How do bats hover, stop in mid air, change direction rapidly to chase insects?
Bats are mouse- like mammals, noctirnal, and can fly. Their wings are modified hands. Scientists have wondered how they can change direction, even hover like a hummingbird at a feeder. It sseemed that their wings were not aerodynamically set to do this: and they could not beat as fast as a hummingbird: and they are much heavier than sinsects that can do this like bumble bees. They did know that bumblebees create a tiny vortex above their wings. A vortex is a whirling cone of air like a tornado. Just like a tornado, the vortex above the bee's wing sucks things up, in this case the bee, so it can fly and hover. But when the scientists did their math, they calculated that a bat would have to have a much bigger vortex.
To test the bat, they put bats in a wind tunnel. Sure enough they saw that the bats wings did make a vortex big enough to allow them to manoeuvre in the way they do, even hover.
The amazing thing is that the vortex has to keep in contact with the wing. If it loses contact, the bat would fall like a stone. So the bat must be able not only to make just the right kind of vortex, but it must control the vortex so that it does not lose contact with the wing. The wing must be able to sense the change in pressure that signals when the vortex will lose contact, and change the way it controls the vortex.
Scientists are going to try to make robots that can fly by making vortices above their wings.
