On Albert Einstein's seventy-sixth and final birthday, a friend gave him a simple toy made from a broomstick, a brass ball attached to a length of string, and a weak spring. Einstein was delighted: the toy worked on a principle he had conceived fifty years earlier when he was working on his revolutionary theory of gravity--a principle whose implications are still confounding physicists today.
Starting with this winning anecdote, Anthony Zee begins his animated discussion of phenomena ranging from the emergence of galaxies to the curvature of space-time, evidence for the existence of...