User talk:DemonDeLuxe

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[edit]  :Image:Foucault_pendulum_precession2.png

Hi DemonDeLuxe,

Your animation is graphically marvellous. I make animations too, but nowhere like that. I hope you can teach how to make that kind of animation. (at 1MB, it is very big though, the wikipedia servers are struggling to kkep up with demand as it is. Personally I try very hard to keep my GIF-animatons as small as possible, I rarely exceed 100KB)


About the physics of the Foucault pendulum. The current text of the physics portion of the article is only partly mine. Later edits may have added inconsistencies. I believe that I have a solid grasp of the physics of the Foucault Pendulum.

Of course the swing of the pendulum bob is a harmonic oscillation

Your graph
Your graph

Let a pendulum bob be located on the northen hemisphere. Then the following statements apply:

  • When the pendulum bob swings from south to north, it does not follow a straight line with respect to the earth underneath, the line curves to the right.
  • When the pendulum bob swings from north to south, the line curves to the right.
  • When the pendulum bob swings from west to east, the line curves to the right.
  • When the pendulum bob swings from east to west, the line curve to the right.

It is common to describe the motion of a northern hemisphere pendulum. Your animation, if valid, is a depiction of a southern hemisphere pendulum.

I am pretty sure that the pointed diagram is a satisfactory approximation. The curvature of the line of swing is proportional to the velocity of the pendulum bob with respect to the earth. At the two outermost points of the swing, the pendulum bob moves very slowly with respect to the earth underneath, hence nothing much happens at the outermost points. Most of the "bending" occurs around the center point, where velocity is largest.

In Fundamental university physics by Alonso and Finn, second edition, there is on page 121 a diagram with sharp points. --Cleonis | Talk 11:36, 17 August 2006 (UTC)

Addendum. The descriptions of demonstrations mention that often a small ridge of sand is made, just at the very outermost point of the swing. A spike that extends from underneath the pendulum bob just grazes the sand. Acoording to the descriptions, the spike draws radial lines on successive swings. --Cleonis | Talk 11:43, 17 August 2006 (UTC)

Addendum 2.
Usually the expression: 'plane of swing' refers to an average over an entire cycle of swing. When so defined the plane of swing is precessing at a constant rate.

Another definition is to define an instantaneous plane of swing: the plane that is parallel to the pendulum bob's instantaneous direction of velocity. When so defined, the plane of swing does not precess at a constant rate within each individual swing-cycle. The precession of the plane of swing is proportional to the velocity of the pendulum bob with respect to the earth.

My guess is that your reasoning here: "The pendulum's motion gets slower the farther the weight swings, so there's more "earth turning underneath" per centimeter (or second) of swinging than more to the center of the motion.", is based on assuming that precession of the instantaneous plane of swing is constant within each cycle. As stated, within each swing-cycle, the rate of precession is not constant. --Cleonis | Talk 12:06, 17 August 2006 (UTC)

Addendum 3:
I have photocopies of the chapter about the pendulum from William Tobin's biography of Foucault, and I have had a look in there. Tobin describes a problem that many demonstrations ran into: even a minute anisotropy of the suspension wire causes a pendulem bob to deteriorate into ellipse-shaped motion before its amplitude has decayed.
Tobin writes: "an ellipsing pendulum is not stationary at the extremity of its path, but has a small tangential velocity there [...]"
To ensure that the pendulum would have negligable tangential velocity at the etremities for as long as possible, Foucault launched the pendulum bob by tying the bob back with a loop of cotton, and after all rocking of the bob had died away, Foucault burned the rope.
This confirms again that a properly swinging pendulum has negligable tangential velocity at the extremities of its path. --Cleonis | Talk 20:00, 17 August 2006 (UTC)

