As a follow-up to yesterday’s post, I was wondering if Copernicus would have been more convincing if he’d used ellipses in his model instead of circles. By using circles Copernicus had to use epicycles like Ptolemy, though not so many. Still, it gave the impression that epicycles were necessary. If that’s the case then why not have a stationary Earth as well? The discovery that planetary motion would be better described by ellipses didn’t come about till Kepler’s work almost a century later. As far as the post title goes, I think Dr* T’s Theory #1 applies here: Any tabloid heading that starts ‘Is this.…’, ‘Could this be…’ etc. can be safely answered ‘No’
So my post title is a bit of a cliché, but the reason I’ve used it is that if the answer is no, then something strange is happening. More accurate is less convincing?
The reason I think that is that Copernicus’ model wasn’t isolated from the rest of thought for that period. It used and built on a number of assumptions of the time. One of those ideas was the creation of the universe by a perfect being. Another was the idea that a circle was a perfect shape, derived from classical geometry. By telling people the Sun was at the centre of the universe and not the Earth, Copernicus was asking people to make a big shift in their thinking. A lot of people thought it nonsense. If he’d made the orbits elliptical as well then many people who would have been willing to listen to Copernicus’ ideas would have balked at that, reducing his potential audience further. In terms of numbers, the population of mathematically minded people who could examine his work was small enough already.
If he’d reduced the number of initial readers further, would his ideas have spread enough for others to pick them 50 years later? It’s impossible to say, but if Copernicus hadn’t given Kepler the idea of a putting the Sun at the centre of universe, could Kepler have discovered it independently? It’s hard to say but, given how Kepler struggled with letting go of circles and using ellipses, I think it’s unlikely.
This is why I’m wary of histories of science that are purely about who got it right and who got it wrong. Copernicus’ use of circles isn’t ‘right’, but it was necessary at the time.
I’ve «cough» borrowed the portrait of Copernicus from Prof Reike’s page on Copernicus. It’s well worth visiting if you want to find out more about the astronomer.
You can read more about Kepler’s discovery of the elliptical path of planets at:
Boccaletti 2001. From the epicycles of the Greeks to Keplerʼs ellipse — The breakdown of the circle paradigm
I’ve been trying to watch Cosmos by Carl Sagan. I’ve never seen it and it’s proving to be a bit of a struggle. He definitely can write. Some of the sequences are fantastic, but some of it is badly dated. The thing that really grates to me is his dismissal of Ptolemy and his geocentric universe. For Sagan at best Ptolemy’s system held back astronomy by 1,500 years. At worst he’s only worth mentioning to say he’s dead wrong, like in the first episode.
It’s not really fair to lay into Sagan for his attitude to Ptolemy. His work is a product of its time and it was written over thirty years ago. But the idea that Ptolemy was clearly wrong seems to the popular understanding of Renaissance astronomy. The question here is Why did some people oppose the heliocentric theory of the universe? not Who in their right mind would accept it? It overlooks the power of the Ptolemaic system. If you followed Ptolemy’s work you could predict where the planets would be with enough accuracy for naked-eye astronomy. If Copernicus had only used simple circles, then his model might have seemed better, but he too needed to add epicycles and fudges to make his system match the observable sky. It needed fewer epicycles, but it was hardly perfect.
Popular belief is that the problem was solved when Galileo picked up his telescope and proved the heliocentric theory. In fact a recently published paper by Christopher Graney, The Telescope Against Copernicus: Star Observations by Riccioli Supporting a Geocentric Universe in the Journal for the History of Astronomy shows that the telescope could have dealt a serious blow to the Copernican model of the universe.
[Cross-posted to Revise & Dissent]
Valerie Shrimplin’s Sun Symbolism and Cosmology in “Michelangelo’s Last Judgment” is a difficult book to write about. I like it, but it tackles such a varied range of sources that it raises a lot of intriguing questions. Certainly more than can be covered in one blog post so, for now, I’ll leave them for a later post. For now I’ll start from the popular, if incorrect, view of the arrival of Copernicanism.
Sometime in the 16th century Nicolaus Copernicus discovered that contrary to the teachings of the church, the Earth went round the Sun. Fearing condemnation by the Church he refused to publish his theory until his death. The next day Galileo buys a copy of the book and is inspired to discover Jupiter’s moons with a telescope. This proves Copernicus’s theory and he tells the world about it. In the Vatican all hell breaks loose, figuratively speaking. The Inquistion is sent to deal with Galileo, much to his surprise, and so the church becomes an army of darkness in the War for Enlightenment.
The above is nonsense, but perhaps a fair stereotype of the Science vs. Religion battle that continues to this day. So what would it mean if there was a depiction of a heliocentric universe in the Sistene chapel dating from the sixteenth century in full view of everyone?
The Last Judgement: Image from Wikipedia.
In the midst of all assuredly dwells the Sun. For in this most beautiful who would place this luminary in any other or better position from which he can illuminate the whole at once? Indeed, some rightly call Him the Light of the World, others, the Mind or ruler of the Universe: Trismegistus names him the visible God, Sophocles’ Electra calls him the all-seeing. So indeed the Sun remains, as if in his kingly dominion, governing the family of Heavenly bodies which circles around him.
Shrimplin begins her book with this quote which could be read as a description of Michelangelo’s Last Judgement. It’s not. It’s from De revolutionibus orbium coelestium. Ok, so Michelangelo could have been inspired by Copernicus. The problem is that Michelangelo finished his painting in 1541 and De Revolutionibus was not published until 1543.
Last Judgement. Fresco in the Sistene Chapel by Michelangelo.
IN THE MIDST OF ALL assuredly dwells the Sun. For in this most beautiful who would place this luminary in any other or better position from which he can illuminate the whole at once? Indeed, some rightly call Him the Light of the World, others, the Mind or ruler of the Universe: Trismegistus names him the visible God, Sophocles’ Electra calls him the all-seeing. So indeed the Sun remains, as if in his kingly dominion, governing the family of Heavenly bodies which circles around him.
The most interesting talk of the NAM historical session was the excellently titled Michelangelo Code. Valerie Shrimplin based her talk on part of her PhD thesis Sun Symbolism and Cosmology in Michelangelo’s ‘Last Judgement’ available from Truman State University Press. It tackles something that initially doesn’t seem to be a problem. She also covers this in her paper of the same title in the Sixteenth Century Journal (Vol 21.4 1990 pp 607–44 JSTOR) which I’ve lifted the above quote from. The text above seems a reasonable description of Michelangelo’s Last Judgement. In fact it’s from De Revolutionibus, by Nicholas Copernicus describing his heliocentric cosmology. Did Michelangelo paint Copernicus’s heavens in the Sistine Chapel?
It seems unlikely. De Revolutionibus was published two years after Michelangelo finished the chapel. After Copernicus’s death heliocentricism became controversial. It could be accepted as a mathematical device, but as a representation of reality, which is how Michelangelo uses it, it would later be seen as heresy. The accepted explanation is that Michelangelo came to place Christ in a central position independently, but this is an odd explanation when you look at other depictions of the Last Judgement and what it is supposed to do.