10 ms·

Galileo was right, but so were his critics (2015)

87 points by vo2maxer 7y ago

deleted 7y ago
[deleted]
anovikov 7y ago
Can anyone explain why from the XVII century standpoint, heliocentrism required stars to be huge, much bigger than Sun? Which observation or measurement hinted at that? Yes there was lack of observable star parallax. But XVII measurement precision was so, so much worse than the one required to detect parallax (15" was best precision achieved at the time vs <1" required to tentatively detect parallax and ~0.3" required to be sure about it), that stars could "be" 50x closer than they really are, and 50x smaller, and the world would still "fit" the observations if one assumes that parallax is just tad small enough to escape detection. Which means, nearly every star being much smaller than Sun. Such a small star is impossible, but since source of the stellar energy wasn't known anyway, that couldn't be determined.
- nphard85 7y ago
  Google sent me to: https://www.scientificamerican.com/article/the-case-against-copernicus/problem-with-star-sizes/ https://www.scientificamerican.com/article/the-case-against-... "The most devastating argument against the Copernican universe was the star size problem. When we look at a star in the sky, it appears to have a small, fixed width. Knowing this width and the distance to the star, simple geometry reveals how big the star is (right). In geocentric models of the universe, the stars lie just beyond the planets, implying that star sizes are comparable to that of the sun (below). But Copernicus's heliocentric theory demands that the stars be extremely far away. This in turn implies that they should be absurdly large—hundreds of times bigger than the sun (bottom). Copernicans could not explain away the anomalous data without appeals to divine intervention. In reality, the stars are far away, but their apparent width is an illusion, an artifact of the way light behaves as it enters a pupil or telescope—behavior that scientists would not understand for another 200 years."
  - anovikov 7y ago
    Ah so the Airy disk was confused for the star size? Then true; but that is sick, one had to just observe same star with the same telescope, once with full aperture and once with the aperture diaphragmed to half diameter, to observe that the star has become 2x larger (and 4x dimmer). Also let's see, so a typical telescope aperture of the era have been 25-30mm (bigger will make focal ratio too big and chromatism totally unacceptable), which means Airy disk 5" big, or 1/40000 of the distance. Assuming stars being 1/15 parsec away to make their parallax just barely unobservable, it means yeah, stars 25x the size of Sun, which is whole lot and isn't a reasonable assumption. But measuring Airy disk size is easy by using a hair put in the focal plane to see how quickly it crosses (will be 1/2 vs 1/4 of a second)... Easy experiment to check that Airy disk isn't a "star".
    - chopin 7y ago
      Good reply but you have to know that you need to look for this. This is only obvious in hindsight.
    - fsh 7y ago
      Diffraction of light was only understood in the mid 19th century. They simply had no idea what to look for. In Galilei's time, making optical instruments was mostly based on trial and error.
      - whatshisface 7y ago
        They wouldn't have needed to know what to look for if they had noticed that the "width" they ascribed to the stars changed with every measurement. Every single telescope size would have led them to a different figure, and if they had cared about pursuing quantitative inconsistencies they would have not only realized that they weren't measuring the width of the star, but also that the determining factor was the telescope's aperture.
      - anovikov 7y ago
        OK one easier way to confirm that Airy disk isn't a "star". Speed of Moon movement vs stars was well known and is around 0.5'' per second, and Airy disk was 4-5'' wide. So, when a star is occulted by Moon, it should have disappeared slowly as the Moon "slides" over it, during ~10 seconds. In fact, it disappears instantly, because Airy disk isn't a star...
- nestorD 7y ago
  The reasonning of Tycho Brahe, taken from "The Great Ptolemaic Smackdown" (which could probably provide a much better answer to your questions) : - Procyon has the same diameter and brightness as Saturn. - If Procyon is much farther than (say) 100 times Saturn’s distance, simple geometry proves its actual size would dwarf the sun. - All the stars would dwarf the Sun, which would then be the only pea in a universe of melons, which is absurd. - But if Procyon were any closer, there would be visible parallax from the Earth's revolution. - There is no visible parallax. - Lack of parallax plus the apparent size of the stars therefore requires a stationary Earth. QED. The problem with heliocentrism is that it requires a lot of additional hypothesis that are not needed by other (better performing !) models.
  - chopin 7y ago
    > Procyon has the same diameter and brightness as Saturn. How could he possibly that have determined? I don't think that Brahe could measure this he hadn't even a telescope. The apparent diameter you see from stars is diffraction limited.
    - antepodius 7y ago
      They didn't know that, and assumed the apparent diameter was the true diameter (as you would).
    - shadowprofile77 7y ago
      Yes but diffraction of light wasn't understood at the time, or until a couple centuries later.
      - anovikov 7y ago
        Tycho was pre-telescope... so he had no idea that Saturn has a bigger visual diameter than Procyon... But, he could at least figure it out indirectly - by noticing that all stars twinkle a lot, while planets do not (or only a bit, on the worst nights).
  - DiogenesKynikos 7y ago
- correct_horse 7y ago
  Nature [1] cites Graney [2] that Galileo may have confused stars for their Airy disks. Nature's phrasing makes it seem that we're not entirely sure of Galileo's exact confusion. > Graney suggested in 2008 that Galileo's observations of stars were actually diffraction patterns called Airy disks [1] https://www.nature.com/news/2010/100305/full/news.2010.105.html https://www.nature.com/news/2010/100305/full/news.2010.105.h... [2] https://link.springer.com/article/10.1007/s00016-007-0345-3 https://link.springer.com/article/10.1007/s00016-007-0345-3
nestorD 7y ago
On that subject, I recommend reading the wonderful "The Great Ptolemaic Smackdown"[0] blogposts. [0]: https://tofspot.blogspot.com/2013/10/the-great-ptolemaic-smackdown-table-of.html https://tofspot.blogspot.com/2013/10/the-great-ptolemaic-sma...
pvitz 7y ago
I guess he hasn't read Feyerabend's defense of the church in "Against Method".
- pvitz 7y ago