Still, I think that, seeing that the pendulum's movement must get slower towards the extremes of it's swings (otherwise a swing would never end), while earth continues it's spin at constant speed, the relative sideways shift per cm of "graph path" must be greater than in the middle of a swing at the pendulum's maximum speed.
--DemonDeLuxe 07:54, 18 August 2006 (UTC)
My answer to this remark is in addendum 2. In my enthusiasm, I kept adding addendums. In retrospect I feel I shouldn't have flooded your talk page like that. Please read addendum 2, it discusses the point you are raising.
I confirm again that the pendulum swing is to a satisfactory approximation a harmonic oscillation; the amplitude as a function of time follows a sine-curve.
For me, the starting point of thinking about the Foucault pendulum is that its swing is a harmonic oscillation! --Cleonis | Talk 08:25, 18 August 2006 (UTC)


It just occurred to me: your animation is correct for the following situation: A foucault pendulum located on the southern hemisphere that swings so slowly that it takes 24 hours to complete 8 swings.
My diagram is strictly speaking physically unrealistic: my diagram shows on one hand the 'spikyness' that applies in the case of a Foucault pendulum performing thousands of swings in 24 hours. On the other hand, my diagram shows a large angle from one swing to the next, which physically corresponds to the case of a pendulum that swings in the order of ten times in 24 hours.
Strictly speaking, my diagram is a hybrid, moving away from what is physically realistic in order to bring particuler features more into focus.
Actual Foucault pendulums swing thousands of times in 24 hours. Clearly, it is not possible to produce a transparent diagram or animation that remains true to that. --Cleonis | Talk 10:16, 18 August 2006 (UTC)

[edit] Compromise between style and bandwith

I have started a website of my own with physics articles.
http://www.cleonis.nl/physics/physics.php
Some articles contain multiple animations. I reduce bandwidth as much as possible. I find it very hard to produce a (semi)3D-animation under 200 KB, but I did manage several. Please check out my animations, and tell me whether you think they are effective. --Cleonis | Talk 10:36, 18 August 2006 (UTC)

[edit] Featured picture nomination

I've nominated your image Image:Zipper animated.gif to be a Featured Picture. Please see Wikipedia:Featured picture candidates/Image:Zipper animated.gif for discussion. Thanks. howcheng {chat} 21:42, 25 September 2006 (UTC)

[edit] 2ndFeatured picture nomination

your various .gifs are impressive. I've also nominated your image Image:Newtons cradle animation book.gif to be a Featured Picture. You can go to Wikipedia:Featured picture candidates/Newton's Cradle to see the debate. Good luck! NauticaShades(talk) 16:24, 2 October 2006 (UTC)

[edit] FPC Promotion
An image created by you has been promoted to featured picture status
Your image, Image:Zipper animated.gif, was nominated on Wikipedia:Featured picture candidates, gained a consensus of support, and has been promoted. If you would like to nominate an image, please do so at Wikipedia:Featured picture candidates. Thank you for your contribution! Fir0002 10:43, 7 October 2006 (UTC)

Well Done! --Fir0002 10:43, 7 October 2006 (UTC)

This is to let you know the Featured Picture you uploaded and/or nominated Image:Zipper animated.gif is scheduled to be Picture of the day on December 3, 2006, when it will be featured on the Main Page. Congratulations! howcheng {chat} 17:51, 2 November 2006 (UTC)

[edit] FP nomination

I have nominated your picture Image:The price of coffee 2.jpg at Wikipedia:Featured picture candidates and there are some questions of the reviewers I ca't answer. Do you mindo to take a look? Alvesgaspar 16:34, 23 November 2006 (UTC)

[edit] Departure

[I copied this from his Commons user talk page -- Robert See Hear Speak 21:39, 10 March 2007 (UTC)]

Hi, this is Mathias Schindler from the German language Wikipedia. A couple of months, DDL requested his user page to be locked. A few weeks later, we received word that DDL is no longer alive. I still don't have first hand knowledge but another community where he contributed to confirmed his suicide. It still hurts. -- 217.51.5.171 16:17, 17 February 2007 (UTC)