Hugo Holbling

(Disclaimer: I'm not sure how much sense this will make as i had alot of moderating work to do while attempting to compose it.)

In fact, further work on your part would show you that the actual research we have done throws up more difficulties than answers. Vorkosigan notes that:

This may be so but it does not help us here. Copernicus’ system was not simple; indeed, he introduced so many epicycles and secondary epicycles that in the academic literature (that is, the research that has not been done) we find, for example, Cohen noting that

Swerdlow has done some interesting work in this area, of course, and there has been much disagreement with regard to the required circles.

Copernicus hoped that he could devise a system that would be as empirically adequate as the Ptolemaic but would adhere to the principle that motion would be uniform and circular. Ptolemy had abandoned this idea many years previously (precisely because it did not accord with the observations), so it is decidedly relevant to wonder why Copernicus insisted on it. Swerdlow notes this principled disagreement but attributes it to a physical difficulty implicit in Copernicus idea of De Revolutionibus Orbium Coelestium (my italics).

It is agreed in the literature that Copernicus’ system did not provide for results more in agreement with observations, while the question of the ease of calculation does not appear to have been discussed in his time. The re-instating of circular motion seems to have been considered the most important point, as Reinhold mentions, and this assumption would then lead to a rejection of Ptolemy, but not before. In any case, the Ptolemaic system had explained retrograde motion but Copernicus claimed to have done so more simply; generally speaking his system may be qualitatively simpler but quantitatively it is no better at all, which may be why some historians have focused on the philosophical aspect (for example, Grant, although he now appears to have changed his mind). It is useless to appeal to Copernicus’ idea of constant, circular motion as an explanation because – as noted above – Ptolemy had considered it himself and rejected it (as Kepler would later do).

Vork notes that

However, it was far from clear that the earth moved at that time, or later when Galileo was investigating to that end. The idea of the motion of the earth was counter-intuitive and the Aristotelians had provided convincing reasons why (such as the famous Tower Argument), with Galileo still working to overcome them many years later. This is a sub-topic but the question of the earth’s movement was not resolved and indeed the consensus then was against it – rendering Copernicus’ system straightforwardly incorrect. Vork is of course right to point out that Copernicus suggested that the motion of the earth required a change in the sun’s location but the question asked in the OP was to wonder why he would do such a thing when the argument went the other way.

As noted, it is mistaken to suppose that the Ptolemaic system did not account for the observed behaviour, since it did and moreover did so at least as well as Copernicus’ system. The latter does not depart far from his predecessor, even in the layout of his work, causing Dreyer to complain that the system suffered from a “want of new observations”. Although Copernicus may have given new credence to the heliocentric hypothesis, the fact that the motion of the earth was not clear for some time yet prompts us to wonder if there were philosophical or other reasons why he would insist on it. His system was to be contradicted in most of its details by Kepler’s after the understanding of motion had changed.

Bill

Oh, come on now! There must have been matters which Copernius explained that Ptolemy did not explain, thus negating the thrust of your first quoted sentence, above.

Again, beginning on the Copernicus page I linked to in my prior post, we have the testimony of the man who was so impressed with the work of Copernicus that he took his manuscript and published it: Perhaps I missed it, but I didn't see any discussion of what Rheticus had to say about why Copernicus felt compelled to put the Sun at the center of things. And, if we continue reading the Copernicus page we discover: I note the reference to the Greek Muse Urania, so I recognize that this is hardly an objective description. Still, nonetheless, we have firsthand testimony to the effect that something in the observations made by Copernicus and/or his predecessors (whose records Copernicus had) compelled Copernicus to reject the Earth-centered model of Ptolemy. And later on the Copernicus page we find this: If we follow the link to the Tycho Brahe page we find a description of his own theory: So, it appears that Brahe himself had confirmed the falure of observation to conform to the model of Ptolemy and only his inability to confirm the scale of the universe led him to accept that the Earth was at the center of things. His own theory was that everything else revolved around the Sun, and that allowed him to resolve these discrepanices with Ptolemy through the simple artifice of a change of reference point, holding the Earth fixed and allowing the rest of the universe to move around it as required to conform with observations.

Of course, the ultimate beneficiary of all of these observations would be Kepler, the end of whose page contains this observation: In other words, even when we get down to Kepler, who was finally able to set forth the mathmatical laws for a heliocentric solar system, we are still dealing with a true believer in Christianity and divine grace.

Before the 21st century, there was never a time when scientific observations really challenged faith. All such perceived challenges could easily be resolved by referring to Gould's concept of Magisteria. This just makes it all the more absurd that the Catholic Church would treat Copernicus, Galileo, and the rest of these scientists the way that it did.

But to summarize, I must absolutely disagree when you assert that "it is mistaken to suppose that the Ptolemaic system did not account for the observed behaviour, since it did and moreover did so at least as well as Copernicus’ system." Reticus and Brahe testify convincingly that this was not the case, and I'm strongly inclined to take their word over yours.

== Bill

Hugo Holbling

That may be, but i am strongly disinclined to continue a debate with someone not prepared to study the voluminous literature on these subjects and instead rely on internet encyclopedia entries. Arguing that "come on now! There must have been..." is not very impressive.

