by Jaime Trosper June 24, 2017 Physics
In Brief
A video from BBC Earth Unplugged delves into the physics of self-siphoning beads, or Newton's beads. These beads seemingly levitate, defy gravity, and jump out of containers — but why and how?

It’s pretty much a rite of passage for young children to create crafts with beads. However, what most children (and adults, for that matter) don’t realize is just how much beautiful physics there is behind something as simple as bead chains.

In this video, BBC Earth Unplugged shows what happens when 8,000 beads, stretched into a 164-foot (50-meter) chain, meet a beaker.

The YouTube description is as follows:

These beads seem to levitate, defy gravity, and jump out of the beaker. But how and why do they act like this? We met up with Steve Mould, the science guy from Britain’s Brightest, to explore the science behind the “self-siphoning beads” — also known as “Newton’s Beads.”

To get a closer look at the phenomenon, we filmed them in slow motion to try to work out what exactly was happening, and how the behavior changes with height.

Look at it as a sort of tug-of-war. You can see the outer chain is going to be travelling really quickly as it falls, which means the inner chain is going to be travelling really quickly as well. If you’ve got something traveling really quickly, it’s got momentum. So you’ve got the inner chain traveling up, but it wants to change, so it’s traveling down. It can’t do that in an instant, because that would require infinite force.

What it does instead is change direction slowly over the course of a loop, so that’s why it almost has to be a loop — because it needs that time and space to change directions.