The Insights of Genius

From: Sir Isaac Newton: The Universal Law of Gravitation

"But as we increase the muzzle velocity for our imaginary cannon, the projectile will travel further and further before returning to earth. Finally, Newton reasoned that if the cannon projected the cannon ball with exactly the right velocity, the projectile would travel completely around the Earth, always falling in the gravitational field but never reaching the Earth, which is curving away at the same rate that the projectile falls. That is, the cannon ball would have been put into orbit around the Earth. Newton concluded that the orbit of the Moon was of exactly the same nature: the Moon continuously "fell" in its path around the Earth because of the acceleration due to gravity, thus producing its orbit."

Newton's thought trail is a mark of his genius. He examines an ordinary occurence- the flight of a projectile and imagines what could happen if velocity were increased. He concludes that there would be a point at which the velocity would produce an orbital effect. In ascertaining this he takes into account the rounded shape of the earth which enables the "continuous fall" concept- the curvature away of the earth matching the rate of the falling projectile. Newton linked his theoretical ponderings to the behavior of real physical entities and in so doing advanced his own comprehension. This subsequently advanced the understanding of humanity; a remarkable consequence of a thought process.