The Orrery
An Easytorecall Article
Detail from the painting "The Orrery" by Joeseph Wright of Derby 1734-1797.
You can view this and more of Joseph Wright's work at the Derby Museum and Art Gallery, in The Strand, Derby.
Page Contents:
What is an Orrery?
The Scale Problem
A Brief History
Online Orrery Simulations
Make your own Orrery Simulation
Make your own Hands on Orrery
Where can I visit to see some Orreries?
Where can I buy an orrery?
Orrery Simulation
Instructions for making your own Orrery Simulation
An orrery is, quite simply, a mechanical model of the solar system. To see some superb examples visit www.orrerymaker.com which is the website of Brian Greig who specialisies in creating facsimilies of historical scientific instruments. Quite often an orrery is used in teaching children the basics of how the solar system works and many schools encourage children to make their own.
The major problem with any solar system model is one of scale. For example, suppose the sun were modelled as, say the size of a golf ball (roughly 4.3cm diameter), then Jupiter, the largest planet in the solar system would, on that scale, be a bit less than half a centimeter across, the earth would be slightly less than half a millimeter and the moon would have to be a one tenth of a millimeter in diameter.
Jupiter Earth Sun
But the biggest problem with any solar system model is the actual distance of the planets from the sun.
Suppose, again, we made the sun the size of a golf ball. Then if we decided we wanted the distances to be modelled to scale, the earth would have to be over 4.5 meters from the sun and Pluto, the furthest planet from the sun, would have to be placed over 180 meters away!
For this reason some people think that orreries can be misleading and not very useful - I disagree. If we bear in mind the scale problems, then orreries can not only be extremely useful as teaching tools, but very beautiful in their own right.
A Brief History
Nicolaus Copernicus (1473-1543) was born in Poland. A keen astronomer, Copernicus is most remembered today for his book De Revolutionibus published in 1541 in which he put forward the theory that the earth, along with the other planets in the solar system, orbits the sun and not the other way around as was commonly believed at the time.
The position of the Church, which was extremely powerful in Europe then, was that the earth was fixed at the centre of the universe with the sun, planets and stars revolving around it. Part and parcel of this belief was that the heavens were perfect.
Copernicus' sun centred theory was championed by Kepler (1576-1630), a brilliant mathematician who went on to develop his three laws of planetary motion on the assumption that the earth, along with the other planets, orbited the sun.
Also famous in this connection is Gallileo (1563-1642), who spent the last 1
0 years or so of his life under house arrest for refusing to acknowledge that the sun centred model was only a theory.
The telescope in Gallileo's day was a relatively new invention. So we shouldn't be too surprised to learn that it was Gallileo who was the first to turn his telescope to the sky. He was therefore the first to observe Jupiter's four major moons, now known as the Gallilean moons, orbiting Jupiter. This was clearly in oposition to the beliefs of the day where everything was supposed to orbit the Earth. He also saw craters on the moon - to him this was further proof that the heavens were not perfect.
Please click here to see an animated gif showing the four moons orbiting Jupiter.
However, by the begining of the 1700s, the sun centred system was generally accepted and it was at this time that the first model of the solar system was made.
George Graham (1674-1751) was a renowned clockmaker - you can see his tomb in Westminster Abbey. He made the first model of the solar system.
A copy of this model was made by the instrument maker John Rowley who had been commssioned by Charles Boyle, Earl of Orrery. Thus a model of the solar system became known as an orrery. The model which you can see on the right was made around 1712 and is now held at the Science Museum.
The Electric Orrey from the University of St Andrews is simple to use and shows the inner and outer solar system. The inner and outer solar systems are shown separately for ease of viewing and show the relative positions of the planets from todays date onwards. You can also speed it up if you like!
Solar System Simulator is worth having a look at. It can seem a bit slow but you can always leave it running and check on the progress of the planets now and again!
A very good virtual solar system can be found at www.nationalgeographic.com. In order to view this properly in 3D you need to download the Viscape plug in. (If you can't get the link on the page to work you should be able to find Supercape Viscape Universal at Tucows). Also the plug in won't work with Firefox, (urrrrgh) but it will work with Internet Explorer. However, it is worth it! The simulation is interactive plus each view is accompanied by explanatory notes.
Take a virtual fly by tour of the solar system with Planet 10 from www.planet-science.com You can zoom in or out and view the planets from above or from the side. Very good indeed. (You may need to install the latest Shockwave player.) The software is written by Wired Science which is part of Planet Science which in turn is owned and run by the National Endowment for Science Technology and the Arts. This particular simulation uses Shockwave.
Make your own Orrery Simulation
First go to Easytorecall's Orrery Simulation to see what it will look like.
If you know what you are doing, you can find the images here.
If you don't quite know what you are doing, we have prepared a set of instructions to walk you through it.
Instructions to make your own hands on Orrery
Don Rogerson, from Alaska, has made an orrery for his children out of Lego! No detailed instructions, but plenty of pictures (more here) that might give the more adventurous some ideas.
Eli Whitney Museum gives diagramatice instructions for making an orrery using wood, a few washers and of course models for the sun and the inner planets. This is a great project to do with your children.
Build a Solar System is from San Francisco's Exploratium (great site by the way). It allows you to calculate at the click of a button all the sizes you need to build a true scale model of the solar system plus a couple of ideas on how you could put this into action. Excellent for children to get a feel of just how big the solar system really is. The National Optical Astronomy Observatories from the US 
has more detailed instructions for this kind model in The Thousand Year Model or, The Earth as a Peppercorn.
