An orrery is a mechanical model of the solar system.
Although orreries date from the time of the Greeks, British clock makers George Graham and Thomas Tompion built the first modern orrery in 1704. The Fourth Earl of Orrery commissioned a copy of the original instrument for his own use, thereby lending his name to the device.
An orrery is essentially a clock. When set in motion, the orrery shows the relative periods of the sun, the earth and its moon, and the planets in relation to each other. They are not usually built to scale, and may not contain all the planets and their satellites. A grand orrery contains all the planets known at the time of its construction. One method of dating a grand orrery is to note the planets and moons the instrument contains.
The devices were popular in the eighteenth and nineteenth centuries. King George II owned an orrery (1750 copy of his orrery at left), as did Thomas Jefferson (Jefferson's orrery here). John Winthrop taught astronomy at Harvard using an orrery (picture at right) that instrument maker Benjamin Martin built in London in 1767.
An orrery figures in my Regency comedy romance, Gifts Gone Astray. Since the latest planet discovered by 1817, the time of the story, was Uranus (then called George's Star after George III), my fictional grand orrery has Uranus as the last planet. In the upper left of the cover of Gifts Gone Astray (click on the image to enlarge it), you can see part of the orrery.
Gifts Gone Astray, blurb and excerpt on my "My Books" page, available from The Wild Rose Press, Amazon, Barnes and Noble, All Romance Ebooks and other places where ebooks are sold. See sidebar.
Thank you all,
Pictures from Wikipedia.