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Orrery, c1770 - part 2

TLF ID R6377

This is a mechanical model of part of the solar system, commonly known as an orrery, manufactured by English mathematician and instrument maker Benjamin Martin in about 1770. This bronze model features a cylindrical clockwork mechanism with an orb representing the Sun placed in the centre. Extending from this on an arm is a model of the Earth mounted on a tilt mechanism. Technically speaking, this mechanical model is known as a tellurion because it shows only the movements of the Earth and not of the Moon or the other planets. The orrery stands 38.5 cm high and is 25.5 cm in diameter.

Educational details

Educational value
• The first orrery was built in about 1704 by watchmaker George Graham, who gave a copy to instrument maker John Rowley of London around 1713, with Rowley then being commissioned to make another copy for his patron, Charles Boyle, the Fourth Earl of Orrery - hence the name 'orrery'.
• This particular orrery was built by renowned London instrument maker Benjamin Martin (1704-82). Due to his innovative designs, Martin was considered one of the greatest designers and manufacturers of microscopes of his time and had a significant influence on the development of optical instruments.
• By accurately representing the Earth's spin, presenting the Sun as central and as the source of light, and showing the Earth rotating around the Sun, this orrery would have made it easy for people to understand the role of the Sun in creating day and night on Earth.
• Lines of latitude and longitude are marked on the model of the Earth. Latitude is a measure of the distance of a place north or south from the equator and was easy for sailors to determine through celestial navigation. Longitude describes the location of a place on the Earth's surface either east or west of a north-south line called the prime meridian (usually the one that passes through Greenwich in London). Longitude could not be accurately determined until a special chronometer was invented by English watchmaker John Harrison in 1761. It was one of the most significant inventions of the time and finally allowed sailors to navigate accurately at sea.
• This orrery differs from earlier orreries in that the Earth is on an extended arm, while earlier models fixed the planets on a rotating plate.
• The 18th and 19th centuries were a time of renewed interest in automata, reflecting the idea that mechanical science could unlock the secrets of nature. Apparatus such as this became popular during this period, while typical automata of the 19th century included depictions of flute players, singing birds and even a lawyer arguing in court.
• While orreries were popular educational devices, they are often inaccurate representations and need to be regarded as illustrative rather than realistic models. Most orreries include other planets in the solar system and while they correctly represent the relative speeds of different planets, few can accurately show the relative sizes of the planets and their planetary orbits because the planets' actual scale would require the machine to be extremely large.
Year level

4; 5; 6; 7

Learning area
• Science

Other details

Contributors
• Contributor
• Name: Museum Victoria
• Organization: Museum Victoria
• Description: Content provider
• URL: http://www.museum.vic.gov.au/
• Name: Education Services Australia
• Organization: Education Services Australia
• Description: Data manager
• Person: Benjamin Martin
• Description: Author
• Person: Jon Augier
• Description: Author
• Name: Museum Victoria
• Organization: Museum Victoria
• Publisher
• Name: Education Services Australia Ltd
• Organization: Education Services Australia Ltd
• Description: Publisher
• URL: http://www.esa.edu.au/