Lecture 11: The Scientific Revolution, 1600-1642

I do not feel obliged to believe that that same God who has endowed us with senses, reason, and intellect has intended to forgo their use and by some other means to give us knowledge which we can obtain by them.

---Galileo, Letter to Grand Duchess Christina (1615)

In a previous lecture I suggested that before Isaac Newton could conceive of and demonstrate the laws of universal gravitation, a practical understanding of motion was required (see Lecture 10). This practical understanding of mechanics would be provided by an Italian astronomer and mathematician by the name of GALILEO GALILEI. Born at Pisa in 1564, Galileo studied medicine and mathematics and became a professor at Pisa in the late 1580s. But because the largely Aristotelian faculty was hostile to him, Galileo decided to move on to Florence. Eventually he settled at Padua and between 1592 and 1610 his mathematics lectures at the university attracted students from across the Continent.

The key to all of Galileo's discoveries was the accurate measurement of time. Accurate measurement of time was essential if the mechanics of motion were to be explained. By 1600, there were no accurate clocks or time keeping devices. There were clocks, of course, but none of them were at all precise. Medieval clocks were convenient for dividing the day but not for keeping precise time. Galileo was fascinated with time. As the story goes, Galileo was attending a religious service at Pisa in 1583. His thoughts began to wander and as he gazed about he noticed the swinging motion of a lamp that hung from the ceiling. It was then that Galileo was struck by the uniform motion of the pendulum. The pendulum, if kept swinging at a constant rate, keeps near perfect time. Galileo experimented with various sorts of motions and falling bodies. This, after all, was what helped him determine the mechanics of motion. His observations of falling bodies at Pisa are only the most well known of his experiments. He rolled balls of varying size and weight down slopes with varying angles of incline. He showed that an object thrown into the air falls to the earth along a parabola. What he ended up doing was casting doubt on Aristotelian mechanics -- he challenged the monopoly on scientific education enjoyed by university clerics who had, so he thought, learned nothing since their earliest encounter with Aristotle.

Around 1609 Galileo had news of a development from Holland -- a lens grinder had taken two lenses and placed them at opposite ends of a metal tube. A rudimentary telescope was the result. Galileo made his own telescope as well as a compound microscope. Galileo directed all of his attention to the heavens. He was the first man to see craters on the moon, sun spots and the rings of Saturn. He also observed the phases of Venus. He determined that the Earth's moon was not a source of light but rather of reflected light. He saw the moons of Jupiter. And of course, Galileo was also a Copernican: "Sol est centrum mundi, est omnio immobile motu locali," ("The sun is the center of the universe and the earth moves.")

In 1611, Galileo packed his brass telescope in his bag and decided to go to Rome. The previous year, Galileo had reported his findings in his book, THE STARRY MESSENGER. Criticism of Galileo's observations began immediately. The authorities at Rome would not even look through his telescope. Why not? They had absolute faith in Aristotle. Not only that, if you think about it, the telescope reveals the existence of things which are not really there. Look at the heavenly body called Saturn with the naked eye. Do you see its rings? Of course not. In Galileo's day, seeing something that could not be seen with the naked eye was the same thing seeing apparitions or hearing voices -- it was the work of the Devil! The religious authorities at Rome were uneasy with the New Science. Copernicus, Kepler and Galileo seemed to be turning the world upside down. The sun was the center of the cosmos, the earth moved and the sky seemed to hold hidden visions. In effect, the Scientific Revolution had created an invisible world behind the visible world and those men of an older generation, weaned on Aristotle and Aquinas were fearful of it.

On April 12, 1615, Cardinal Bellarmine (1542-1621) wrote his famous LETTER TO FOSCARINI, a letter which expressed his displeasure with Copernican theory. The following year, Galileo was summoned to Rome and ordered to desist teaching Copernican theory. He was, however, free to think about Copernican theory, but he could not teach it or write about it. Galileo agreed to this condition but still maintained that his mechanical philosophy described the natural world better than any alternative explanation. He was confident, extremely confident, that his position was the correct one. So confident was Galileo that in 1632 he imagined that the decree regarding his public advocacy of Copernican theory could be overturned. He began to criticize the clergy,

who would preach the damnability and heresy of the new doctrine from their very pulpits with unwanted confidence, thus doing impious and inconsiderate injury not only to that doctrine and its followers but to all mathematics and mathematicians in general.

The new science, so though Galileo correctly, was unsuited to pulpit discussion. In fact, Galileo was more than aware of this necessity and in the defense of the new science, we can see the first stage of a century long struggle between faith and reason.

The new science was also unfit for public discussion. On the one hand, as a practical man with an eye toward the applicability of science, Galileo knew that the new science could improve the human condition. On the other hand, however, he argued that it was necessary not to allow the public too much knowledge regarding the motions of the heavenly bodies -- at the very least, the public mind ought to be enlightened slowly and cautiously:

The shallow minds of the common people must be protected from the truth about the universe lest they should become confused and obstinate in yielding assent to the principle articles that are absolutely matters of faith.

