Introduction
A recent survey showed that the LessWrong discussion forums mostly attract readers who are predominantly either atheists or agnostics, and who lean towards the left or far left in politics. As one of the main goals of LessWrong is overcoming bias, I would like to come up with a topic which I think has a high probability of challenging some biases held by at least some members of the community. It's easy to fight against biases when the biases belong to your opponents, but much harder when you yourself might be the one with biases. It's also easy to cherry-pick arguments which prove your beliefs and ignore those which would disprove them. It's also common in such discussions, that the side calling itself rationalist makes exactly the same mistakes they accuse their opponents of doing. Far too often have I seen people (sometimes even Yudkowsky himself) who are very good rationalists but can quickly become irrational and use several fallacies when arguing about history or religion. This most commonly manifests when we take the dumbest and most fundamentalist young Earth creationists as an example, winning easily against them, then claiming that we disproved all arguments ever made by any theist. No, this article will not be about whether God exists or not, or whether any real world religion is fundamentally right or wrong. I strongly discourage any discussion about these two topics.
This article has two main purposes:
1. To show an interesting example where the scientific method can lead to wrong conclusions
2. To overcome a certain specific bias, namely, that the pre-modern Catholic Church was opposed to the concept of the Earth orbiting the Sun with the deliberate purpose of hindering scientific progress and to keep the world in ignorance. I hope this would prove to also be an interesting challenge for your rationality, because it is easy to fight against bias in others, but not so easy to fight against bias on yourselves.
The basis of my claims is that I have read the book written by Galilei himself, and I'm very interested (and not a professional, but well read) in early modern, but especially 16-17th century history.
Geocentrism versus Heliocentrism
I assume every educated person knows the name of Galileo Galilei. I won't waste the space on the site and the time of the readers to present a full biography about his life, there are plenty of on-line resources where you can find more than enough biographic information about him.
The controversy?
What is interesting about him is how many people have severe misconceptions about him. Far too often he is celebrated as the one sane man in an era of ignorance, the sole propagator of science and rationality when the powers of that era suppressed any scientific thought and ridiculed everyone who tried to challenge the accepted theories about the physical world. Some even go as far as claiming that people believed the Earth was flat. Although the flat Earth theory was not propagated at all, it's true that the heliocentric view of the Solar System (the Earth revolving around the Sun) was not yet accepted.
However, the claim that the Church was suppressing evidence about heliocentrism "to maintain its power over the ignorant masses" can be disproved easily:
- The common people didn't go to school where they could have learned about it, and those commoners who did go to school, just learned to read and write, not much more, so they wouldn't care less about what orbits around what. This differs from 20-21th century fundamentalists who want to teach young Earth creationism in schools - back then in the 17th century, there would be no classes where either the geocentric or heliocentric views could have been taught to the masses.
- Heliocentrism was not discovered by Galilei. It was first proposed by Nicolaus Copernicus almost 100 years before Galilei. Copernicus didn't have any affairs with the Inquisition. His theories didn't gain wide acceptance, but he and his followers weren't persecuted either.
- Galilei was only sentenced to house arrest, and mostly because of insulting the pope and doing other unwise things. The political climate in 17th century Italy was quite messy, and Galilei did quite a few unfortunate choices regarding his alliances. Actually, Galilei was the one who brought religion into the debate: his opponents were citing Aristotle, not the Bible in their arguments. Galilei, however, wanted to redefine the Scripture based on his (unproven) beliefs, and insisted that he should have the authority to push his own views about how people interpret the Bible. Of course this pissed quite a few people off, and his case was not helped by publicly calling the pope an idiot.
- For a long time Galilei was a good friend of the pope, while holding heliocentric views. So were a couple of other astronomers. The heliocentrism-geocentrism debates were common among astronomers of the day, and were not hindered, but even encouraged by the pope.
- The heliocentrism-geocentrism debate was never an ateism-theism debate. The heliocentrists were committed theists, just like the defenders of geocentrism. The Church didn't suppress science, but actually funded the research of most scientists.
- The defenders of geocentrism didn't use the Bible as a basis for their claims. They used Aristotle and, for the time being, good scientific reasoning. The heliocentrists were much more prone to use the "God did it" argument when they couldn't defend the gaps in their proofs.
