Weird Internet Ideas: Supporting Geocentricism

This post is just collecting bits from a couple of comments I made here in relation to a curious species of argument that crops up from time to time. It is not literally people arguing that the Earth is at the center of the Solar System but rather various kinds of excuse making for those who supported geocentricism post-copernicus and post-Galileo and/or giving various kinds of rationalizations for the Catholic Church’s persecution of Galilelo and attempted suppression of the heliocentric model.

The discussion started with somebody pointing to this book: which I guess I’m going to have to buy and read and review at some point now [sigh].

A previous sighting of this odd position was one I covered here in the in the 2nd worst nomination for Best Related Work in the 2015 Hugo awards:

While popular culture prefers to paint Galileo as persecuted by the Church for his science — indeed, consequently founding a counter-religious illuminati of scientists — careful study of history reveals that Galileo was not “persecuted” for his beliefs, but rather he was sanctioned by Rome for his personal actions in defiance of a church order of which he was a member. – Why Science is Never Settled 
By Tedd Roberts

Galileo could have been wrong in all sorts of ways. We know he was wrong about the sun being the center of the Universe and we have a more sophisticated under of relative motion these days – but even if we swap who said what there is a substantial ethical issue. If Galileo had been advocating the GEOcentric model and the Church had adopted the HELIOcentric model then charging him with heresy, threatening him with torture and placing him under house arrest for the rest of his life would still be wrong. Well ‘wrong’ at least by my pajama-wearing cocoa-sipping partisan of gay marriage, gun control, socialized medicine standards.

The claim I was addressing at File 770 though was this:

It was rational at the time to think Galileo was wrong and Tycho Brahe right.

Rational? Well in the sense of ‘not bat-dropping insane’ given the available evidence but not in the sense of ‘best hypothesis based on the evidence and reasoning’.

Brahe’s suggested model was already a massive concession to heliocentrism. Basically it involved the planets orbiting the Sun (which by that point for a decent astronomer was absurd not to accept) but to have the moon, stars and Sun orbit the Earth. The question is why would he bother with such a model? Because he thought the Earth was special and that because it was a big lumpy thing that it couldn’t move. Why special? Because of his religious and philosophical beliefs rather than because of empirical observation – and the second objection (the Earth is a big rocky lumpy thing and hence can’t be revolving around etc) was a belief that really wasn’t sustainable anymore once people could see that the moon was also a big rocky lumpy thing that definitely did move around on a regular basis.

Here is the man himself: “What need is there without any justification to imagine the earth, a dark dense and inert mass, to be a heavenly body undergoing even more numerous revolutions than the others, that is to say subject to a triple motion, in violation not only of all physical truth but also of the authority of Holy Scripture, which ought to be paramount.”

Now, I do think this is a wonderful example of how rational and learned people can cling to beliefs despite the evidence of THEIR OWN RESEARCH for cultural, philosophical and religious reasons.

Think about this. It was Tycho Brahe who effectively killed the scholastic/Aristotlean view of the ‘heavens’. In that view everything beyond the moon was essentially unchanging (a view that was both religious and philosophical in nature – a reflection of earthly corruption below and divine perfection above). Brahe’s observations of a supernova allowed him to demonstrate that this was an occurrence in what was supposed to be celestial sphere of fixed stars (i.e. beyond the planets). In doing so he effectively killed the whole notion of the duality of the imperfect Earth (and moon) and perfect heavens. Now without that idea the whole geocentric model no longer made any sense except as a pure article of faith. There was NO reason to regard it as being particularly true as the only thing it brought to the party was the philosophical distinction between the crappy earth and perfect heavens.

The heliocentric model’s problem (and its problem with the Church) was that despite its computational advantages it violated that pure-heavens/crappy-earth distinction. Now if that distinction was taken as a given then you could argue that geocentrisim (or Brahe’s mashup mix of the two) was rational in so far as the pure-heavens/crappy-earth distinction was axiomatic for the crazy-mixed up view of the universe courtesy of Thomas Aquinas making Artistotle trendy in the Catholic church hundreds of years earlier.

Now here is a mystery – why do I keep writing about Thomas Bloody Aquinas? I no sooner stop writing about him in one odd context derived from SF/F related blog reading then I end up writing about him in another context and now he has snuck up on me again!

I’m being cyber-stalked by the ghost of Thomas Aquinas.

