Fascinating, but I'm not sure why.

I figured it would find some sort of natural equilibrium and settle into a routine, but it didn't! Madness!

IT WON'T STOP! Sat glued to this thing praying for it to stop and cease the hypnotic random motion...

also - those have to be some *crazy* good bearings in that thing. wonder how much $?

It's not random - just chaotic!

Chaotic Motion Pendulum is Chaotic!

I wonder what kind of a light show it would give with a glowstick!

If you drop it from the precise point it was dropped from in this video and observe again, will it be random? What other conditions would factor into its perceived random movement? (These aren't rhetorical questions. I'm curious.)

I would pay large money to ride that at Disneyland...

>> ^poolcleaner:
If you drop it from the precise point it was dropped from in this video and observe again, will it be random? What other conditions would factor into its perceived random movement? (These aren't rhetorical questions. I'm curious.)


It is indeed chaotic motion -- if you attempt to recreate the exact same conditions of movement you will get different results. The reason is that there are many "balance points" where the motion could go either one way or the other, and there is no way to predict which way it will move. Sort of like balancing a ball exactly at the top of a curve -- you know it will fall one way or the other, but you can't predict which.

^There's nothing truly random about it, though. It certainly appears random, but if it were released again in identical conditions the exact same thing would happen.

Of course it's probably not possible to replicate identical conditions. You'd probably need to simulate it on a computer in order to make it completely identical.

> chaos

Oh great and everytime they do this damn test it kills butterflies in Indonesia

I've been sick for about a week and quite honestly watching this thing makes me ill.

That reminds me, I need to wear tighter fitting pants the next time I go jogging.

Reminds me of mens gymnastics high bar and or parallel bars.

Attach an LED to the end, turn off the lights, and then take a long exposure picture until the motion gets boring.

Do this as many times as you want with different colored LEDs. Post all results onto DeviantArt. Profit.

I thought I was watching a clip of the Arsenio Hall show.

Ass eric3579 Totally Stole my first thought right out of my head!
..all give my second thought:

shouldn't be so had to put this thing a vacuum bell.

..but then, youtube doesn't like 20 min videos : (

I'm sure it's not hard to write a formula to calculate the moment and potential of a double-pendulum system given initial conditions and duration.

This video ends too soon. I think it's still going!

if you want to see chaotic motion, just get on a bus and wait for a granny to get on after, with the bus pulling away before they manage to sit down.

>> ^syncron:
I'm sure it's not hard to write a formula to calculate the moment and potential of a double-pendulum system given initial conditions and duration.


It is hard actually, because the second pendulum rotates around a moving axis, which fucks up your equations royally.

Without gravity and friction it would make a nice flower pattern

For these types of systems, the resulting motion varies wildly given very small changes in the initial conditions. So, for all practical purposes, you can't make it do the same thing twice, since you will always have some error in your knowledge of the initial conditions and even that small difference (the error) will result in a wildly different result. For the same reason, you can't practically tell what it's going to do either even if you know the equations since tiny error in your knowledge of the initial conditions again yields wildly different results. Stable systems, like the earth's orbit, feature negative feedback for deviations so that small errors are brought back into line making it stable. I think systems like this one are the opposite. I think that's what's going on anyway.

>> ^HaricotVert:
Attach an LED to the end, turn off the lights, and then take a long exposure picture until the motion gets boring.
Do this as many times as you want with different colored LEDs. Post all results onto DeviantArt. Profit.


http://en.wikipedia.org/wiki/File:DPLE.jpg

There's a simulation you can play around with here, and some explanation of the maths behind it:
http://www.myphysicslab.com/dbl_pendulum.html

It is not a matter of just practicality. The frikken moon and sun would have to be in the exact same positions never mind the constantly shifting magnetic field of the earth. You would have to rewind all the vibrations in the universe to get the same motion when it goes on for that long with so many moments where either pendulum could go either way. Nature is soft and wave-like so there is no same spot one could start them at and the waves that we see as atoms will never be the same ever again so there is no same thing to line up the same. And you don't even have precise moments in time since movement and geography of nature is smooth and not step-like so you cannot even release the waves that make up the object at a certain time. In short: Too many variables in a system like this to reproduce it (it is cause and effect but causes that go back into infinity).

-Karl

I want to see two side by side.

This is a variation on a lawn ornament mobile i saw once. rich people pay big money for novelties like this.

> and the waves that we see as atoms will never be the same ever again

I doubt quantum variations are a major player here. Air motion, temperature? Maybe to some degree. Temperature of the metal in the axis of the pivots? (Resulting in differing dimensions and clearances) Probably.

Difficulty of setting up the exact same starting dimensions, temperatures, motions... a huge YES

i want a grandfather clock with one of these

That pendulum looks like it's had one too many forces exerted upon it. Someone shut it off before it gets in a car and wobbles itself off the road.

I remember modelling these types of systems in University using Calculus of Variations. The technique involves considering the energy (kinetic, potential) of the various components. It's really very powerful, and was a ton of fun to model, but this was way back in the early 80s so the details are a bit fuzzy. Anyway, go lookup Calculus of Variations if you want to grok more.

LOL Karl. I guess I should have prefaced that I was talking about a macroscopic level. The earth orbit is regular and this thing isn't. It isn't a matter of starting it in the same position either. You know what I meant, but I take your point about the one time, forward-only experiment of the universe.