope action as a type of avoiding gravity effect. It is no such thing, the gyroscope and handle still weigh 24 lbf even when spinning, this demonstration just shows that the gyroscope supplies the countering torque so that it doesn’t fall, and the energy for this force comes from the rotational motion of the rotor. Once again, there is nothing magical about this once you understand the underlying physics. A little later, when we discuss a NASA report reputing to debunk Laithwaite’s claims, we will provide a proper physics explanation of this gyroscopic action.

Also, if the boy had not been placed upon a rotating base, he could not have held the gyroscope against its precessional motion and probably would have dropped it. But, two things saved the boy and the demonstration. The first is that by placing the boy on a rotating base, the base would take up the precessional motion of the gyroscope. And secondly, by spinning such a large and weighty rotor to such a high angular velocity meant that the angular momentum was quite large and therefore the precessional motion was quite small and thus not nearly so noticeable during the Professor’s demonstration.

During his lectures, Professor Laithwaite proposed three chief polemics concerning gyroscopes and Newton which he attempted to experimentally demonstrate. First of all, he believed that a gyroscope’s precession is not attendant by a centrifugal force, as he attempted to demonstrate using a gyroscope supported by a 300 times lighter “Eiffel tower” (see the fourth and fifth video clips of the Christmas Lecture on www.gyroscopes.org). In other words, a gyroscope’s rotary precession does not generate any centrifugal force. Secondly, Professor Laithwaite believed that the angular momentum of precession is not conserved, that it was somehow considerably smaller than what one would calculate from Newton’s equations using the moment of inertia (mass distribution) of the gyroscope (see video clips 6, 7, 12, and 15). He believed that it required no force to stop the precessional motion of a gyroscope, that the precession could be stopped instantaneously by an “infinite” acceleration that required no force[13]. And lastly, the Professor contended that if the precession is speeded up, the gyroscope will rise without there being any consequent downward reactive force (essentially antigravity, in other words; see video clips 8 and 10, for example). And, according to Professor Laithwaite, his demonstrations reputedly proved these polemics, all of which directly violated Newtonian Mechanics. But the demonstrations didn’t prove any of the three, and, in particular, it is my opinion that Professor Laithwaite knowingly performed his demonstrations in a manner to hide from view the actual behaviors of the gyroscope in an effort to deceive his audience and convince them of his polemics. On the other hand, if his experiments had been performed in a more controlled fashion, then all of his mysteries would vanish into thin air, and the gyroscope would be found to follow Newton’s Laws.

I leave you to view the other video clips and make your own arguments against the “no angular momentum” and “infinite accelerations” that the Professor states and attempts to demonstrate. As I mentioned above, after viewing these videos, I was left with the distinct impression that this is not just pseudoscience where a researcher is naively fooling himself, rather this constitutes fraud where a charlatan is purposely deceiving his audience. And this is especially not a case of a scientific “heretic”, someone being squelched by the scientific establishment simply because his ideas are revolutionary (a la Copernicus), as implied by the title of the BBC documentary on Professor Laithwaite. Professor Laithwaite, in answer to the critics of his private lecture at the RIGB, quoted in his Christmas Lecture the famous physicist Freeman Dyson: “Most of the crackpot papers that are submitted to the Physical Review are rejected, not because it is impossible to understand them, but because it is possible. Those that are impossible to understand are usually published.” (Freeman Dyson, “Innovations in Physics”, Scientific American, September 1958.) Professor Laithwaite also liberally quotes from Lewis Carroll’s Through the Looking Glass, implying that physics is mysterious and mythical. The Professor was especially fond of quoting "Jabberwocky".