My correspondent then offered one example of a defense of Brahe’s position:

Brahe was measuring the apparent diameters of stellar discs as between 2 arcminutes and 20 arcsecs, depending on their magnitude. Galileo found them to be a consistent few arcseconds which astronomers at the time thought to be more accurate since the telescope removed “adventitious rays”. But there was no parallax observed in stars throughout the year. Now, according to the Copernican model, this is because the stars are so distant that the parallax was too small to be measured. In the 17th century, they could measure down to about an arcsecond, so in modern units the stars had to be at least about a parsec away for no parallax to be observed. But at that distance, a 2 arcsecond disc would mean a star the size of Earth’s orbit. If stellar parallaxes were even smaller, then this would mean that they’d have to be even larger.

Basically, when we look at things some distance a way and we then move we should notice relative shifts in position because of the change in angle which we are looking at things. No parallax effects were visible among the stars and in telescopes stars appeared to be discs. Much of this has been superseded by later discoveries. Stars looked like discs because of issues with telescopes and the stars are too far for us to notice parallax without really, really good telescopes. Copernicus’s model took the ‘stars are really far away’ approach and Brahe poo-pooed that notion because the discs people saw would have to be ginormously ginormous.

Now, remember that at this point in history (early 17th century) what does a RATIONAL person know about stars:

  1. They appear fixed (as opposed to planets, comets, the moon and other things)
  2. They appear to move relative to an observer on Earth
  3. They are not like anything on Earth or near it
  4. When you look at them through a telescope they look like discs (a newish discovery which we now know to be due to instrumentation)
  5. Occasionally new ones appear (as Brahe discovered)
  6. They are further away than the furthest planet and that according to either model is a long, long way away

So given that how big is TOO big for a star to be RATIONALLY? Rationally I don’t know anything about the possible size range of stars if I live in the early 17th century. Bigger than anything that I have ever encountered? Rationally that is a possibility I’d have to accept as under either model they must be pretty sizable to be further away than any planetary orbit and still look like discs. Rationally at what size should our rational person of the time say is ‘too big’ for an estimated size of a star? Despite the measurement, the careful observation and the geometry, that argument was simply an argument from incredulity. A rational person would not rely on star size as a valid argument.

Arguably a rational person of the time could pick a hybrid geocentric/heliocentric model which has the stars smaller and closer and with no need to explain parallax? Well they could but then you’d have to explain why everything orbits around the Earth rather than say, Jupiter. Put enough effort into and enough fudge factors (of which both the Ptolemaic and Copernican systems had to have) you could probably get a workable Joviancentric model together :). You’d be stuck for a defensible explanation of the seasons and actual parallax issues with other planets have to be explained in other ways (i.e. parallax also helps confirm the Copernican model when looking at planets and less so when looking at stars).

Also, despite public denials, it has been found that Exxon executives were planning on the basis of the heliocentric model…no, wait, I’m getting my historical periods science-denial topics mixed up again.

8 thoughts on “Weird Internet Ideas: Supporting Geocentricism

  1. They appear to move relative to an observer on Earth

    Nope. That was the point of “no parallax”. They did NOT move relative to an observer on Earth.

    You’re also missing something in point 4 – they appeared to be roughly THE SAME SIZE.

    Now, consider the Copernican position – “the stars are very big and very far away”. Based on the evidence available, not only would they have to be far away, they’d have to be arranged in such a way so that either

    – i, they were all about the same size arranged in a globe centered on the Sun-Earth system OR

    – ii, even more mind-boggling, they’d still have to be centered on the Sun-Earth system but the further away they were from Earth, the bigger they were on a consistent basis.

    Either way, the Copernican system, according to the evidence of the time, was arguing for Divine engineering to make the Sun-Earth system a Very Special Place. And it did so in a fashion that blew up sizes and distances to ludicrous proportions just to slide around the inconvenient fact that there was no parallax observed.


    1. Perhaps I worded it oddly: when a person looks at the stars from Earth, those stars appear to move ie across the sky, rising in the east and setting in the west.
      But yes relative to one another it looked like (back then) that they had fixed relative positions.


    2. But…you are back to the same argument from incredulity. What would be a ludicrous size fir a star? Even with the ammendments you suggest nothing indicates any upper limit for star size. In Brahe’s model they are still big things.


  2. No, I’ve read the “Setting Aside All Authority” book. RDF is right. Brahe is not like you portray him. You’d have to explain why there’s just this one itty-bitty sun with its ittier-bittier little planets surrounded by these huge stars. The Copernicans brought in all sorts of “God did it” stuff to explain the star sizes, all along the lines that the reason why there’s just this one itty-bitty sun is because the stars are the guardians of heaven. Real rational. Meanwhile, Brahe also noted absence of physical evidence for rotation.


    1. My point is that the Copernican model is weak in areas that other models are weak including Brahe’s. There are implications that run counter to sensible but unspotted beluefs about astronomical distances but those implications were just as reasonable as existing beliefs.


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