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two worldviews
Galileo's class
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Copernican's map of the universe, published in 1660, has the Sun at its center. Galileo's advocacy of this theory angered Pope Urban VIII.(Photo courtesy of Granger Collection, New York)
Hal Herman
special edition of the washington post
Wednesday, September 9, 1998; page H01On June 22, 1633, Galileo Galilei was put on trial at the headquarters of the Inquisition in Rome. It seemed that all the powerful forces of the Roman Catholic Church were against the famous scientist. Under threats of torture, imprisonment and even burning at the stake, he was forced to kneel to "give up, curse and hate" a lifetime of brilliant and dedicated thought and work.

At the time, the 69-year-old, who cited his "wretched state of health" in his defense, Galileo was accused of "strong suspicion of heresy". He had to "with an honest heart and without hypocrisy" renounce his belief that the sun, not the earth, is the center of the universe, and that the earth moves around the sun, not the other way around, as prescribed by church teaching.

When he was ready to do so, at least verbally, there was no more serious threat. For example, as part of his punishment he had to recite seven psalms of confession a week for three years. He was also under house arrest for the rest of his life.

Finally, his work, Dialogue between Ptolemy and Copernicus Concerning the Great World System (1632), was the focus of the trial, added to the Index Librorum Prohibitorum, the index of forbidden books kept by the Inquisition.

Ten cardinals attended the trial of Galileo. Pope Urban VIII was not there in person, but he was there in spirit as his personal anger and frustration were the driving forces behind this extraordinary procedure. Urban recognized how seriously Galileo's new science challenged established church doctrine. Worse, Galileo claimed that the Book of Nature was written in mathematical language rather than biblical terms.

In 1623, at the age of 55, Cardinal Maffeo Barberini changed his name to Urban VIII. Before that he was known as a warm, compassionate, intelligent man and one of the few people with whom Galileo believed he could have an intelligent discussion about his work.

During Galileo's visit to Rome shortly after Urban's election, the famous scientist was given six audiences, each lasting more than an hour, a remarkable allocation of the pope's time. In fact, it was largely because of Urban's choice that Galileo came to the conclusion that he could confidently write down the dialogue.

Both were born and raised in Florence and attended the University of Pisa, where Galileo studied medicine and Urban earned a law degree. As a cardinal, Barberini even mediated on Galileo's behalf in a conflict with church authorities in 1616, when Galileo was warned that his support for the heliocentric view of the universe could cause problems.

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The Roman Catholic Church dictates that the earth, not the sun, is the center of the universe. This classical or Ptolemaic view is shown in engravings from 1660.(Photo courtesy of Granger Collection, New York)
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Galileo was then told that he could treat the concept as a hypothetical idea. But he does not present it as reality, nor should he think so.

By 1632, some 16 years after this ominous event, Galileo was a well-known and respected scientist and the official astronomer and philosopher at the court of the Grand Duke of Tuscany.

In deciding to publish the dialogue, Galileo followed a strict protocol. His book was reviewed by a church censor and the church officially approved it. Apparently he tricked all the officials into thinking that his idea was only hypothetical. He almost published a heretical work without angering the Pope.


Yet Galileo was neither a sneering atheist nor an angry religious refugee. He attended Catholic schools, both of his daughters became nuns, and most importantly, he considered himself a faithful son of the Church. He felt he was trying to save the church, not hurt it. He tried to prevent the church from having to defend teachings that he believed had been refuted.

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In 1610, Galileo showed the Venetian council members the moons of Jupiter that he had discovered with a telescope.(Photo courtesy of Granger Collection, New York)
Nevertheless, the mere mention of Galileo's name provoked Urban's anger. At some point before the trial, the Tuscan ambassador in Rome, a good friend of Galileo, had just entered the papal chambers when he was furiously attacked: "Your Galileo dares to meddle in what he ought not, and with the last important and dangerous. topics which these days can encourage."

Galileo was not the first to challenge authority.

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In 1543, the Polish astronomer Copernicus proposed a heliocentric (day-centered) system. As a canon of the Polish Catholic Church, he was aware of the potential problems and delayed publication for years. He probably overestimated the impact of his work, which turned out to be one of the greatest unread works in history.

As long as the doctrine is shrouded in Latin, just another long academic treatise that few people read or care about, the Church can safely ignore it. The book was never indexed, a sure sign of incompetence—at least until 1616, when Galileo's support of the doctrine forced the Church to recognize the richness of Copernican's revolutionary ideas.

Around 150 AD traditional views were codified by Ptolemy of Alexandria, an astronomer and geographer who compiled an astronomical system to explain the apparent movement of the night sky. Ptolemy's solution was a system in which the Earth stood motionless at the center of the universe, and the moon, sun, planets, and stars revolved around it, all embedded in a system of concentric crystal balls.

The advantage of Ptolemy's system was that it worked, allowing astronomers to predict the movements of celestial bodies with some degree of accuracy. For his calculations, Ptolemy assumed that all these bodies follow circular paths.

