Check your wallet -- not for money but for your business cards. Are they still there? If not, they may be part of a worldwide math challenge. Over the past month, people around the world have been building a mathematical structure out of more than a million business cards.
Over the next several weeks, sites across the globe will celebrate mathematics through puzzles, magic and fun as they celebrate the life and accomplishments of Martin Gardner. In case there isn't one of these events near you, let's have one right here.