Giordano Bruno: A Martyr, Yes, but Not for Science

[John_Harshman]

@PdotdQ

Back then they did not know the sizes and masses of planets and stars.

Wait. Weren’t there pretty good estimates of the distance from the earth to the sun and of the sun’s angular size? That translates to knowledge that the sun is frickin’ huge. One might argue that it’s huge but fluffy, but one coudn’t just assume it.

What did Brahe mean by “triple motion”? Rotation, revolution, and what?

@PdotdQ

in 1806, the first measurement of stellar parallax was performed

You’re saying that’s the first evidence of heliocentrism? That would seem to accuse everyone from Kepler until then of not doing science. Now it seems to me that Kepler’s laws are inconsistent with the Tychonian system, and Newton’s universal gravitation is too. It’s a fine answer to the parallax problem that measures of stellar angular diameter were flawed and the stars were very far away.

Anyway, Galileo’s book didn’t as far as I know confront the Tychonian system at all and it had nothing to do with the charges against him. At most you could say that he failed to consider all the alternative hypotheses. But is that not doing science?

[PdotdQ]

@John_Harshman

One might argue that it’s huge but fluffy, but one coudn’t just assume it.

From Tycho’s quote that I mentioned, it seems that that is indeed what they assumed. Regardless, the Earth was thought as special back then, and there is no reason to think that just because in other systems small things always revolve around big things, in this very special system the Sun cannot revolve around the Earth.

@John_Harshman

Now it seems to me that Kepler’s laws are inconsistent with the Tychonian system, and Newton’s universal gravitation is too.

That’s why I say that I am not sure when the exact date is - I think the exact date would depend on what one means with geocentrism being debunked. Newton’s Law of Gravity is indeed inconsistent with geocentric systems, and its publication could perhaps be used as the date when geocentrism fails. However, despite it being very convincing, Newton’s Law of Gravitation would be theoretical, not observational proof.

I just read an article on the first attempts of detecting the stellar parallax by James Bradley in 1725 (Bradley's Discovery of Stellar Aberration). While failing to detect the stellar parallax, Bradley detected fortuitously the stellar aberration, which would also prove heliocentrism (~60 years after Galileo instead of ~160 years for stellar parallax). Too bad Newton died before Bradley’s discovery, but if one requires observational proof, this might be a good date to quote as when geocentrism fails.

@John_Harshman

At most you could say that he failed to consider all the alternative hypotheses. But is that not doing science?

Galileo knew of Tychonian systems, it was the chief opposition of Copernican systems. Instead of agreeing that there was not yet enough evidence to decide which system was correct, he insisted that his theory was the correct one. Indeed, the situation was even worst: evidence at the time (the lack of stellar parallax) went against Copernican systems. Still he insisted that he was correct - without proof. This was not a scientific act.

[John_Harshman]

@PdotdQ

From Tycho’s quote that I mentioned, it seems that that is indeed what they assumed. Regardless, the Earth was thought as special back then, and there is no reason to think that just because in other systems small things always revolve around big things, in this very special system the Sun cannot revolve around the Earth.

It seems to me that in that case Galileo isn’t the one who wasn’t doing science.

@PdotdQ

However, despite it being very convincing, Newton’s Law of Gravitation would be theoretical, not observational proof.

For a scientist, you seem awfully focused on “proof”. Kepler’s laws make sense of observations; they’re confirmed by those observations. Kepler’s laws make no sense in a Tychonian context. Universal gravitation makes sense of Kepler’s laws and many other observations too. The data that sparked both Kepler and Newton are thus ultimately incompatible with Tycho. And some of Galileo’s discoveries are too, in a looser sense.

@PdotdQ

Galileo knew of Tychonian systems, it was the chief opposition of Copernican systems.

Was it, though? Or was the Ptolemaic system still the chief opposition? Again you harp on that word “proof”, which isn’t what science does. Galileo had good evidence against the Ptolemaic system and some evidence against the Tychonian system. The mountains of the moon are more evidence, incidentially, that the earth shouldn’t be considered “special”. And parallax is only an argument if you assume that the stars are not too far away. Anyone making that assumption without evidence isn’t doing science!

[PdotdQ]

@John_Harshman

It seems to me that in that case Galileo isn’t the one who wasn’t doing science.

Why is that? I don’t think it’s not scientific to say that small things revolving around big things in other systems do not necessarily mean that it has to be the case for the Earth-Sun system, regardless if they think the Earth is special or not.

@John_Harshman

For a scientist, you seem awfully focused on “proof”.

I’m being sloppy with my language. I mean evidence in the Bayesian sense that is strong enough to make the posterior conclusively peaked.