  I am not sure why I have been downvoted, but it is a fact that Feyerabend discussed that the Church was acting reasonable and rational in Galilei's case. This was well before this book, so I don't think the book's claim is entirely new.
  - spindle 7y ago
    I agree - the book's main claim has been the orthodoxy in history of science for decades. (No doubt there are many new details in the book - I haven't read it.)
  - selimthegrim 7y ago
    I've criticized Feyerabend in the past, but I entirely agree with him in this case.
DiogenesKynikos 7y ago
This is very poor history. A constant theme among apologists for the 17th Century Catholic Church is the claim that the Church was somehow defending scientific rigor. That idea is quickly dispelled by simply reading the Inquisition's 1616 findings on heliocentrism: > Proposition to be assessed: > (1) The sun is the center of the world and completely devoid of local motion. > Assessement: All said that this proposition is foolish and absurd in philosophy, and formally heretical since it explicitly contradicts many places the sense of Holy Scripture, according to the literal meaning of the words and according to the common interpretation and understanding of the Holy Fathers and the doctors of theology. > (2) The earth is not the center of the world, nor motionless, but it moves as a whole and also with diurnal motion. > Assessment: All said that this proposition receives the same judgement in philosophy and that in regard to theological truth it is at least errouneous in faith. The Church wasn't calling for scientific rigor. It was calling for adherence to orthodoxy - in this case, its interpretation of Scripture. Graney and others make an ahistorical argument: they cherry-pick one observation (the apparent angular diameter of stars), and then apply modern arguments not known to people at the time (the actual size of stars) to say that Galileo's scientific argument was weak. They ignore all the other observations that strongly favored heliocentrism at the time (the phases of Venus, the discovery that Jupiter and its moons form their own Copernican system, the greater parsimony of the heliocentric system when it comes to explaining things like retrograde motion of planets, and so on), and focus on the argument about sizes of stars. But Galileo had a perfectly reasonable answer to the star-size argument: the stars might be very large, and different measurements of stellar angular diameters were inconsistent with one another. Countering with modern knowledge about the true sizes of stars doesn't give any insight into who had the stronger argument in the early 1600s. On balance, the argument for heliocentrism was already much stronger at the time. And of course, forcing Galileo, under threat of torture, to publicly accept the Church's interpretation of Scripture did nothing to aid science.
- josefx 7y ago
  > It was calling for adherence to orthodoxy - in this case, its interpretation of Scripture. This paper[1] points out that the "proposition is foolish and absurd in philosophy" is denouncing its scientific rigor. Of course they are also pissed at him for reinterpreting Bible verses, that is how the church got involved in the mess first place. [1]https://arxiv.org/ftp/arxiv/papers/1402/1402.6168.pdf https://arxiv.org/ftp/arxiv/papers/1402/1402.6168.pdf
carlob 7y ago
In Rome, on top of the church of Saint Ignatius (you know the one that has a tromp l'oeil dome), just behind the building that used to house the very first Jesuit school (ask a Jesuit and they will say the very first school in the modern sense), used to be the Vatican astronomical observatory. Nowadays there is nothing much left to see, since all of the scientific instruments were moved to a museum in Florence when Rome became part of Italy in 1870. The place is not open to the public, but if you know a friendly Jesuit you can take an elevator from within the church and take a look around. The first time I went there, the Jesuit who was accompanying me told me that Galileo had visited this place, and that the story of church vs. science that we've all learnt in school was very simplified. Apparently Riccioli defended a hybrid geo-heliocentric model (due to Tycho Brahe) where the earth is at the center of the universe, the sun and moon revolve around it, but all the other planets revolve around the sun. We now know neither the sun, nor the earth is at the center of the universe, so both models were equally wrong, however according to my Jesuit guide, Riccioli's point of view was the only one that would have been both theologically acceptable and scientifically sound. I guess what is really wrong about the classical story of Galileo's trial is that the catholic church is not and never was a monolithic entity: there are factions, dissent, political agendas. If you're interested in further reading on Riccioli the Wikipedia page is very detailed: https://en.wikipedia.org/wiki/Giovanni_Battista_Riccioli#Arguments_Concerning_the_Motion_of_the_Earth https://en.wikipedia.org/wiki/Giovanni_Battista_Riccioli#Arg...
- throw0101a 7y ago
  > used to be the Vatican astronomical observatory. The observatory was later moved to Castle Gandolfo: * https://en.wikipedia.org/wiki/Vatican_Observatory https://en.wikipedia.org/wiki/Vatican_Observatory After the light pollution got too bad, its use was retired, and now things are run out of Arizona: * https://en.wikipedia.org/wiki/Vatican_Advanced_Technology_Telescope https://en.wikipedia.org/wiki/Vatican_Advanced_Technology_Te... The head dude is Brother Guy, and he has some interesting interviews if you search for him: * https://en.wikipedia.org/wiki/Guy_Consolmagno https://en.wikipedia.org/wiki/Guy_Consolmagno
  - martinbalsam 7y ago
Irrelevantant 7y ago
Total misinterpretation and tangent, but I do feel on the long timeline, Earth is at the center of the universe. In terms of primitive people this is true. In terms of visible universe this is true. In terms of the eventual interstellar expansion, I think it will once again ring true. Modern era is too focused on the quirks of the language. Gravitation center is not the only center!
- lisper 7y ago
  According to all the data that I have direct access to, I am the center of the universe!
  - whatshisface 7y ago
    If I'm not the center of the universe, how can scientists explain why my nose never moves?
dr_dshiv 7y ago
