BBC Future

Head Squeeze

Is bigger always better?

If fleas were the size of dogs could they jump over the moon? No, says Hannah Fry, the strength of animals varies with size, and explains everything from fleas to Usain Bolt.

Have you ever heard the claim that if a flea was the size of a dog it could jump over the moon? Well it isn’t possible; the flea’s exoskeleton would explode on impact.

To explain why, Hannah Fry looks at the science behind how the strength of animals changes with size, and how this explains why sprinters like Usain Bolt have the body shape they do.

For more videos subscribe to the Head Squeeze channel on YouTube.

If you would like to comment on this video or anything else you have seen on Future, head over to our Facebook page or message us on Twitter.

BBC © 2014 The BBC is not responsible for the content of external sites. Read more.

This page is best viewed in an up-to-date web browser with style sheets (CSS) enabled. While you will be able to view the content of this page in your current browser, you will not be able to get the full visual experience. Please consider upgrading your browser software or enabling style sheets (CSS) if you are able to do so.