So let's continue our exploration of the birth of modern science ...

Since early history, the scientists who studied the heavens were the only scholars to use mathematics, and the terms astronomer, astrologer and mathematician were virtually interchangeable. They calculated the dates of the holy days, developed methods to draw astrological charts, and forecast the position of the zodiac signs and the movement of the planets. However, despite their skillful observations, measurement and calculations, many questions remained unanswered. They could not account for the changes in the brightness of the planets, nor for their apparent retrograde movement. Their models did not explain why Venus and Mercury were never seen far from the sun, and they could not even agree on the order of the planets. However, it was not their role to ponder such theological matters. They were mathematicians, and calculation was what they did.

All this changed in 1514, when a Polish astronomer, Nicolaus Copernicus (1473-1543) circled amongst a few of his friends an unsigned hand-written book, Little Commentary. In his book, Copernicus introduced the heliocentric model, in which the sun, rather than the earth, was at the center of the universe, and all planets, including earth, were orbiting around it. With a single model, Copernicus could explain the apparent movement of the planets, the sun and the stars. His model could also account for the changes in the brightness of the planets, and offered a singular method of ordering them and calculating their relative distances from the sun with amazing accuracy (less than 10% difference from our current measurements.) Copernicus knew, however, that the clear advantages of his model would not protect him from the hostile reaction of the orthodox authorities and the Inquisition, and it was not until 1543 – the year of his death – that he eventually published his complete work On the Revolutions of the Heavenly Spheres.