I'm surprised that Christianity never went back to its roots to show how Jesus is compatible with our knowledge that the universe contains over 100 billion galaxies. It's not too hard, if you'll bear with me for 2 minutes. Mental health trigger warning: this might unintentionally make an atheist believe in God and Jesus. If you have a background with religious trauma, avoid this post. It is weird stuff. Ok, that said, the first point to make is that "God the father", in early and orthodox Christianity, wasn't a person, except as an allegory. The One God was rather the incomprehensible concept of Oneness -- more akin to a mathematical singularity than Zeus. This was discussed extensively by Philo of Alexandria (b.25 BC), one of the biggest influences on early Christians. That Oneness was also described by Plato and the Pythagoreans. Pausing there -- I find this Oneness concept to be a really fascinating idea, especially as we now accept that the entire universe was born out of a single point in the big bang. Also, Oneness is more or less a culturally universal phenomenon in mystical and psychedelic experiences. This god of Oneness is a very different perspective than the "guy in the sky" perspective -- but it is actually still compatible with Christian orthodoxy. Where does Jesus fit in? Jesus was the "Logos" -- translated poorly as "the word" -- which was understood by the contemporary stoics and jewish-greek philosophers (Philo) as "the eternal emanation of the Oneness". We need the logos as the oneness is really kind of boring with no diversity. So, Jesus was viewed as the allegorical "son" of the oneness (the father). That's why Jesus was there since the beginning of time. But, the mystery of the Christian faith is that the cosmic logos incarnated as a human -- the Jesus story is the story of the logos becoming flesh. Make sense? What troubled me was the Christian idea that you have to believe in Jesus to have eternal life. I found that irritating and disturbing. Why would belief in Jesus give eternal life?? Here is my best-faith interpretation: if you believe that we are all part of an eternal, common, cosmic logos, like if you really believe that we are the logos, then of course we don't die, we live on for ever, since we are the logos. So, in shorthand, believe in Jesus and you live for ever. Of course, theology got weird when people wanted the allegorical stories to be true and adopted the absurd idea of biblical literalism. For instance, Theophilus was a 4th century Alexandrian pope who first wrote a treatise on why it was foolish to believe that the One god was a material person -- but then had to backtrack when the monks literally started rioting in the streets [1]. So, there you have it: orthodox christianity can be galactic in scope, philosophically sound and compatible with empirical physics. No supernatural required, but plenty of mystery. [1] https://books.google.nl/books?id=9joABAAAQBAJ&lpg=PA37&ots=xBsDihrVyW&dq=Theophilus%20riot%20monks&pg=PA37#v=onepage&q=Theophilus%20riot%20monks&f=false https://books.google.nl/books?id=9joABAAAQBAJ&lpg=PA37&ots=x...
throw0101a 7y ago
For a general timeline of events that led up to the 'Galileo affair' and what happened after, check out "The Great Ptolemaic Smackdown": * https://tofspot.blogspot.com/2013/10/the-great-ptolemaic-smackdown-table-of.html https://tofspot.blogspot.com/2013/10/the-great-ptolemaic-sma... The fact that the Earth moves was not 'proven' (or more technically, had strong empirical evidence for that hypothesis) until 1806 when Giuseppi Calandrelli reported parallax in α-Lyrae. That's ~250 years after Copernicus, and ~150 after Galileo. Note that by 1700 or so, everyone had switched to Kepler's model: not necessarily because they thought it was "right" (there was no empirical way to tell), but primarily because the math was much easier and it got correct results. There were actually seven models floating around during the 1600s: * Heraclidean. Geo-heliocentric. Mercury and Venus circle the Sun; everything else circles the Earth. * Ptolemaic. Geocentric, stationary Earth. * Copernican. Heliocentric, pure circles with lots of epicycles. * Gilbertian. Geocentric, rotating Earth. (proposed by William Gilbert in De magnete) * Tychonic. Geo-heliocentric. Sun and Moon circle the Earth; everything else circles the Sun. * Ursine. Tychonic, with rotating Earth. * Keplerian. Heliocentric, with elliptical orbits.
- acqq 7y ago
  "The Great Ptolemaic Smackdown" pops up often on the web, but it is completely dishonest. Its arguments are “it was not proven then” and „Galileo wasn‘t skilful enough not to insult the pope.” It also intentionally misleadingly avoids to show to the readers the actual papers and sentence made by inquisition which are preserved and completely disprove the quasi-arguments.
  - throw0101a 7y ago
    How was the Copernicus' model any better than Ptolemy's? Over the course of 1500 years after Ptolemy's publication there were more accurate measurements, so Copernicus threw in more epicycles to have the model better match observations, but that's just another layer of indirection. But how are C's epicycles any less 'ad hoc' than P's? They hardly look any different, at least to a layman: * http://astro-andy.eu//img/the_solar_system_of_mlp_ptolemaic.jpg http://astro-andy.eu//img/the_solar_system_of_mlp_ptolemaic.... * https://casswww.ucsd.edu/archive/public/tutorial/images/history/epicycles.gif https://casswww.ucsd.edu/archive/public/tutorial/images/hist...
Nasrudith 7y ago
Those apologetic efforts always fall flat it seems because the justifications always make it clear that the rot is far deeper. "He wasn't facing torture for pursuit if the truth but for undermining their power and authority" is an even worse look than being deluded fundamentalists. Nothing of their intentions changes the outcome that came from their actions which they are fully responsible for. Whether Archimedes was stabbed for being impertinent, rage of the invaders at his years of countersiege engines, or even if he starved to death in the siegr his death was still a great loss regardless of why or how and Rome was fundamentally alsays responsible! There can be no reason which results from such exercises as apologism ammounts to justifying travesties to assuage their own cognitive dissonance and deserver bad reputations. It fundamentally a perpetuation of the evils of the past through rationalization.
- SiempreViernes 7y ago
  There is a difference between being an apologists and wanting the history of science to be cleaned of anti-papal propaganda you know.
  - whatshisface 7y ago
    The difference is mainly up to whether it's a papist or an atheist telling you about it.
jariel 7y ago
This is easily as much an issue of popular history as it is of Science. Someone needs to make a Netflix special about this to set the plebes straight. And I include myself in that grouping!
mannykannot 7y ago
The real issue is one of free inquiry versus authoritarianism (of any sort, not just religious). Galileo did not have all the facts, and he was reckless in how he addressed authority, but today, many of us are fortunate in living in circumstances where free inquiry (and also freedom of religion) became the norm.
- whatshisface 7y ago