For younger children, Enchanted Learning has templates you can use to make a solar system mobile. There is something a little more elaborate along the same lines from Southern Indiana Education Center.
Where can I see some orreries?
The Science Museum in London has a fine collection of orreries on display, some of which you can see some online.
Greenwich Observatory has a couple of orreries you can see. If you haven't been to Greenwich before, I would definitely recommend the Planetarium. Only a couple of pounds to get in - excellent value and much better that the London Planetarium in my view!
The Armagh Observatory is an astronomical research institute that not only owns several orreries but also has an interactive project called The Human Orrery which allows people to play the part of the moving planets. The Observatory also hosts the Armagh Planetarium and the Armagh AstroPark. Click here for a list of historical instruments owned by the Obervatory. You might want to use your browser's find on page feature to find details of all of them. Please note that the observatory itself is not generally open to the public, but occasional public tours are organised on request.
Scottish visitors might be interested to know that the University of Aberdeen Natural Philosophy Collection houses a fine collection of historical scientific instruments. However, access to the public is limited at the moment and only a small part of the collection is open for public viewing.
The Whipple Museum is part of Cambridge University and is open to the public on weekday afternoons. You can find some fascinating historical scientific instruments including some magnificent orreries in the Upper Gallery.
The Museum of the History of Science is housed in the Old Ashmolean Building in Broad Street Oxford, and has several orreries to see. They are open in the afternoons every day of the week. Free Admission.
Techniquest in Cardiff Bay is a science discovery centre with many interactive exhibits including an orrery.
The Exploratory in Bristol, also a science discovery coentre, has a large solar system model called the Solar System Way which includes detailed models of the planets and their moons.
Ferguson's Orrery
These orreries are a working representation of the Earth and Moon system, and include all of the planets 
known at that time.
James Ferguson was born in Keith, Scotland in 1710, he was a self-taught scientist and astronomer. He was elected a Fellow of the Royal Society in 1763. He became a friend of Dr. Benjamin Franklin when he visited Britain to lobby Parliament about tax grievances. Ferguson designed a variant of Dr. Franklin’s famous three-wheeled clock for which he received acclaim.
The brass plaques with engraved zodiac signs are copies of the original drawings by James Ferguson.
All moving parts; planets, decorative balustrades, ornamental figures (large model), engraved dials and zodiac plaques are manufactured from solid brass. The exception is the solid gem stone blue earth globe ball; (jewel globe: lapis lazuli for oceans, a variety of other semi-precious stones are used for countries, such as: turquoise, or jade, or tigers eye). The base is 
manufactured from stained American white oak (Quercus alba), a wood that is used extensively in cabinet making.
Both models run electrically. Small model achieves full rotation in ½ hour. The large model in 5 minutes. The large model can also be disconnected from the motor and hand turned to see planets, earth and moon rotation at a higher speed for demonstration purposes. Both models may have the planets moved by hand to specific positions.
Currently the only places you can buy these orreries from (are far as we can find out) are:
http://www.theprezzyshop.co.uk
http://www.devonclocks.com
http://www.widescreen-centre.co.uk
http://www.green-witch.com
http://curiousminds.co.uk
Solar System Planetarium Model Making Kit
Build your own glow in the dark solar system planetarium model of 30cm span. Assemble, paint and highlight it with glow effects. Watch it glow in the dark as in real Space. It's an inspiring science craft. Contains 1 set of 3-dimensional Solar System planetarium model, 1 brush, 1 stripe of paint pots and glow paint, 1 set stand and rotating arms, 9 steel bars, 1 sand paper, 1 Saturn ring template and detailed instructions with bonus wall chart of Solar System.
http://curiousminds.co.uk £8.50 +P&P £2.00 = £10.50
3D Solar System Mobile Making Kit
An inspirational science craft for the whole family. Build your very own designed solar system mobile which revolves and glows in the dark. Mobile is 75cm x 75xm when built. It's amazing! Contains full set of snap to build, no glue needed solar system plastic planets, full set of easy-to-assemble hanging structure and hanging Lines, 2 paint strips, glow paint, paint brush, bonus wall chart with fun facts of solar system (size:42cm x 60cm). painting and assembling instruction sheet.
http://curiousminds.co.uk £14.99 +P&P £3.00 = £17.99
Helios Planetarium/Orrery with Northern Sky Dome
This stunning fully electric model shows the planets orbiting the Sun at their correct relative speeds with a removable Star dome.
The planets from Mercury to Saturn orbit the Sun at their correct relative speeds and the Moon orbits the Earth in synchrony.
Subjects to study:
* The Planets in their Orbits (length of a year, inferior and superior planets and more)
* The Moon and its Phases
* Eclipse Basics
* The Time - solar, sidereal and G.M.T.
The orrery can have all its planets displayed or just one or two. The planets can be positioned for any year or month up to 2020. The speed and direction of rotation can be changed!
Show how the stars and constellations have fixed locations in space whilst the planets orbit the Sun.
Additional subjects to study with the star dome:
* The Ecliptic and the Zodiacal constellations
* How the planets appear to move against the night sky
* Use of the Helios outside at night - where should the stars appear in the sky?
The domes show the stars around the ecliptic plus those over either the Northern or Southern hemispheres. Looking through the dome you see the stars visible at night!
To deliver the levels of understanding, accuracy is at the core of the Helios with planets revolving at their correct relative speeds and the star dome showing all major stars and constellations.
www.cochranes.co.uk
Article: Copyright 2000-2011 easytorecall.com
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