Even though it didn't actually hit British physicist Isaac Newton on the head as legend has long held, that fallen apple did a whole lot more. In 1665, recently graduated from Trinity College in Cambridge, Newton was mostly confined to his home because of the plague. According to his account, he was indoors looking through a window at an apple tree in his yard when he saw the apple fall from the tree to the ground. It was that moment that his thoughts on gravity began to formulate. He would later publish Principia to describe universal gravitation and his three laws of motion. Two descendants of his original apple tree stand in the Isaac Newton Institute for Mathematical Sciences and the University Botanic Garden, both in Cambridge.