After you've read some of the science blogs for long enough, you start to think that there isn't any amount of crackpottery that can surprise you. For instance, reading Good Math, Bad Math will expose you to an endless amount of mathematics abuse, from bible code crazies to horrible mathematical 'proofs' of God. If you read Pharyngula, you will encounter so many creationists and Biblical literalists to make you want to become a Pharisee.
But I was really stunned when I discovered (h/t Pharyngula) another science blog where trolls are actually arguing in favor of geocentrism, the long-debunked view that the Earth is the fixed center of the universe and everything else revolves around it.
It turns out that there's even a website, www.geocentricity.com, which is apparently the home of 'biblical astronomy' (I'm not gonna honor it with a link). The site was created and is operated by an apparent Ph.D. in astronomy, Dr. Gerardus D. Bouw. It is hardly worth attacking such a crazy site with criticism, but it is a perfect illustration of the difference between good scientific theories and bad 'scientific' theories: the absence or presence of numerous ad hoc assumptions, respectively.
But first, let's look at some 'highlights' of Biblical astronomy, starting with what might be called their mission statement on the front page:
This site is devoted to the historical relationship between the Bible and astronomy. It assumes that whenever the two are at variance, it is always astronomy—that is, our "reading" of the "Book of Nature," not our reading of the Holy Bible—that is wrong. History bears consistent witness to the truth of that stance.
So the fundamental assumption of Biblical astronomy is that the Bible is infallible. Even if astronomical evidence appears which contradicts a literal reading of the Bible, the Bible is assumed to be true and the experimental evidence wrong. This is reminiscent of Steven Colbert's famous (joke) statement, "Facts have a well-known liberal bias." We hardly need to read any further on the geocentricity page, because this statement has conclusively demonstrated that whatever they think they're doing there, it's not science. Science requires developing theories which explain the experimental evidence, not interpreting the experimental evidence to fit one's theory.
Let's push on anyway. Under the FAQ, "Why geocentricity?", the following statement appears:
To hear tell, geocentrism, the ancient doctrine that the earth is fixed motionless at the center of the universe, died over four centuries ago. At that time Nicolaus Copernicus (picture below), a Polish canon who dabbled in astrology, claimed that the sun and not the earth was at the center of the universe. His idea is known as heliocentrism. It took a hundred years for heliocentrism to become the dominant opinion, and it did so with a complete lack of evidence in its favor.
Here we find two rhetorical tricks that are often used by crackpot scientists. The first of these is a relatively tricky straw man argument. Though Copernicus may have suggested that the Sun is the center of the universe (though I doubt he even explicitly said that), modern physics says no such thing. In modern parlance, heliocentrism is simply the statement that, as the dominant mass in the solar system, the Sun is more or less the central point of motion. The Sun is not assumed to have a special place in the center of the universe. This misunderstanding of heliocentrism is not corrected anywhere in the FAQ.
The straw man argument sets up the second logical fallacy, that of a false dichotomy. By pretending that heliocentrism vs. geocentrism is simply a case of Sun vs. Earth, the author is attempting to put them on equal footing and pretend that you've got only two choices - Sun as center of universe or Earth as center of universe. Astrophysics is far, far more complicated than the author would like you to believe.
There is an appalling lack of quantitative analysis in the entire web site. Some legitimate general relativity references are thrown in as evidence that geocentrism is no different than 'heliocentrism', though they provide nothing of the sort. I suspect the author of the site threw them in knowing full well that his target audience would not be reading subtle general relativity arguments. I won't delve into these GR arguments here, but to note an amusing contradiction: the author is using papers on relativity (which is a theory which implies there is no 'preferred' frame of reference) to argue that the Earth is the unmistakable center of the universe (which suggests that the Earth IS the 'preferred' frame).
One can also download a 160-page primer on geocentricity from the web site. Anyone hoping for more quantitative analysis, however, will be disappointed: the primer is completely devoid of any quantitative proof of the validity of the geocentric system, but instead lists scripture and explains how the experimental observations can be shoehorned to fit the scriptural view.
There's a lot to mock here, but we'll restrict ourselves to commenting on one point: the idea of retrograde motion. From the perspective of Earth, the planets do NOT orbit the Earth in a continuous circular motion, but instead sometimes 'turn around' and go the other way for a time. This is illustrated magnificently by this applet. The reason for this retrograde motion is that the Earth is moving faster in its orbit than Mars is. As we approach the closest point of approach to Mars, the illusion is created that Mars is moving backwards, as we are in fact overtaking and passing the planet.
This system created a big problem for Ptolemy, who championed the geocentric system in 2nd century Greece. He solved the problem by introducing 'epicycles' for the planets: in addition to them moving in their circular orbits around the Earth, they are moving in a smaller circular path around their own central orbits. These epicycles worked quite well, but not perfectly, and additional 'circles within circles' needed to be introduced to correct the model. The system became much simpler when Copernicus introduced the Sun-centered solar system, and even simpler when gravitational theory was introduced and understood.
The geocentricity people manage to come up with a motion of the planets that reproduces these 'epicycles'. The amusing thing is that their extremely complicated picture shows that the Earth remains at an equal distance from the Sun at all times, and Mars remains an equal distance from the Sun at all times as well! The picture (Fig. 13 in their primer) strongly suggests, unintentionally, that Mars' motion is dictated by the position of the Sun, not the Earth!
The overall problem with the 'theory' of Biblical geocentrism, is its ad hoc nature. Their theory starts from the Bible. It turns out that astronomical observations don't match the Bibles' 'literal truth', so they introduce, one by one, and independently, 'patches' for their theory to make it fit the data. The result is a 'theory' which is extremely complicated and inconsistent, and has as many explanations as there are observations. A good scientific theory tends to replace a number of complicated observations with a fewer number of scientific principles.
We'll have more to say about ad hoc theories later, in particular concerning relativity theory (something else the geocentrists don't seem to understand).