The birth of heliocentrism.
By the 16th century, astronomers have plotted the movements of the most important celestial bodies in the sky. Observing the motion of the Sun, the Moon and the stars, it would seem obvious that the Earth is motionless and everything orbits around it. This model (called geocentrism) had only one minor flaw: the planets would sometimes make a loop in their motion, "moving backwards". This required a lot of very complicated formulas to model their motions. Thus, by the virtue of Occam's razor, a theory was born which could better explain the motion of the planets: what if the Earth and everything else orbited around the Sun? However, this new theory (heliocentrism) had a lot of issues, because while it could explain the looping motion of the planets, there were a lot of things which it either couldn't explain, or the geocentric model could explain it much better.
The proofs, advantages and disadvantages
The heliocentric view had only a single advantage against the geocentric one: it could describe the motion of the planets by a much simper formula.
However, it had a number of severe problems:
- Gravity. Why do the objects have weight, and why are they all pulled towards the center of the Earth? Why don't objects fall off the Earth on the other side of the planet? Remember, Newton wasn't even born yet! The geocentric view had a very simple explanation, dating back to Aristotle: it is the nature of all objects that they strive towards the center of the world, and the center of the spherical Earth is the center of the world. The heliocentric theory couldn't counter this argument.
- Stellar parallax. If the Earth is not stationary, then the relative position of the stars should change as the Earth orbits the Sun. No such change was observable by the instruments of that time. Only in the first half of the 19th century did we succeed in measuring it, and only then was the movement of the Earth around the Sun finally proven.
- Galilei tried to used the tides as a proof. The geocentrists argued that the tides are caused by the Moon even if they didn't knew by what mechanisms, but Galilei said that it's just a coincidence, and the tides are not caused by the Moon: just as if we put a barrel of water onto a cart, the water would be still if the cart was stationary and the water would be sloshing around if the cart was pulled by a horse, so are the tides caused by the water sloshing around as the Earth moves. If you read Galilei's book, you will discover quite a number of such silly arguments, and you'll see that Galilei was anything but a rationalist. Instead of changing his views against overwhelming proofs, he used all possible fallacies to push his view through.
Actually the most interesting author in this topic was Riccioli. If you study his writings you will get definite proof that the heliocentrism-geocentrism debate was handled with scientific accuracy and rationality, and it was not a religious debate at all. He defended geocentrism, and presented 126 arguments in the topic (49 for heliocentrism, 77 against), and only two of them (both for heliocentrism) had any religious connotations, and he stated valid responses against both of them. This means that he, as a rationalist, presented both sides of the debate in a neutral way, and used reasoning instead of appeal to authority or faith in all cases. Actually this was what the pope expected of Galilei, and such a book was what he commissioned from Galilei. Galilei instead wrote a book where he caricatured the pope as a strawman, and instead of presenting arguments for and against both world-views in a neutral way, he wrote a book which can be called anything but scientific.
By the way, Riccioli was a Catholic priest. And a scientist. And, it seems to me, also a rationalist. Studying the works of such people like him, you might want to change your mind if you perceive a conflict between science and religion, which is part of today's public consciousness only because of a small number of very loud religious fundamentalists, helped by some committed atheists trying to suggest that all theists are like them.
Finally, I would like to copy a short summary about this book:
In 1651 the Italian astronomer Giovanni Battista Riccioli published within his Almagestum Novum, a massive 1500 page treatise on astronomy, a discussion of 126 arguments for and against the Copernican hypothesis (49 for, 77 against). A synopsis of each argument is presented here, with discussion and analysis. Seen through Riccioli's 126 arguments, the debate over the Copernican hypothesis appears dynamic and indeed similar to more modern scientific debates. Both sides present good arguments as point and counter-point. Religious arguments play a minor role in the debate; careful, reproducible experiments a major role. To Riccioli, the anti-Copernican arguments carry the greater weight, on the basis of a few key arguments against which the Copernicans have no good response. These include arguments based on telescopic observations of stars, and on the apparent absence of what today would be called "Coriolis Effect" phenomena; both have been overlooked by the historical record (which paints a picture of the 126 arguments that little resembles them). Given the available scientific knowledge in 1651, a geo-heliocentric hypothesis clearly had real strength, but Riccioli presents it as merely the "least absurd" available model - perhaps comparable to the Standard Model in particle physics today - and not as a fully coherent theory. Riccioli's work sheds light on a fascinating piece of the history of astronomy, and highlights the competence of scientists of his time.
