Why care about the manuscript that launched Galileo to fame? Because it is a landmark in the history of science and Christianity. This is the paper that Galileo wrote when he first turned his telescope to the heavens to see mountains on the moon and satellites orbiting Jupiter. Why does that matter? Because it changed everything about how man thought about the order of the world.
“Galileo did not believe that science, as a method of demonstration and reasoning capable of human pursuit, would ever answer all questions of interest to humanity, or even very many of them. How he arrived at that view is the story of his life and work.” -Stillman Drake
Part 3: Scientific Significance
It seemed to many scholarly philosophers that Galileo was breaking with the traditional physics of Aristotle.1 In some ways, he was. He was breaking with the conclusions of Aristotle about how the natural world was ordered, but not with the epistemology Aristotle taught and defended. In fact, Galileo was careful to guard the approach to knowledge that held experience and observation as necessary for establishing truth.
He believed that the visible world was describable by universal truths, but took it a step further by also insisting that universal truths of nature were subject to mathematical verification as well. He believed that the study of motion involves not only the application of logic, as Aristotle had believed, but also the application of mathematics.2
Galileo is often referred to as the “Father of Modern Science” because he showed that natural phenomena obey mathematical laws.3 Even though Sidereus Nuncius is the work that launched Galileo to fame, it wasn’t his first principal writing. Galileo had already written numerous manuscripts, letters and treatises regarding his ideas of motion and mechanics as they relate to natural philosophy.4His Pisan manuscript De motu (On Motion) in 1592 directly addressed Aristotelian physics, applying mathematical ideas taken from Archimedes to causal ideas taken from Aristotelian philosophy.5 Galileo served as the chair of mathematics at Padua from 1592-1610 and wrote the manuscript posthumously published as Le Meccaniche (On Mechanics) in 1600. It is believed by historians to be a summary of his public lectures on the statics of simple machines.6
Galileo thought his most significant discovery revealed in Sidereus Nuncius was the four satellites orbiting Jupitor because if it were true, then that would prove that the contradicting idea of natural philosophers that the earth was the center of all celestial motions was in error.7 Since the second century A.D. the Ptolemaic system was the model that adequately accounted for observed cosmological phenomena, and philosophers and theologians accepted this model because perfect circular motion seemed an appropriate explanation for perfect and unchanging heavenly bodies described by Aristotle.8 This model held that the motionless, round earth was in the center of the universe with the moon, sun and planets moving about it in systems of circles and epicycles.9
Early in the sixteenth century Copernicus, an astronomer, reluctantly published computations that introduced greater order and symmetry to the conception of the heavens, but his model required removing the earth from its distinguished position at the center of the universe. A preface to his book clearly advised readers that the ideas were not absolute or literal and only hypothetical, and no storm of controversy erupted on its publication just before his death in 1543.10 It was not considered heretical to study such systems as long as they were hypothetical devices and not taken as absolute realities.11Copernicus described two centers of heavenly motion; the Earth with the moon revolving around it and the Sun with the Earth and the other planets revolving around it. Those who opposed Copernican theory thought it was absurd to think that an orderly and harmonious creation could have more than one center of motion. Galileo’s observations taken as true proved that there were at least two centers of motion, the Earth and Jupiter.12
1. Marvin Perry, Myrna Chase, Margaret C. Jacob, James R. Jacob, Western Civilization: Ideas, Politics, and Society (NY: Houghton Mifflin Harcourt, 2009), p. 406.
3. Peter Hodgson, Ph.D., Galileo: Science and Religion, DVD, (IN: International Catholic University, 2000/2005), Lecture 2 – Galileo and the Renaissance.
4. Stillman Drake, Essays on Galileo and the history and philosophy of science, Volume 3 (Toronto: University of Toronto Press Incorporated, 1999) p.153-154.
5. Stillman Drake, Galileo: A Very Short Introduction (NY: Oxford University Press, Kindle Edition, 1980), Kindle Location 351-352.
6. Drake, Essays, pp. 153-154.
7. Drake, Galileo, Kindle Location 583.
8. Stillman Drake, Discoveries and Opinions of Galileo (NY: Doubleday & Company, 1957), p.11.
9. Perry, p. 154.
10. Drake, Discoveries, p. 13.
11. Drake, Discoveries, p. 15.
12. William E. Carroll, Ph.D., Galileo: Science and Religion, DVD, (IN: International Catholic University, 2000/2005), Lecture 1 – The Legend of Galileo.