@John_Harshman

The data that sparked both Kepler and Newton are thus ultimately incompatible with Tycho.

Their current orbital data is compatible with both Kepler and Tycho. Note that Tychonic system is a coordinate transformation away from heliocentrism! Newton’s data include terrestrial data and the axiom that physics on Earth is the same as physics in “the Heavens”. This definitely did not support Tycho, which is why I claimed that it could be said that the publication of Newton’s Principia was the date geocentrism died.

@John_Harshman

Was it, though? Or was the Ptolemaic system still the chief opposition?

I am not a historian, but I am pretty sure about this, given that even Jesuits in China are using Tychonic systems during Galileo’s time.

@John_Harshman

And parallax is only an argument if you assume that the stars are not too far away.

I believe that back then their rudimentary telescopes do give evidence of stars being not too far away. I also heard that they do not fully understand diffraction and thought that the unresolved light from stars are its actual sizes, which contributes to this debacle.

@John_Harshman

Anyone making that assumption without evidence isn’t doing science!

Speaking of assumptions without evidence, so would you agree that Galileo’s act that

@PdotdQ

Instead of agreeing that there was not yet enough evidence to decide which system was correct, he insisted that his theory was the correct one. Indeed, the situation was even worst: evidence at the time (the lack of stellar parallax) went against Copernican systems. Still he insisted that he was correct - without proof.

Was not scientific?

[TedDavis]

@John_Harshman

Nicolas of Cusa, heartily endorsed the plurality of worlds and was later declared a saint, not a heretic.

Could this be documented? I couldn’t (in a quick and perhaps superficial search) turn up anything on it. Did he advocate it or just suggest it as a notion?

I’m no student of Cusanus myself, and thus can’t verify everything said about him here, but it’s consistent with what I’ve read in several scholarly print sources:

Nicholas Of Cusa – A Medieval Scholar And Mystic With Highly Unorthodox Ideas...

I’d have to see the Latin to endorse the exact words of the translated passages on that cite, and honestly I have no time to give to that right now. My guess is that the Latin sentences containing “let us suppose,” “we will suppose,” and “It may be conjectured” were written in the subjunctive mood (Latin/Lesson 1-Subjunctive - Wikibooks, open books for an open world), and without seeing the precise verb forms I’m unsure how best to translate them. In medieval natural philosophical discourse (the relevant genre), the subjunctive was often used to express hypothetical possibilities of many types, often what we would call “hypotheses” today–including hypotheses that the author takes very seriously as possible truths. That’s how the scholars I’ve read interpret Cusa’s ideas of multiple inhabited worlds.

This is the best I can do without tracking down and carefully reading his Latin–and I can’t do that now.

[John_Harshman]

It looks clear to me, based on the quotes in that article, that Cusanus presented his views on extraterrestrial life as speculation. The Church doesn’t seem to have had much problem with speculation. Bruno, on the other hand, actually asserted his ideas to be true. Big difference. Nor does Cusanus, based on that, seem to be talking about the same idea of an infinite universe as Bruno; in fact he says that how the universe can have no center is not comprehensible.

[PdotdQ]

@John_Harshman

Nor does Cusanus, based on that, seem to be talking about the same idea of an infinite universe as Bruno; in fact he says that how the universe can have no center is not comprehensible.

Wait, I’m pretty sure that’s not correct. Here’s a more reliable source (the SEP) Cusanus, Nicolaus [Nicolas of Cusa] (Stanford Encyclopedia of Philosophy)

This “ontological relativity” leads Cusanus to some remarkable conclusions about the earth and the physical universe, based not on empirical observation but on metaphysical grounds. The earth is not fixed in place at some given point because nothing is utterly at rest; nor can it be the exact physical center of the natural universe, even if it seems nearer the center than “the fixed stars.” Because the universe is in motion without fixed center or boundaries, none of the spheres of the Aristotelian and Ptolemaic world picture are exactly spherical. None of them has an exact center, and the “outermost sphere” is not a boundary. The universe is therefore “infinite,” in the sense of physically unbounded.

[TedDavis]

Why did Galileo get arrested? Ask 10 historians and you might get 11 answers. I am skeptical of any answer that doesn’t include multiple factors. For a glimpse of the complexity of this question, listen to my podcast here: https://www.veracityhill.com/episodes/episode-126-galileo

I can’t promise to interact much with any comments, but I hope to read them occasionally.

[TedDavis]

@John_Harshman

When, in your opinion, was there evidence to distinguish the Tychonian model from the Copernican?

And hey, his dialogue concerned the two chief world systems, not multiple systems.

