Astroblog

C'mon. At least post a cross-link to PT. That's too nice an analysis to not get even wider distribution.
 

(comment cross-posted from The Panda's Thumb, 'cause it's kind of important.)

Speaking of getting things straight, you mean Kevin Miller, not Ken Miller. Authorship of the canonical high school biology textbook != scriptwritership of Expelled.
 

A few corrections (albeit remembered from long-ago research and with no ready references):

First, Copernicus's system started out with fewer epicycles than Ptolemy's, but was not as accurate. Copernicus modified it to make it more accurate than it started out to be (although I do not recall whether it was in fact more accurate than Ptolemy's) but as a result it had even more epicycles than Ptolemy's. Heliocentrism was a popular idea, but it was not more practical until Kepler discovered his Laws.

Second, in spite of its greater complexity, Galileo remained convinced of the Copernical model as Copernicus presented it -- with circular orbits and epicycles, and without Kepler's elliptical orbits -- throughout his career. In other words, Galileo was wrong. He was certainly more right than those who continued to defend the Ptolemaic system, but he was not without his own flaws, scientifically.

Finally, those flaws extended beyond science. He was a stubborn and tactless man, and this got him in trouble with the Church far more than his science. He was in fact on good personal terms with the Pope in power when he was convicted (I recall their being friends, but that may not be accurate), but insulted the intelligence of any who disagreed with him, which included several very powerful bishops. His book, which you describe as possibly the foundation of modern astronomy, was written at the request of the Pope, who wanted to see its ideas fully fleshed out and submitted to the scientific community. However, Galileo did two things that steered Church opinion against him: he was insulting to his opponents (who, as I mentioned, were politically powerful) and he wrote his book in Italian, not Latin.

In other words, his theory was presented as a popular science book! The Church's problem with this is that his taunts against his opponents were able to be read by the masses, rather than just the elites, thereby compounding his tactlessness. My point here is that, sometimes, popular-science books are important. Darwin's Origin was essentially a popular science book as well.

So, the fact that the ID movement has published only popular science books is not in and of itself a condemning fact. Of course, they are still wrong; publishing popular science books that misunderstand and misrepresent their subject material, and mislead their audience, is simply much easier than doing the same in established scientific venues.
 

I'm afraid you're wrong about the complexity. The Heiocentric system had about 30 fewer epicycles than the geocentric system, so the same levels of accuracy (remember, the heliocentric system didn't have to worry about retrograde motion).

Although published in Italian, the Dialogue was not what we would consider a popular book (in order to make it "scholarly", it was just translated into Latin) in terms of the detail.

Scholarly publishing has change over the past 400 years, and while books and monographs are less important than peer-reviewed papers now days, a good book can be very important.

Nothing the ID crowd has published can be described as a "good book" even in Galileo's sense.
 

Actually, it was Galileos' discovery of the moons of Jupiter that put paid to the geocentric system of Ptolemy. His observations left no doubt that the 4 objects he discovered with his telescope revolved around Jupiter.
 

Ian,

Thank you for this! I would be interested in hearing Ed Darrell's comments as well, since he's written about Galileo on his blog (for example, here).
 

Galileo's observations of the phases of Venus were what really put the nails in the coffin of the Ptolemaic system. Brahe came up with an ad hoc save, wherein Mercury and Venus orbited the sun (like moons of the sun), while the sun and the other planets orbited earth. But that was far from elegant or otherwise preferable, hence his assistant, Kepler, didn't buy it (the latter seems not to have liked Brahe overmuch either).

I know that Feyerabend and others have tried to argue that the Copernican model wasn't preferable to the Ptolemaic system, especially prior to seeing the phases of Venus. It was, though. The reason is that it actually explains some observations, while Ptolemy's system is only descriptive. That is to say, the Copernican model explains "retrograde motion" via a simpler means, which is that the planets were orbiting the sun--orbits were a known phenomenon, meaning that a known (science uses the known to explain the unknown) phenomenon explained the unknown in that model.

Of course there were still many questions remaining, including the epicycles in Galileo's model. Yet the feat of actually explaining the more prominent and troubling retrograde motions by having the planets orbit the sun ought not to be considered trivial.

It's a bit like the difference between evolution and ID. Both can accommodate biological information, but only evolution actually has an explanation, has empirical causes. You can say that it pleased God to put planets in epicycles, and that He desired that the planets (including the sun) orbit a point slightly offset from the earth (earth really wasn't the center in the final versions of "geocentrism), but that's just cheating. Actually explaining "retrograde motion" certainly beats merely modeling epicycles in a system that you prefer for religious and philosophical reasons (as late geocentrists did--early ones had physics objections, as one would if one accepted Aristotelian physics). Never mind that questions remained (as Feyerabend rather simplistically points out), explanations come out of the attempt to explain, and by building upon explanations--and note that Kepler built upon the actual explanatory model in order to meet the challenges remaining in that model.

