[HN Gopher] Weighing Up Galileo's Evidence
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Weighing Up Galileo's Evidence
Author : Hooke
Score : 69 points
Date : 2024-06-24 03:35 UTC (1 days ago)
(HTM) web link (www.historytoday.com)
(TXT) w3m dump (www.historytoday.com)
| bonzini wrote:
| It is easy to treat Galileo as fighting the obscurantist church
| of the 15th century, but as the article explains briefly:
|
| > provocatively voiced the pope's own arguments through an obtuse
| Aristotelian called Simplicio
|
| ... Galileo's ordeal with the inquisition was mostly due to him
| making fun of the pope (probably not a good idea). The truth is
| that until Kepler introduced elliptical orbits and variable
| orbital speeds, the Copernican heliocentric model still needed
| epicycles and was not much better than the ptolemaic model.
|
| And the church didn't even care _that_ much. Copernicus himself
| was a priest and, while he himself was wary of publishing it and
| framed it as a way to do astronomical calculations without any
| kind of philosophical implication, in the end it circulated
| without much fuss.
|
| This of course should not diminish his contributions to the
| scientific method and his other contribution to astronomical
| observations (mostly the satellites of Jupiter and the rings of
| Saturn, though his instrument wasn't good enough to recognize
| them as rings).
| gwd wrote:
| > 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?
| michaelmrose wrote:
| Galileo could have not had the Pope's words come out of the
| mouth of a moron. If I was the Pope I would have correctly
| inferred the insult.
| darkerside wrote:
| Painted as not only stupid but disingenuous.
| gjm11 wrote:
| This http://law2.umkc.edu/faculty/projects/ftrials/galileo/di
| alog... appears to be an English translation of the fourth
| and final "day" in the Dialogue. Here's the last thing
| Simplicio says:
|
| [begins]
|
| You need not make any excuses; they are superfluous, and
| especially so to me, who, being accustomed to public debates,
| have heard disputants countless times not merely grow angry
| and get excited at each other, but even break out into
| insulting speech and sometimes come very close to blows.
|
| As to the discourses we have held, and especially this last
| one concerning the reasons for the ebbing and flowing of the
| ocean, I am really not entirely convinced; but from such
| feeble ideas of the matter as I have formed, I admit that
| your thoughts seem to me more ingenious than many others I
| have heard. I do not therefore consider them true and
| conclusive; indeed, keeping always before my mind's eye a
| most solid doctrine that I once heard from a most eminent and
| learned person, and before which one must fall silent, I know
| that if asked whether God in His infinite power and wisdom
| could have conferred upon the watery element its observed
| reciprocating motion using some other means than moving its
| containing vessels, both of you would reply that He could
| have, and that He would have known how to do this in many
| ways which are unthinkable to our minds. From this I
| forthwith conclude that, this being so, it would be excessive
| boldness for anyone to limit and restrict the Divine power
| and wisdom to some particular fancy of his own.
|
| [ends]
|
| That doesn't seem like it's quite the same as what you're
| saying you read. Simplicio ends up professing a sort of pious
| agnosticism about what Galileo is talking about. I don't get
| any particular sense from this that we're meant to think "oh,
| hey, Simplicio is much smarter than we were giving him credit
| for being".
|
| (I do not know enough about any pope's astronomical opinions
| to have a useful opinion on how closely Simplicio's professed
| positions match those of the pope, or how likely it is that
| Galileo was and/or seemed to be making fun of the pope. My
| highly inexpert impression was that Simplicio wasn't modelled
| on the pope specifically but on other people with whom
| Galileo had more of a grudge.)
| gwd wrote:
| Thanks for that; this part in particular:
|
| > I do not therefore consider them true and conclusive;
| indeed, keeping always before my mind's eye a _most solid
| doctrine that I once heard from a most eminent and learned
| person_ , and before which one must fall silent,
|
| Assuming that the following really is the "theological
| angle" suggested by the Pope, it's literally saying that
| the Pope is a most eminent and learned person, and that the
| argument he's made is "solid doctrine" and an unassailable
| argument. And Simplicio isn't coming up with the argument
| himself; he's saying he's heard it from this other eminent
| and learned person. All that's perfectly consistent with a
| good-faith attempt to flatter the Pope's wisdom and
| influence, and accommodate his request regarding the
| theological "escape hatch".
