Maggie: We are discussing Copernicus today, right?
John: Yes. But first we need to talk about the medieval background that gave rise to Copernicus.
The Medieval Background
Maggie: I thought that astronomy died after Ptolemy.
John: That is not exactly correct. Astronomy did not advance as a science in the western world until Copernicus, and some would say that it retreated. But there were some developments that kept it alive that we should mention.
Maggie: Before we begin, can you tell me why some people call the medieval time the “Dark Ages”?
John: What a really good question.
There are many different reasons. But for our purposes, it has to do with the loss of the Greek language. Remember from our previous discussions that most of the advancements in western astronomy were written in Greek?
John: Well, after the fall of Rome, knowledge of the Greek language died away among western scholars and most of the important Greek texts became unavailable. As a result, all of the astronomical knowledge that previously existed in the western world through these texts was lost.
Maggie: Including the works of Aristotle and Ptolemy?
John: Yes, including these. Western scholars did not have access to these works and even if they did, they couldn’t read Greek. So astronomy was set back many hundreds of years.
Maggie: How did this change?
John: The first thing that we need to remember is that while astronomy was losing ground in the western world, this was not the case elsewhere. The Islamic world was making incredible advances during this time.
Maggie: I don’t know anything about Islamic astronomy. Perhaps we can talk about this after we finish our conversations on western astronomy?
John: Agreed, and we can cover both Islamic and other eastern advances. But for our purposes here, it is enough to know that the Islamic nations were keeping astronomy alive, making advances in astronomy, and preserving the great astronomical texts.
Then, starting in the Tenth century, western scholars began to have contact with Islamic centers of learning. This is our second point.
Over the next couple-hundred years, western scholars traveled to places like Spain to study with Islamic scholars. They then brought their knowledge back to Europe, along with astronomical books that they had translated into Latin, including Ptolemy’s Almagest.
Maggie: That had to blow their minds.
John: It did. Can you imagine what these scholars thought when the first read the Almagest?
Maggie: It must have freaked them out when they realized that Ptolemy was far ahead of them, even though they were scholars.
What happened next?
John: That is our third point: at this same time, western scholars also rediscovered Aristotle.
Maggie: From the Islamic nations again?
John: Most likely. And here is what is weird. Although Ptolemy had made advancements on the astronomy of Aristotle, it was Aristotle’s theory that came to be more generally accepted.
Maggie: Why, because that does not make any sense to me.
John: It is because of Thomas Aquinas. He was a Dominican monk who lived around 1225 to 1274. And he was incredibly smart: Albert Einstein smart. And he loved Aristotle. He studied and adopted Aristotle’s theories, but he applied them to develop a Christian theology. This included Aristotle’s astronomy, which he applied to develop a distinct Christian cosmology.
Maggie: Oh, wait, wait, wait. I get it. Because Aristotle was applied in a Christian context, he was accepted by the Christian church, which held power in most of Europe at that time.
John: Exactly right, my friend. Aristotle’s cosmology became widespread and accepted for this exact reason. And it was so well accepted that it became incorporated into the academic curriculum of the time, so students also learned it and passed it along.
Maggie: So let me sum this up. After the fall of Rome, astronomy took some steps backwards. This was because the Greek texts were lost to the western world for a time. But starting in the Tenth century, western scholars started studying with Islamic scholars and relearned Greek and the Greek texts, including the texts of Aristotle and Ptolemy. But then Thomas Aquinas applied Aristotle in a Christian context, and as a result, Aristotle’s theories came to dominate the western world. Am I right?
John: Exactly right. And nice summary. So what do you think comes next?
John: Here is a picture of Copernicus:
Maggie: Can you start by telling me something about his personal life? I like knowing something about the astronomers before I try to understand their theories.
John: Me too.
His full name is Nicolaus Copernicus. He was born in Poland and lived from 1473 to 1543. When he was 17, he entered the Polish University at Krakow. It was one of the leading mathematical universities of the time and had a strong reputation in astronomy.
Then in 1496, Copernicus went to Italy to study church law, which was fortuitous. Just four decades earlier, in 1453, the city of Constantinople had fallen to the Muslims. Before it fell, many scholars of the Greek traditions had left the city for universities in Italy. So when Copernicus arrived, Greek was being taught in several places and Greek philosophy was widespread. Scholars in the universities had also become fascinated by astronomy and puzzled by the debate over planetary movement.
Maggie: So that is how Copernicus learned about Aristotle?
John: Right! Copernicus arrived in Italy to study church law, but became fascinated with both Greek and astronomy, learning both. In fact, he became so well versed in astronomy that, in 1500, he gave a scholarly lecture on the subject.
Then, in 1503, he moved back to Poland and became a church canon.
Maggie: What’s that?
John: Think of it as a kind of church administrator. He wasn’t a priest, but someone who managed the affairs of a church.
More importantly for us, he also became a private astronomer, studying the stars and planets.
Maggie: What was the name of his famous book?
John: You are asking all the right questions and making my job so easy.
He developed his theories in a book entitled On the Revolutions of the Heavenly Spheres. It was published in 1543, the year that Copernicus died.
Maggie: And that is where he came up with the heliocentric view of the universe, which was a major paradigm shift in astronomy?
John: It makes me so happy that you remember the terms that we previously used. And yes, exactly. Copernicus’s book facilitated a paradigm shift because after its publication astronomy shifted from a geocentric (earth centered) theory to a heliocentric (sun centered) theory.
Maggie: So cool! Tell me more about his theory.
John: Copernicus was bothered by the fact that Aristotle’s theory did not line up with his observations. The more he studied the universe and the planetary movements, the more he became convinced that he could solve many of the problems if he placed the sun at the center of the universe. The planets then rotated around the sun.
Here is a picture of his universe.
Maggie: It looks like the planets rotate around the sun in perfect circles.
John: Yes, Copernicus maintained the Aristotelian obsession with perfect concentric circles. It was a flaw in his theory that would be resolved latter by Johannes Kepler. He also kept the idea that the stars were perfectly fixed in space.
Maggie: Copernicus’s theory seems so easy, I don’t understand why it took so many centuries for scholars to come up with it.
John: You have to remember that much of the western world was under the power of the church during the medieval time period. The church believed that the earth was at the center of the universe because human beings were at the center of God’s creation. So a theory that made the earth a mere planet that rotated around the sun flew in the face of church teaching.
Maggie: So Copernicus was defying church teaching?
John: Exactly, which is why he did not try to publish his complete theory earlier in his life.
But when his book was published, it solved many of the problems of the Aristotelian system. It was predominantly a mathematical treatise, working out the math for a heliocentric universe. But it was radical.
Here are a couple cool quotes from his book:
“At rest in the middle of everything is the sun.”
“For in this most beautiful temple who would place this lamp in another of better position than that from which it can light up the whole thing at the same time.”
Maggie: I love these radical scholars who had the courage to change the world.
John: Yeah, me too.
Maggie: I am looking forward to our next discussion.