Nicolaus Copernicus

Nicolaus Copernicus was an astronomer who lived during the late 1400s and early 1500s. He was born in 1473 in the city of Toruń, in what is now Poland. At that time, many people believed that Earth was the center of the universe. Copernicus suggested a different idea. He said that the Sun is at the center and that Earth moves around it. This idea is known as the heliocentric model, which means "Sun-centered model."

Copernicus studied many subjects when he was young. He learned mathematics, law, medicine, and astronomy. Astronomy is the study of objects in space, such as stars and planets. He studied at universities in Poland and Italy. Even though he worked mainly as a church official, he spent much of his free time observing the sky. He used simple tools, since telescopes were not yet invented.

At the time Copernicus lived, the common model of the universe was called the geocentric model. "Geo" means Earth. In this model, Earth was believed to stay still while the Sun, Moon, and planets moved around it. This model had been taught for many centuries. Copernicus noticed that this model was very complex and did not explain some movements of the planets well, such as when a planet appears to move backward in the sky.

Copernicus proposed that Earth is one of several planets that travel around the Sun. He also said that Earth spins on its axis, which explains day and night. An axis is an imaginary line through the center of a spinning object. In his model, the Moon still moves around Earth, but Earth itself moves through space. This helped explain the order of the planets and their changing positions in the sky.

Copernicus wrote his main ideas in a book called De revolutionibus orbium coelestium. The title means "On the Revolutions of the Heavenly Spheres." He worked on this book for many years. It was printed in 1543, the same year he died. The book used careful math to describe how the planets move around the Sun. At first, the book was read mostly by scholars.

After Copernicus died, other astronomers studied his ideas further. Some agreed with him and made new observations. Others disagreed. Over time, more evidence supported the Sun-centered model. Copernicus is remembered today as an important figure in the history of astronomy because he gave a clear description of a Sun-centered system using observation and calculation.