Major Figures of the Scientific Revolution

Galileo

Mathematics and engineering professor Galileo Galilei of Pisa was the first to make extensive use of the telescope to study the planets. With this new invention—at that time no more than a plain narrow tube a little over a yard long, with concave and convex lenses inside—he was able to see things in the heavens that had simply not been visible to his predecessors.

Looking through his telescope in 1610, Galileo realized immediately that Jupiter had its own moons in orbit around it, just as the Earth had a moon. This discovery alone proved that Earth was not the center of the universe around which all other objects orbited. When Galileo published his new knowledge of the heavens, Kepler and most of Europe’s intellectuals, including the Jesuit astronomers, eagerly accepted them.

Through his telescope, Galileo saw the rings around Saturn, although he did not understand what they were. He observed that, contrary to Aristotle’s assertion that all heavenly bodies were perfect, smooth spheres, the surface of the Earth’s moon was craggy and irregular. Since the Church had accepted Aristotle’s theory of the universe, this meant that Galileo was well on his way to making an enemy of one of Europe’s most powerful institutions.

In 1632, Galileo published Dialogue on the Two Great Systems of the World. Written in the form of an imaginary dialogue between Copernicus and Ptolemy, this work discussed theories about planetary orbits and tides. A lifelong and devout Catholic, Galileo dedicated the Dialogue to Pope Urban VIII. It was clear that he anticipated no trouble from the Church because of his writing; he had carefully refrained from discussing certain forbidden topics, such as the work of Kepler.

To Galileo’s surprise, Urban VIII summoned him to Rome to appear before the Inquisition on the charge of defying the Holy Office’s policy against writing about Copernican theory. Galileo produced documentary proof of his assertion that he was permitted to write speculatively about Copernican astronomy. Despite this evidence, the Inquisition refused to face the public mockery that would have resulted from making a mistake over a figure so internationally famous as Galileo. The Holy Office therefore sentenced Galileo to deny the validity of his own discoveries, then placed him under custody of the liberal archbishop of Siena, who encouraged him to continue working and writing. In effect, Galileo remained under house arrest until his death in 1642. He was free to study, experiment, and write, although it proved difficult (though not impossible) to find publishers in the face of a Holy Office ban on anything he might produce.

Within the next few years Galileo’s works spread throughout Europe in various translations and editions. His last book, The Two New Sciences, discussed the structure of matter, the strength of materials, and the laws governing natural motion. He discovered the laws of falling bodies and the mathematical formula we use to describe acceleration.

Defending his own writings in his later personal correspondence, Galileo argued that God had given human beings the ability to observe and reason. What people could see and understand with their five senses must be the truth; for instance, that planets moved around the sun. He argued that if this appeared to conflict with the scriptures, then human understanding of the scriptures must be at fault.

Newton

The year of Galileo’s death saw the birth of Isaac Newton in rural Lincolnshire, England. Newton attended Cambridge University and studied the works of Galileo and Kepler. Newton revolutionized scientific thinking in Europe with his discovery of the principle of gravity—the single, constant force in the universe that attracted objects to one another. Newton realized that it was gravity that attracted the planets to the sun and the moons to the planets; gravity was what kept each body in a regular orbit at a constant distance from the larger mass around which it revolved. Newton’s work explained how gravity could be calculated mathematically; he was the first scientist to apply calculus to astronomy.

The importance of Newton’s discovery of the principle of gravity cannot be underestimated. It revolutionized European thinking, proving once and for all that the people could understand the way their own world worked. Before Newton, Europeans had understood the universe as operating by divine whims that they could not hope to understand; after Newton, they understood it as operating by fixed, comprehensible laws. For the first time, an understanding of the world could be based on human reason and experience, not on faith.

Like Galileo and those who had gone before him, Newton believed that his scientific theories were perfectly compatible with Church teaching. In his view, the law of gravity was a divine creation, and he was doing honor to God by revealing his divine plan. Unfortunately, the Church could not accept this view; as it had always done, it reacted to independent intellectual endeavor with suspicion and hostility. In a sense, the Church was right to recognize the threat posed by scientific discovery. Since science proved that the Church had been teaching an inaccurate and false theory of the structure of the universe, all Church teaching was called into question. The Scientific Revolution permanently weakened the place the Church held in popular regard.

Practice questions for these concepts can be found at:

The Scientific Revolution and the Enlightenment Practice Test