Why did Copernicus revolutionize concepts about the Universe?

Copernicus is said to be the founder of modern astronomy. His investigations were carried on quietly and alone, without help or consultation.

He made his celestial observations from a turret situated on the protective wall around a cathedral. His observations were with just his eyes, as a hundred more years were to pass before the invention of the telescope.

In 1543, Copernicus published a book about a new idea he had. Most people in his day thought that the Earth was at the centre of the Universe. They thought that the stars were little holes in a glass ball that surrounded the Earth. But, Copernicus disagreed. According to him, the Universe is not centred around the Earth, but that the Earth is actually a planet circling the Sun. Not many people liked his book or his ideas, for they went against the philosophical & religious beliefs that had been held during the medieval times. Copernicus died in 1543, and was never  to know what a stir his work had caused. Of course, we know today that Copernicus was right!