When you visit our ‘Domes of Discovery’ gallery, don’t forget to look up!
Mounted next to the massive Congo Schmidt telescope, you’ll find an intriguing celestial mechanism…
What is an orrery?
Simply put, an orrery is a moving model of our solar system. Ours shows the orbits of the major planets around the Sun, as well as showing the Moon in orbit around the Earth.
Our orrery has a clockwork mechanism with 52 brass gears, so that the planets orbit around the Sun at roughly the right speeds in relation to each other. You’ll notice how the inner planets move a lot faster than the outer planets!
The sizes of the planets and their orbits are not to scale because otherwise the Sun would have to be a lot bigger (about half the diameter of Dome F!) since the Sun’s diameter is over 100 times the diameter of the Earth. Also, the real planets do not move in perfectly circular orbits like the ones in our orrery; in fact, they all move in slightly different oval (‘elliptical’) orbits, which are very difficult to represent mechanically.
Why is it called an orrery?
Working models of the Solar System have been around since antiquity. The the first modern orrery was built in 1704 by clockmakers George Graham and Thomas Tompion. The orrery’s key feature is that it is Sun-centred (‘heliocentric’). In the late 17th Century, this was a model of the Solar System scientists were only just beginning to accept. The design for Graham and Tompion’s model was given to John Rowley. He made a copy in 1713 for his patron Charles Boyle, 4th Earl of Orrery. This is where the name comes from.
See it in action!
Check out this short video of our orrery in motion. You’ll see how it shows planets orbiting the Sun, the Moon orbiting the Earth, and the Earth spinning on its axis.
You can find our orrery in the ‘Domes of Discovery’ gallery located in Dome F.
More images