|
| Unfortunately, it's also fairly open to being construed as
| being a sarcastic insult... or even an attempt at a sort of
| "dog whistle", where "devout" people take it as face value,
| but people "in the know" take it as being sarcastic.
|
| EDIT: And, seriously:
|
| > I know that if asked whether God in His infinite power
| and wisdom could have conferred upon the watery element its
| observed reciprocating motion using some other means than
| moving its containing vessels... From this I forthwith
| conclude that, this being so, it would be excessive
| boldness for anyone to limit and restrict the Divine power
| and wisdom to some particular fancy of his own.
|
| It's not saying "God could just magic things to make the
| water appear to move like this"; it's "There are lots of
| other possible reasons why the water might appear to move
| like that".
|
| It sounds to me like a description of necessary scientific
| humility. We have these observations, this one theory _is_
| consistent with them, but there lots of other
| possibilities, so we should keep an open mind and not be
| too insistent on one particular theory.
| lupire wrote:
| Simplicio was the correct one in that part of the book!
|
| Galileo's arguments about the tides were deeply flawed.
| Simplicio's "I don't buy it" is the correct response.
| baryphonic wrote:
| 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).
| jcranmer wrote:
| > Galileo also couldn't explain the lack of an observed
| parallax effect between opposite seasons given the ideas
| about optics at the time.
|
| That's not entirely correct. The lack of parallax was
| explained by the stars being far away; the problem with
| _that_ explanation is that Brahe had measured the apparent
| stellar diameter of stars, which implied that for the stars
| to be as big as they appear to be to us, they would have to
| be far, far larger... which violates the underlying
| Copernican principle that the sun is but a normal star.
| graemep wrote:
| The Copernican model was heliocentric, surely? It placed
| the sun motionless at the centre of the universe. That
| makes the sun anything but a normal star.
| noslenwerdna wrote:
| The copernican principle is separate from the model.
| Basically it says that our position in the universe is
| random - we don't exist at the center of the universe.
|
| https://en.wikipedia.org/wiki/Copernican_principle
|
| "Hermann Bondi named the principle after Copernicus in
| the mid-20th century, although the principle itself dates
| back to the 16th-17th century paradigm shift away from
| the Ptolemaic system, which placed Earth at the center of
| the universe. Copernicus proposed that the motion of the
| planets could be explained by reference to an assumption
| that the Sun is centrally located and stationary in
| contrast to the geocentrism. "
| mannykannot wrote:
| _" Hermann Bondi named the principle after Copernicus in
| the mid-20th century, although the principle itself dates
| back to the 16th-17th century paradigm shift away from
| the Ptolemaic system, which placed Earth at the center of
| the universe... Copernicus himself was mainly motivated
| by technical dissatisfaction with the earlier system and
| not by support for any mediocrity principle."_
|
| Copernicus' solar-system model is entirely separable from
| any assumptions about star size distribution, and the
| latter was apparently not a concern of his (nor do I
| recall seeing anything to the contrary elsewhere.)
|
| On account of this separability, the mediocrity principle
| cannot be used to eliminate heliocentric models of the
| solar system from consideration, at least unless there's
| good evidence for it.
|
| Nevertheless, the presumed huge size of the stars was
| seen as more or less of a problem (depending on which way
| one leaned on the heliocentricity issue), but it turned
| out that the apparent size of the stars was merely an
| artifact created by diffraction (the Airy disk) [1],
| making it possible to hold both that the sun is well
| within the range of stellar sizes and that other stars
| are far enough away that their parallax is difficult to
| observe.
|
| [1] https://en.wikipedia.org/wiki/Airy_disk
| graemep wrote:
| That sort of makes sense but the comment I replied to was
| still mistaken in linking the 20th century "Copernican
| principle" to debates in the time of Galileo.
|
| IMO calling something so greatly at odds with
| Copernicus's model the "Copernican principle" is
| misleading (if not outright nonsensical) and explains why
| the commentor I corrected confused the two. What a good
| idea to name something completely at odds with
| Copernicus's view of the universe after him.
|
| Its like "Gell-Mann amnesia" but without the humour or
| self awareness.
