A Simple Guide to the Universe as the Medieval’s Saw It (Plus Something About Galileo)
I’ve been doing some interesting reading lately about the Middle Ages. The Middle Ages are particularly interesting to learn about because we already have some pretty strong ideas about what they were like. When you hear “Middle Ages” or “Medieval” your mind immediately is filled with images of castles, knights in shining armor, jesters, grubby peasants, witch burning, and the Catholic Church. If we were asked to explain what the Middle Ages were, we’d probably have to say that they were a period of ignorance and violence between the fall of the Roman Empire and the Renaissance. What we usually fail to realize (and what I was completely ignorant of) was that the people of the Middle Ages had an incredibly complex and developed conceptual model of the universe. We think that if they looked up at the stars at all they just wondered what they were; in reality they knew exactly what they were, where they were, and how all that related to themselves. C. S. Lewis’ book The Discarded Image deals with this model, and it’s a fascinating read. It also helps us shed some light on a historical event that we all “know” very well, but don’t truly understand: the trial of Galileo.
We are taught two main facts about Galileo: he discovered that the earth orbits around the sun, and the church forced him to deny his findings and then put him under house arrest until his death. The standard explanation for why the church refused to consider the idea that the Earth orbits the sun is that it would go against their religious principles. Everything must orbit the Earth because the Earth is the most important and central part of all creation. If the Earth revolves around the Sun then we would lose our “place of honor” in the universe. After all, Christianity teaches that God Himself became a man and died for our salvation: therefore Earth must be the center of the universe. The Church didn’t like Galileo proposing otherwise and used its power to shut him up for good. This is a nice, neat little story about how religion and science will always be at odds. It’s also complete codswallop.
To understand why, we have to understand what the Medieval conception of the universe was. Let’s start at the most basic building blocks. Medieval scholars believed that (almost) everything material was defined by its position relative to “The Four Contraries” (or Opposites). The Four Contraries were Moist, Dry, Hot, and Cold.
The four elements that made up everything (almost, I’ll get to that later) come from the combination of these four Contraries. Fire is a combination of Dry and Hot, Water of Moist and Cold, and so on.
Most of us are familiar with the four “classical” elements, Earth, Wind, Fire, and Water. The people of the Middle Ages believed that everything that existed under the moon was made up of these four elements. I say under the moon because the Medieval model had no conception of space as an empty vacuum. Instead they believed that everything beyond the moon was filled with Aether (also known as Quintessence, one of the coolest sounding words ever). Aether was the purest substance possible. It was completely transparent and made up the “atmosphere” of space.
Have you ever (probably in science class) taken a glass beaker and filled it with equal parts water and oil? As you know the oil will form a solid layer on the top, with the water falling below. If you poured in several liquids of different densities into the beaker and waited long enough they would all form individual “pure” layers based on density. Medieval scholars understood this just as well as we did, and they applied it to the universe. Aether could never mix with the four classical elements because it was “purer” than them. Even if you could somehow stir up air or earth or water past the moon and into the aether it would soon settle back down to earth. The four elements each had their own level of purity. Earth was the least pure, and it formed the “bottom layer” of the universe, so to speak. Next in purity was water, which sits on top of earth in the oceans lakes and rivers. After that comes air, which forms the atmosphere above earth and water. Finally fire makes up the final layer before we reach the aether. This may seem surprising to us, but it made sense from the Medieval point of view. They believed that the fire we see on earth is “impure” fire, full of contaminants like ash and smoke. They conceived that fire in its purest form was completely transparent, nothing but pure heat. If you’ve ever watched the heat distortion come off the top of a fire and “rise” to the sky then you can probably understand why they thought this way.
This leads us to one of the most important things to understand about the Medieval Model. Contrary to popular belief the people of the Middle Ages did not believe that the Earth was flat. It had been well known that the Earth was round ever since the days of the Greeks: they even had a fairly accurate estimate of the Earth’s circumference. They also understood gravity; not mathematically or scientifically (that would wait until Newton), but in principle. They knew that since the Earth is a sphere and gravity pulled all things “down” relative to your position then all things must be pulled toward the center of the Earth. Therefore Earth must be at the center of the universe. After all it wouldn’t make sense for all things to be pulled toward just any random point. Note that the center of the universe is not a much honored position in this case: it would be more accurate to say that Earth is at the bottom of the universe. Earth was literally made up of the impure dredges of the cosmos, the clogged up drain of the universe.
This point is made even clearer when we look at Medieval Astronomy. We already know that the five elements form five layers around the Earth from most impure to most pure: earth, water, air, fire, and aether, like so.
The Moon’s orbit acts as a boundary between Earth and the rest of the universe. Under the moon is all that is impure: beyond it is nothing but purest aether; literally Heaven. The model continues from there. Each planet (and the sun) also orbits around the Earth of course, and each one forms another boundary into a higher level of Heaven. The Stellatum is the second to last layer, and it contains all the “fixed” (unmoving) stars, forming the backdrop of space. The final layer is the Prime Mover, which is the sphere that causes all the other spheres to rotate. The Prime Mover is the edge of the universe. Beyond it is nothing but God, eternal and limitless. Notice, again, that Earth is the farthest location in the universe from God’s “home”. We’re far closer to Hell, which they believed was encased at the center of the Earth.
Then there’s the matter of scale. We know that space is big. Really big. Incredibly big. I mean just the idea of a light year, a single light year, is immensely, fantastically, amazingly large. And there are trillions of light years of space out there! So we’re familiar with the immensity of space. It would be easy to assume, because the Medieval Model of space is finite with a defined “edge” at the Prime Mover, that the Medieval’s universe must have been rather small. But Medieval man still had some idea of the scale of the universe. They believed that in comparison to the rest of the spheres Earth was smaller than a pinprick. One popular work, the South English Legendary estimated the distance between the Earth and the Stellatum to be over 120 million miles. When it comes to scale, C.S. Lewis explains it best:
“For thought and imagination, ten million miles and a thousand million are much the same . Both can be conceived…and neither can be imagined…the really important difference is that the medieval universe, while unimaginably large, was also unambiguously finite. And one unexpected result of this is to make the smallness of Earth more vividly felt. In our universe she is small, no doubt; but so are the galaxies, so is everything—and so what? But in theirs there was an absolute standard of comparison…The world ‘small’ as applied to Earth thus takes on a far more absolute significance (The Discarded Image pgs. 98-99).”
So let’s summarize: Earth is the bottom of all creation, millions of miles from God, insignificantly tiny compared to the rest of the universe, and made up of a collection of the impure dredges of all existence with Hell itself at its center. This is our “place of honor” in the universe, and it’s what most people misunderstand about the impact of Galileo’s theory. Galileo didn’t make the Earth too unimportant: he gave it back its importance. Today we may think of the Earth as many things: small, insignificant, fragile. But we no longer consider it the garbage heap of the universe. We no longer consider it the lowest place in all creation. Compared to the dead worlds we’ve discovered so far Earth is something very special and precious indeed.
So why did the Church reject his theory outright, forcing him to deny its truth? That is a case that could take up a whole book itself, and this post is long enough already. The only point I wanted to make is this: Galileo’s ideas were not rejected because they made man too small. If anything, they made man far too large.