Reading: "The Trial of Galileo" by Chris Impey

On the first day of October in 1632, the dreaded Inquisitor of Florence, Italy knocked on the door of the famous astronomer, Galileo Galilei and served him with a summons to appear before the Inquisition in Rome within 30 days. The noted scientist was being forced to answer charges that he had promoted heresy in his latest book. Galileo was 68 years old, and these charges were extremely serious. Anyone found guilty of heresy could be sentenced to death.

What was Galileo's crime, according to the Catholic Church? Galileo had taken a stand against traditional views about the nature of the universe. He presented startling new evidence that our planet is not at the center of the universe. Galileo's own work, plus that of other scholars, had clearly convinced him that Earth and other planets moved around the Sun. These ideas seemed strange at the time. When people looked out from Earth, it certainly seemed that Earth was stationary and at the center of things, as if all bodies in the sky moved around us. The slow and difficult progress of Galileo's ideas shows how science works, sometimes in the face of opposition. Also, this new thinking was part of a famous revolution that affected the way all humans thought about their place in the universe.

The radical new idea that Earth is not a unique central body, but only a typical and average part of the universe, is called the Copernican revolution. This revolution in our sense of our place in the universe is named after the Polish scientist Nicolaus Copernicus, who had suggested in the 1500s that Earth was not at the center of the solar system. The Copernican revolution is one of the most important ideas in history, because it indicates that we are part of a larger cosmic environment, not the Masters of Nature living in the Capital of the Universe.

Galileo had come under fire from the Church for publicly advocating the ideas of Copernicus. He had published his initial conclusions supporting Copernicus in 1610. Six years later, a high-ranking Catholic official visited Galileo and advised him that Copernicus's view went against the teachings of the Roman Catholic church. The official directed that Galileo should not "hold or defend" these views, although he might discuss them as hypotheses. Galileo was shaken by this encounter but the pressure did not stop him from continuing his scientific work. Early in 1632, Galileo had published his masterwork, A Dialogue on the Great World Systems, in which two fictional characters debate whether or not the Earth is central. This is the book that got Galileo in trouble with the Church, because he presented the Copernican idea in strong and plain language and he used the rhetorical device of having the less clever character unsuccessfully defend the Church’s position.

After he received the summons to appear before the Inquisition, Galileo surrendered himself in Rome. The trial began in 1633. The surviving transcript shows the dilemma Galileo faced. At the beginning, Galileo was sure he could clear himself. One of the first questions from the Inquisitors was about what had happened during the cardinal's visit in 1616. Galileo described the visit and presented as evidence a 1615 letter from the Cardinal commending him for "speaking [only] hypothetically and not with certainty" about these issues. A second letter from the Cardinal, written in 1616, gave the order that "the Copernican opinion may neither be held nor defended, as it is opposed to Holy Scripture." Based on these letters, Galileo argued that his book debating the sides of the argument was within the spirit of the instructions he had been given.

According to the Inquisitors, Galileo had clearly leaned toward Copernicus. Worse yet, the Inquisitors produced their copy of the Cardinal's instruction, which contained an added phrase that Galileo was not to "teach that opinion in any way whatsoever." Galileo brandished his letter and denied that he had ever been told this last phrase. Some modern scholars believe that the Inquisitors' document was a forgery written by them after 1616. In any case, only one thing would satisfy the Inquisition. Galileo had to renounce his belief in the Copernican idea and deny that Earth moved around the Sun. The Inquisitors showed Galileo — by then an old man of 70 — the instruments of torture that might be used on him if he refused to cooperate. There was also a real possibility of his being burned at the stake, which had happened to the mystic and astronomer Giordano Bruno 33 years earlier.

Galileo faced an impossible moral dilemma. Should he risk death to defend his scientific observations in front of the secret Inquisition court, or should he recite a confession that would satisfy the judges and live to fight another day? He gave his answer. Even under the threat of death, he told them, he would never say that he was not a good Catholic or that he had tried to deceive anyone. However, under duress he would be willing to and say that he did not believe the new Copernican idea. In the end, he trusted that copies of his book would get out and that the scientific evidence would speak for itself. He begged the judges to "take into account my pitiable state of bodily illness, to which, at the age of 70 years, I have been reduced by ten months of constant mental anxiety." The trial came to a climax on June 22, 1633, when Galileo was summoned to kneel before the judges to hear his sentence and to recite a confession of error. The judges read a lengthy condemnation that included the Church's strong opposition to the Copernican revolution. Galileo was sentenced to house arrest for life. The Inquisitors ordered his book banned. He had to repeat his confession in public, saying that he would "abandon the false opinion that the Sun is the center... and that the Earth is not the center and moves," and vowing to "abjure, curse, and detest the aforementioned errors and heresies...."

There are several postscripts to this story of the confrontation between Galileo and the Catholic Church. As Galileo had hoped, his book was published elsewhere in Europe, and within a few decades his ideas were widely accepted. The Church could not stop the spread of new scientific ideas. In 1757, Galileo's book was removed from a list of books banned by the Catholic Church. In 1983, Pope John Paul II took up Galileo's case, and in 1992, he formally proclaimed that the Church had erred in condemning Galileo, and that science is a valid realm of knowledge "which reason can discover by its own power." This story perhaps makes clearer something that puzzles many people today — why academics, scientists, and intellectuals are so concerned about maintaining the freedom to pursue and express controversial views. The real point of Galileo's story is not the conflict between science and the church, it is the fact that entrenched ideology is the enemy of human understanding. As shown by Italy in the 1600s, or Germany in the 1930s,or the Soviet Union in most of this century — and even by episodes in the United States — it is very easy for an overzealous society to silence the voices of people who express unpopular ideas. History shows that unpopular ideas, like Galileo's, may turn out to be true!