If you have any interest in the history of astronomy you should be following The Renaissance Mathematicus blog and this post, The last great naked eye astronomer, is a perfect example of why. This is a post about Johannes Hevelius who has to be one of the most famous unheard of astronomers ever.
That doesn’t make sense I know. There are a lot of people who haven’t heard of Hevelius, but if you have heard of Hevelius, then the idea that people haven’t heard of him seems nonsense because his work is everywhere in astronomy.
Scutum in the Uranographia by Hevelius. Source: Wikipedia.
Everyone’s happy that most constellations are ancient, but what is less well-known is that not every star was in a constellation. There were gaps between constellations filled with faint and boring stars. These were called αμορφοι amorphoi or unformed stars by the Greeks. This is no good if you want to do science, because things like comets don’t stick to the interesting parts of the sky. That’s why mapping was so important in the Renaissance. In the case of Hevelius, his maps were so useful that he formed seven constellations that stay with us to this day.
I’ll admit constellations like Lacerta or Vulpecula aren’t famous constellations, but he was working with the haps between constellations. The fact that his charts were made of constellations visible in Europe shows he was working in a highly competitive space.
It’s easy to take this kind of work for granted. The output can be seen as an uncontested fact, but Thony’s post put’s Hevelius’s work into the context of its time including the often intense scientific rivalry between astronomer defending personal and national status.
The also shows that while with hindsight it seems obvious that telescopes would bring more accurate measurements, at any given time in history it’s not always obvious that new technology is The Next Big Thing, it could be a distraction or Expensive Dead End.
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.
Mathematicians have a concept, Omega, that is defined as something so huge that any attempt to define it actually defines something smaller. In a similar vein I reckon that any attempt to describe the ingenuity of the Antikythera Mechanism actually ends up describing something less ingenious instead. More research on the device has been published recently in the Journal for the History of Astronomy. I realise that people might be dropping on to this entry from a search engine, without having read any of the earlier posts, here’s a quick recap of what the mechanism is.
Astrolabes at the Museum for the History of Science at Oxford.
If you ever want to embarrass me, try to get me to enthuse about a display of astrolabes. They’re the kind of thing I should love. They’re devices for showing what is visible in the sky at any given time. They’re very similar to the planispheres that people use today. The mathematics behind them is elegant. The best also tend to have extraordinarily ornate metalwork to complement the sophistication of the devices. Yet, when they’re hanging up like this, they leave me cold.
I think the reason is that an astrolabe on display is a dead astrolabe. There are better ways to show a static night sky. What you need is an astrolabe in motion to appreciate them. That’s what makes this talk by Tom Wujec so good. He demonstrates how you could use an astrolabe to tell the time. In his hands, an astrolabe becomes a lot more interesting.
It’s easy to underestimate how much you can do if you’re willing to observe intently. What I also like about this talk is that Tom Wujec emphasises the importance of connecting with the night sky. You could claim accurate clocks have broken this connection, but I’m not sure that’s the case. Where I live light pollution is often so bad that I could not use an astrolabe. He’s right to point out that you can lose things with progress. Ironically Global Astronomy Month with try to show how immense the universe is, while artefacts like this show that on a day-to-day basis for urban dwellers the visible world is much smaller than the cosmos of the past.
You can see many astrolabes like the one below at the Museum of the History of Science, Oxford.
A Persian Astrolabe at the Museum for the History of Science at Oxford.
Note: Giulio Magli was one of the examiners of my thesis, so his book is hardly likely to get a bad review.
This review rounds off a trilogy to go with Skywatchers, Shamans and Kings and People and the Sky. Like the other two books this could be said to be part of a World Archaeoastronomy approach, but Giulio Magli adds a twist. Some of this is down to the approach he’s taken to archaeoastronomical sites, but he also adds a bit more.
Magli’s approach is similar to what I would have done if I was writing an introduction to archaeoastronomy book. He tackles the sites around the world. So take a deep breath because in his opening section of twelve chapters — slightly over half the book — he covers. Palaeolithic Europe, Prehistoric Britain, the temples of Malta, Egypt, Babylon, East North America with the Hopewell and Cahokia, West North America with Chaco and the Anasazi, Northern Mexico and Tenochtitlan, The rest of Mesoamerica and Palenque, The Incas, Nazca and Polynesia. That leaves massive holes where you would expect to find India, China, Korea and Japan and a lack of African material. That’s more due to the state of play in academic archaeoastronomy at the moment than a fault of Magli. In general Africa has been greatly overlooked and there’s not a lot of integration between Asian astronomy and the rest of the world. It’s getting better, but it’s still under-represented compared to the Mayans and Prehistoric Europe.
If this had been the sum total of the book I wouldn’t be that enthusiastic about it. It’s not bad. It’s written from an astronomical point of view with some amusing digs against archaeologists. If you were interested in archaeoastronomy and approaching it from astronomy and not anthropology I’d recommend this over Aveni or Krupp’s book as an introduction to the field. What really marks out the book as worth reading is section 2.
I had a slight worry earlier today. I have an idea that I think has cross-over relevance between SETI and Ancient History about ancient speculations on extraterrestrial life. I was slightly alarmed when I read Jean Schneider’s new pre-print on arXiv, The Extraterrestrial Life debate in different cultures. In it Schneider argues that arguments about life on other worlds can be traced back to ancient Greece. It sounds like an idea I’ve been kicking around for a couple of months. It was a topic raised by the atomists like Democritus and Leucippus who said that in an infinite cosmos with an infinite number of atoms there must be infinite worlds. Plato rejected this idea, as did Aristotle who argued for a hierarchical cosmos. Schneider says debates in other cultures are derived from this and then asks why it should be only the Greeks who speculated on offworld life.