Geocentrism and the Middle Ages

Flyer for the Geocentrism conference
The site might have
exceeded bandwidth...

I was over reading one of my favorite blogs - Bad Astronomy - when I stumbled on an article Phil Plait had written about an upcoming conference about Geocentrism. He does an amazing job in this particular article deconstructing the theory. In brief, geocentrism (lower-case g) is using the Earth as a frame of reference when describing the universe (much as heliocentrism is used to describe the sun as the center of our solar system). But geocentrism doesn't necessitate the belief that Earth is the center of the universe, fixed, and unmoving - it simply posits that Earth can be viewed as stationary in relation to other objects in the universe. There is another Geocentrism (with a capital-G) that believes that the Earth is immovable and fixed in the universe and the rest of the universe revolves around us (i.e., it's the center of the universe). It's this Geocentrism that Phil takes to task in a way that I can only envy. I have some good understanding of Newtonian physics and relativity, but he understands and can communicate it in a way that I appreciate and enjoy. And I encourage you to check out the article.
The reason that I'm even remotely interested in this is that there's a whole heap-load of myths about what the inhabitants of the middle ages believed, Geocentrism being prime among them. I mean, they all thought that the Earth was the center of the universe and that the world was flat, right? It wasn't until Christopher Columbus came along in 1492 and proved them wrong. Oh, yeah, and that Galileo guy got punished for believing that the sun was the center of the solar system, right? Fortunately, no.
Just a couple of things about this whole thing. First, the Greeks back in the long-ago's BC knew the world was round. How? They'd done experiments with wells in Alexandria and Syene showed that the sun didn't create the shadow the same way it would were the world flat. In fact, those shadows proved it had to be a sphere. (By the way, it was really Eratosthenes in the second century BC.) Plus, they'd seen eclipses and the shadow of the Earth on the moon is round (although you could likely argue that's because the moon is round). Regardless, Eratosthenes had calculated the circumference of the spherical Earth quite accurately (for the day). It was relatively well-known (by the semi-educated, at least) that the Earth was not flat. For the average medieval peasant, though, eking out an existence on a small plot of land for a feudal system that destroyed any potential for advancement, whether the world was flat, spherical, or a Mobius strip was just not something they cared about. So, Columbus was wrong. Not about the world being a sphere (because he and most everyone else knew that), but apparently he couldn't do basic math and thought the world was much smaller than it was. And on his way west he hit that big landmass between him and India. Oops - his bad.

Tractatus de Sphaera -
with Ptolemaic System

Second, let's take the geocentric/heliocentric/acentric thing with Galileo. The problem was that those self-same Greeks who had determined that the world was a sphere also contended that it wasn't moving. I mean, if it was, wouldn't it leave everything behind? If the ground were to suddenly move, the things that weren't fixed to it (birds, etc) would move in space and not of their own volition. Since that wasn't happening, the ground had to be firm and not moving. They created the Ptolemaic system (shown right) which laid out that the heavens were a series of spheres set around the Earth. This worked great until they started looking at all of the planets outside the orbit of the Earth (Mars, etc) - those planets moved backwards sometimes (went retrograde - something with which astrologers were very familiar) and if everything were just moving around above us, that couldn't easily happen. So they added spheres to the spheres and that seemed okay for a while. But then Copernicus said that maybe this whole Geocentric thing was bunk. And then something weird happened with Galileo - he found moons orbiting another planet (Jupiter). And he found that the phases of Venus were far better explained by it orbiting the Sun than orbiting the Earth. Suddenly Copernicus' theory was looking pretty good. In the end, the primary charge against Galileo was that they thought he was saying that the sun, not the Earth, was the center of the universe. Again, a heliocentric view is perfectly valid using frames of reference, but Heliocentric (capital-H) is still very wrong.

Tychonian System

There was a major contender to Copernican theories at the tie and that was the theory of Tycho Brahe (he of the silver nose). His system (shown right) moved some of the planets to the orbiting the sun and the rest orbiting the Earth. It was sort of an amped up version of the Ptolemaic system that tried to address some of the things that Galileo had observed (Brahe was a scientist, after all). In the end, though, Occam's Razor sliced through the whole mess and what made the most sense (and made the math look really pretty, something that every mathematician and astronomer likes to see) was a model where the Earth was just another of the wanderers around an average star we call Sol.
For the Geocentrists out there (and thankfully there are far fewer than the number who believe that Obama is a muslim), the math just doesn't really work out for an Earth-as-the-center-of-the-universe model. One thing Phil raises is that Pluto would need to travel faster than the speed of light to race around the world and rise on the next day. And that doesn't even include the other much-further-away objects out there. It may seem like they're going that fast, but we all know that the 186,282 miles per second limit isn't just a good idea, it's the law. Of course, most of the bases for these theories comes not from scientific observation (because that would pretty much destroy any potential for the theory to be correct), but rather it's because in the poetic parts of the bible there are statements like "the world also is stablished, that it cannot be moved" (Psalms 93:1). Okay - so maybe Archimedes is wrong (the whole lever and world thing?), but the Psalms wax poetic, not scientific. Not eating pork? Good idea when you couldn't cook your meat thoroughly. The world being fixed and stationary? Yeah, not so much.
In the interests of full disclosure, I will point out that one of my relatives is a staunch Geocentrist. He wrote an entire paper about why Copernicus and Kepler were wrong. My cousin Jack included it in the book on the deVaux family history. Admittedly, I got lost in the mathematics and couldn't finish it. Then again, I also staunchly believed in geocentrism, not Geocentrism, so it made it more difficult to find the gumption to read it with an open mind. Wait - that's what we need more of in the world. Oh, snap. Guess I need to find that book and get to reading...

N.B.: the two manuscript pics are from Wiki, so if you happen to see them, you'd be right in asserting that I foisted stole borrowed creatively commons'd them.
N.B. 2: N.B. means nota bene, which means "note well". I will use that rather than footnotes for most things I post. I know that some people have never seen this (having been told so by some people).