The Orrery

I am interested in ways people model the universe on the large or small scale. This is very much a developing interest for me—mostly still in the stages of understanding how people model things rather than what they say about the ways we think about the universe (although that’s where I’d like to end up).

An orrery clock in the British Museum

One object I really love is the Orrery. An orrery is a model, usually movable or even mechanical, of the solar system. Orrerys are often objects of beauty and that’s why they attract me; I am sure I am not the only one to find them initially interesting for purely aesthetic reasons.

My research, if you can call it that, about the orrery threw up something interesting. The geocentric model of the universe, which preceded Copernicus’ modern heliocentric model of the universe, would have made a more complicated orrery, particularly with epicycles to account for certain stubborn planets’ retrograde (backwards) motion.

Since an orrery is a fairly obvious thing to make, perhaps that’s why the three dimensional model of the universe did not really exist in the modern world until after the heliocentric model was widely accepted. It is easy to put a sun in the centre and then a series of concentric circles outside it.

According to this Whipple Museum web page,

London clock- and instrument-maker George Graham (circa 1674-1751), worked with Thomas Tompion (active 1671-1703), to create a number of particularly finely made heliocentric (sun-centred) models. These can be viewed as the predecessors of the orrery.

 The orrery gets its name from a man called Charles Boyle, the 4th Earl of Orrery, who was made an early orrery by "celebrated instrument maker" John Rowley as a gift for his son (the 5th Earl of Orrery), making the Earls part of the long list of non- and semi-scientists whose interest in science has nevertheless been enough to be significant (albeit in a small way).

Astronomy was fashionable and the orrery took off in the 18th century, ostensibly as a teaching tool. Beautifully made, they were no doubt also something you showed off to your friends as a status symbol of your scientific interest. This role of the orrery is captured in the famous painting by Joseph Wright, A Philosopher giving a lecture on the orrery, in which a lamp is place in the position of the sun. 

   
Wikipedia observes that not only is this painting lovely, it is perhaps significant that the people's faces are seen in various phases (as in the moon), from full to crescent to new. I'll buy that. It would be fun to recreate this photo in a modern setting.

There are lots of orreries around. There is one at the History of Science Museum in Oxford and at least one more at the British Museum. There is clearly one at the Whipple Museum in Cambridge. There is an enormous one featured in the BBC made-for-tv movie Einstein and Eddington (its subject matter rather obvious) and they've appeared in a number of other stories. People do love there and can you blame them? They are compelling. Every teacher who has created a walking solar system using pupils and a variety of balls from the store cupboard knows that they are useful tools.

You can tell from the Wright painting that getting down to the level of the orrery is important and I think that "getting inside" may be a theme of modeling the universe. We are of course in the solar system and we can draw the solar system on a piece of paper, but what we really want to do is to bring the scales into a manageable size. But I think actually what the real delight is is actually the reverse: our heads down close to the orrery, we are actually attempting to experience the solar system as if we are solar-system-sized. Instead of being minute in comparison, we are collosal and all-powerful.