Select Page

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