July 5, 1687: When Newton explained why you don't float away
The Day the Universe Got Organised (Mostly) People were worried, mostly about everything, but particularly about why things stayed on the ground. Apples fell. Horses galloped. Cannonballs soared (briefly) and came crashing down. But no one was quite sure why the moon didn’t join in and plummet to Earth in the same enthusiastic fashion. And then on July 5, 1687, Isaac Newton published a book with a title so long it felt like a Latin riddle: Philosophiæ Naturalis Principia Mathematica. In three