Copernicus

Men have always been fascinated by the stars. Centuries ago, as people looked up at the sky, they saw that some stars did not twinkle but wandered across the sky as bright points of light. These "wandering" stars were what we now call the planets. There were five planets that could be seen by ancient men - Mercury, Venus, Mars, Jupiter and Saturn.

The ancient Greeks were great watchers of the sky and also great thinkers. As they watched the stars night after night, it was natural for them to think that the earth stood still and the stars, planets, sun and moon were going round and round the earth in space. They thought the sun was between Venus and Mars.

For centuries, men believed this was how the stars moved. To explain the wandering of the planets, however, was very difficult.

Then one day at Cracow University in Poland, about the year A. D. 1500, a young scientist named Nicolaus Copernicus began thinking about the way in which the stars and planets moved.

Suppose, Copernicus said, the earth was not at the centre of the stars and the planets, but that the sun was instead. Suppose that the earth itself was a planet just like Mars and Venus and that the earth and all the other planets were round and round the sun at different distances from it. "After all," he said, "since light comes from the sun, it is only proper that the sun and not the earth should be at the centre of everything."

The ancient Greeks had made the mistake of thinking that because the stars and planets seemed to move as they looked at the sky, the earth must be still. If you have sat in a train and looked out at the trees rushing by, it is easy to understand their mistake. The trees seem to be moving backwards, but really it is the train that is moving forwards.

Not all of Copernicus' ideas were right. Although he thought, correctly, that the moon went round and round the earth, he also thought the stars were fixed on a large ball outside where the planets moved. He thought the stars did not move at all, but only the earth, moon and planets.

Copernicus was so frightened of what everyone would think of his new ideas that he did not write them down in a book until he was almost dying. Yet he was the first person to explain properly our solar system.

Copernicus was born at Torun. He studied mathematics at Cracow, canon law and astronomy at Bologna and medicine at Padua. His treatise has the title in Latin "De Revolutionibus Orbium Coelestium".

(from "Finding Out")