How can it be that a tiny ant can lift many times its own weight, while a beached whale cannot support its own weight? Why are large mammals so rare while bacteria are so abundant? Why do some organisms live for hours, while others live for over a century? Using size as a beacon, L. Mahadevan, Harvard Professor of Applied Mathematics and 2009 MacArthur Fellow, will describe how the intersecting worlds of mathematics, physics, and engineering allow us to understand life's variations. Free with museum admission.