| noslenwerdna wrote:
| Fair enough
| bazoom42 wrote:
| > 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.
| XorNot wrote:
| There's a weird amount of apologism for the actions of the
| Church towards Galileo. "Oh but he _insulted an authority_ "
| - like, that doesn't make it better.
|
| I mean they also just straight up incinerated a man for
| daring to suggest aliens might exist[1].
|
| Organized religion is, and remains, an authoritarian system
| of oppression.
|
| [1] https://en.wikipedia.org/wiki/Giordano_Bruno
| moi2388 wrote:
| Did you know that in quite some countries you are
| officially not allowed to mock foreign leaders either? I
| mean it's usually not enforced, but it's definitely part of
| the law
| XorNot wrote:
| You seem to think this is some sort of "gotcha".
|
| I can, and other citizens have told our Prime Minister
| exactly what they think of him to his face. They're
| completely free to do so.
| moi2388 wrote:
| Not a gotcha, just showing that's it's not only the
| church
| josefx wrote:
| The works of Copernicus circulated for almost a century
| before they where put on the index for their association with
| Galileo.
| bazoom42 wrote:
| OK that explanation make the church seem even more moronic
| that in the usual narrative.
|
| Gallileo was certainly correct in calling the pope an
| idiot, even if it was unwise.
| munchler wrote:
| > the evidence for Riccioli's system is weighing down the scale-
| pan, while Galileo's less substantiated suggestion rises upward
|
| What exactly is the difference between the two theories? It would
| be interesting to see them both in the context of the time.
| rcxdude wrote:
| 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)
| isidor3 wrote:
| I found this series to be a great read on some of the history of
| Galileo and the status of scientific understanding at the time I
| believe part of it has made the rounds on hn before:
| http://tofspot.blogspot.com/2013/10/the-great-ptolemaic-smac...
| throw0101b wrote:
| There were seven models floating around in the early 1600s:
|
| 1. Heraclidean. Geo-heliocentric. Mercury and Venus circle the
| Sun; everything else circles the Earth.
|
| 2. Ptolemaic. Geocentric, stationary Earth.
|
| 3. Copernican. Heliocentric, pure circles with lots of epicycles.
|
| 4. Gilbertian. Geocentric, rotating Earth. (proposed by William
| Gilbert in De magnete)
|
| 5. Tychonic. Geo-heliocentric. Sun and Moon circle the Earth;
| everything else circles the Sun.
|
| 6. Ursine. Tychonic, with rotating Earth.
|
| 7. Keplerian. Heliocentric, with elliptical orbits.
|
| See:
|
| * https://tofspot.blogspot.com/2013/08/the-great-ptolemaic-sma...
|
| * ToC: https://tofspot.blogspot.com/2013/10/the-great-ptolemaic-
| sma...
|
| * PDF: https://faculty.fiu.edu/~blissl/Flynngs.pdf
|
| By the mid-/late-1600s people leaned toward Kepler, mostly
| because the math was easiest.
|
| With regards to evidence for the Earth's motion, the first
| inkling was in 1728 with stellar aberration with in g-Draconis:
|
| * https://en.wikipedia.org/wiki/Aberration_(astronomy)#Discove...
|
| The first for the _rotation_ of the Earth (around an axis) was in
| 1791 by Guglielmini:
|
| * https://en.wikipedia.org/wiki/Giovanni_Battista_Guglielmini
|
| We finally got parallax in 1806 by Giuseppi Calandrelli in
| a-Lyrae.
|
| Stellar parallax was considered since at least Aristotle, as he
| mentions in his _On the Heavens_ (II.14), and since it is not
| observed then it is reasonable to conclude that there is no
| motion (it took several thousand years to develop instruments to
| actually measure it).
|
| Daniel Whitten's "Matters of Faith and Morals _Ex Suppositione_ "
| is an interesting read.
| lupire wrote:
| 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.
| Valgrim wrote:
| Keep in mind that there was nothing indicating that the sun
| and the stars were of the same nature, or that they were so
| far away. When you think about it, all stars appear equally
| distant to the naked eye, so the idea that stars were fiery
| stones dispersed on a vast celestial sphere was absolutely
| plausible. This solid, physical sphere was the thing
| rotating.
|
| Also people had little understanding of the scale of things.
