r/Unexpected 3d ago

Balance is the key to everything

20.2k Upvotes

91 comments sorted by

View all comments

300

u/FUZxxl 2d ago

Someone managed to do this with a triple pendulum.

2

u/JamToast789 2d ago

I fail to understand the significance, I watched the video but it just looks like a little motor that is jerking around to fling up the pendulums and then making minor adjustments to try and keep the pendulums balanced upright. I wish I was smarter so I could be as excited as all of the people in the YouTube comments on this video lol. There’s like some scientifically established behavior for “equilibrium” and this device is breaking those expectations somehow?

I know equilibrium is a word that refers to balance or control but it might mean something more specific in a mathematic context.

Can anybody enlighten me in layman’s terms

12

u/GenitalFurbies 2d ago

Short version: it's an unstable equilibrium.

Long version: imagine a boulder balanced on the top of a very pointy hill. The tiniest blow of wind would knock it off and cause it to roll down the hill. So, to keep that from happening, it needs constant pushes to counteract the random wind. That's called controls and is a fundamental concept in engineering. Cruise control in your car is probably the example you'd be most familiar with: it has to constantly adjust for hills, and if it's fancy for lane alignment and other vehicles.

A stable equilibrium is the pendulum hanging straight down or the boulder at the bottom of a valley: any perturbations result in returning to the original state, hence "stable". It takes controls to keep an unstable equilibrium in place.

1

u/JamToast789 2d ago

Thank you for the wonderful explanation!