2.2: Heliocentrism vs. Geocentrism: A Case Study

The difficulty with applying the scientific method to this type of astronomical “experiment” is that one cannot “experiment” on this big of a system. There is no control group. However, we can still use the structure of the method to show how, over several centuries and several countries in Europe, heliocentrism became the norm.

Hypothesis: The First Modern Statement of the Theory

A Pole with the Latin pen name Nicolaus Copernicus (1473-1543) determined that the best way to explain all the “odd” astronomical data was to switch the positions of the Sun and the Earth. Poland was (and still is) a predominantly-Catholic country in Eastern Europe, so for much of his life Copernicus kept this theory to himself. Copernicus did not want to question the Church and be subject to persecution (or worse) from Poland’s secular leadership, especially as the Reformation spread throughout Europe.

Copernicus was not the first to profess of the heliocentric theory: some ancient and even medieval writers wrote about this possibility: Most labeled it as nonsense after weighing it with the common sense, beauty, and sense of self-worth attained from geocentrism.

Copernicus was convinced throughout his mature life that heliocentrism was the correct theory to describe the movement of the Earth and the Sun—however, the data still did not match perfectly, even with a heliocentric Earth-Sun swap in the system.

Nonetheless, Copernicus wanted to publish his views, and he did so in 1543, the last year of his life. He did this intentionally, as he knew he was dying and therefore knew that the Church couldn’t persecute him too much—on this planet, at least. Approving the final proofs of his book (On the Revolutions of the Heavenly Bodies) from his death-bed, Copernicus died before the book came out. However, as he had suspected, the Church was not pleased: Church officials placed the book on the Index.

The Data: Galileo Galilei and His Telescope

Throughout the next century, the Copernican system (as heliocentrism was now called) gathered more and more followers among the small new scientific community. This was especially true after more sophisticated observations emerged from the development of the telescope. However, it should be noted that, throughout the 17th century, the common people had not yet “converted,” as the theory still seemed like nonsense, especially when the Church labeled it as incorrect.

Though the telescope originally arrived in Europe through Holland, an Italian scientist, Galileo Galilei (1564-1642), perfected it and first aimed it at the night-time sky for scientific purposes. What he discovered was a major blow to Aristotelianism: the moon and the Sun were not perfect spheres but had ridges, mountains, and sunspots (first seen by Galileo and, many historians suspect, the cause of his later blindness).

The biggest observation that started to convert some in the scientific community to heliocentrism, however, was the published discovery of new moons. In his book The Starry Messenger (1610), Galileo wrote of sightings of four moons of Jupiter, which he named after his patrons, calling them “the Medicean Stars.” (Does that name look familiar from Chapter 1?) The fact that Galileo observed moons orbiting around a planet that was not Earth directly contradicted Aristotle’s and the Church’s position that the Earth was the center of everything in the universe. Jupiter was now seen to have moons while revolving around the Sun itself. Why couldn’t the Earth’s motion be the same, especially if this new system better described the observations coming from telescopes all over Europe?

At that point in 1610, however, Galileo refrained from commenting on the significance of his theory, fearing Church retaliation. Galileo waited until a mathematician pope was in Rome (another 20 years and then some) before coming out strongly in favor of the Copernican system in his book written in Plato’s dialogue style: Dialogue Concerning Two Chief World Systems (1632). While the geocentric-favoring figure technically had the last word, it was clear from the text that the evidence for heliocentrism far outweighed the evidence for geocentrism.

Advocates of geocentrism, however, claimed that the telescopes were faulty, that Galileo twisted the data, or that God had put this new evidence as a test for believers’ true faith. The Church put the book on the Index and the Inquisition put Galileo on trial and showed him instruments of torture that could be used to convince him of the geocentric truth. Galileo backed down and publicly took back his views, but he did not escape punishment. Fearing that Galileo would flee to Protestant Northern Europe, Church officials placed him under house arrest: he was grounded for the rest of his life, conducting small inclined plane experiments as his eyesight continued to fail him.

The Mathematical Conclusion: the Law of Universal Gravitation

The Church was right to fear the continuation of Galileo’s work in the North. In Anglican England, a brilliant young mathematician and scientist named Isaac Newton (1643-1727) was convinced that heliocentrism described the true way God had set up the universe. (We might call Newton a mystic today, in addition to a scientist, as he spent just as much time on alchemy and determining the exact date/time of God’s Creation of the universe as he did on gravity.)

Newton undertook to develop a system of precise mathematical laws that would support heliocentrism and accurately describe the entirety of the data about the planets. Luckily, he was a genius and his Latin book Principia Mathematica (1687) presented some very convincing mathematical manipulation and argued for a new math-based law that would more accurately describe the entirety of the known universe: the Law of Universal Gravitation. With gravity guiding him, Newton was not just able to describe the past observations. He was able to predict future observations such as eclipses, something that had not been possible under any variant of the geocentric theory ever proposed.

With Newton’s findings, the world was literally flipped upside-down. By the mid-18th century, heliocentrism had prevailed and geocentrism was seen as a superstition of the past. Nonetheless, due to the ever-critical nature of the scientific method, major holes in Newton’s theory came to light relatively quickly: while Aristotle’s theory lasted more than 2000 years, the “truth” of Newton’s theory lasted 300 or so. (We used to see about this “relatively quick light” in Chapter 7. [Ask Greenfield about Einsteinian space-time if you want the full story.])

The new world of scientific questioning (and uncertainty) was in place, and nothing physical, chemical, or biological could ever again be viewed with complete faith (and therefore without skepticism).

(The Church was a little behind the curve, though: the Inquisition’s errors with Galileo were finally apologized for in 1992.)


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