Catster Tips
Share this image

So How DO Cats Always Land on Their Feet, Anyway?

In less than a second, your cat does seven things to turn right side up. It's all about physics.

 |  May 7th 2013  |   4 Contributions


Do you remember those times you sat in high school science classes, bored stiff, thinking, “When am I ever going to use this stuff as an adult?” But would you have found physics more interesting if someone showed you that, say, the law of conservation of angular momentum explains how a cat can right himself if he falls from a decent height?

Well, the fine folks at Smarter Every Day have done that in their latest video.

Image: Screen capture from Smarter Every Day video

First of all, if you’ve watched a cat fall, you might have noticed that he swings his tail all over the place. You might even have noticed that his tail moves in the opposite direction from the front of his body -- so you might have thought it’s all about the tail. But because even bobtailed cats can turn themselves from upside-down to right-side-up, there’s obviously something else going on. Here’s what really happens.

1. Your cat determines where the ground is

Your cat figures out which way is down, either by looking or by using his “internal gyroscope,” the tiny bones in the inside of the ear that help him determine his orientation in space.

When he first falls, a cat figures out where the ground is and starts pulling in his front paws. Image: Screen capture from Smarter Every Day video

2. He divides his body into two separate rotational axes

That’s a fancy way of saying that he twists himself into a position that allows the back of his body to rotate in the opposite direction from the front of his body.

3. He pulls his front legs in

If you’ve watched figure skating, you’ve probably noticed that a skater can make herself spin faster if she pulls her arms in toward her body. Your cat does the same thing: He pulls his front legs closer to his body to speed up the rotation in the front half of his body.

The Law of Conservation of Angular Momentum at work: When a cat falls, he twists the front and back of his body in opposite directions to make the force equal out. Image: Screen capture from Smarter Every Day video

4. At the same time, he stretches his rear legs

By doing this, your cat is making his back half turn more slowly than the front half. Because he’s twisting slowly in one half and quickly in the other, he reaches his moment of inertia -- the point where opposing forces equal each other and stop angular motion. If that didn’t happen, your cat would spin wildly out of control until he made a very un-graceful landing on the floor.

5. When he gets his front paws under him, he extends his front legs

Now that your cat has his front legs where he wants them to be, he stops them from moving. But now his back half needs to stop turning in the opposite direction or he’s still going to fall on his face.

The cat extends his front legs to stop his front half from rotating and brings his rear legs closer to the axis along which he's spinning so that his back half catches up with his front half. Image: Screen capture from Smarter Every Day video

6. He moves his back legs closer to his body

Now that your cat’s front half has stopped moving, his back half is going to want to start moving in the same direction his front half was, not in the opposite direction as it had been earlier in the fall. To assure that this happens quickly, he pulls his back legs closer to his body.

7. Once his back legs are facing the ground, he stretches them out

Now all four of your cat’s legs are facing the ground, and he can land safely.

Here’s the video if you want to check it out for yourself.

Do you have any other science questions about your cat? Anything you’ve always wanted to know but were afraid to ask? Let me know in the comments, and I might answer your question in a future article.

More cool stuff about cats by JaneA Kelley:

About JaneA Kelley: Punk-rock cat mom, science nerd, animal shelter volunteer, and all-around geek with a passion for bad puns, intelligent conversation, and role-play adventure games. She gratefully and gracefully accepts her status as chief cat slave for her family of feline bloggers, who have been writing the cat advice column, Paws and Effect, since 2003. JaneA dreams of making a great living out of her love for cats.

Contributions

Tip: Creating a profile and avatar takes just a minute and is a great way to participate in Catster's community of people who are passionate about cats.

blog comments powered by Disqus