Imagine sitting in a classroom. Let’s say there are 30 people in the class. What are the odds that two people in the room have the same exact birthday? Mathematician Amir Aczel poses this question to a packed auditorium and engages the front rows in what is known as the “birthday problem.” The results may surprise you.
More from this series: The Illusion of Certainty

This program is part of The Big Idea Series, made possible with support from the John Templeton Foundation.