Rating is available when the video has been rented.
This feature is not available right now. Please try again later.
Published on Mar 12, 2012
TED-Ed's mission is to capture and amplify the voices of great educators around the world. We do this by pairing extraordinary educators with talented animators to produce a new library of curiosity-igniting videos. You can nominate a teacher, nominate an animator or suggest a lesson here: http://ed.ted.com