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That man Eddy again … and was Ptolemy a fraud?

5 November 2012

I've been flicking through the archive of the late Janek Pietron and have come across some interesting papers that he stored for future reference. In a review of EC Krupps, In Search of Ancient Astronomies, published in the journal Archaeoastronomy (see http://terpconnect.umd.edu/~tlaloc/archastro/journal.html#vol1 or www.shpltd.co.uk/aa.html) in 1978, Eddy is mentioned in an overview of Native American archaeoastronomy north of Mexico. The reviewer, Ronald Hicks of Ball State University, generally finds his work agreeable. However, the reviewer of Robert Newton's book The Crime of Claudius Ptolemy, John Hopkins University Press:1977 is not so kind. JP Harrington of the University of Maryland says Newton's attempt to prove Ptolemy fabricated the entire corpus of observations he claims to have made himself comes across as disagreeable. Newtons says he even falsified data he attributes to earlier astronomers in order to force agreement with his own theories. It is Newton's tone that comes in for criticism, an overriding sense of righteous indignation, and various references to lies, fraud, failure and incompetence. The reviewer makes the point that Newton is not himself an astronomer and is prone to make his own howlers as in for instance saying naked eye stars in our galaxy are receding due to the expansion of the universe. However, in spite of that, the reviewer is impressed by Newton's book and the amount of evidence he marshals in support of his thesis. What has got the goat of Newton, setting him on a high horse, is that the observations in the Almagest do not compare with modern retro-calculations of what Ptolemy should have seen. For example, Ptolemy says that the autumn equinox occurred at 14 hours on 25th Sept 132AD when it actually occurred, according to Newton, at 9.9 hours on the 24th Sept 132AD. It was almost a day off. It seems that Ptolemy may have made an extrapolation from Hipparchus (147BC) rounded to the nearest hour, and Newton claims the situation is self evident with other observations in the Almagest. In other words, the reviewer suggests, Ptolemy used tables rather than actual observations. This was the position of Delandre in his History of Medieval Astronomy and Mercier, in his History of Ancient Mathematical Astronomy opines that Neugebauer accepted the Ptolemaic data without questioning any of it. Long before Newton wrote his book people had thought there was something wrong with the Almagest as far as solar data was concerned, and his star catalogues. It has been claimed he also borrowed this from Hipparchus but corrected the positions of the stars for precession in the interval. Ptolemy, it seems, is guilty of updating the work of Hipparchus.

Ptolemy's work has been used to make the bold claim there is an error in classical chronology of some kind, shifting the crime elsewhere, so to speak. Dionysius Exigiius also used tables in order to arrive at the Birth of Christ and the Anno Domini dating system. Why has one been held up for scrutiny and not the other?

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