Many academicians of the time didn't really see things that way, though. Explaining the heavens wasn't so much the point, as to merely have a good predictive model. They needed a predictive model for calendars and simply to have knowledge of the heavens, and the Ptolemaic system was as good as the Copernican for that. However, empiricists like Galileo, and his intellectual heirs in modern science, don't want mere predictions, they want entailed predictions. It's difficult to say just how entailed the predictions of the Copernican system were, considering that they didn't know why planets were in orbit at all, but at least it explained the unknown by the known (planets do orbit), rather than assuming an unknown explanation (epicycles) for the not understood phenomenon.

There was one more advantage to the Copernican system, which is that without exception, each successively more distant planet from the sun moved in a slower orbit. Even though Copernicus and Galileo had no explanation for this, it was an intriguing and apparently important correlation that arose in that model, while distances were merely uncertain and accidental (like ID's understanding of homologies and similar genes) in the Ptolemaic system. Even unexplained correlations matter to science (but not to pseudosciences like ID, which doesn't even appreciate the correlations explained by inheritance plus mutation), so this correlation was intuitively understood to be important by those who preferred the Copernican model.

Copernicus, Galileo, and Kepler were instrumental in overthrowing consensus, mainly because they correlated and explained phenomena which had not been explained or previously correlated. Kevin wants to make consensus itself out to be the enemy, mainly becaues he wants to replace the consensus model built upon correlation and explanation, with a "model" which dissolves correlation and voids explanation.

And of course, one really doesn't have to go back to Galileo to show how a consensus on an incorrect model is overthrown by a more explanatory and correlative model. One need only observe that Paleyism, which was largely the consensus at the beginning of the 19th century in spite of its even-then apparent problems, fell to the Darwinian revolution (even if natural selection wasn't well accepted at first). Explanation and correlation trumped the "Goddidit" of both Ptolemy's and Paley's system, and some still fight against explanation because they are enamored of non-explanatory models.

One last thought: If consensus itself is the enemy, why shouldn't we doubt the heliocentric model of our solar system (no, I don't want to get into the fact that we don't exactly orbit the sun)? Kevin appears not to be bothered by consensus in astronomy, only that in biology. Yet he can't actually use evidence to fault consensus in biology, so he merely complains about consensus itself, while oblivious to how hypocritical he's being.

Glen Davidson
 

Perhaps I should amend my comments to say that Brahe's model did have one advantage, which is that it didn't have the question of the lack of observed stellar parallax hanging over it.

However, when the distance to the stars is not known, you cannot insist that stellar parallax must be observable in the 1600s and earlier if we live in a heliocentric system. Thus the lack of observed stellar parallax did not much bother astronomers, especially after Kepler came up with his spectacularly successful model.

Glen Davidson
 

Hmm -- I may well be wrong. My last venture into the history of astronomy culminated with a reading of Arthur Koestler's The Sleepwalkers about fifteen years ago. I have not actually compared the original or revised Copernican systems against the established Ptolemaic alternative.

However, I do recall Koestler (and I apologise if he has since been discredited as a reference -- and would appreciate being pointed towards a more reliable one if that is indeed the case) remarking that the Ptolemaic system worked. It was Copernicus's commitment to the Aristotilean ideal of "uniform" circular motion (quotes used because the eccentrics used in his system rendered the motion of the planets anything but uniform) that led him to heliocentricity, rather than the inherent elegance of the idea or the accuracy of its predictions. Yes, it is true that retrograde motion is explained simply and easily by the Copernican model, but other facets of planetary motion, which were ultimately accounted for by Kepler's elliptical orbits and variable orbital velocities, required considerable tweaking. I should look into the relative complexities of each, of course, for which failure I do apologise.

As for the popular-science-book aspect of the Discourses, I have read from multiple sources (again, some fifteen years ago -- so no references that I can recall, aside from Koestler) that the Catholic Church's main objection to it was that the lay public could read it (and that reading it would make many high-ranking people look like fools). Whether or not it was actually much read, the perception by the Church officials was that it was damaging to their image, and that its author had to be discredited. I have read excerpts of the Discourses, which were at least translated into rather casual language, and did not dwell overmuch on technicalities; honestly, I thought the work as close as one could find to a Renaissance popular-science book. But my point is that, whether or not it filled that niche, the Church hierarchy perceived it as such, and that was more damaging to Galileo than was the book's actual content.

Finally, I apologise profusely if my remarks were construed in any way to defend the dreck put out by Intelligent Design proponents. I am myself a macroevolutionary biologist (only two papers published so far, but I am still in grad school -- and in any event I have generated more data than pretty much anyone in the ID movement in the last ten years), and oppose pretty much everything that the ID people stand for. I also oppose sloppy scholarship, and am compelled to point out that Galileo's situation was more complicated than is commonly recognised. I do apologise if I have details wrong.

Perhaps my main point is that our moral high ground is lost if we ignore or suppress inconvenient facts that render our position more complicated than we might like. Reality, whether exemplified through science or history, is complex, and glossing over such details only makes our opponents' jobs all the easier.
 

Glen--how could Tycho Brahe, who died in 1601, have come up with an ad hoc response to Galileo's observations of the phases of Venus in the 1610s? And Ptolemy, in the Almagest, made the absence of stellar parallax one of his chief arguments in favor of a geocentric cosmos. Tycho thought it supported his system because he could detect parallax in planets and comets but not in the fixed stars. Your general point is worthwhile but it's not well served by careless historical examples.