Isaac Newton’s first discovery concerned gravity.

Scientists knew of gravity, and Johannes Kepler had theorized that it had something to do with the movement of the planets, but this was not enough for Newton.

When he saw an apple fall from a tree at his family’s farm, he wanted to know the laws at work and to find the mathematical formulas to show how the laws worked.

Newton realized immediately he needed a new system of mathematics for his calculations.

He invented calculus, a system that uses symbols and numbers to measure infinitesimal and changing quantities. The laws of gravity were no longer a mystery.

Newton discovered that the entire universe is held together by gravity.

Every object attracts every other object, and the force can be calculated using the mass of the objects and the distance between them, the greater the mass, the greater the attraction, and the greater the distance, the weaker the attraction.

Once astronomers had Newton’s formulas for gravitational pull, they could account for all the known movements of the solar system.

The English astronomer Edmond Halley was the scientist who first found out about Newton’s discoveries and urged him to publish his findings. Halley used Newton’s formulas to predict that a comet that had appeared in 1682 would reappear in 1758.

The comet returned in 1758 and became known as Halley’s comet.

At almost the same time Newton was developing his system of calculus, the mathematician Gottfried Wilhelm Leibniz was developing a similar system in Germany.