100 years ago, Albert Einstein put a capstone on the work he'd begun 10 years earlier during his "miracle year" of 1905. He did this by creating the Theory of General Relativity, proving that what we feel as gravity is acceleration caused by the curvature of space-time (there's a reason this theory deserves the video explainer below). Although not a scientist by training, author and Aspen Institute CEO Walter Isaacson has written definitive biographies of Steve Jobs, Benjamin Franklin and others, including 2007's Einstein: His Life and Universe. To commemorate its anniversary, Isaacson explained for Fusion the physics dilemma that vexed Einstein, and how he came to solve it:

Sources: Fusion | h/t Digg