Sir Isaac Newton ponders why the planets orbit the sun and what allows them to maintain that orbit. Very soon after he sits down under an apple tree, Humphrey bangs his head against one of the limbs, causing an apple to fall on Newton's head. It is at this moment that Isaac Newton has an epiphany and starts to develop the concept of gravity.
Newton presents his findings on gravity to a group of scientists. Among the attendees are Sir Robert Hooke. During his explanation of the inverse-square law, Newton notices that Hooke appears to be stealing his work, so he abruptly ends his presentation.