FIRST OFF ALL FORGET THE APPLE One probably didn’t really fall on the head of Sir Isaac Newton in 1665, knocking loose enlightenment about the nature of falling bodies. And while you’re at it, forget what you learned about gravity in school. That’s not how it really works. But don’t take our word for it. Let the main contenders in the history of gravitational theory duke it out themselves. Round 1: Newton “Gravity really does exist,” Newton stated in 1687. “[It] acts according to the laws which we have explained, and abundantly serves to account for all the motions of the celestial bodies.” Before Newton, no one had heard of gravity, let alone the concept of a universal law. Cambridge University, where Newton studied, was closed due to plague in 1665. Finding respite at his childhood home, the 23-year-old plunged into months of feverish mathematical brainstorming. This, plus a dubious apple descent in the back orchard, laid the foundation for his masterwork Philosophiae Natural