The following PDF file gives further details on Professor Laithwaite's Christmas Lectures and his antigravity claims:

Eric Laithwaite also claimed, in both print and during his lectures, that torques applied to spinning gyroscopes produced infinite (or nearly infinite) accelerations and decelerations. Here is a snippet from the 1974/5 Christmas Lectures where the Professor claims extremely large acceleration/deceleration: (Laithwaite-Xmas_InfA-1080p.mov). [This video includes a short excerpt from the RIGB 1974 Christmas Lecture and it is not clear who own copyright on this video so I will not upload it to YouTube. Rather, in a classroom educational setting I will show this short excerpt so that we can learn how best to argue against the infinite acceleration claim of Laithwaite.]

Description of the video's experiment: In this video Professor Laithwaite hangs a weight from the gimbal ring of a gyroscope. This causes the gyroscope to precess about the vertical axis. As the gyroscope precesses, the Professor "catches" the weight and the precession stops immediately, apparently instantaneously. Laithwaite then claims that the angular momentum of the precessional motion vanished almost instantaneously, and that in order to do so requires a simply enormous acceleration.

See if you can argue for or against the Professor's argument. Hint: Recall the Mystical, Mythical, Magical Gyroscope Demonstration (link: FPF-02 Mystical, Mythical, Magical Gyroscope ) where we found that a torque applied to the axle of a gyroscope produced a precessional motion in the perpendicular plane, but when the torque is zero the gyroscope does not precess. So torque = precession while no torque = no precession. In mathematical terms, the equation that expresses this fact is \Gamma = \dot{L} where \Gamma is the torque and \dot{L} = dL/dt , the rate of change of the angular momentum L .
Solution: Laithwaite claims that the acceleration/deceleration of the gyroscope's precessional motion is enormous. At one point he even claimed that the acceleration is infinite. He attempts to demonstrate this by "picking up" the weight supplying the torque to the gyroscope's spin axis, the precession appears to stop immediately. But this is not the deceleration of a moving inertial mass, as he implies. Rather it is the cessation of the change in the angular momentum vector of the spinning rotor. Recall that a torque ( \Gamma ) causes a change in the angular momentum ( L ). In fact, the rate of change of the angular momentum is equal to the torque: \Gamma = \dot{L} where \dot{L} denotes the time rate of change (first time derivative dL/dt) of L . In words, the angular momentum does not change unless there is a non-zero torque, or a non-zero torque causes the angular momentum to change. Without a torque, the angular momentum is constant -- this is the famous Conservation of Angular Momentum that we discussed during the Astronaut: Turn Around? Demonstration (link: FPF-01 Astronaut: Turn Around? ). So let's apply this to Laithwaite's demonstration. When the weight is suspended from the gyroscope's gimbal, it applies a torque to the spinning rotor's axle. This torque causes the rotor's angular momentum vector to change continuously - we see the changing angular momentum vector appears as the precessional motion. When the torque vanishes, the rotor's angular momentum no longer changes, it is constant. We see this as the cessation of the precessional motion. No torque means a constant angular momentum vector for the rotor which means that the gyroscope is not precessing. The precessing stops just as quickly as the torque stops since the change in the angular momentum vector is caused by the torque. The Professor is confusing inertia with angular momentum. The angular momentum vector, without any externally applied torque, is constant and so there is no precessional motion. When there is an applied torque, this torque changes the angular momentum vector producing what we see as the precessional motion. The precessional motion is not a type of "inertial motion" that undergoes an infinite deceleration when the torque is removed. Rather the "inertia" of the spinning rotor, its angular momentum, remains constant (no precession) unless a torque is present. There is nothing mysterious about this, it follows directly from Newton's Laws. There is no infinite acceleration/deceleration. The precessional motion stops just as quickly as the torque is removed from the gyroscope.

