Walking and slithering aren’t as different as you think

Abrahamic texts treat slithering as a special indignity visited on the wicked serpent, but evolution may draw a more continuous line through the motion of swimming microbes, wriggling worms, skittering spiders and walking horses. A new study found that all of these kinds of motion are well represented by a single mathematical model. "This didn't come out of nowhere-this is from our real robot data,” said Dan Zhao, first author of the study in the Proceedings of the National Academy of Sciences and a recent Ph.D. graduate in mechanical engineering at the University of Michigan. "Even when the robot looks like it's sliding, like its feet are slipping, its velocity is still proportional to how quickly it's moving its body. Unlike the dynamic motion of gliding birds and sharks and galloping horses-where speed is driven, at least in part, by momentum-every bit of speed for ants, centipedes, snakes and swimming microbes is driven by changing the shape of the body. This is known as kinematic motion.