Foucault's pendulum

{{Sources needed}}
{{Astronomy}}
Foucault's Pendulum was a device invented by [[physicist]] {{wpl|Léon_Foucault|Léon Foucault}} in 1851. Its purpose was to demonstrate the [[Earth]]'s rotation. 

==Background==

[[File:Tasc a 2426814 f0018 oc.jpg|thumb|Note by Vincenzo Viviani from 1661 that describes an issue where all pendulums show clockwise precession.]]

The movement of the pendulum was first noticed by {{wpl|Vincenzo_Viviani|Vincenzo Viviani|,}} an Italian scientist in 1661. In his hand-written note he describes the motion:

{{cquote|We observed that all the pendulums from one thread deviate from the first vertical, and always in the same direction, i.e., according to the lines AB, CD, EF, etc. from right to left of the back parts, etc.|||Vincenzo Viviani (1661).}}

Wikipedia {{wpl|Foucault pendulum|states}} that Viviani never realized the connection to Earth's rotation, but considered it a nuisance.{{cn}}

==The experiment==

The device consisted of a heavy pendulum that was suspended form high ceiling. When put in motion, the pendulum does what pendulums do, it swings back and forth. But over time, its precession, that is, plane of oscillation changes due to Earth's rotation around its axis.

==The bitching and whining from flat-earthers==

In his [https://youtu.be/SauZfMS-lZo?feature=shared&t=16301 crank video], [[flat Earth]]er Eric Dubay shares thoughts from himself, Samuel Rowbotham, {{wpl|William_Carpenter_(flat-Earth_theorist)|William Carpenter|,}} and {{wpl|Elizabeth,_Lady_Blount|Lady Blount}}. Since Dubay is the only one alive, it's only fair to assume he co-signs the thoughts of the ones he quotes.
  
Dubay described the experiment as straight up "''pseudoscience''". He quotes Blount, who complained about the absolute speeds, talked about the experiment as a show. Dubay then quoted Carpenter, who has trouble grasping relative motion by laughing at the idea that earth moves under the pendulum, and who then made false claims about the pendulum's precession of being opposite of what it should be. The mocking description of the experiment with the backdrop of street-charlatans' tricks is nothing but [[appeal to ridicule]].
    
==="Foucault's Pendulums do not uniformly swing in any specific direction!"===

Dubay rambles on to his first point: "''Sometimes they rotate clockwise, and sometimes counter-clockwise. Sometimes they fail to rotate and sometimes they rotate far too much.''" 

Immediately, Dubay misrepresents what the pendulum experiment is about. The pendulum wasn't supposed to always run in the same direction, like he implies. It's about the pendulum's precession direction and speed:

The direction of the precession depends on the latitude:

# The pendulum rotates clockwise on the northern hemisphere, always.
# The pendulum rotates counter-clockwise on the southern hemisphere, always.
# On the equator, the pendulum doesn't rotate. It doesn't fail to rotate like Dubay describes it, it's '''expected''' to not rotate there.
# The claim that the pendulum rotates too much wasn't given any proof so [[Logical_razor#Hitchens.27_razor|Hitchen's razor]] it is. The most the pendulum ever rotates is 360° in 24 hours, at the poles, and it has been [https://www.nytimes.com/2002/09/24/science/here-they-are-science-s-10-most-beautiful-experiments.html?pagewanted=all&src=pm demonstrated] at the South Pole.

The speed also depends on the latitude. It increases when moving from the equator to either pole, where the precession is 360° / 24h.

===The rotation direction can be altered!===

[[File:Le petit Parisien illustre 2nov1902.jpg|thumb|A technique of sending off Foucault's pendulum without causing sideways motion, by burning its suspension wire, has been known for at least 120 years.]]

Dubay then tries to imply the experiment setup is not reliable: "''Scientists who have repeated variations of the experiment have conceded time and again that quote "it was difficult not avoid giving the pendulum some slight lateral bias at starting. The behavior of the pendulum pendulum actually depends on 1. the initial force beginning its swing and 2. The ball and socket joint used which most readily facilitates circular motion any other."''"

An [https://youtu.be/J7RwAcL4Iq0?si=LLRRwSd5305JONYU&t=9268 image] on the video claims the pendulum is "''completely adjustable so one can control gravity''". The only thing the device's [https://www.3bscientific.com/product-manual/1000748_EN.pdf manual] says is adjustable, is the fucking feet. If your laundry washing machine prefers being level, why wouldn't a 6,570 USD scientific instrument that is basically an advanced swinging plumb line? The pendulum's bottom position triggers a switch that maintains a timing circuit that actuates the electromagnet that helps maintain the pendulum's amplitude. The device does not control or counteract gravity, it counteracts air resistance that's slowly slowing the pendulum down. 

Dubay is however right when he says adding sideways motion will cause the precession to be faster. This can be seen e.g. in [https://youtu.be/WOHC3ONtWLk?feature=shared&t=18 this] painting video that uses the motion to create a pendulum rosette.

What Dubay conveniently leaves out, is that a simple method of sending off the pendulum, without any lateral movement, was figured out long ago. The pendulum was tied to a pole with a string, and the string was then cut by burning it. Burning was done because e.g. scissors/knives would have disturbed the system. Fire weakened the string until it tore itself in the direction of tension, i.e., in the direction the pendulum was supposed to travel. The pendulum was introduced in 1851, and in Le petit Parisien article about the experiment's 50 year anniversary, the [https://en.wikipedia.org/wiki/File:Le_petit_Parisien_illustre_2nov1902.jpg illustration] shows this method as already in use. Today, even amateur experiments [https://youtu.be/M8rrWUUlZ_U?feature=shared&t=132 do this] when they want accuracy.

