Part of the show The Christmas Q & A Show
Peter in Great Shelford asked:
Humans spend all our lives one way up. So when we stand on our heads, everything is upside down. Bats spend half their life hanging upside down, so which way does a bat think is the right way up?
Now I've been having a look into this, and at Thomas Nagel's 1974 work, "What is it like to be a bat?". Basically, bats don't ever go the right way up. They fly sort of head down, and they hang feet up head down, and basically, that's the way they think the world is. There have been some experiments done trying to put bats in low gravity, and basically bats don't really care which way is up. There have been some experiments done with bats and gravity, where most things, if you put them in wrong gravity or reduced gravity, they start rolling over and they get very confused, whereas bats just don't really care. They can fly upside down, they don't really mind. So bats generally hang upside down rather cleverly, and they don't seem to mind which way is up. And here's a good bat joke for you: There's a bat hanging upside down in a cave, and he sees another bat standing on the floor and he says "What are you doing down there?" And the other bat says "Yoga". [Chris] I can beat that! There's three vampire bats in a cave. And they're really hungry. And they can't get hold of any blood to save their lives. And then one day one of them says "I'm so desperate I'm going out of this cave, I'm going to find us something to eat". So he goes flying out of the cave and five minutes later he's back. He's got his mouth drenched in blood. And the other bats go "where did you get that wonderful blood?" and he says "come to the mouth of the cave and I'll show you". And they all go to the mouth of the cave, and he points out and says "You see that tree over there?" and they say "yeah" and he says "I didn't".