More or less all, starting from the first elementary, know story of the apple that, accidentally fall from the branch of a tree on the head of the scholar Isaac Newton, would later come to inspire the theory of gravity, in practice a real revolution in science.
But it is reality or just a folk tale that was handed down more or less unchanged in recent centuries?
The anecdote, in particular, It is surely invented, but an element of truth, as often it happens in these cases, and there is the same Newton to confirm, as he was to report to the archaeologist William Stukeley, that the notion of gravity was inspired by trivial fall of an apple (Stukeley brings him back in his "Conversations“).
The fact that the fruit always fall and in fact only vertically, and never horizontally or upward, It had to be necessarily signify the existence of a law of attraction of the Earth against objects and people who live there.
Newton later extended this law to space, the Earth-Moon system, thanks to Kepler's laws, He was also able to demonstrate that this force is proportional to the square of the distance (Photo gives: media.inaf.it).