Why Does a Pool Table Need a Super Strong Magnet?

In a pool table's 30 year life span, it can rack up half a million games. What's underneath the green felt that keeps this game playable? MACHINES: HOW THEY WORK Thursdays 10/9c on Science http://www.sciencechannel.com/tv-shows/machines-how-they-work/ Subscribe to Science Channel: http://bit.ly/SubscribeScience Check out SCI2 for infinitely awesome science videos. Every day. http://bit.ly/SCI2YT Download the TestTube app: http://testu.be/1ndmmMq