A LesserWrong user (LesserWrong-er?) has a thought-provoking post on The Copernican Revolution from the Inside, with two questions in mind: (1) if you lived in 17th century Europe, would you have accepted heliocentrism on an epistemic level, and (2) how do you become the kind of person who would say yes to question 1? It’s interesting in the sense the often-asked question of “What would you be doing during the Civil Rights Movement/Holocaust/Other Time of Great Societal Change” is, in that most people realize they probably would not be a great crusader against the norm of another time. But as someone in Charlottesville in the year 2017, asking about what you’d be doing in scientific arguments is less terrifyingly relevant than asking people about how they’d deal with Nazism, so we’ll just focus on that.
For once on the internet, I recommend reading the comments, in that I think they help flesh out the argument a lot more and correct some strawmanning of the heliocentrists by the OP. Interestingly, OP actually says he thinks
In fact, one my key motivations for writing it — and a point where I strongly disagree with people like Kuhn and Feyerabend — is that I think heliocentrism was more plausible during that time. It’s not that Copernicus, Kepler Descartes and Galileo were lucky enough to be overconfident in the right direction, and really should just have remained undecided. Rather, I think they did something very right (and very Bayesian). And I want to know what that was.
and seems surprised that commenters think he went too pro-geocentrist. I recommend the following if you want the detailed correction, but I’ll also summarize the main points so you don’t have to:
- Thomas Kehrenberg’s comment as it corrects factual errors in the OP regarding sunspots and Jupiter’s moon
- MakerOfErrors for suggesting the methodological point should be that both geo- and heliocentric systems should have been treated with more uncertainty around the time of Galileo until more evidence came in
- Douglas_Knight for pointing out a factual error regarding Venus and an argument I’m sympathetic to regarding the Coriolis effect but evidently am wrong on, which I’ll get to below. I do think it’s important to acknowledge that Galilean relativity is a thing, though, and that reduces the potential error a lot.
- Ilverin for sort of continuing MakerOfError’s point and suggesting the true rationalist lesson should be looking at how do you deal with competing theories that both have high uncertainties
It’s also worth pointing out that even the Tychonic system didn’t resolve Galileo’s argument for heliocentrism based on sun spots. (A modification to Tycho’s system by one of his students that allows for the rotation of the Earth supposedly resolves the sunspot issue, but I haven’t heard many people mention it yet.)
Also, knowing that we didn’t have a good understanding of the Coriolis effect until, well, Coriolis in the 1800s (though there are some mathematical descriptions in the 1700s), I was curious to what extent people made this objection during the time of Galileo. It turns out Galileo also predicted it as a consequence of a rotating earth. Giovanni Riccioli, a Jesuit scientist, seems to have made the most rigorous qualitative argument against heliocentrism because cannon fire and falling objects are not notably deflected from straight line paths. I want to point out that Riccioli does virtually no math in his argument on the Coriolis effect (unless there’s a lot in the original text that I don’t see in the summary of his Almagestum Novum). This isn’t uncommon pre-Newton, and no one would have the exact tools to deal with Coriolis forces for almost 200 years. But one could reasonably try to make a scaling argument about whether or not the Coriolis effect matters based only on the length scale you’re measuring and the rotation speed of the Earth (which would literally just be taking the inverse of a day) and see that that heliocentrists aren’t insane.
It’s not a sexy answer to the second question, but I think “patience for new data” goes a long way towards making you the kind of person who can say yes to the first question. You hear the term “Copernican revolution” thrown around like a very specific event, and I think it’s pretty easy to forget the relative timeframes of major players unless this is your bread and butter. Copernicus’ De revolutionibus came out in 1543. Newton’s Principia came out in 1687, which gives a physical explanation for Kepler’s empirical laws and results in them becoming more greatly accepted, and so can be considered a decent (if oversimplified) endpoint for the debate. Galileo began to get vocal about heliocentrism in the early 1610s. The Almagestum Novum came out in 1651. For over a century, people on both sides were gathering and interpreting new data and refining their theories.
I also like this article for a related point, albeit one a bit removed from the author’s thesis. In considering the question of how should accept new theories, we see the historical development of one theory overtaking another as “scientific consensus”. Earlier this year, rationalist Scott Alexander in a post on Learning to Love Scientific Consensus concisely summarized why the typical “consensus is meaningless” trope of just listing times consensus has turned out to be wrong isn’t particularly useful in understanding science:
I knew some criticisms of a scientific paradigm. They seemed right. I concluded that scientists weren’t very smart and maybe I was smarter. I should have concluded that some cutting-edge scientists were making good criticisms of an old paradigm. I can still flatter myself by saying that it’s no small achievement to recognize a new paradigm early and bet on the winning horse. But the pattern I was seeing was part of the process of science, not a condemnation of it.
Most people understand this intuitively about past paradigm shifts. When a creationist says that we can’t trust science because it used to believe in phlogiston and now it believes in combustion, we correctly respond that this is exactly why we can trust science. But this lesson doesn’t always generalize when you’re in the middle of a paradigm shift right now and having trouble seeing the other side.