Furthermore, modern implementations of the pendulum use what's called a Charron ring, which actually reduces any elliptic movement. Page 3 of [https://pearl-hifi.com/06_Lit_Archive/02_PEARL_Arch/Vol_16/Sec_53/Philips_Tech_Review/PTechReview-19-1957_58-236.pdf this article] shows a thick metal ring called 'B'<ref group=note>Who says engineers can't be creative?</ref>, bolted into three metal rods. When the pendulum swings to a side, its wire will always hit the ring. If the pendulum has any sideways movement, it will cause friction between the wire and the ring, which will then eat the sideways momentum. Once the sideways moment has been eliminated, the Charron ring merely acts as a pivot point that doesn't alter the direction itself. The original paper of the Charron ring can be found [https://articles.adsabs.harvard.edu//full/1931LAstr..45..457C/0000471.000.html here].    

The Charron ring can also be seen in [https://www.3bscientific.com/product-manual/1000748_EN.pdf miniaturized versions]. Section 2.1.3 of the manual: "''In order to prevent elliptical motion, a [Charron] ring is used in Foucault's pendulum.''"

The Charron ring prevents elliptic motion even in versions that use electromagnets to maintain the amplitude of the swing. One method to do this is called [https://phys.libretexts.org/Bookshelves/Classical_Mechanics/Essential_Graduate_Physics_-_Classical_Mechanics_(Likharev)/05%3A_Oscillations/5.05%3A_Parametric_Excitation parametric excitation], which sounds fancy but basically something any kid can do, and they do almost intuitively, when they pump a swing without touching ground, by pulling on the chains when traversing up. This shortens the chain slightly, and increases their speed and amplitude. Similarly, the magnet shortens the pendulum slightly at the right moment (the floor has an electromagnetic switch that detects when the pendulum is right above it).

Dubay cranks on:

==="If the alleged constant rotation of the Earth affected pendulums any way, then there should be no need to manually start pendulums in motion!"===

The Earth's rotation affects the precession, not the amplitude. The method to increase the pendulum's speed was already discussed above, and we don't see Earth operating that electromagnet to create parametric excitation. Besides, even parametric excitation requires a little bit of initial speed. Imagine a kid trying to pump the swing after they've merely sat on it. They'll mostly just wobble about until they manage to get enough speed.

===OG-flerf complaints===

Next, Dubay quotes Rowbotham: 

'''["There's too many variables to account for!"]'''

"''First, when a pendulum constructed according to the plan of Mr. Foucault is allowed to vibrate, it's 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.''"

'''["This does not prove causality!"]'''

"''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.''"

'''["Ball joint ruins everything!"]'''

"''Thirdly, why was not the peculiar arrangement of the point of suspension of the pendulum specially considered in regards 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-in-socket joint is one which facilitates circular motion more readily than any other''"

The ''variable plane of vibration'' could not be more vague an argument. The speed of precession changes by latitude. The non-uniform variation place and timing is not explained. Changes in precession speed? Small changes in airflows in the demonstration room might explain small variations. The velocity of the pendulum varies with the amplitude, and this doesn't convey measurement error to any extent. The direction of precession is also devoid of all context. Did Rowbotham also mean it changes on the opposite side of equator? If not, what? Also, small inconsistencies do not matter. We're not interested in the amplitude of the pendulum, or the pendulum's speed, or the pendulum's frequency that depends on the length of the wire it hangs from.

The precession direction and speed are all that matter, as with properly initialized experiment, pendulum weight, length, or start amplitude, do not change what's observed. Science is not unclear about the expected precession direction claim:
* '''Northern hemisphere:''' clockwise precession, 
* '''Southern hemisphere:''' counter-clockwise precession, and
* '''Equator:''' no precession.

In fact, science is so confident about the causality between the experiment and Earth's rotation, it has a {{wpl|Foucault_pendulum#Precession_rate_calculation|formula}} to predict the exact precession rate:

'''<center>ω = ω<sub>Earth</sub> sin φ</center>'''

where  

* '''ω<sub>Earth</sub>''' is Earth's angular velocity '''π(86400 rad/s)''', and 
* '''φ''' is the latitude.

This is the "globe earthers'" claim. All flerfs need to do, is prove the formula wrong in a controlled experiment. But they never will, because they know it will go just as well as [[The_Final_Experiment|TFE]] did.

As for the "''ball-in-socket joint is one which facilitates circular motion more readily than any other''", it's extremely unclear what Rowbotham actually wanted to see used. If the pendulum was attached to a swivel that did not allow lateral movement, it would have prevented the precession mechanically.  Both Rowbotham and Dubay failed to name a better option, that does not prevent the pendulum from demonstrating what it should be allowed to demonstrate, and then explain why it's a better option.

Why would the ball-in-socket joint induce sideways motion itself? Kickbikes wheels do not restrict the kickbike going forward, should the kickbike be propelling itself forward on its own? Why do loose ball bearings not roll about on their own when left unsupervised?<ref group=note>Note to self: Test this with the damned 10mm sockets just in case.</ref>

And finally: Flerfs have never provided an explanation for the phenomenon on their model. If the Earth is flat, why is it that by moving the apparatus towards the edge of the pizza-land, slows the precession until, on the other side of the pizzaland's equator, the precession magically changes direction. The Sun and Moon can't be the reason, given that their distance above the experiment does not change the precession rate.

==Notes==
{{reflist|group=note}}

==References==
{{reflist|2|80%}}

[[Category:Anti-intellectualism]]
[[Category:Astronomy]]
[[Category:Conspiracy theories]]
[[Category:Denialism]]
[[Category:Flat Earth]]
[[Category:Silly "Earth" theories]]

Categories: Anti-intellectualism, Astronomy, Conspiracy theories, Denialism, Flat Earth, Silly "Earth" theories