Galileo's condemnation: The real and complex story

Aristotle's illusory machinery of rotating crystalline spheres is driven by an unmoved mover. But what in Ptolemy's system make his planets circle empty centers, and what makes these empty centers circle other empty centers? Some supernatural being? Another problem for Ptolemy is that in his system, the moon is constantly moving close to, and then away from, the earth as it makes its monthly rounds. Yet no one observes this to-and-fro movement occurring in nature. Ptolemy's geostatic system may not have been scientifically real, but the calculations based on it worked, and therefore Arabic thinkers called it "The Greatest."

Copernicus

Nicholas Copernicus (1473-1543) was a canon in the Catholic Church and trained in medicine. He thought God had made the Universe efficiently, harmoniously, and orderly. Therefore, Copernicus eliminated Ptolemy's equant and switched the earth's position with the sun's. However, Copernicus retained the eccentrics and epicyclic planetary motion, as shown in Figure 2. Since the sun is offset from the centers of motion, this is not a true heliocentric configuration, thought it is usually called that. More correctly, it is a heliostatic system.

Copernicus was aware that he would be criticized by Aristotelians in the Church and without. In his dedicatory letter to Pope Paul III, he claimed that his idea was not that unique, because the Pythagoreans and other ancients had held that the earth moves. In addition, Copernicus pointed out that Lactantius (c. 240 - c. 320), who was called the "Christian Cicero" by Renaissance Humanists, "speaks quite childishly about the earth's shape when he mocks those who declared that the earth has the form of a globe (6)." Thus, Church theologians, even well-respected ones, could be in error concerning the physical world. Finally, Copernicus cited supporters for his idea within the Church, Nicholas Schonberg, Cardinal of Capua, Tiedemann Giese, Bishop of Chelmno, and "not a few other very eminent scholars (7)."

Brahe

One of the greatest astronomers of the time was Tycho Brahe (1546-1601). Brahe's beyond-the-state-of-the-art instruments showed no stellar parallax. In other words, he saw no evidence that the earth was moving in an annual orbit. Copernicus had been aware of this problem and argued that the stars were about forty times more distant than previously thought.

Brahe's extremely accurate measurements indicated that the stars had to be more than 700 times further in order to not observe parallax. Brahe could not accept that result. It meant that the universe was more than 300 million times what it would be if the earth did not move. Why would God have created all that wasted space (8)? Brahe therefore developed his own system in which the moon, sun, and stars rotated around a geocentric earth, but the planets rotated around the sun. In this system, there are no imaginary centers of rotation and, considered as a model, it made accurate predictions.

Kepler

Johannes Kepler (1571-1630), laboring tirelessly with Brahe's treasure trove of accurate data, finally deduced that the planets go in elliptical orbits with the sun at one focus of the ellipse. He published this finding in 1609, along with another planetary law, in his New Astronomy (9). He apparently sent a copy to Galileo and then waited expectantly for a reply or at least an acknowledgment, but it never came (10). We know from a 1612 letter to him that Galileo was aware of Kepler's findings on planetary motion, but he ignored them (11).