  >he was reckless in how he addressed authority I think that might border on victim blaming. The Church had the power to persecute intellectuals who they felt were running too far, but that doesn't mean they had any rightful authority. If an illegitimate power is running around your society trying to get people to cow down to it, anyone who stands up to them by failing to cow down appropriately should be described as "heroic" moreso than "reckless." If nobody had ever stood up to the illegitimate authority, they would still be running things and imprisoning people for insulting them today. We are in great debt to everyone who was reckless in 1610.
  - mannykannot 7y ago
    I did not intend it as such, but as an observation about the reality of his world. Fortunately, things have improved in many places. Galileo's act of resistance was one among many that brought about this change, and science was more of a beneficiary than a leader of this social revolution.
- TopHand 7y ago
  If you truly believe this, just try asking questions regarding global climate change, even questions that pop up because your trying to grasp the model and see if you don't get smacked down and gagged!
stevespang 7y ago
. . .Ever since the seventeenth century, the celebrated “Galileo affair” has been one of the featured items on the list of dark moments in the history of Catholicis" . . . dark moments in the history of catholicism ? How about massive ingrained and institutionalized pedophilia ?
YeGoblynQueenne 7y ago
>> Riccioli’s work and the star size problem tell us that what was going on in the seventeenth century was not the brave and reasonable Copernicans against powerful forces arrayed to cover up the truth, so much as it was the scientific process at work: a vigorous debate, with good arguments and careful observations on both sides, as each worked to figure out what the truth was. Yes, vigorous scientific debate with arguments on both sides, as for example the argument of the Inquisition that heliocentricism was heresy. An argument that the Inquisition certainly defended vigorously. Galileo was tried and found guilty of heresy, forced to recant his heretic views and spent the latter period of his life under house arrest. It seems the way the scientific process works has changed since Galileo's arrest. We don't expect scientists who voice controversial opinions (i.e. ones that go against the accepted consensus) to be arrested, tried and imprisoned, for voicing such opinions.
seemslegit 7y ago
Looks like the Vatican reputation management campaigns are alive and well, I suppose given those deep pockets backed by taxless ownership of good chunks of Europe it would be naive to expect them to go away. But for the record - Galileo could be arguing that the earth revolves around his ass and the Church would still be damnable for persecuting him or anyone else and "critics" is not the word one uses for anyone wielding arrest and execution powers to enforce a monopoly on science and thought in general.
mvcalder 7y ago
I helped my daughter with a science fair project in which we mapped the relative position of the sun and mars as viewed from a "stationary" earth, when all three correctly followed Newton's laws. I was very surprised how it turned out. I expected odd cycles or other misbehavior, but actually things were smooth and round. It was eye opening.
- Seenso 7y ago
  > I expected odd cycles or other misbehavior, but actually things were smooth and round. It was eye opening. How long did you map them? My understanding is that to see the "odd cycles and misbehavior" you need to make observations over the course of months at the right time of year. https://en.wikipedia.org/wiki/Apparent_retrograde_motion https://en.wikipedia.org/wiki/Apparent_retrograde_motion
- mannykannot 7y ago
  This should be more widely known, as it gives some insight into the nature of scientific truth. I understand that the explanation of this surprising result is related to harmonic analysis, such as Fourier series - the evolution of any periodic process in time can be just as correctly represented by a collection of harmonics of the correct amplitude and phase. This does not, however, seem to lead one to gravity, while Kepler's laws do. One thing that Newton showed is that epicycles are unnecessary as part of an explanation of planetary motion. If you were to apply the epicyclic model with sufficient precision to show the gravitational effects between the planets, I would guess you would have to include, for any one planet, epicycles with frequencies that are harmonics of the other planets' orbits. Without a theory of gravity, there is no obvious reason why that should be so.
michaelmrose 7y ago
This is interesting minutia but a closer look at the details entertains but doesn't change the fundamental picture for me. It was a battle of new ideas vs orthodoxy. It seems fairly obvious that all parties had world views that were partially informed by their religious views and what they thought were scientific ideals. The fact that the catholic church employed more than one person with a brain and tried to use him to refute Galileo while also crushing him with the power of law doesn't improve their position from my perspective. I don't see a lot of daylight between Riccioli and scientists employed by the petroleum industry or Phillip Morris. Looking purely at the scientific case the bizarre world of epicycles seems like a vastly greater sin than star size or an entirely misunderstood Coriolis Effect that Riccioli posited but failed to calculate or measure correctly. I would go so far as to suggest that a stationary earth might seem intuitively obvious to a illiterate savage but anyone with a mathematical mind and access to a telescope ought to have figured out that stasis isn't the natural state of anything in the universe. One might suggest that he author started from a place of wanting to present the Church he cares very much for in a better light and presented the best possible defense for its misbehavior. The best that can be said for him is that like a good attorney he believes in his client and defends him honestly. This doesn't make him correct. Science is the process of arriving at increasingly accurate models of reality by finding ways to test theories. This is inherently at odds with religion which is the process by which priests interpose themselves between man and god to derive status and importance by serving as the only valid conduit between man and both imaginary spiritual goods like salvation and the temporal goods they acquired by selling the former. This is a problem when the shtick you have been selling everyone is universal truth because constantly having to revise it to be more in line with secular ideas makes it increasingly clear it was far from universal and once its clear that its just your best effort and not a very good one at that the long term viability of your mission is in doubt.

