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Copernicus, Kepler and Galileo

Nicolaus Copernicus

Nicolaus Copernicus,
brilliant and obedient

Giordano Bruno

Giordano Bruno, burned at the stake
February 17, 1600

Johann Kepler

Johann Kepler

Rotating Earth

Rotating Earth. For ages people looking at the sky thought the heavens were spinning rather than the earth.


Galileo Galilei

Despite its suppression, still alive among a few intellectuals was the theory by Nicolaus Copernicus (Koppernigk), said today to have been the founder of modern astronomy. Copernicus (1474-1543) had been a brilliant Catholic cleric in Poland. For relaxation he painted, translated poetry from ancient Greek into Latin and dabbled in celestial observations with the naked eye. From his observations he theorized that the earth, rather than standing still, rotated around its axis daily and traveled around the sun yearly – resurrecting what had been known among Hellenistic intellectuals in ancient times. The Catholic Church and Martin Luther, more common in brain power, considered themselves better informed on the matter than Copernicus. Luther described Copernicus as an "upstart astrologer " trying to be clever. He is reported to have quipped that sacred scripture tells us that Joshua commanded the sun to stand still, not the earth (Joshua 10:12-13). The Catholic Church also claimed that Copernicus's claim defied common sense.

Opposition from the Church led Copernicus to shelve his theory, but Church opposition did not kill the idea. A student of astronomy mentioned the idea to a young Protestant German named Johann Kepler, who in the late 1500s and into the early 1600s was trying to figure out the changing distances between planets. Kepler discovered that Mars was moving about the sun not in a perfect circle but in an ellipse – contradicting Plato's belief about perfection and the heavens. Kepler proposed that laws about materiality that applied to things on earth applied also to the heavens.

Around the year 1608, in Holland, the telescope was invented – a tube with a convex lens at one end and a concave lens on the other. The invention has been described as a collaboration between two makers of spectacles and a third person who was a mathematician. A 35 year-old scientist named Galilei Galileo, from Pisa Italy, heard about the invention, and in 1609 he made his own telescope, with a magnifying power of eight.

Galileo was a Catholic and a progressive thinker. Aristotle's views, previously considered radical in Europe, had become the conservative point of view, and, like Francis Bacon, Galileo was opposed to Aristotelian ideology. Galileo was interested in the mechanics of motion, and he was at odds with Aristotelian professors talking of things sinking or floating according to their will or essential natures and of things falling because they wanted to return home, as if the inanimate contained spirit and will. Galileo had grasped the idea of force as mechanical. He drew revolutionary conclusions that in the 20th century would seem common sense: that bodies in motion continued to move except as slowed by some force. His views annoyed theologians, but his ideas interested those wanting to measure the flight of cannon balls.

In 1610, with his telescope, Galileo discovered the moons of Jupiter, and soon afterward he found spots on the sun and the hills and valleys on the surface of the moon. This ability to see where others could not got him into trouble with the Church, whose authorities put ideology ahead of scientific, or empirical discovery. Their theology was deemed correct, and it was for Galileo to conform to it, not for the Church to adopt the science of Galileo or anyone else's science. Galileo had demonstrable evidence that Copernicus had been correct. And among some of the Aristotelians of the old scholastic school of thought – who forgot Aristotle's admonition to investigate – came condemnation of the telescope.

In 1611, Galileo visited Rome and exhibited the wonders of the telescope to the pontifical court. He tried to produce scriptural confirmation of the view that the earth went around the sun. The Church warned him that he should limit himself to study of the physical world and to avoid applying his ideas to theology. In 1616 the Church condemned as absurd and heretical the view that the earth moved around the sun, and the Church made expressions of this view forbidden reading. Pope Paul V instructed Galileo to refrain from teaching the doctrine, and Galileo promised to obey.

The Church, meanwhile, had been burning a few at the stake for their heresies. Giordano Bruno had been burned to death in Rome for his Pantheism. Another Pantheist, Lucilio Vanini, was condemned as an atheist and burned at the stake in 1619 in Toulouse, in southern France.

In 1624, Galileo went to Rome and received permission from the Pope to write a description of the rival Copernican and Ptolemaic theories. Pope Urban VIII gave him permission on condition that he do so without favoring the Copernican system and that he write a conclusion that expressed the view of the Church. Galileo returned to Florence and set to work, and in January 1632 his work was published. It was applauded by intellectuals across Europe, and it was too popular to suit the Church. Jesuits complained that Galileo's book was a bad influence. It says something about the common attitude of the time that friends of Galileo criticized him for being in love with his own genius and showing little respect for others by pursuing ideas not commonly accepted nor approved by their Church.

In August, 1632, the Church prohibited further sales of the book. And, in October, Galileo was ordered to appear before the Inquisition in Rome. Galileo arrived in Rome in February 1633 as ordered. He was treated with deference and not jailed. Galileo appeared before ten judges, at the same spot where Bruno had heard his sentence of death. The Inquisition accused Galileo of having violated the ruling by the Church in 1616 that he refrain from "teaching or discussing" Copernicanism in any way. The agreement Galileo had received from Urban VIII in 1624 was described as having been received under false pretenses, that the permission had been an extortion. Galileo recanted his beliefs that the earth moved around the sun. His sentence of imprisonment was changed to banishment. He was ordered to recite once a week for three years the seven Penitential Psalms, and he remained confined to his estate just outside Florence, where he lived until his death in 1642.


Western Tradition, by Eugen Weber, program 25

A History of Science and Its Relations with Philosophy and Religion, by Sir William Dampier, 1948

Wisdom of the West, by Bertrand Russell, 1959

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