My dad sent me a link to the Harvard Natural Sciences Lecture Demonstrations that features a 15-pendulum setup, apparently based on a Russian design of some age, in which each pendulum is of a monotonically increasing length. The video, linked below, shows what happens when all the pendulums are set in motion at the same time: they change from swinging in sync, to swinging in a wave, in double waves, in apparent discord (or randomly), and then back again.
It’s the “and back again” that is so fascinating. One full expects to move from order to disorder, or even from disorder to order, but my brain was not fully prepared for events to transition from one state to the other and then back again, and then back again. What it seemed to suggest to me in the moment is that apparent randomness in some contexts is simply a transitional state between two different kinds of order. (This may be the intended function of the demonstration for all I know.)
[The video is 1:46 long. Well worth your fascination.](http://sciencedemonstrations.fas.harvard.edu/icb/icb.do?keyword=k16940&panel=icb.pagecontent216589%3Ar%241%3Fname%3Dindepth.html&pageid=icb.page80863&pageContentId=icb.pagecontent341734&view=view.do&viewParam_name=indepth.html#a_icb_pagecontent341734)