Astronomy

Astronomy is older than recorded history. It was first used to figure out when the seasons would change. Today it is used to calculate the age of the universe.

Astronomy is the study of everything in the universe beyond Earth. It is one of the oldest sciences. For thousands of years people have gazed at the sky to try to learn about the stars, the planets, and everything else in the universe.

The night sky changes as the year passes. Starting about 10,000 years ago, people studied the changing positions of the sun and the stars to decide when to plant and harvest crops. The earliest astronomers lived before recorded history. Our first knowledge of ancient astronomy dates from about 2,500 years ago, when Greek astronomers carefully recorded what they had learned. They believed that the Earth was at the center of the universe and that the stars and other planets circled the Earth.

Beginning of modern astronomy

            The Polish scientist Nicolaus Copernicus (1473-1543) was the first person to suggest correctly that the Earth revolved around the sun, not the other way around. The Italian astronomer Galileo Galilei (1564-1642) was the first to use a telescope to study the sky, and he saw things no one else had seen. Although Galileo believed, like Copernicus, that the planets orbited the sun, he could not explain why.

            The person who answered that question was the English mathematician Isaac Newton (1642-1727). Newton discovered that all objects possess a force called gravity that attracts other objects. A large object such as the sun produces enough gravity to hold the planets in orbit around it. Moons orbit planets for the same reason. Because of Newton’s discoveries scientists came to accept the idea that the Earth and other planets revolve around the sun.