THE Greek astronomer Ptolemy, who declared the Earth was the centre of the universe, was not only wrong, it seems he fudged his data too.
That鈥檚 the conclusion of physicist Dennis Duke from Florida State University in Tallahassee, who examined the calculations in the Almagest, a book written by Ptolemy sometime in the second century AD. Duke has reason to be suspicious about Ptolemy: he has already proved that Ptolemy plagiarised extensively from earlier observations made by Hipparchus for his own catalogue of stars.
This time, Duke studied how Ptolemy had worked out the orbits of Mars, Jupiter and Saturn 鈥� the only outer planets known to the Greeks. In Ptolemy鈥檚 model, each planet traces small circles, called epicycles, while following a larger circular orbit around the Earth. When Duke calculated the orbits based on Ptolemy鈥檚 data, they did not match the orbits that Ptolemy himself came up with (Archive for History of Exact Sciences, DOI: 10.1007/s00407-004-0086-5).
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This was hundreds of years before astronomers realised that planets follow elliptical orbits. 鈥淭he answers he arrived at were known to him before he started doing the calculation,鈥� Duke surmises.
He likens the situation to students taking a laboratory class in physics. 鈥淵ou ask them to measure the acceleration due to gravity and sure enough, they come up with 9.8 metres per second per second, but when you go through their lab notes carefully, there鈥檚 no way they could have got that.鈥