"In 1666 a young scientist was sitting in a garden when an apple
fell to the ground. This made him wonder why apples fall
straight down, rather than going off to the side or upwards. The
scientist was Isaac Newton, and the incident inspired him to
come up with his theory of gravity, a theory that explained the
movements of planets as well as apples. But what happened
next? Do you think that Newton then gathered evidence that
proved beyond all doubt that his theory was true? Not according
to Karl Popper (1902–94)."