My answer is the same as @PdotQ. Aberration of starlight was the first hard evidence of the actual motion of the earth–roughly a century after Galileo’s trial. I may have mentioned this in the podcast.

And, yes, Galileo’s book was about just two systems, Copernicus and Ptolemy. The omission of Tycho was a deafening silence. Had I been alive at that time, Tycho was the man. His system explained everything Galileo saw, whereas Ptolemy began to be discarded at that point. Keep in mind that Tycho was, by far, the greatest observational astronomer who ever lived at that point in history. His ideas were not to be trivialized–and IMO Galileo made an enormous tactical error to leave them out. I have the impression that he deliberately (Galileo did many things deliberately) left Tycho on the margins, in order to place before his readers a false dichotomy that Copernicus had to win.

[TedDavis]

@John_Harshman

It looks clear to me, based on the quotes in that article, that Cusanus presented his views on extraterrestrial life as speculation. The Church doesn’t seem to have had much problem with speculation. Bruno, on the other hand, actually asserted his ideas to be true. Big difference.

OK, fair enough, but let’s be a bit more critical, John, since you’re stressing the need for scientific evidence. Where exactly was Bruno’s evidence? Where (for that matter) is any actual evidence today for multiverse? This stuff is all wild speculation, then and now. Perhaps those ideas will prove right in the end, but presently they are all what Galileo called “worlds on paper.”

So much of astronomical discourse at that time was self-consciously speculative. Indeed, the time-honored tradition, said to have originated with Plato, was that the goal of astronomy was simply to “save the appearances,” i.e., to find hypothetical mathematical models that can be used reasonably well to predict where planets would be on given nights, not to discover physical reality. This must be kept in mind.

In this light, Galileo’s claim that the earth really does move and the Sun really does not, was very hard to accept–especially given the utter inability to see parallax or any other observational evidence of the earth’s motion.

[John_Harshman]

@TedDavis

Where exactly was Bruno’s evidence?

It isn’t clear that Bruno was much concerned with evidence. He just had a lot of ideas. But I would suppose that the idea of infinite space comes with the hypothesis that stars are similar to the sun. That’s a sort of unifying idea.

@TedDavis

Where (for that matter) is any actual evidence today for multiverse?

How did that enter the discussion?

@TedDavis

Galileo’s claim that the earth really does move and the Sun really does not, was very hard to accept

It’s a simpler explanation for the data available at the time than Tycho’s system. Why should a stationary earth be the default assumption? Why, in fact, should a crystal sphere containing the stars be a default assumption? There are suggestions that the stars might be at different distances, because they have different brightnesses. And the idea that they might be similar to the sun is helpful there, which also suggests that they might be too far away to show parallax with the methods available at the time.

[PdotdQ]

I think I can answer some of these:

@John_Harshman

It’s a simpler explanation for the data available at the time than Tycho’s system.

Tycho’s system is a coordinate transformation of Copernicus’ heliocentrism, i.e. they have the exact number of free parameters and thus the exact same level of simplicity/complexity. I don’t know what exactly constitutes as “simple” for people circa 1600s/1700s, but this is a mathematical way to describe simplicity that we used today, and people back then knew about it too (I think).

@John_Harshman

And the idea that they might be similar to the sun is helpful there, which also suggests that they might be too far away to show parallax with the methods available at the time.

Actually, the idea that other stars are similar to the sun is the one that suggests that parallax should be seen by methods available at the time. At the time, they did not know much about the diffraction of light; Airy’s seminal work was in 1835 (c.f. Airy disk). As such, they thought that the entire spot of an unresolved star observed from a telescope is the actual angular size of the star.

Given that, here is the argument by Tycho: If stars are similar to the sun, and not enormously huge, this means that these stars must then be located close to the Earth in order to have their (again, now we know to be wrong) angular sizes. Because they are close, then parallax should have been seen, even with the telescopes of their times.

[John_Harshman]

@PdotdQ

Tycho’s system is a coordinate transformation of Copernicus’ heliocentrism, i.e. they have the exact number of free parameters and thus the exact same level of simplicity/complexity.

Oh, come on. Tycho’s system is a kludge. It’s an odd hybrid of Ptolemy and Copernicus. Earth’s rotation is also simpler than the idea that everything else is making big daily circles, especially if the stars are considered as free bodies, not all embedded in a crystal sphere.

@PdotdQ

As such, they thought that the entire spot of an unresolved star observed from a telescope is the actual angular size of the star.

I’ll admit to that.

[PdotdQ]

@John_Harshman

Oh, come on. Tycho’s system is a kludge.