In another film clip from Laithwaite's Christmas Lectures, he claims that the precessional motion is reactionless, that is, that there is no reaction to the gyroscope's movement. He attempts to show this by placing a 300 gram gyroscope on a 1 gram tower and watching the heavy gyroscope precess around the tower instead of the light tower revolve around the gyroscope. He then says, "Friction on the table. I can hear my critics now. He has friction." Laithwaite then places the tower on ice and claims that there is only a minuscule amount of friction. Based upon this, the Professor claims that there is no reaction to the movement of the gyroscope. Here is the video clip: (Laithwaite-Xmas_NoReaction-1080p.mov). [Since this video includes a short excerpt from the RIGB 1974 Christmas Lecture and it is not clear who owns the copyright, I will not upload this video to YouTube. Rather, in a classroom educational setting, I will show this short excerpt so that we can learn how best to argue against the "reactionless" claims of gyroscope antigravitists.]
Description of the video's experiment: In this film clip from Laithwaite's Christmas Lectures, he claims that the precessional motion is reactionless, that is, that there is no reaction to the gyroscope's movement. He attempts to show this by placing a 300 gram gyroscope on a 1 gram tower and watching the heavy gyroscope precess around the tower instead of the light tower revolve around the gyroscope. He then says, Friction on the table. I can hear my critics now. He has friction.'' Laithwaite then places the tower on ice and claims that there is only a minuscule amount of friction. Based upon this, the Professor claims that there is no reaction to the movement of the gyroscope.

See if you can argue for or against the Professor's demonstration. Hint: Watch the video carefully, especially the slow motion part.
Solution: A careful viewing of the demonstration shows that the tower wobbles as the gyroscope precesses. At one point the gyroscope even topples the tower. This means that indeed there is a reaction to the gyroscopes movement, and the tower resists this through friction with the tabletop. The so-called "frictionless" ice block experiment is a red herring, as when this experiment is performed under controlled nearly frictionless conditions, say on a air table, on wet ice, and even on a field of ball bearing balls, the center of mass of the system stays put while the gyroscope and its tower support revolve around their center of mass. The gyroscope does not violate Newton's Laws, in other words: there is no "reactionless"-ness to the gyroscopic effect. Rather there was much more friction in Laithwaite's ice block demonstration than the Professor admits to having - it was not "frictionless" as he claims. Of course, it is precisely this so-called "reactionless" gyroscopic behavior that led to reactionless propulsion engines for space travel that Laithwaite and Dawson obtained an US Patent for in 1999.
[The videos of Professor Laithwaite's Christmas Lecture are available on the www.gyroscope.org website. This website does not provide the source of the videos nor how they were obtained, thus I assume that they were recorded either by the RIGB or the BBC, and copyrighted by the RIGB.]

## Summary:

• Gyroscopes display some unusual and perhaps counterintuitive behaviors, but these behaviors do not violate Newtonian Mechanics.
• These gyroscopic behaviors not only follow Newton's Laws, a simple Newton's Law Explanation predicts both their qualitative nature (directions of motion) and quantitative characteristics (functional dependencies of the precessional motions on rotor spin rate and applied torques).
• Eric Laithwaite's demonstrations of gyroscopic antigravity are deceptive and even fraudulent, as a careful viewing of the RIGB Christmas Lectures and the BBC "Heretic" documentary show.
• Eric Laithwaite claims antigravity effects, reactionless mass transfer, and infinite acceleration effects for gyroscopes and he has stated, in print and during interviews, that these effects violate Newton's Laws. This is not the case, all of the effects that Eric Laithwaite claims violate Newton's Laws in fact can be readily explained by Newton's Laws. (Unfortunately, there are a number of individuals who have taken up Laithwaite's causes and continue to claim antigravity and reactionless effects for gyroscopes, even obtaining patents on these.)

And now for this month's Puzzler solution...

• ## A Mysterious, Magical, Mythical Coin Discovered!

How many revolutions will the 1992 quarter make as it is rotated around another quarter? The knurled edges of the quarters mean that there is no slippage during this operation; it is just as if the quarters were two gears with meshed teeth.

