101 years ago today, Albert Einstein published the paper "Does the Inertia of a Body Depend Upon Its Energy Content?" in Annalen der Physik, forever imprinting into the minds of physics buffs (and mental_floss readers) the relationship between energy and mass when the speed of light is constant.

Also, um, happy birthday to Cosimo de Medici, Sam Adams, Thomas Nast, Meat Loaf, Shaun Cassidy, Gwyneth Paltrow, Lil Wayne, and me.