Admittedly my training biased me from seeing it as anything but a coordinate transform of the Copernican system. Such coordinate transformations do not change the complexity of a model. In terms of anachronistic, modern scientific analysis, the Bayesian Occam’s Razor we used today cannot distinguish between them based on their complexity alone.

[gbrooks9 (GeorgeB)]

The irony of cosmology is that Galileo and others of his time didn’t know enough about how light bends to explain why stars had the appearance of being massively huge. The unwashed masses don’t realize what a bind heliocentrists were in - - even after Galileo’s writings were first published.

But we must presume that Galileo suspected there were some valid complications on the “star” business… reasoning that it would be easier to solve the star question than to refute the three findings, made possible by telescope, which he thought trumped all the other observations of the day:

[1] He saw that not everything revolved around the Earth by seeing the moons of Jupiter pass in front of Jupiter and behind it.

[2] Second, he saw the phases of Venus and saw that sometime Venus passed behind the sun.

[3] And thirdly, he was able to use heliocentrism to explain why the planets displayed retrograde motion.

But could Galileo have been wrong about these things? Sure. He could have been wrong.

But this is miles away from attempting to portray Galileo’s martyrdom as having nothing to do with science.

Many denominations, churches and their promoters consider metaphysical reality to be their legitimate area of expertise. This is true almost by definition. But when authorities use religion as a justification to interfere with the free exploration of the natural order - - it’s pretty much the very crux of the entire argument:

From time to time, in this or that century, denominationally or theologically motivated “actors” can and do attempt to impose their social and/or legal powers to interfere with the work of Scientists. Of course, sometimes this is merited, if the science being explored has ethical problems. But turning a telescope towards the night sky does not enter that sphere of possibilities.

What I find especially odd is that we are here, on these boards, struggling mightily with the whole scope of problems that religiosity poses for a legitimate application of evolutionary sciences on a proper understanding the Universe.

And yet at the very same time, have pro-Evolutionists arguing that religion does NOT cause problems for science or scientists. Does anyone else find this a bizarre pattern of denialism?

[jongarvey]

@PdotdQ

I believe that back then their rudimentary telescopes do give evidence of stars being not too far away. I also heard that they do not fully understand diffraction and thought that the unresolved light from stars are its actual sizes, which contributes to this debacle.

True. I’ve read that owing to aberration, brighter stars produced larger images, thus misleading astronomers into assuming they were relatively close.

[PdotdQ]

@gbrooks9

But we must presume that Galileo suspected there were some valid complications on the “star” business… reasoning that it would be easier to solve the star question than to refute the three findings,

Copernicans at the time thought that the stars are indeed “massively huge”. The reasoning is theological instead of scientific. As stated by Cristoph Rothmann (a heliocentric astronomer) as a response to Tycho Brahe:

for in fact divine Sapience and Majesty is far greater than they understand. Grant the vastness of the Universe and the sizes of the stars to be as great as you like—these will still bear no proportion to the infinite Creator. It reckons that the greater the king, so much greater and larger the palace befitting his majesty. So how great a palace do you reckon is fitting to GOD?

This is a theological and not a scientific objection. Interestingly, it includes the axiom that the Earth-Sun system is special. Remember, these are the heliocentrists, who supposedly thought that the Earth is not a special place.

Now, none of [1], [2], or [3] are problems for geocentrists.

@gbrooks9

[1] He saw that not everything revolved around the Earth by seeing the moons of Jupiter pass in front of Jupiter and behind it.

This is only a problem for Ptolemaic models. Having things revolve around things other than Earth is not a problem for other forms of geocentrism. Indeed, all of the planets revolve around the Sun in the Tychonic model.

@gbrooks9

[2] Second, he saw the phases of Venus and saw that sometime Venus passed behind the sun.

Again, only a problem with Ptolemaic models. Compatible with geocentrism in the for example, Tychonic, Capellan, or Riccioli’s models.

@gbrooks9

[3] And thirdly, he was able to use heliocentrism to explain why the planets displayed retrograde motion.

This one is not even a problem in Ptolemaic models, through the use of epicycles.

So again, none of [1], [2], or [3] are problems for geocentrists.

[John_Harshman]

Another weird wrinkle: how can you say that stellar parallax “proves” heliocentrism? Why couldn’t the stars all be doing little epicycles? Why, it’s just a transformation of coordinates.

[John_Harshman]

@PdotdQ

it includes the axiom that the Earth-Sun system is special

I haven’t managed to spot that axiom in what you said. Could you clarify?

[John_Harshman]

Question for @PdotdQ: How does the Tychonian system deal with earth’s rotation?