The notion of “trusting” scientific consensus I think gets to a larger point. There are way more non-scientists than scientists, so most people aren’t in a place to rigorously evaluate contemporary analogues to the Copernican revolution, so you often have to trust consensus at least a little. Also scientists aren’t scientists of every field, so even they can’t evaluate all disputes and will rely on the work of their colleagues in other departments. And given how many fields of science there are, there’s always probably at least one scientific revolution going on in your lifetime, if not several. Fortunately they don’t all take 150 years to resolve. (Though major cosmological ones can take a long time when we need new instruments and new data that can take a long time to acquire.)
But if you want to be the kind of person who can evaluate revolutions (or maybe attempts at revolutions), and I hope you are, then here’s a bit more advice for the second question à la Kuhn: try to understand the structure of competing theories. This doesn’t mean a detailed understanding of every equation or concept, but realize some things are more much important to how a theory functions than others, and some predictions are relatively minor (see point 4 below for an application to something that I thing pretty clearly doesn’t fall into a revolution today). To pure geocentrists, the phases of Venus were theory-breaking because geocentrism doesn’t allow mechanisms for a full range of phases for only some planets, and so they had to move to Tycho’s model. To both groups writ large, it didn’t break the scientific theories if orbits weren’t perfectly circular (partly that was because there wasn’t really a force driving motion in either theory until Kepler and he wasn’t sure what actually provided it, so we see how several scientific revolutions later, it gets hard to evaluate their theories 100% within the language of our current concepts), though people held on because of other attachments. Which leads to a second suggestion: be open-minded about theories and hypotheses, while still critical based on the structure. (And I think it’s pretty reasonable to argue that the Catholic Church was not open-minded in that sense, as De revolutionibus was restricted and Galileo published his future works in Protestant jurisdictions.) In revolutions in progress, being open-minded means allowing for reasonable revision of competing theories (per the structure point) to accommodate new data and almost maybe more importantly allows for generating new predictions from these theories to guide more experiment and observation to determine what data needs to be gathered to finally declare a winning horse.
- Let me explain how I corrected my view on the Coriolis effect. We mainly think of it as applying to motion parallel to the surface of the Earth, but on further thought, I realized it does also apply to vertical motion (something further from the center of the Earth is moving at a faster rotational velocity than something closer, though they do have the same angular velocity). Christopher Graney, a physics and astronomy professor at Jefferson Community and Technical College who I will now probably academically stalk to keep in mind for jobs back home, has a good summary of Riccioli’s arguments from the Almagestum Novum in an article on arXiv and also what looks like a good book that I’m adding to my history/philosophy of science wishlist on Amazon. The Coriolis effect arguments are Anti-Copernican Arguments III-VI, X-XXII, and XXVII-XXXIII. Riccioli also addresses the sunspots in Pro-Copernican Argument XLIII, though the argument is basically philosophical in determining what kind of motion is more sensible. It’s worth pointing out that in the Almagestum, Riccioli is collecting almost all arguments used on both sides in the mid-17th century, and he even points out which ones are wrong on both sides. This has led some historians to call it what Galileo’s Dialogue should have been, as Galileo pretty clearly favored heliocentrism in Dialogue but Riccioli remains relatively neutral in Almagestum.
- I’m concerned someone might play the annoying pedant by saying a) “But we know the sun isn’t the center of the Universe!” or b) “But relativity says you could think of the Earth as the center of the Universe!”. To a), well yeah, but it’s really hard to get to that point without thinking of us living in a solar system and thinking of other stars as like our sun. To b), look, you can totally shift the frames, but you’re basically changing the game at that point since no frame is special. Also, separate from that, if you’re really cranking out the general relativity equations, I still think you see more space-time deformation from the sun (unless something very weird happens in the non-inertial frame transform) so it still “dominates” the solar system, not the Earth.
- For a good example of the “consensus is dumb” listing of consensuses of the past, look at Michael Crichton’s rant from his “Aliens Cause Global Warming” 2003 Michelin Lecture at CalTech beginning around “In science consensus is irrelevant. What is relevant is reproducible results.” Crichton gets close to acknowledging that consensus does in fact seem to accommodate evidence in the plate tectonics example, but he writes it off. And to get to Crichton’s motivating point about climate science, it’s not like climate science always assumed man had a significant impact. The evolution of global warming theory goes back to Arrhenius who hypothesized around 1900 that the release of CO2 from coal burning might have an effect after studying CO2’s infrared spectrum, and it wasn’t until the 60s and 70s that people thought it might outweigh other human contributions (hence the oft-misunderstood “global cooling” stories about reports from the mid-20th century).
- Or to sum up something that a certain class of people would love to make a scientific revolution but isn’t, consider anthropogenic climate change. Honestly, specific local temperature predictions being wrong generally isn’t a big deal unless say most of them can’t be explained by other co-occurring phenomena (e.g. the oceans seem to have absorbed most of the heat instead of it leading to rising surface temperatures), since the central part of the theory is that emission of CO2 and certain other human-produced gases has a pretty large effect due to radiative forcing which traps more heat in. Show that radiative forcing is wrong or significantly different from the current values, and that’s a really big deal. Or come up with evidence of something that might counter radiative forcing’s effect on temperature at almost the same scale, and while the concern would go away, I think it’s worth pointing out it wouldn’t actually mean research on greenhouse gases was wrong. I would also argue that you do see open-mindedness in climate science, since people do still pursue the “iris hypothesis” and there are actually almost always studies on solar variability if you search NASA and NSF grants.