The full article can be found under this link. I recommend it to everyone interested in the topic. It shows that geocentrists at that time had real scientific proofs and real experiments regarding their theories, and for most of them the heliocentrists had no meaningful answers.
Disclaimers:
- I'm not a Catholic, so I have no reason to defend the historic Catholic church due to "justifying my insecurities" - a very common accusation against someone perceived to be defending theists in a predominantly atheist discussion forum.
- Any discussion about any perceived proofs for or against the existence of God would be off-topic here. I know it's tempting to show off your best proofs against your carefully constructed straw-men yet again, but this is just not the place for it, as it would detract from the main purpose of this article, as summarized in its introduction.
- English is not my native language. Nevertheless, I hope that what I wrote was comprehensive enough to be understandable. If there is any part of my article which you find ambiguous, feel free to ask.
I have great hopes and expectations that the LessWrong community is suitable to discuss such ideas. I have experience with presenting these ideas on other, predominantly atheist internet communities, and most often the reactions was outright flaming, a hurricane of unexplained downvotes, and prejudicial ad hominem attacks based on what affiliations they assumed I was subscribing to. It is common for people to decide whether they believe a claim or not, based solely by whether the claim suits their ideological affiliations or not. The best quality of rationalists, however, should be to be able to change their views when confronted by overwhelming proof, instead of trying to come up with more and more convoluted explanations. In the time I spent in the LessWrong community, I became to respect that the people here can argue in a civil manner, listening to the arguments of others instead of discarding them outright.
tl;dr: The side of rationality during Galileo's time would be to recognise one's confusion and recognise that the models did not yet cash out in terms of a difference in expected experiences. That situation arguably holds until Newton's Principia; prior to that no one has a working physics for the heavens.
The initial heliocentric models weren't more accurate by virtue of being heliocentric; they were better by virtue of having had their parameters updated with an additional 400 years of observational data over the previous best-fit model (the Alfonsine tables from the 1250s). The geometry was similarly complicated; there was still a strong claim that only circular motions could be maintained indefinitely, and so you have to toss 60 or so circular motions in to get the full solar system on either model.
Basically everyone was already using the newer tables as calculational tools, and it had been known from ancient times that you could fix any point you wanted in an epicyclic model and get the same observational results. The dispute was about which object was in fact fixed. Kepler dates to the same time, and will talk about ellipses (and dozens of other potential curves) in place of circular motion from 1610, but he cannot predict where a planet will be efficiently. He's also not exactly a paragon of rationality; astrology and numerology drive most of his system, and he quite literally ascribes his algebraic slips to god.
A brief but important digression into Aristotle is needed; he saw as key that was made was that the motion of the planets is unceasing but changes, whereas all terrestrial motions ceased eventually. He held that circular motions were the only kind of motion that could be sustained indefinitely, and even then, only by a certain special kind of perfect matter. The physics of this matter fundamentally differed from the physics of normal stuff in Aristotle. Roughly and crudely, if it can change then it has to have some kind of dissipative / frictional physics and so will run down.
Against that backdrop, Galileo's key work wasn't the Dialogue, but the Siderius Nuncius. There had been two novae observed in the 40 years prior, and this had been awkward because a whole bunch of (mostly neo-Platonists) were arguing that this showed the heavens changed, which is a problem for Aristotle. Now Galileo shows up and using a device which distorts his vision, he claims to be able to deduce:
From a viewpoint which sees a single unified material physics, these observations kill Aristotelian cosmology. You've got at least three centers of circular-ish motion, which means you can't mount the planets on transparent spheres to actually move them around. You have an indication that the Sun might be rotating, and is certainly dynamic. If you kill Aristotle's cosmology, you have to kill most of his physics, and thus a good chunk of his philosophy. That's a problem, because since Aquinas the Catholic church had been deriving theology as a natural consequence of Aristotle in order to secure themselves against various heresies. And now some engineer with pretensions is turning up, distorting his vision and claiming to upend the cart.
