At this point in my research, I can’t think of a more unscientific parlour trick than the plumb bob swung from a height which is heralded as the pinnacle of proof for the spinning ball earth.
If you are satisfied that the pendulous proof posited by Foucault is undeniable evidence of the rotation of a ball earth, then this blog is probably not for you. However, if you’re interested to learn that these parlour tricks run slow, fast, clockwise and anti-clockwise, rarely display the correct rotation rate and are often powered by motors with controls – then read on….
Engraving in L’Illustration of Foucault’s pendulum in the Panthéon in 1851.
Below is poor Roger Bowley, a University of Nottingham Professor, desperately fighting his common sense whilst trying to explain the principles of the Foucault Pendulum. At one point he even swears when describing the need for the inclusion of a motor to drive it.
[Don’t miss his brain fart near the end when the paradoxes of the heliocentric universe start to break down]
You put a little motor in the top and give it a little jiggle…
Read the rest below and see how they rationalise the inclusion of motors (they conceal in the roof) to run the pendulum
Title: The New Foucault Pendulum at Monash University
Authors: Moppert, C. F. & Bonwick, W. J.
Journal: Quarterly Journal of the Royal Astronomical Society, Vol. 21, P. 108, 1980
It would seem that even the most outwardly ardent heliocentric personalities such as the 7th Astronomer Royal George B. Airy and Reverend Baden Powell, Savilian Professor of Geometry at Oxford University had views about Foucault’s pendulum in private that were diametrically opposed to their public espousals 
This, however , is what the public heard
Other’s were less malleable to the Establishment’s position:
“Astronomers have made experiments with pendulums which have been suspended from the interior of high buildings, and have exulted over the idea of being able to prove the rotation of the Earth on its ‘axis,’ by the varying direction taken by the pendulum over a prepared table underneath – asserting that the table moved round under the pendulum, instead of the pendulum shifting and oscillating in different directions over the table! But, since it has been found that, as often as not, the pendulum went round the wrong way for the ‘rotation’ theory, chagrin has taken the place of exultation, and we have a proof of the failure of astronomers in their efforts to substantiate their theory.” -William Carpenter, “100 Proofs the Earth is Not a Globe”
“First, when a pendulum, constructed according to the plan of M. Foucault, is allowed to vibrate, its plane of vibration is often variable – not always. The variation when it does occur, is not uniform – is not always the same in the same place; nor always the same either in its rate or velocity, or in its direction. It cannot therefore be taken as evidence; for that which is inconstant cannot be used in favor of or against any given proposition. It therefore is not evidence and proves nothing! Secondly, if the plane of vibration is observed to change, where is the connection between such change and the supposed motion of the Earth? What principle of reasoning guides the experimenter to the conclusion that it is the Earth which moves underneath the pendulum, and not the pendulum which moves over the Earth? What logical right or necessity forces one conclusion in preference to the other? Thirdly, why was not the peculiar arrangement of the point of suspension of the pendulum specially considered, in regard to its possible influence upon the plane of oscillation? Was it not known, or was it overlooked, or was it, in the climax of theoretical revelry, ignored that a ‘ball-and-socket’ joint is one which facilitates circular motion more readily than any other?” -Dr. Samuel Rowbotham, “Earth Not a Globe, 2nd Edition”
“2. But did not Foucault’s pendulum prove that the earth revolves in twenty-four hours upon its axis? In the introduction to Ray’s Elements of Astronomy Mr. Peabody calls it “a beautiful experiment.” Andrew White triumphantly exclaims: “And in 1851 the great experiment of Foucault with the pendulum showed to the human eye the earth in motion around its own axis.” (Warfare, 1900, I, p. 157.) Let us glance briefly at the instrument called the pendulum. Foucault’s pendulum had a sixty-one pound ball on a steel-wire 223 feet in length. If we let a pendulum occillate in a direction north and south, then will its even oscillation, as Foucault assumes, be unaffected by the rotation of the plane, and consequently the earth will move ahead below its swinging-line. Now, if this is to prove the rotation of the earth, the deviation of the earth below from the swinging-line of the pendulum must be in all cases the same. But the trouble is, the deviation is not the same with all pendulums. The heavier the bob, the slower becomes the deviation of the pendulum; the lighter the bob, the more rapidly the deviation. Since the rotation of the earth upon its axis, if existing, must be a uniform one, necessarily with all pendulums the deviation should be uniform; but this is not the case. Or does the earth move with different velocity under different pendulums?
