As you look at the sky at night, you can see the moon, the stars, and the planets. It seems as if the Earth is at the center of the Universe.It seems as if everything in the sky moves around the Earth. In the daytime, it also seems as if the sun moves around the Earth.
For hunderds of years, people believed thatthe Earth did not move. They believed that the Earth was at the center of things. They believed that the sun, moon, stars, and planets moved around the Earth.
But about 400years ago some people who watched the skies began to make discoveries. They observed many things that did not fit in with the idea of our Earth as the center of the Universe. Theydiscovered more about how far away the sun and stars are. They knew that faraway things seem to move very slowly even when they are going fast. They knew that when we aremoving, things look different to us than when we are standing still. For example, when you ride on a merry-go-round the crowd seems to whirl by you.
An astronomer named NicolausCopernicus did much reading, thinking, and observing about the new discoveries. He searched for a new idea to explain what happens in the sky. He wanted the new idea to explainall the things, new and old, that were known. In 1543, he published a book about his new idea. He surprised many people by saying that the sky does not move. Rather, he said,the Earth turns on its axis and, at the same time, makes an orbita round the sun. He showed that planets other than the Earth also go around the Sun.
Copernicus did his workwithout a telescope. Yet much of his work is still accepted even after four hundred years ago. Copernicus was a Pathfinder who changed man’s thinking about the universe.