• Legend contends that Sir Isaac Newton formulated his theory of gravity when an apple fell from a nearby tree. 
• Before Newton, Johannes Kepler discovered that the orbits of all planets revolving around the sun (earth included) were elliptical.
• Galileo was the first to determine that free-falling bodies all fall with the same acceleration regardless of their mass. He formulated this law with the help of empirical evidence gathered by dropping spheres of different masses from the Leaning Tower of Pisa.

Of course, it is not by watching falling apples alone that one arrives at the Universal Law of Gravitation; it was necessary to understand the theory as applicable to all instances of gravitation both on earth and in the sky. The moon in the painting hovers over Newton in the form of a ripe apple. The image illustrates Newton’s idea of universal gravitation as the driving force behind both the planet’s motion and the movement of an apple or a stone.

Newton’s 17th Century theory of gravitation serves space science in the 21st Century. His formulas are used today to calculate first and second cosmic velocity in space during rocket launches.