Storm in a Teacup: The Physics of Everyday Life

by Helen Czerski

In 1977, an enterprising scientist named Barrie Frost persuaded a pigeon to walk on a treadmill. This is one of those experiments that would probably win an IgNobel prize these days, as the perfect example of a piece of science that makes you laugh and then makes you think. As the treadmill belt slowly moved backwards, the bird had to walk forward to stay in the same place. The pigeon apparently got the hang of it quite quickly, but something was missing as it plodded along. If you’ve ever sat in a town square and watched pigeons strut around in search of food, you’ll have noticed that their heads bob backwards and forwards as they walk. I’ve always thought it looks like a really uncomfortable thing to do, and it seems odd to put in all that extra effort. But the pigeon on the treadmill wasn’t bobbing its head, and that told Barrie something very important about the bobbing. The bird obviously didn’t need to do it in order to walk, so it wasn’t anything to do with the physics of locomotion. The head-bobbing was about what it could see. On the treadmill, even though the pigeon was walking, the surroundings stayed in the same place. If the pigeon held its head still, it saw exactly the same view all the time. That made the surroundings nice and easy to see. But when a pigeon is walking on land, the scenery is constantly changing as it goes past. It turns out that these birds can’t see ‘fast’ enough to catch the changing scene. So they’re not really bobbing their heads forwar...