Most people know the story of Newton and the falling apple, which led to his discovery of the law of gravity. But what else do we know about this great scientist and his place in the history of science?
Isaac Newton was born on Christmas Day, 1642, and grew up in the English countryside. From an early age, he was fascinated by the mysteries of nature. A central scientific problem of his time was the question of motion. Why do objects move? Scientists observed stones rolling down hills, wind blowing leaves, and objects falling to the ground. After Copernicus, they also began to accept that the Earth itself moved. This led them to ask: "Are there universal laws governing all these different kinds of motion?"
The ancient Greeks had believed that different rules applied to motion on Earth and in the heavens, and that some earthly motions were unnatural.
Galileo Galilei was the first to challenge this Greek view. A follower of Copernicus, he found it illogical to have separate rules for earthly and celestial motion. He made two key discoveries: first, he demonstrated that motion is not unnatural—an object in motion tends to stay in motion. Second, he developed a mathematical formula to describe the motion of falling objects on Earth.
However, Galileo did not provide a complete explanation for all motion in the universe. Since Copernicus, much work had been done to observe and record the movements within the solar system. The task remained for a great mathematical mind to synthesize this knowledge into universal laws.
At age twenty-three, Newton moved from Cambridge to his country home. There, he pondered the problems of motion. As he later recounted, while sitting in his garden one evening, he noticed a falling apple. This simple event sparked his curiosity about the nature of falling objects.
He realized that the force causing the apple to fall must operate equally well at greater distances from Earth's center—on top of buildings or mountains. Newton wondered if this same force extended even farther, all the way to the moon. Could it be the force that kept the moon in orbit around Earth? And if so, could the same force explain the orbits of the planets around the sun? This line of thought prompted Newton to seek a mathematical expression for his revolutionary idea.