87 points by vo2maxer 7y ago

deleted 7y ago

[deleted]

Can anyone explain why from the XVII century standpoint, heliocentrism required stars to be huge, much bigger than Sun? Which observation or measurement hinted at that? Yes there was lack of observable star parallax. But XVII measurement precision was so, so much worse than the one required to detect parallax (15" was best precision achieved at the time vs <1" required to tentatively detect parallax and ~0.3" required to be sure about it), that stars could "be" 50x closer than they really are, and 50x smaller, and the world would still "fit" the observations if one assumes that parallax is just tad small enough to escape detection. Which means, nearly every star being much smaller than Sun. Such a small star is impossible, but since source of the stellar energy wasn't known anyway, that couldn't be determined.

nphard85 7y ago
Google sent me to: https://www.scientificamerican.com/article/the-case-against-copernicus/problem-with-star-sizes/ https://www.scientificamerican.com/article/the-case-against-... "The most devastating argument against the Copernican universe was the star size problem. When we look at a star in the sky, it appears to have a small, fixed width. Knowing this width and the distance to the star, simple geometry reveals how big the star is (right). In geocentric models of the universe, the stars lie just beyond the planets, implying that star sizes are comparable to that of the sun (below). But Copernicus's heliocentric theory demands that the stars be extremely far away. This in turn implies that they should be absurdly large—hundreds of times bigger than the sun (bottom). Copernicans could not explain away the anomalous data without appeals to divine intervention. In reality, the stars are far away, but their apparent width is an illusion, an artifact of the way light behaves as it enters a pupil or telescope—behavior that scientists would not understand for another 200 years."
- anovikov 7y ago
  Ah so the Airy disk was confused for the star size? Then true; but that is sick, one had to just observe same star with the same telescope, once with full aperture and once with the aperture diaphragmed to half diameter, to observe that the star has become 2x larger (and 4x dimmer). Also let's see, so a typical telescope aperture of the era have been 25-30mm (bigger will make focal ratio too big and chromatism totally unacceptable), which means Airy disk 5" big, or 1/40000 of the distance. Assuming stars being 1/15 parsec away to make their parallax just barely unobservable, it means yeah, stars 25x the size of Sun, which is whole lot and isn't a reasonable assumption. But measuring Airy disk size is easy by using a hair put in the focal plane to see how quickly it crosses (will be 1/2 vs 1/4 of a second)... Easy experiment to check that Airy disk isn't a "star".
  - chopin 7y ago
    Good reply but you have to know that you need to look for this. This is only obvious in hindsight.
  - fsh 7y ago
    Diffraction of light was only understood in the mid 19th century. They simply had no idea what to look for. In Galilei's time, making optical instruments was mostly based on trial and error.
    - whatshisface 7y ago
      They wouldn't have needed to know what to look for if they had noticed that the "width" they ascribed to the stars changed with every measurement. Every single telescope size would have led them to a different figure, and if they had cared about pursuing quantitative inconsistencies they would have not only realized that they weren't measuring the width of the star, but also that the determining factor was the telescope's aperture.
    - anovikov 7y ago
      OK one easier way to confirm that Airy disk isn't a "star". Speed of Moon movement vs stars was well known and is around 0.5'' per second, and Airy disk was 4-5'' wide. So, when a star is occulted by Moon, it should have disappeared slowly as the Moon "slides" over it, during ~10 seconds. In fact, it disappears instantly, because Airy disk isn't a star...
nestorD 7y ago
The reasonning of Tycho Brahe, taken from "The Great Ptolemaic Smackdown" (which could probably provide a much better answer to your questions) : - Procyon has the same diameter and brightness as Saturn. - If Procyon is much farther than (say) 100 times Saturn’s distance, simple geometry proves its actual size would dwarf the sun. - All the stars would dwarf the Sun, which would then be the only pea in a universe of melons, which is absurd. - But if Procyon were any closer, there would be visible parallax from the Earth's revolution. - There is no visible parallax. - Lack of parallax plus the apparent size of the stars therefore requires a stationary Earth. QED. The problem with heliocentrism is that it requires a lot of additional hypothesis that are not needed by other (better performing !) models.
- chopin 7y ago
  > Procyon has the same diameter and brightness as Saturn. How could he possibly that have determined? I don't think that Brahe could measure this he hadn't even a telescope. The apparent diameter you see from stars is diffraction limited.
  - antepodius 7y ago
    They didn't know that, and assumed the apparent diameter was the true diameter (as you would).
  - shadowprofile77 7y ago
    Yes but diffraction of light wasn't understood at the time, or until a couple centuries later.
    - anovikov 7y ago
      Tycho was pre-telescope... so he had no idea that Saturn has a bigger visual diameter than Procyon... But, he could at least figure it out indirectly - by noticing that all stars twinkle a lot, while planets do not (or only a bit, on the worst nights).
- DiogenesKynikos 7y ago
correct_horse 7y ago
Nature [1] cites Graney [2] that Galileo may have confused stars for their Airy disks. Nature's phrasing makes it seem that we're not entirely sure of Galileo's exact confusion. > Graney suggested in 2008 that Galileo's observations of stars were actually diffraction patterns called Airy disks [1] https://www.nature.com/news/2010/100305/full/news.2010.105.html https://www.nature.com/news/2010/100305/full/news.2010.105.h... [2] https://link.springer.com/article/10.1007/s00016-007-0345-3 https://link.springer.com/article/10.1007/s00016-007-0345-3

nestorD 7y ago

On that subject, I recommend reading the wonderful "The Great Ptolemaic Smackdown"[0] blogposts. [0]: https://tofspot.blogspot.com/2013/10/the-great-ptolemaic-smackdown-table-of.html https://tofspot.blogspot.com/2013/10/the-great-ptolemaic-sma...

pvitz 7y ago

I guess he hasn't read Feyerabend's defense of the church in "Against Method".

pvitz 7y ago
I am not sure why I have been downvoted, but it is a fact that Feyerabend discussed that the Church was acting reasonable and rational in Galilei's case. This was well before this book, so I don't think the book's claim is entirely new.
- spindle 7y ago
  I agree - the book's main claim has been the orthodoxy in history of science for decades. (No doubt there are many new details in the book - I haven't read it.)
- selimthegrim 7y ago
  I've criticized Feyerabend in the past, but I entirely agree with him in this case.

