Weighing Up Galileo's Evidence

> Tychonic. Geo-heliocentric. Sun and Moon circle the Earth; everything else circles the Sun.

Interesting. Isn’t that (disregarding the Galaxy) functionally the same as a heliocentric system?

What do you make of the Antikythera mechanism?

Which model does it fit? Or does it point to a different model?

https://www.tiktok.com/t/ZTNFPxAMV/

https://en.m.wikipedia.org/wiki/Antikythera_mechanism

I'd think that the Earth rotating would be obvious much, much sooner, since that's far less work than the entire universe orbiting around the Earth every day, while also having individual objects orbiting on their own monthly, annual and other cycles. And spinning tops are common toys.

> Galileo's ordeal with the inquisition was mostly due to him making fun of the pope (probably not a good idea).

And at least one history I read on the subject questions whether Galileo was even intending to make fun of the Pope. My memory of the basic story that book told:

- The Pope encouraged Galileo to publish a book with his new theories, but just told him to add a theological "escape hatch" (provided by the Pope himself) to make sure he wasn't viewed as heretical

- The book is a dialogue between three people, one of whom, "Simplicio", is kind of stupid and backwards the whole book, but in the last chapter says effectively, "Actually I've just been pretending this whole time to be foolish; but actually I"m wise, and let me tell you why." He then gives the Pope's argument and the book ends -- giving the Pope the last word, as it were.

- At the time no books can be printed unless they're officially approved by the Church as being non-heretical. The book was reviewed, and approved, by two different Papal censors in two different cities. It was only sometime later that the Pope became offended by his words being placed in Simplicio's mouth; in what the author I read thought was almost certainly a misunderstanding.

As the author said, Galileo was encouraged to write the book; was told some theology to put into it; he did so. The book was submitted for review and approved twice. What more could Galileo have done?

If I could read Renaissance Italian I'd go back and read it and judge for myself. Anyone here read it that can weigh in on the theory that Galileo never meant to offend the Pope?

Galileo also couldn't explain the lack of an observed parallax effect between opposite seasons given the ideas about optics at the time.

When Kepler's model arrived, it was so much better at predicting the positions of all planets except Mercury than any previous model that it was clearly superior. Galileo's was bad at predicting and just contradicted the accepted observations of the day.

IMO Galileo should be better remembered for objects of different masses falling at the same rate and the original idea that all motion is relative (when observing from an internal frame).

> And the church didn't even care _that_ much.

They cared enough to put heliocentric books on the index of forbidded books for centuries. Gallileo might have offended the Pope, but the works of Copernicus was also forbidden.

The main myth is that: Galileo was obviously right given the evidence at the time, and that the Catholic Church pursued him entirely because they were unwilling to change their view. The evidence instead suggests that the Catholic Church was primarily concerned (oppressively so) about explicit interpretation of scripture, but not so much (as an institution) concerned about matters of speculation about models of the solar system, especially when they were specifically couched as such, and they were also quite willing to adjust their interpretations of scripture if those interpretations were actually falsified by evidence. The problem was the Galileo a) didn't have that evidence (and the evidence he tried to present was wrong: the book that got him in trouble focused on an argument from the tides where he assumed the tides go up and down once a day! He had some other better ideas but the experiments/observations didn't work, sometimes due to sheer bad luck), b) was advocating for a model that absent that evidence was mathematically equivilent to a geocentric model (there were many: only the simplest were eliminated by the new observations of phases of Venus) but more complex (Kepler had the right idea but Gallileo was insistent on the epicycles of circles), and c) made a lot of friends into enemies by generally being an arrogant credit-hoarder, as well as having more unreasonable enemies.

The events that lead up to the house arrest were quiet chaotic as well: an almost comedy of errors meant that Gallileo's book never got a full review in context before publishing and so the implied insult of the Pope was published with Gallileo seemingly believing it had been approved beforehand (seemingly Gallileo had understood the Pope's attitude to be a "just make sure you put a small fig leaf on it until we change our official position" instead of "You don't actually have enough evidence to disprove this other theory, but it's worth writing something up considering both"). The trial also involved a bunch of skullduggery where various documents were fabricated (by parties unknown, though some would have needed to be inside the church) to paint Galileo as if he had directly opposed the church on matters of scripture, which was what ultimately got him in trouble.

So, was the Catholic church extremely overbearing and oppressive in regulating the speech and writings of others? Yes, for sure. But on a quite limited scope: they cared relatively little for scientific speculation. Could Galileo have basically published the same information and not gotten into trouble? Also yes. It took a dedicated conspiracy to try to paint him as attacking the church and him pissing off almost all his friends (including one quite powerful one) for him to get punished.

So, the full story makes the church and pope appear a little more reasonable. It's still unreasonable that they were in the position of "Falsify the current consensus or keep your statements couched in speculative terms", but it's far from "No, shut up with your obvious truth". Similarly, Galileo looks a lot less reasonable: basically insisting he's correct when his own proposal is unwieldy and still only correct in a few more details than the consensus, and it appears mostly by accident because he was unable to actually collect convincing evidence for those details (it's notable that he also didn't really convince many others either. Eventually Kepler's model took over due to mathematical convenience and then more precise measurements provided the evidence Galileo lacked). And there's a whole third part where some even more unreasonable people are trying to take Galileo down for a much smaller slight, and eventially their efforts do contribute to that.

Not all that much: they both suffered from assuming that everything was perfect circles, so they needed nested epicycles to match observations. Galileo's model actually needed more than Riccoli's (one reason why it was not so popular). They both predicted the observed motions of planets equally well, the two main differences were the nature and position of the stars and whether the earth or sun were at the center, Those two are related: if the earth is at the center, then you can put the stars more or less wheverever you want in the model and things don't change. If the sun is at the center, you need to put the stars very far away because the observations of the day didn't show any parallax of the stars due to the earth's rotation around the sun. This was unpopular because both telescopic and naked eye observations of the stars appears to show them as a disk (about the same size as Saturn) instead of a point, which would mean stars would need to be even larger than the solar system to match observations. It was only centuries later that this was shown to be an optical illusion. The other objection was the Galilean model also requires the earth to rotate around its own axis, which was also an unpopular idea for a variety of reasons, chiefly it creates a bunch of questions which need a good understanding of ideas like mass, velocity, and momentum to answer, and it wasn't until Newton that all that was really put into a good framework. The most robust argument was related to coriolis effects: if the earth is rotating, you would expect that a dropped object would not fall straight down, but instead land slightly west of the point where you dropped it. People had tried this experiment and did not see the effect (mostly because it's really small). So Galileo more or less could not really produce an experiment which his model could explain and Riccioli's model could not, and for the areas where it differed he could only really shrug his shoulders and say 'maybe the effect is too small to measure'.

(Not for lack of trying: apart from the dropping weights experiments done by others, Galileo also attempted to measure parallax of two stars that are close together in the sky. Unfortunately he picked a binary system where the stars are also close together in distance, and so he didn't see anything. He also had an argument based on the tide, which was apparently what originally convinced him of the idea. This argument was unfortunately obviously wrong in some important ways: he thought that the tides were due to the earth spinning and 'pulling along' the oceans, and his model worked out that the tides would rise and fall once a day, in contradiction to the experience of every sailor at the time)