15/08/2011 GMT
from Discovery Hosted by BBC World Service
Explorations in the world of science.
Embed this episode
No transcript yet.
Frequently asked questions
How long is this episode of Discovery?
This episode is 18 minutes long.
When was this Discovery episode published?
This episode was published on August 15, 2011.
Can I download this Discovery episode?
Yes. Use the download control on the episode player to save the publisher-provided media file.