What Galileo does not have is a coherent alternative package of physics and cosmology. He claims to be able to show a form of circular inertia from first principles. He claims that this yields a form of relativity in motion which makes it difficult to discern your true motion without reference to the fixed stars. He claims that physics is kinda-sorta universal, based on his experience with cannon (which Aristotelian physics would dismiss because [using modern terminology] experiments where you apply forces yourself are not reproducible and so cannot yield knowledge). This means his physics has real issues explaining dissipative effects. He doesn't have action at a distance, so he can't explain why the planets do their thing (whereas there are physical models of Aristotelian / Ptolemaic models).
He gets into some pro forma trouble over the book, because he doesn't put a disclaimer on it saying that he'll retract it if it's found to be heretical. Which is silly and it gets his knuckles rapped over it. The book is "banned", which means two things, for there are two lists of banned books. One is "burn before reading" and the other is more akin to being in the Restricted Section; Galileo's work is the latter.
Then he's an ass in the Dialogue. Even that would not have been an issue, but at the time he's the court philosopher of the Grand Duke of Tuscany, Cosimo I de' Medici. This guy is a secular problem for the Pope; he has an army, he's not toeing the line, there's a worry that he'll annex the Papal states. So there's a need to pin his ears back, and Galileo is a sufficiently senior member of the court that Cosimo won't ignore his arrest nor will he go to war over it.
So the Inquisition cooks up a charge for political purposes, has him "tortured" (which is supposed to mean they /show/ him the instruments of torture, but they actually forget to), get him to recant (in particular get Cosimo to come beg for his release), and release him to "house arrest" (where he is free to come, go, see whoever, write, etc). The drama is politics, rather than anything epistemological.
As to the disputes you mention, some had been argued through by the ancient Greeks. For example, everyone knew that measurements were imprecise, and so moving the earth merely required that the stars were distant. It was also plain that if you accepted Galileo's observations as being indicative of truth, then Aristotelian gravity was totally dead, because some stuff did not strive to fall (cometary tails were also known to be... problematic).
Now, Riccioli is writing 20 years later, in an environment where heliocentrism has become a definite thing with political and religious connotations, associated to neo-Platonism, anti-Aristotelean, anti-Papal thinking. This is troublesome because it strikes at the foundational philosophy underpinning the Church, and secular rulers in Europe are trying to strategically leverage this. Much like Aquinas, Riccioli's bottom line is /written/ already. He has to mesh this new stack of observational data with something which looks at least somewhat like Aristotle. Descartes is contracted at about the same time to attempt to rederive Catholicism from a new mixed Aristotilean / Platonist basis.
As a corollary, he's being quite careful to list every argument which anyone has made, and every refutation (there's a comparatively short summary here). Most of the arguments presented have counterpoints from the other side, however strained they might seem from a modern view. It's more akin to having 126 phenomena which need to be explained than anything else. They don't touch on the apparently changing nature of the planets (by this point cloud bands on Jupiter could be seen) and restrict themselves mostly to the physics of motion. There's a lot of duplication of the same fundamental point, and it's not a quantitative discussion. There are some "in principle" experiments discussed, but a fair few had been considered by Galileo and calculated to be infeasible (eg. observing 1 inch deflections in cannon shot at 500 yards, when the accuracy is more like a yard).
Obviously Newton basically puts a stop to the whole thing, because (modulo a lack of mechanism) he can give you a calculational tool which spits out Kepler and naturally fixes the center of mass. There are still huge problems; the largest is that even point-like stars appear to have small disks from diffraction, and until you know this you end up thinking every other star has to be larger than the entire solar system. And the apparent madness of a universal law is almost impossible to understate. It's really ahistorical to think that a very modern notion of parsimony in physics could have been applied to Galileo and his contemporaries.
Thank you for that informed account of the history.
You mention three times, without attributing it to any contemporary of Galileo, that the telescope "distorted the vision", which is a tendentious description. Given that the military application of the telescope was grasped as soon as the instrument became known, who at the time made this criticism? Did they similarly eschew its terrestrial use for the improvement of vision?