| There is nothing indicating that the moon is smaller than
| earth or that the sun is much, much bigger than earth, and
| both appear equally large in the sky...
| throw0101b wrote:
| > _Also people had little understanding of the scale of
| things. There is nothing indicating that the moon is
| smaller than earth or that the sun is much, much bigger
| than earth, and both appear equally large in the sky..._
|
| The Ancient Greeks were actually quite clever about trying
| to calculate things:
|
| * https://physicsteacher.blog/2021/05/31/from-the-earth-to-
| the...
|
| * https://en.wikipedia.org/wiki/On_the_Sizes_and_Distances_
| (Ar...
|
| * https://en.wikipedia.org/wiki/On_Sizes_and_Distances_(Hip
| par...
| throw0101b wrote:
| > _I 'd think that the Earth rotating would be obvious much,
| much sooner_ [...]
|
| How _exactly_ could you tell the difference between one
| moving reference and another? Einstein eventually showed us
| that it is not possible.
|
| As this US Navy video shows, having the Earth stand still and
| having the 'celestial sphere' move actually makes celestial
| navigation using a sextant possible / mathematically easy:
|
| * https://www.youtube.com/watch?v=UV1V9-nnaAs /
| https://www.youtube.com/watch?v=cun0DGZ6-sk
|
| The Ancients / pre-Moderns concluded that the stars were on
| one celestial sphere and the wanderers ( _planetes_ in Greek)
| were on others.
| gizmo686 wrote:
| Einstein did not show that. The principal you are referring
| to is, ironically, Galilean relativity, and attributable to
| Galileo. Einstein's contribution was combining the
| principle of relativity with a constant speed of light.
|
| Additionally, under both systems, relativity only applies
| to intertial reference frames. Rotating reference frames
| are detectable.
|
| You can detect Earth's rotation without any external
| observations using a pendulum. Although such an experiment
| would not be done until Leon Foucault about 2 centuries
| after Galileo.
| rcxdude wrote:
| You can tell the difference between rotating and not,
| because a rotating reference frame is not inertial. In
| fact, the geocentrists knew this, because one of the
| longest-standing objections to the idea that the earth
| rotated was that you would expect a falling object to be
| displaced from the apparent vertical due to the rotation,
| these experiments were done, and the displacement was not
| observed (it turns out, because the effect was so small,
| but no-one would have the mathematical tools to work this
| out until Newton).
| ralfd wrote:
| > 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?
| nico wrote:
| 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
| mrkeen wrote:
| > Galileo Galilei's muttered protest symbolises the triumph of
| scientific rationality over blinkered, obstructive theology. In
| the face of all the facts - or so runs the mythology - Pope Urban
| VIII had refused to accept that the earth is in perpetual motion
| around the sun. He condemned the heretical astronomer to the
| relatively mild punishment of house arrest,
|
| Weaselly writing! What is claimed as "myth" here? That theology
| was obstructive? Did the Pope put his thumb on the scales or not?
| Did the Pope sentence Galileo to house arrest?
|
| > the pope won that round of the battle by sentencing him to nine
| years of house arrest.
|
| Right.
| rcxdude wrote:
| 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.
| erelong wrote:
| Galileo was thought to be in the wrong not necessarily for
| scientific views, but for implied theological arguments based on
| those views.
|
| For example, scientifically and theologically I thought
| geocentrism was the prevailing view at that time among scientists
| (God created the earth as a kind of "moral center" of the
| universe of God's Creation?); today acentrism (universe has no
| center) seems to be a prevailing scientific view. So by this
| logic, Galileo was wrong by modern scientific standards, and
| theologically some still argue for a kind of geocentrism or other
| such views (such as "galileowaswrong.com" or other such sites)
| against Galileo's theological views.
|
| Hence Galileo was rightly criticized for lacking religious
| caution; his rebellious attitude against religion (again, not
| necessarily for supporting a speculative scientific view) indeed
| has caused centuries of harm, pitting science against religion,
| whereas true science can never contradict religious truth.
| tech_ken wrote:
| Feyerabend has an interesting account of this in "Against
| Method". One thing I also found very interesting in his telling
| is the role of the telescope in revolutionizing naval warfare.
| Galileo in part was motivated, and supported by, a sort of proto-
| military-industrial complex.
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