DiogenesKynikos 7y ago

This is very poor history. A constant theme among apologists for the 17th Century Catholic Church is the claim that the Church was somehow defending scientific rigor. That idea is quickly dispelled by simply reading the Inquisition's 1616 findings on heliocentrism: > Proposition to be assessed: > (1) The sun is the center of the world and completely devoid of local motion. > Assessement: All said that this proposition is foolish and absurd in philosophy, and formally heretical since it explicitly contradicts many places the sense of Holy Scripture, according to the literal meaning of the words and according to the common interpretation and understanding of the Holy Fathers and the doctors of theology. > (2) The earth is not the center of the world, nor motionless, but it moves as a whole and also with diurnal motion. > Assessment: All said that this proposition receives the same judgement in philosophy and that in regard to theological truth it is at least errouneous in faith. The Church wasn't calling for scientific rigor. It was calling for adherence to orthodoxy - in this case, its interpretation of Scripture. Graney and others make an ahistorical argument: they cherry-pick one observation (the apparent angular diameter of stars), and then apply modern arguments not known to people at the time (the actual size of stars) to say that Galileo's scientific argument was weak. They ignore all the other observations that strongly favored heliocentrism at the time (the phases of Venus, the discovery that Jupiter and its moons form their own Copernican system, the greater parsimony of the heliocentric system when it comes to explaining things like retrograde motion of planets, and so on), and focus on the argument about sizes of stars. But Galileo had a perfectly reasonable answer to the star-size argument: the stars might be very large, and different measurements of stellar angular diameters were inconsistent with one another. Countering with modern knowledge about the true sizes of stars doesn't give any insight into who had the stronger argument in the early 1600s. On balance, the argument for heliocentrism was already much stronger at the time. And of course, forcing Galileo, under threat of torture, to publicly accept the Church's interpretation of Scripture did nothing to aid science.

josefx 7y ago
> It was calling for adherence to orthodoxy - in this case, its interpretation of Scripture. This paper[1] points out that the "proposition is foolish and absurd in philosophy" is denouncing its scientific rigor. Of course they are also pissed at him for reinterpreting Bible verses, that is how the church got involved in the mess first place. [1]https://arxiv.org/ftp/arxiv/papers/1402/1402.6168.pdf https://arxiv.org/ftp/arxiv/papers/1402/1402.6168.pdf

carlob 7y ago

In Rome, on top of the church of Saint Ignatius (you know the one that has a tromp l'oeil dome), just behind the building that used to house the very first Jesuit school (ask a Jesuit and they will say the very first school in the modern sense), used to be the Vatican astronomical observatory. Nowadays there is nothing much left to see, since all of the scientific instruments were moved to a museum in Florence when Rome became part of Italy in 1870. The place is not open to the public, but if you know a friendly Jesuit you can take an elevator from within the church and take a look around. The first time I went there, the Jesuit who was accompanying me told me that Galileo had visited this place, and that the story of church vs. science that we've all learnt in school was very simplified. Apparently Riccioli defended a hybrid geo-heliocentric model (due to Tycho Brahe) where the earth is at the center of the universe, the sun and moon revolve around it, but all the other planets revolve around the sun. We now know neither the sun, nor the earth is at the center of the universe, so both models were equally wrong, however according to my Jesuit guide, Riccioli's point of view was the only one that would have been both theologically acceptable and scientifically sound. I guess what is really wrong about the classical story of Galileo's trial is that the catholic church is not and never was a monolithic entity: there are factions, dissent, political agendas. If you're interested in further reading on Riccioli the Wikipedia page is very detailed: https://en.wikipedia.org/wiki/Giovanni_Battista_Riccioli#Arguments_Concerning_the_Motion_of_the_Earth https://en.wikipedia.org/wiki/Giovanni_Battista_Riccioli#Arg...

throw0101a 7y ago
> used to be the Vatican astronomical observatory. The observatory was later moved to Castle Gandolfo: * https://en.wikipedia.org/wiki/Vatican_Observatory https://en.wikipedia.org/wiki/Vatican_Observatory After the light pollution got too bad, its use was retired, and now things are run out of Arizona: * https://en.wikipedia.org/wiki/Vatican_Advanced_Technology_Telescope https://en.wikipedia.org/wiki/Vatican_Advanced_Technology_Te... The head dude is Brother Guy, and he has some interesting interviews if you search for him: * https://en.wikipedia.org/wiki/Guy_Consolmagno https://en.wikipedia.org/wiki/Guy_Consolmagno
- martinbalsam 7y ago

Irrelevantant 7y ago

Total misinterpretation and tangent, but I do feel on the long timeline, Earth is at the center of the universe. In terms of primitive people this is true. In terms of visible universe this is true. In terms of the eventual interstellar expansion, I think it will once again ring true. Modern era is too focused on the quirks of the language. Gravitation center is not the only center!

lisper 7y ago
According to all the data that I have direct access to, I am the center of the universe!
- whatshisface 7y ago
  If I'm not the center of the universe, how can scientists explain why my nose never moves?