In Galileo's mind, the new science was a body of knowledge intended for the learned elite. It was not intended for public consumption.

Furthermore, Galileo argued, the new science did not contradict the deeper meanings of the Holy Scriptures. The wise man should seek the true sense of the Scriptures, the true meaning. But, in matters of physical problems, we ought not begin from the authority of Scriptural passages but from sense experience and necessary demonstrations: in a word, natural philosophy. Aristotle had not observed enough, nor as freely as Church authorities believed and so Galileo and the rest of his fellow revolutionaries went beyond The Philosopher -- they had done a much better job of using their senses. By arguing that man must look beyond the literal meaning of the Scriptures, Galileo unwisely put himself in disagreement with Council of Trent. In 1546, the Council prohibited "any attempt to twist the sense of Holy Scripture against the meaning which has been and is being held by our Holy Mother Church." The Council, of course, was clearly reacting to the onslaught of the Lutheran Reformation. The medieval synthesis had been assaulted on several fronts but in one last ditch effort, Rome built its last defense -- Galileo was the fall guy!

In 1623, Galileo's friend and admirer Maffeo Barberini was elected Pope Urban VIII (1568-1644). An intelligent but vain man, Barberini had much in common with Galileo -- both men considered themselves above the common man. Galileo enjoyed six audiences with Baberini and was rewarded with lavish gifts from him. Galileo reasoned that the time was now right to publish a new defense of Copernican theory. His confidence at an all time high, he spent four years composing the new Copernican manifesto. His Dialogue Concerning the Two Chief World Systems, Ptolemaic and Copernican, was cleared by Church censors, one of whom was Galileo's former student, and was published at Florence in 1632. As the title suggests, Galileo grounded his manifesto in the form of a dialogue rather than a treatise. The dialogue, Galileo reasoned, was a device through which an argument for Copernican theory could be made without violating the papal decree of 1616. Two of the conversants -- Salviati and Sagredo -- are sympathetic to Copernican theory. Simplicio, the third participant, represents Aristotle and the Scholastics and is presented as fool. Galileo's enemies were quick to inform the Pope that the official cosmology of the Roman Catholic Church had been put in the mouth of Simplicio. The Pope ordered an investigation and so in August 1632, less than six months after it had appeared, the Inquisition banned further sales of the book. Galileo's book was placed on the Index of Forbidden Books and there it remained until 1757.

Galileo was ordered to appear before the Inquisition at Rome. He awaited intervention by the Pope, his former friend, but it never came. He also believed, quite innocently, that he could show that Copernicanism was not in any direct opposition to Church dogma, However, as Galileo found out, what was at issue was not so much heliocentricity but authority. Galileo quickly realized what was at stake. The now seventy year old Galileo was interrogated relentlessly and threatened with torture. The Church had a strong defense -- it was clear that Galileo had violated the prohibition placed upon him in 1616. He could believe Copernican theory but not publicly defend it. To prove their position, the Church produced the forged minutes of Galileo's meeting with Cardinal Bellarmine in 1616. Unfortunately for Galileo, by 1632, Bellarmine was dead. The document produced by the Church was clearly forged. It acknowledged that Galileo could not hold, teach or defend Copernican theory in any way. This was a much stronger prohibition than Galileo could recollect. (See the Galileo Trial Documents) Without a defense of any kind, Galileo took his only reasonable option and on June 22, 1633, he recited the required abjuration on his knees:

Wishing to remove from the minds of your Eminences and of every true Christian this vehement suspicion justly cast upon me, with sincere heart and unfeigned faith I do abjure, damn, and detest the said errors and heresies, and generally each and every other error, heresy and sect contrary to the Holy Church; and I do swear for the future that I shall never again speak or assert, orally or in writing, such things as might bring me under similar suspicion.

The trial at an end, the abjuration made public, the broken Galileo spent his remaining eight years under house arrest at his villa outside Florence. It was at this time that he wrote perhaps his finest book, the Dialogues Concerning Two New Sciences, a study of motion and inertia. His eldest daughter, Sister Marie Celeste (1600-1634), whom he had sent to a convent against her wishes twenty-three years earlier, stayed with him to the end. Every day she said the seven Psalms of penitence ordered by the Holy Office as part of his sentence.

Galileo continued to gaze at the stars through his telescope until 1637, when his sight finally failed him. "This universe that I have extended one thousand times," he wrote, "has now shrunk to the narrow confines of my own body." The trial and condemnation of Galileo marked the climax of the first wave of the Scientific Revolution. He had helped to unlock some of the mysteries of the cosmos for his fellow man.

However, his trial also signified something else. The weight of papal authority which had brought Galileo to his knees also succeeded in halting the growth of the new science in Italy. It is no accident then, that following Galileo's death in 1642 that the greatest advances in science would come from outside Italy in countries like England, Holland and Germany. These were, after all, Protestant countries with a tradition of protest and toleration. But 1642 also signifies something else for it was in that year that the man most responsible for producing modern science was born. That man was Isaac Newton (see Lecture 12).