To help them match the observed activity, which is much more complex, he added an extra set of smaller circular orbits called epicycles. The result is very complex geometry, but that's the best it can be.

Copernicus's ideas turned Ptolemy's ideas upside down. Copernicus believed that the Ptolemaic system was too complicated. He postulates the following: Suppose the sun is at rest and the earth moves doubly. It rotates on its axis once a day and goes around the Sun once a year.

Ptolemy and Aquinas

Copernicus was not the first to propose this heliocentric theory. Several ancient Greeks, including the astronomer Aristarchus of Samos, suggested it around 260 BC. Like Galileo, he was convicted of impiety, but apparently did no harm. However, Aristarchus failed to provide any evidence for the heliocentric theory, and it stalled.

Ptolemy's system was the first to be thorough enough to handle the large number of observed celestial movements. It corresponds to what people "saw with their own eyes".

Later, Ptolemy's description of the universe took root in Catholic teaching, primarily through the writings of the 13th century theologian and philosopher Thomas Aquinas. For example, the centrality of man is an important part of Christian teaching and integrates well with an earth-centered (on-earth) cosmology.

Christian ideas about heaven and hell also fit perfectly with geocentrism, which holds that the heavenly bodies are perfect and unchanging. In other words, all things in heaven are eternal and immortal, while growth and especially degeneration and decay are limited to Earth as punishment for the sins of our biblical ancestors.

It is not difficult to find astronomical references in the Bible. For example, Psalm 19: "The heavens declare the glory of God, and the firmament declares his works... In [heaven] he pitches a tent for the sun, and the sun rises as a bridegroom when he comes out of his chamber, and as a strong man who rejoices, he runs joyfully, from the end of the sky it rises and goes around to the end of the sky.

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What could be clearer than that? And if the sun doesn't move, how can Joshua make it stand still?

In such an atmosphere, the heliocentric universe is a disturbing concept because its implications are more important than the theory itself. As bold a move as Copernicus' theory was, it did not provide a significant advance in simplicity and accuracy.

Copernicus still insisted on the idea that the paths of the celestial bodies must be circular because circular motions are the "most perfect" type. This fixation on a circular orbit forced him to move the center of the system away from the center of the Sun, to which it belonged, thereby depriving his system of the essential simplicity which would otherwise have been its greatest advantage.

Copernican beliefs differed from contemporary beliefs in other ways. For example, what causes celestial bodies to move across the sky? Angels, said Aquinas. No, said Copernicus, the essence of a perfect circle is that it spins forever.

His basic reason for believing in his heliocentric theory is also instructive: "There is no better place than the center of the lamp that illuminates the whole universe." The German astronomer, physicist and mathematician Johannes Kepler set the heliocentric master on the right track primarily by discovering that planetary orbits are ellipses, not circles.

Interestingly, although Galileo and Kepler were contemporaries and corresponded, and although Kepler was one of the few leading scientists who supported heliocentrism, Galileo never used his work. Galileo also insisted on circular orbits, showing the difficulty of breaking old patterns.

Objections to the heliocentric theory still need to be answered. After years of debate, Galileo finally realized that something more substantial was needed, but found no existing evidence to use.

Much of Galileo's evidence is based on his own observations with telescopes that he designed and built himself. To answer the scholastic objection that a body cannot have two simultaneous motions, he brings up Jupiter's moons, which apparently move around Jupiter as it moves around the Earth or the Sun—which doesn't really affect the argument. It is a perfect tradition to deal with the celestial bodies, and Galileo showed that the sun has spots and the moon has mountains.

As for the objection to the Copernican theory, which required Venus to show aspects that had never been seen before, Galileo said that his observations also showed Venus in aspects. However, these observations were mostly made in 1609 and 1610 with very primitive telescopes. It required a trained eye to understand them, and many of Galileo's contemporaries saw only a flickering grain of light.

However, his Letter on Sunspots (1613) was the first to establish that only the heliocentric theory was sufficient for his telescopic observations. He triumphantly concluded: "Perhaps this planet [Saturn], like the horned Venus, is in admirable harmony with the great Copernican system, and for the general discovery of this doctrine it is now favorably looked upon. The wind blows against us, so that we need don't worry about clouds or crosswinds."

But there are problems for the Catholic Church. In 1616, the influential Jesuit theologian Cardinal Robert Bellarmine warned Galileo that he was in danger. Bellarmine made the Church's position very clear in the letter.

Commenting on the writings of the Carmelite Paolo Antonio Foscarini, who supported the Copernican system, Bellarmine writes: "I mean, if there is any evidence that the sun is in space... it would require careful consideration in the interpretation of the apparently contradictory scriptures ... but no, I think there is such evidence."

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Bellarmine is right. All of Galileo's evidence, especially telescopic observations, suggested that the Earth could revolve around the Sun, but did not prove that it did. If such a demonstration were to take place, it would shatter an important part of Church teaching. The church authorities feel that it is far better to maintain the status quo and hope that this disturbing situation will disappear.

