Riding on square wheels
The National Museum of Mathematics (MoMath) opened on December 15, 2012, becoming the only museum in the United States dedicated solely to mathematics. The idea for the museum came after the 2006 closure of the Goudreau Museum of Mathematics on Long Island. A group led by founder Glen Whitney, a former hedge fund analyst with a PhD in applied mathematics, decided to create a new institution. They received a charter in 2009 and raised over $22 million in less than four years to open the original 19,000-square-foot facility.
One of the museum's most famous exhibits is a tricycle with square wheels. This vehicle provides a surprisingly smooth ride, which seems impossible. The secret is not in the wheels, but in the track they run on. The surface is a series of specially shaped bumps called inverted catenaries. A catenary is the curve a hanging chain or rope forms under its own weight. The length of each side of the square wheel is equal to the length of the arc of each bump on the track. This precise geometric relationship ensures that the axle of the wheel remains at a constant height, resulting in a perfectly smooth motion. The exhibit features two tricycles of different sizes, allowing both children and adults to ride them simultaneously in opposite directions on a circular track.