Dr. Schoepffer, an eye-witness of the experiment, says: “In an introductory speech Dr. Menzzer at Quedlinburg showed that until then there had been no proof for the Copernican hypothesis, the so-called proofs being, after close investigation, just as many confutations, until the Foucault pendulum showed the rotation of the earth uncontrovertibly. The pendulum was tied, the string was burnt, the swingings began, but the pendulum deviated to the left, instead of to the right. It was hastily brought to rest. New burning of the string. This time the deviation was the one desired, and we were invited again to be present in the church the next morning at eight o’clock, to be convinced that the deviation agrees with the theory. On the following morning, however, we saw that the pendulum during the night had changed its mind, and had from the deviation to the right again returned to the left. To me this new proof did not seem to be quite in order. My belief in the Copernican doctrine was shaken by the speech of Dr. Menzzer, and I concluded to go to Berlin for an explanation.
After seeing the pendulum-experiment here also and, strangely, again with a deviation to the left, I went to Alexander v. Humboldt, who was indeed ever the first refuge of those seeking information. He received me very friendly and spoke the memorable words: I have known, too, for a long time, that as yet we have no proof for the Copernican system, but I shall never dare to be the first to attack it. Don’t rush into the wasps’ nest. You will but bring upon yourself the scorn of the thoughtless multitude.”
Furthermore, I have found, by careful experiments, that a skillful experimenter can let the pendulum deviate either to the left or to the right. And we must not overlook the fact that the deviations may be caused by air-currents, electricity, earth-magnetism, special apparatus, and perhaps many other causes. Blunt and Cox observed the most curious and contrary swingings. Phillips of New York found very great hourly deviations in the swinging-line. Walker observed a peculiarly swift deviation when the pendulum swings in the magnetic meridian. D’Oliveira at Rio de Janeiro stated that the pendulum deviates to the right in the direction of the meridian, but to the left in the direction of the parallel. This deviation, diametrically opposed to the theory, was seen very often. And sometimes the pendulum does not deviate at all. Much more could be said against this “beautiful experiment.” Though beautiful it may seem to the theorist, it certainly is far from being irrefragable evidence for the earth’s motion.“
Fifty Reasons Copernicus or the Bible – Philosophy & Vain Deceit or True Science? Which is Right? by FE Pasche 1915
There’s a slight problem with the Parlour Trick Pendulum, in that it gets effected by eclipses…go figure
Mathematical mysteries: Foucault’s pendulum and the eclipse
In reality eclipses are not the only factors that affect this plumb bob, as you can see below…
“It is the duty of those who, from the behaviour of a pendulum at different latitudes, contend that the earth is spherical, to first prove that no other cause could operate besides greater proximity to a centre of gravity in producing the known differences in its oscillations. This not being done, nor attempted, the whole matter must be condemned as logically insufficient, irregular, and worthless for its intended purpose.”
“The following table comprises the results of the most reliable pendulum experiments which have thus far been made, and. among which the extensive series of observations by General Sabine holds the first place.”
(Particulars are here given of sixty-seven experiments made in every latitude north of the equator, from 0° 1´ 49″ north to 79° 49´ 58″ north; and of twenty-nine experiments in the south from latitude 0° 1′ 34″ south, to Cape Horn, 55° 51´ 20″ south, and South Shetland. 62° 56´ 11″ south.) We have here before us the results […] differing to a remarkable extent, as compared with the results generally from the computed values. General Sabine observes of these discrepancies that ‘they are due in a far greater degree to local peculiarities than to what may be more strictly called errors of observation.’ And already Mr. Bailey (in Memoirs of the Royal Astronomical Society, vol. 7), had expressed the opinion ‘that the vibrations of a pendulum are powerfully affected, in many places, by the local attraction of the substratum on which it is swung, or by some other direct influence at present unknown to us, and the effect of which far exceeds the errors of observation.”
“From the foregoing remarks and quotations it is obvious that the assumption of Sir Isaac Newton that the earth is an oblate spheroid, is not confirmed by experiments made with the pendulum.”
“The Foucault pendulum is a piece of scientific apparatus specifically designed and built to deceive and mislead. It is literally a “humbug” – a sham, a fake, a fraud, an artifice, a pretence, a hoax – and I believe it should be exposed as such.”
Richard G Elmendorf
So, in answer to the title of this blog “Was Foucault’s Pendulum A Fraud” I shall leave the final word to Lady Blount, from her book “The Romance of Science” as diplomacy is not my strong point:
“We believe, with all due deference to the pendulum, and its proprietor, that it proves nothing but the craftiness of the inventor; and we can only describe the show and showman as deceptions. A thing so childish as this ‘pendulum proof’ that it can only be described as one of the most simple and ridiculous attempts to gull the public that has ever been conceived.”
Read more about Foucault’s Follies in this blog post:
Further research here:
 The Popular and Scientific Reception of the Foucault Pendulum in the United States
Author(s): Michael F. Conlin
Source: Isis, Vol. 90, No. 2 (Jun., 1999), pp. 181-204
Published by: The University of Chicago Press on behalf of The History of Science Society
Stable URL: http://www.jstor.org/stable/237048