Rheticus can scarcely be expected to give a fair account of his master, while Brahe's account is fanciful since there were no new observations then nor for the next fifty years through which to become any more dissatisfied with the Ptolemaic system than people already were (as Vork notes). As you would know from a study of the relevant works, all theories contain anomalies; the point is to ask if Copernicus' system improved upon Ptolemy's and the answer is that it didn't in any quantitative sense. This is a standard remark found throughout the literature, if only you would study it. Kuhn's account is of course the most authoritative, given his sublimely detailed appendix and biographical notes, and he gives Copernicus credit where it is due (influencing Brahe in spite of the latter's denials) but not where it is clearly is not. The qualitative case is much more relevant and the mathematization appears to have had an effect on Brahe, Kepler and others.

Interesting questions posed by the fact that Copernicus did not improve quantitatively on Ptolemy are what we are asking here and elsewhere. If you read only Kuhn and past the preface of Copernicus himself you would realise that "Copernicus' system is neither simpler nor more accurate than Ptolemy's." We are asking questions here precisely because "the observations with which Brahe and his contemporaries speeded the downfall of traditional cosmology and the rise of Copernicanism could have been made at any time since remote antiquity."

And what way was that? I hope you are not going to bring up the simplistic conflict account.

Vorkosigan

That is true, but quite irrelevant. Copernicus himself said simple was better, and gave the reasons I listed above. Whether his system is in reality simple has nothing to do with his perception that simple is better. Those are two different points. Copernicus may have genuinely felt his theory was simpler than Ptolemy's, or may have just oversold his system. Either way, whether Copernicus' system is actually simpler is a different point then whether simpler is better.

Because it was simpler. And Ptolemy did too attempt to preserve perfect circular motion inventing dequants, and locating the earth a teensy bit off center.

Yes, but you've wandered off point in a way. "Simplicity" is a value, not a fact. Copernicus believed "simple" was better. He said so and defined what he thought "simple" might be. End of discussion. Whether some other party thinks Copernicus' system was "simple" is not relevant; there are many grounds that one might choose to define "simple." Choosing words "symmetrical" and "simple" might serve several functions -- at least one of which was to enable Copernicus to sell the theory.

Further, Copernicus is not only attacking complexity. As he quite specifically says, he was attacking the ad hoc and incoherent and inconsistent nature of Ptolemaic astronomy. His idea, he claims, resolves those issues. Thus, it is not only "simpler," but simpler in ways that were more consistent and without an ad hoc hypotheses. "More epicycles" can be simpler if fewer of them are inconsistent and ad hoc.

Yes, but this entirely misses the key point at issue. Again, whether others thought the earth moved is pointless. Copernicus did so; that is enough. Why? Because he had read it in the classics, and thought that making the earth move simplified things a bit (he says). Whether there was good evidence for it is not relevant to his decision, since he did not make his decision on evidentiary grounds. Evidence is only relevant for him in attempting to convince others. What he was doing, as he says, was basically brainstorming ways to tinker with Ptolemaic astronomy so that it worked without all the ad hoc assumptions and incoherencies and inconsistencies.

I already discussed this. As Copernicus himself says, he was tinkering with the system, and ended up looking in the old books for inspiration, and then decided that the earth moved.

True. But it did dispense with the ad hoc and inconsistent nature of Ptolemaic astronomy, a notable advance. Further, Copernicus did not claim that new observations annihilated Ptolemy. Rather, he claimed on philosophical grounds that Ptolemy was wrong. I don't even really think he was doing science, so much as geometry and philosophy.

Apparently you are dissatisfied with Copernicus' explanation of his own behavior. It strikes me as a insight he had from wrestling with Ptolemy and polished over many years, and became attached to. Lots of scientific work comes from that 'insight' that is not readily explainable even terms of very complex social causation. If you held a gun to my head I would confess to suspecting that his realization that the earth must be moving was in fact just fallout from working with Ptolemy's ideas, and that his search in the classics was a case of after-the-fact rationalization for his idea.

I think one problem you have here Hugo, is the way you have constructed your approach. In a sense you've placed Ptolemy in the "problem" and are treating him as a given but not an influence, and are thus searching for influences that are "not Ptolemy." I think you have to see that Ptolemy falls on both sides of the line here, and that the most influential text on Copernicus was in fact Ptolemy(!) even though the problem was also Ptolemy.

Vorkosigan

Hugo Holbling

Thanks for your commentary, Vork. I agree that Ptolemy was perhaps the most significant influence on Copernicus but i disagree that i have failed to note this; indeed, i pointed out a few posts back that he had followed Ptolemy's approach too closely for Dreyer.

I accept that the fact of Copernicus' system not being simpler does not impact on his assertion that it was, and i hoped to make this clear by distinguishing between quantitative and qualitative superiority. Nevertheless, this point is important for the philosophy of science - hence my concern.

I am specifically interested in two aspects of this episode currently: firstly, the mathematisation in Copernicus and hence, together with the possibility of hermetic influence thereupon (an area of much recent study in the history of science); and, secondly, why it took so long for someone to sucessfully challenge the Ptolemaic system. I suspect we are alot closer on this question than you may think.