dr_dshiv 7y ago

I'm surprised that Christianity never went back to its roots to show how Jesus is compatible with our knowledge that the universe contains over 100 billion galaxies. It's not too hard, if you'll bear with me for 2 minutes. Mental health trigger warning: this might unintentionally make an atheist believe in God and Jesus. If you have a background with religious trauma, avoid this post. It is weird stuff. Ok, that said, the first point to make is that "God the father", in early and orthodox Christianity, wasn't a person, except as an allegory. The One God was rather the incomprehensible concept of Oneness -- more akin to a mathematical singularity than Zeus. This was discussed extensively by Philo of Alexandria (b.25 BC), one of the biggest influences on early Christians. That Oneness was also described by Plato and the Pythagoreans. Pausing there -- I find this Oneness concept to be a really fascinating idea, especially as we now accept that the entire universe was born out of a single point in the big bang. Also, Oneness is more or less a culturally universal phenomenon in mystical and psychedelic experiences. This god of Oneness is a very different perspective than the "guy in the sky" perspective -- but it is actually still compatible with Christian orthodoxy. Where does Jesus fit in? Jesus was the "Logos" -- translated poorly as "the word" -- which was understood by the contemporary stoics and jewish-greek philosophers (Philo) as "the eternal emanation of the Oneness". We need the logos as the oneness is really kind of boring with no diversity. So, Jesus was viewed as the allegorical "son" of the oneness (the father). That's why Jesus was there since the beginning of time. But, the mystery of the Christian faith is that the cosmic logos incarnated as a human -- the Jesus story is the story of the logos becoming flesh. Make sense? What troubled me was the Christian idea that you have to believe in Jesus to have eternal life. I found that irritating and disturbing. Why would belief in Jesus give eternal life?? Here is my best-faith interpretation: if you believe that we are all part of an eternal, common, cosmic logos, like if you really believe that we are the logos, then of course we don't die, we live on for ever, since we are the logos. So, in shorthand, believe in Jesus and you live for ever. Of course, theology got weird when people wanted the allegorical stories to be true and adopted the absurd idea of biblical literalism. For instance, Theophilus was a 4th century Alexandrian pope who first wrote a treatise on why it was foolish to believe that the One god was a material person -- but then had to backtrack when the monks literally started rioting in the streets [1]. So, there you have it: orthodox christianity can be galactic in scope, philosophically sound and compatible with empirical physics. No supernatural required, but plenty of mystery. [1] https://books.google.nl/books?id=9joABAAAQBAJ&lpg=PA37&ots=xBsDihrVyW&dq=Theophilus%20riot%20monks&pg=PA37#v=onepage&q=Theophilus%20riot%20monks&f=false https://books.google.nl/books?id=9joABAAAQBAJ&lpg=PA37&ots=x...

throw0101a 7y ago

For a general timeline of events that led up to the 'Galileo affair' and what happened after, check out "The Great Ptolemaic Smackdown": * https://tofspot.blogspot.com/2013/10/the-great-ptolemaic-smackdown-table-of.html https://tofspot.blogspot.com/2013/10/the-great-ptolemaic-sma... The fact that the Earth moves was not 'proven' (or more technically, had strong empirical evidence for that hypothesis) until 1806 when Giuseppi Calandrelli reported parallax in α-Lyrae. That's ~250 years after Copernicus, and ~150 after Galileo. Note that by 1700 or so, everyone had switched to Kepler's model: not necessarily because they thought it was "right" (there was no empirical way to tell), but primarily because the math was much easier and it got correct results. There were actually seven models floating around during the 1600s: * Heraclidean. Geo-heliocentric. Mercury and Venus circle the Sun; everything else circles the Earth. * Ptolemaic. Geocentric, stationary Earth. * Copernican. Heliocentric, pure circles with lots of epicycles. * Gilbertian. Geocentric, rotating Earth. (proposed by William Gilbert in De magnete) * Tychonic. Geo-heliocentric. Sun and Moon circle the Earth; everything else circles the Sun. * Ursine. Tychonic, with rotating Earth. * Keplerian. Heliocentric, with elliptical orbits.

acqq 7y ago
"The Great Ptolemaic Smackdown" pops up often on the web, but it is completely dishonest. Its arguments are “it was not proven then” and „Galileo wasn‘t skilful enough not to insult the pope.” It also intentionally misleadingly avoids to show to the readers the actual papers and sentence made by inquisition which are preserved and completely disprove the quasi-arguments.
- throw0101a 7y ago
  How was the Copernicus' model any better than Ptolemy's? Over the course of 1500 years after Ptolemy's publication there were more accurate measurements, so Copernicus threw in more epicycles to have the model better match observations, but that's just another layer of indirection. But how are C's epicycles any less 'ad hoc' than P's? They hardly look any different, at least to a layman: * http://astro-andy.eu//img/the_solar_system_of_mlp_ptolemaic.jpg http://astro-andy.eu//img/the_solar_system_of_mlp_ptolemaic.... * https://casswww.ucsd.edu/archive/public/tutorial/images/history/epicycles.gif https://casswww.ucsd.edu/archive/public/tutorial/images/hist...

Nasrudith 7y ago

Those apologetic efforts always fall flat it seems because the justifications always make it clear that the rot is far deeper. "He wasn't facing torture for pursuit if the truth but for undermining their power and authority" is an even worse look than being deluded fundamentalists. Nothing of their intentions changes the outcome that came from their actions which they are fully responsible for. Whether Archimedes was stabbed for being impertinent, rage of the invaders at his years of countersiege engines, or even if he starved to death in the siegr his death was still a great loss regardless of why or how and Rome was fundamentally alsays responsible! There can be no reason which results from such exercises as apologism ammounts to justifying travesties to assuage their own cognitive dissonance and deserver bad reputations. It fundamentally a perpetuation of the evils of the past through rationalization.