If you were to roll the 1992 quarter all the way around the 1991 quarter so that it returns to its position as shown, then how many rotations, or revolutions, will the 1992 quarter make during its travels around the 1991 quarter? In other words, how often will the head turn over during its roll? Please carefully explain your answer. That is, I want to know why your answer is what it is. I don't want you to just say that when I did the experiment with two quarters, this is what I found. I want you to explain, as best as you can, why you found the result that you obtained empirically.

If you answered 1 (perhaps you said to yourself, "the 1992 quarter is making one circuit around the 1991, so it must make one revolution"), would you believe that I have found a magical quarter that revolves twice during this trip? And I'll sell my magical quarter to you for only 50 cents!

If you do not wish to see the explanation for the coin revolution problem at this time, then skip the following Coin Rotation Explained link, Coin Rotation Explained , to arrive at the actual Puzzler.

And now for the actual Puzzler:

## Puzzler: How long is a Sidereal Day?

The Earth orbits the Sun once in 365.2422 Solar Days (24 hour days), roughly. A Sidereal Day (sidere is Latin for star) is the time it takes the Earth to spin 1 revolution about its axis relative to the distant stars (and therefore not relative to the Sun). If I told you that the rotation direction of the Earth around its axis is the same direction as the Earth's orbit around the Sun, then calculate the length of a Sidereal Day (how many hours, minutes, and seconds in a sidereal day?).

Hint: Remember the Coin revolutions!

The following PDF explains and calculates the length of a sidereal day to within 1/100th of a second:

If you enjoyed the geometrical thinking that went into the above Sidereal Day Puzzler, then you will also enjoy the following Puzzler that really tests your 3-dimensional thinking capabilities...

• ## Dance of the Sun, Earth, and Moon

Knowing six simple facts allows one to determine the geometry of the spins and orbits of the Earth, Moon, and Sun around each other. For instance, the fact that the Sun rises in the East and sets in the West, and the solar day is much shorter than the year, allows us to conclude that from a viewpoint above the North pole the Earth spins in a counterclockwise direction.
Knowing that the sidereal day is slightly shorter than the solar day allows one to determine the direction of the Earth's orbit around the Sun.
Likewise, with the knowledge that the synodic month is longer than the sidereal month, one can find the orbital direction of the Moon around the Earth. And observing that we only see one side of the Moon from the Earth allows us to determine the direction of the Moon's spinning.
Now that we have calculated that the Sidereal Day is shorter than the Solar Day (previous Puzzler), using this information in conjunction with the fact that you know the Sun rises in the East and sets in the West, determine the direction that the Earth orbits the Sun.

We turn now to studying the orbital motions of the Moon. First of all, let's discuss the phases of the Moon and what they mean for the positioning of the Earth, Moon, and Sun, shall we?

Can you "see'" a new Moon at midnight? Draw a diagram to help explain your answer. And lastly, why can we sometimes "see" a very, very dim disk of the new Moon anyway? Where does the light come from, are there lights on the Moon?

Please sketch a diagram showing the relative positions of you (the observer), the Earth, the Moon, and the Sun during a full Moon, a new Moon, a crescent Moon, a gibbous Moon, and a half Moon.

Can you ever see the lunar eclipse of a crescent Moon?

Goodness, you certainly are getting good at thinking through these 3-dimensional problems! You have done a magnificent job! Let's exercise some of your 3-dimensional prowess by continuing on to the Moon's orbital motion.

What is known as the Synodic Month is the time taken by the Moon to orbit the Earth, as measured from new Moon to new Moon. The Sidereal Month, on the other hand, is the period of the Moon's orbit relative to the fixed stars. If I told you that the Synodic Month was longer than the Sidereal Month, please determine in which direction the Moon orbits the Earth.

There is one more interesting motion of the Moon. I'm sure you have noticed that whenever you gaze at the Moon, you always see the same side. In fact, there have only been a handful of humans who have ever personally seen the other side of the Moon (specifically, the Apollo astronauts who have orbited the Moon). Now for the question, does the Moon also spin about its axis?

All of these questions and more are answered in the following PDF file: