ROYAL ASTRONOMICAL SOCIETY / SCIENCE PHOTO LIBRARY ROYAL ASTRONOMICAL SOCIETY / SCIENCE PHOTO LIBRARY
Ferguson's epicyclic diagram. This diagram was published in 1756 by the Scottish astronomer and instrument maker James Ferguson (1710-1776), in his book 'Astronomy explained upon Sir Isaac Newton's Principles'. It shows the Earth at centre, with the Sun tracing a circular orbit. The orbits of Mercury and Venus in this geocentric system are shown by a series of complex epicycles.
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