SiempreViernes 7y ago
There is a difference between being an apologists and wanting the history of science to be cleaned of anti-papal propaganda you know.
- whatshisface 7y ago
  The difference is mainly up to whether it's a papist or an atheist telling you about it.

jariel 7y ago

This is easily as much an issue of popular history as it is of Science. Someone needs to make a Netflix special about this to set the plebes straight. And I include myself in that grouping!

mannykannot 7y ago

The real issue is one of free inquiry versus authoritarianism (of any sort, not just religious). Galileo did not have all the facts, and he was reckless in how he addressed authority, but today, many of us are fortunate in living in circumstances where free inquiry (and also freedom of religion) became the norm.

whatshisface 7y ago
>he was reckless in how he addressed authority I think that might border on victim blaming. The Church had the power to persecute intellectuals who they felt were running too far, but that doesn't mean they had any rightful authority. If an illegitimate power is running around your society trying to get people to cow down to it, anyone who stands up to them by failing to cow down appropriately should be described as "heroic" moreso than "reckless." If nobody had ever stood up to the illegitimate authority, they would still be running things and imprisoning people for insulting them today. We are in great debt to everyone who was reckless in 1610.
- mannykannot 7y ago
  I did not intend it as such, but as an observation about the reality of his world. Fortunately, things have improved in many places. Galileo's act of resistance was one among many that brought about this change, and science was more of a beneficiary than a leader of this social revolution.
TopHand 7y ago
If you truly believe this, just try asking questions regarding global climate change, even questions that pop up because your trying to grasp the model and see if you don't get smacked down and gagged!

stevespang 7y ago

. . .Ever since the seventeenth century, the celebrated “Galileo affair” has been one of the featured items on the list of dark moments in the history of Catholicis" . . . dark moments in the history of catholicism ? How about massive ingrained and institutionalized pedophilia ?

YeGoblynQueenne 7y ago

>> Riccioli’s work and the star size problem tell us that what was going on in the seventeenth century was not the brave and reasonable Copernicans against powerful forces arrayed to cover up the truth, so much as it was the scientific process at work: a vigorous debate, with good arguments and careful observations on both sides, as each worked to figure out what the truth was. Yes, vigorous scientific debate with arguments on both sides, as for example the argument of the Inquisition that heliocentricism was heresy. An argument that the Inquisition certainly defended vigorously. Galileo was tried and found guilty of heresy, forced to recant his heretic views and spent the latter period of his life under house arrest. It seems the way the scientific process works has changed since Galileo's arrest. We don't expect scientists who voice controversial opinions (i.e. ones that go against the accepted consensus) to be arrested, tried and imprisoned, for voicing such opinions.

seemslegit 7y ago

Looks like the Vatican reputation management campaigns are alive and well, I suppose given those deep pockets backed by taxless ownership of good chunks of Europe it would be naive to expect them to go away. But for the record - Galileo could be arguing that the earth revolves around his ass and the Church would still be damnable for persecuting him or anyone else and "critics" is not the word one uses for anyone wielding arrest and execution powers to enforce a monopoly on science and thought in general.

mvcalder 7y ago

I helped my daughter with a science fair project in which we mapped the relative position of the sun and mars as viewed from a "stationary" earth, when all three correctly followed Newton's laws. I was very surprised how it turned out. I expected odd cycles or other misbehavior, but actually things were smooth and round. It was eye opening.

Seenso 7y ago
> I expected odd cycles or other misbehavior, but actually things were smooth and round. It was eye opening. How long did you map them? My understanding is that to see the "odd cycles and misbehavior" you need to make observations over the course of months at the right time of year. https://en.wikipedia.org/wiki/Apparent_retrograde_motion https://en.wikipedia.org/wiki/Apparent_retrograde_motion
mannykannot 7y ago
This should be more widely known, as it gives some insight into the nature of scientific truth. I understand that the explanation of this surprising result is related to harmonic analysis, such as Fourier series - the evolution of any periodic process in time can be just as correctly represented by a collection of harmonics of the correct amplitude and phase. This does not, however, seem to lead one to gravity, while Kepler's laws do. One thing that Newton showed is that epicycles are unnecessary as part of an explanation of planetary motion. If you were to apply the epicyclic model with sufficient precision to show the gravitational effects between the planets, I would guess you would have to include, for any one planet, epicycles with frequencies that are harmonics of the other planets' orbits. Without a theory of gravity, there is no obvious reason why that should be so.

michaelmrose 7y ago

This is interesting minutia but a closer look at the details entertains but doesn't change the fundamental picture for me. It was a battle of new ideas vs orthodoxy. It seems fairly obvious that all parties had world views that were partially informed by their religious views and what they thought were scientific ideals. The fact that the catholic church employed more than one person with a brain and tried to use him to refute Galileo while also crushing him with the power of law doesn't improve their position from my perspective. I don't see a lot of daylight between Riccioli and scientists employed by the petroleum industry or Phillip Morris. Looking purely at the scientific case the bizarre world of epicycles seems like a vastly greater sin than star size or an entirely misunderstood Coriolis Effect that Riccioli posited but failed to calculate or measure correctly. I would go so far as to suggest that a stationary earth might seem intuitively obvious to a illiterate savage but anyone with a mathematical mind and access to a telescope ought to have figured out that stasis isn't the natural state of anything in the universe. One might suggest that he author started from a place of wanting to present the Church he cares very much for in a better light and presented the best possible defense for its misbehavior. The best that can be said for him is that like a good attorney he believes in his client and defends him honestly. This doesn't make him correct. Science is the process of arriving at increasingly accurate models of reality by finding ways to test theories. This is inherently at odds with religion which is the process by which priests interpose themselves between man and god to derive status and importance by serving as the only valid conduit between man and both imaginary spiritual goods like salvation and the temporal goods they acquired by selling the former. This is a problem when the shtick you have been selling everyone is universal truth because constantly having to revise it to be more in line with secular ideas makes it increasingly clear it was far from universal and once its clear that its just your best effort and not a very good one at that the long term viability of your mission is in doubt.