If you can obtain a copy, you might be interested in a paper called The Myth of Astronomical Instrumentalism by Alan Musgrave.

Vorkosigan

I am not sure. This was Yate's old idea that hermeticism gave way to mechanism. It was entirely possible to hold to hermetic sun worship views and yet place earth at the center of the universe. See Ficino's De Sole et Lumane. Telesio argued that since the sun was the origin life, motion must be one of its properties -- this consigns motionlessness to the earth because it is passive. Patrizi De Cherso was another hermticist who rejected heliocentricism. There is nothing in hermetic sun worship that requires placing the sun at the center of the universe. Bruno accepted Copernicus but was actually much closer to modern views, putting the sun at the center of a system of planets, rather than at the center of the universe.

Copernicus does refer to some hermetic views of the importance of the sun, but I think it is easy to see that as an appeal to authority to rationalize the position he had taken rather than as a cognitive resource for his system. The extent of hermetic influence on Copernicus is still the subject of much debate.

Of course.

Vorkosigan

NOGO

Common sense was not all that common considering that a mind like Kepler accepted the new theory without question.

Strange that kepler did not ask himself why Copernicus did what he did but Bede is still asking.

First, Copernicus did not simply say that the earth moved around the sun, that is a gross oversimplification.

Ptolemy had the sun and all the planets moving around the earth.
Copernicus had the earth and all the planets moving around the sun.

BIG DIFFERENCE

Question:
How can you possibly think that all the planets and the sun move around the earth?

Answer:
This is due to the apparent 24 hour cyclic movement of everything you see in the sky including the stars.

It is obvious that Copernicus did not build his system based on this apparent 24 hour cycle. Otherwise he would have had to admit that everything revolved around the earth.

The most fundamental change that Copernicus brought was that the 24 hour cycle was due to the rotation of the observer.

Once that out of the way you start looking at the real movement of the celestial bodies. For example look at the moon at sunset every day. Each day you will notice that the moon is closer and closer to the eastern horizon. So the apparent movement is from east to west but the real movement (much slower) is from west to east.

This example shows the essence of Copernicus' work.
With the 24 hour movement out of the way you take the resultant movements of the planets and low and behold the sun ends up in the middle. This is the way Copernicus tore Ptolemy's system apart and rebuilt it from scratch.

Why did he do this?
My guess is that by observing the sky he preferred to believe that the earth/observer rotated rather than to believe that the whole universe rotated every 24 hours. Call it a hunch.
He had 50/50 chances of being right one or the other did rotated every 24 hours.

What this proves is that religion which attempts to control people's minds ultimately fails on brighter people like Copernicus who give themselves the "Right to Think".

NOGO

Kepler found rules that govern the shapes and orbit trajectories.
Newton explained that and gravity from the same principles.
Christians say it is all done by God.

See they are the same - elegance and parsimony.

Anyone who studied Ptolemy's work for any length of time will certainly see that the universe is like clockwork with mathematical precision. Copernicus did not need to get it anywhere else. It was already in astronomy since Ptolemy or even Aristarchus.
Neither of which got it from the Jewish Bible.

So much nonsense in so little space.
Genesis 1:14
Then God said, "Let there be lights in the expanse of the heavens to separate the day from the night, and let them be for signs and for seasons and for days and years;

The bible states in Genesis 1 that the moon and sun were created so that man can ... tell time.
The ancient Hebrew had a lunar calendar. Every few years they had to add a month to realign the seasons. It never occurred to them that this was less than perfect and therefore unworthy of Yahweh. 3000 years later Yahweh inspired Copernicus that Greeks were not accurate enough for Him and that He required a better model of the universe. Wow!

Our solar year comes to us from the Egyptians and Romans while Christians still celebrate Easter on a lunar calendar.

Bede's point is that Copernicus tore up Aristotle and Ptolemy and based himself on what the BIble said.

The absurity of this statement is awesome.
Catholics were never encouraged to read the Bible.
One can have serious doubt about Copernicus ever reading the old testament. But even if he did I doubt that he search scriptures for his work on astronomy.

Although Copernicus changed things his basic tools and concepts were totally borrowed from Ptolemy. All his geometry and math came from the Greeks. The idea that you can model something with geometry and math came from the Greeks.

If belief in Yahweh/Jesus is required to do anything as Bede seems to be saying then why was Geometry invented by the Greeks and not the Hebrews?

Bede keeps pushing the absurd idea that before science could come about his mighty Christians had to fight off the insfluences of those nasty Greeks and what we have left is pure Christian scientific thinking.

To the rest of us ancient Greeks the pioneers in math and science and we give credit where credit is due. Copernicus and other would have done strictly nothing without the contribution of the Greek (so called Pagan) civilization.

joedad

Copernicus did not come up with this idea. Aristarchus of Samos argued that the Earth was a planet as well and in orbit around the Sun in the third century BCE. So that predates Copernicus by nearly two millenia.

Aristarchus of Samos and the Heliocentric Universe

(Sorry if I missed where this has already been pointed out.)

edit to add: Just saw it in your post NOGO.