If Galileo had not remembered the conversation, perhaps the tension would have eased, at least for a while. The book is smart, lively and very readable. It is also Italian, not Latin, the language chosen by Copernicus, so it is widely read and discussed.


Its 500-page structure is a four-day series of conversations between three participants (Salviati, Sagredo and Simplicio).

Salviati, named after an old friend of Galileo who died in 1614, spoke for Galileo. Sagredo was named in honor of another deceased friend, a wise, impartial host and a man of great power. Simplicio is a synthesis of all Galileo's opponents.

Galileo's technique was to build his opponent's arguments through Simplicio, add some of his own, and then demolish those claims with strong arguments and often devastating irony.

Simplicio, for example, reflected the prevailing belief of the time that the sun, moon, and stars were "destined to serve the earth for no other purpose, requiring no other qualities than light and motion for that purpose."

"What is this?" argued Sagredo. "Are you sure that nature has produced and designed so many vast, perfect, and noble heavenly bodies, which are unchangeable, eternal, and divine, except for the service of this changeable, transitory, and mortal earth. For no other purpose? serve that which you calling the scum of the earth? All the unclean universes and the sink?"

But Galileo knew that all his arguments had to be proven. In fact, the first half of his dialogue is really just a softening of what Galileo considered his crushing blow—the proof.

At the end of the book, Salviati explained precisely the connection between the movement of the Earth and its tides. For Galileo, this was the decisive factor: the Earth's water was moving. That's all I know. Through a series of slow and logical arguments, he showed that this movement of water was proof that the Earth was indeed moving.

Sagredo exclaimed: "If you tell us no more, this alone, in my opinion, far surpasses the vanity brought by many others, so much so that I am horrified at the very sight of them." Disgusting, I am very surprised that with great wisdom... no one has considered the incompatibility between the motion of the contained water and the rest of the vessel that contains it."

Ironically, Galileo also attacked Kepler, who proposed that something in the celestial bodies somehow caused the tides. However, Kepler believed that this celestial cause was magnetism.

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During the conversation, Salviati accused Kepler of "listening and accepting the Moon's dominance over water and mystical properties and such trifles." To Galileo, such action at long distances seemed to exemplify Kepler's mystical tendencies.

Kepler's inspired conjecture was only confirmed much later, when the tides were actually caused by the gravity of the Moon and, to a lesser extent, the gravity (though not magnetic) of the Sun. They are not caused by the movement of the Earth. This is an excellent example of Galileo's linguistic skills as he was persuasive even when he was wrong.

To convince his readers, Galileo clearly had to make strong arguments. To make them more visible, and perhaps to give them some breathing room, he uses Simplicio as a foil. But the sillier Simplicius' arguments, the clearer Galileo's real goal becomes. He decides to take a risk and for most of the book he succeeds.

But at last, perhaps carried away by excessive enthusiasm, convinced that he had found a way out without personal danger, he made Simplicius summarize the position of the Church on the impossibility of obtaining true knowledge of the physical world.

Galileo's intentions

Simplicio said that if God had willed the waters of the earth to move in a different way than the earth moves, he certainly might have done it - "From this I at once conclude that it would be impossible for any Extravagant insolence to restrain it divine power and wisdom to a particular presupposition of its own." The "specific premise" to which Simplicio refers is, of course, the Copernican system.

Simplicius' closing words do not sound like an explosion. Galileo seemed to feel the same way. However, Galileo's enemies later convinced Urban that if the statement came from Simplicius, Galileo's intention must have been to ridicule it, or worse, to ridicule Urban himself.

Galileo was strong-willed, but not stupid. The problem is that Simplicius' claim is a standard argument for the Pope, and the censor instructed Galileo to include it in the book. It is clear that Galileo's opinion must come from Simplicius. It is conceivable that Galileo forgot that this argument was Urban's.

When Urban saw the results, he was furious. Even after Galileo's death in 1642, Urban did not give up. Galileo's longtime patron, the Grand Duke of Tuscany, wants a decent public burial and the construction of a monument at Galileo's tomb in the Basilica of Santa Croce in Florence.

Urban warned that he would take such behavior as a direct insult. Thus, the remains of a great scientist in history were quietly hidden in the basement of the church bell tower for almost a century.

Eventually, Galileo's remains were allowed to be buried under a huge monument at the entrance to the church, where they lie today. Nearby are the tombs of two other famous Florentines: Michelangelo and Machiavelli. The dialogue was first published from the index in 1822.

In the fall of 1980, Pope John Paul II ordered a review of the evidence at Galileo's trial. He was released in 1992. But the fundamental conflict between established religion and modern science is still at play.

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This article is excerpted from Hal Hellman, author of "Great Feuds in Science: Ten of the Liveliest Disputes Ever" (John Wiley & Sons, Inc., 1998).

© Copyright 1998 The Washington Post Company

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