You would think that shaking up a box with a couple of chains inside would end in sadness and a bunch of knotted chains, but as you can see in this video, it doesn't always work out like that. These two chains - both made of plain metal beads - coil and uncoil around each other until they are completely separated. The box is shaking at about 20 Hz, or cycles per second, and the photographs were taken five seconds apart. Although we think of entropy as creating chaos, it can also create a kind of order.
This is not just useful in science videos. Trapping long organic polymers, including DNA, and allowing them to jiggle about, can eventually cause them to separate out from each other without any damage. In that case, there are both wide areas, where the bands can jiggle about, and narrow areas, to allow them to straighten out into long bands, without any tangles. Sometimes entropy can be helpful.
Via Science Mag.