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Did the ancients know about the precession of the equinoxes?

The "precession of the equinoxes" refers to the slow shift in the Earth's axis of rotation, which produces a gradual change in the positions of the constellations. The axis of rotation of the Earth is wobbling, like a spinning top. A complete revolution of the axis takes approximately 26,000 years. This is known to astrologers as the Platonic Great Year.

I was listening today to the BBC programme Start The Week, in which the astrophysicist Jocelyn Bell Burnell was talking about the current Internet flap concerning a Mayan prophecy of the end of the world on 21 December next year. She did a good job of showing this up as an egregious example of pseudoscience, which of course it is. She is due to give the Faraday Lecture on the subject at the Royal Society.

But she also mentioned that the Mayans, along with a number of other ancient peoples, including the Babylonians and Sumerians, all knew about this 26,000 year cycle. But did they?

According to Gary D. Thompson, whose scholarly website on ancient astronomy is the place to go for information about such questions, the idea of ancient Mesopotamian knowledge of the cycle is a myth. In his extensive discussion, The Myth of Babylonian Knowledge of Precession, he writes:

"The hypothesis that the Babylonians knew precession can be confidently dismissed. The hypothesis has been adequately refuted by the studies of the astronomer and Assyriologist Franz Kugler, the mathematician Otto Neugebauer, and the Assyriologist Abraham Sachs."

Wikipedia is equally dismissive of claims for knowledge of precession on the part of the Babylonians and ancient Egyptians, and indeed the Mayans. "There has been speculation that the Mesoamerican Long Count calendar is somehow calibrated against the precession, but this view is not held by professional scholars of Mayan civilization."

Dr Bell is a most eminent scientist, who discovered the first radio pulsar as a postgraduate student (although, controversially, she was not listed as a co-recipient for the subsequent award of a Nobel Prize). Perhaps she has information about the Mayans and others that I don't know of, but I thjnk that in this case she has not been sufficiently sceptical.

I'm interested in the question because I was myself taken in at one time by pseudo-scholarship about ancient knowledge of the precession. I was drawing on a strange book, Hamlet's Mill, by de Santillana and von Dechend. I included their ideas in my own book The Assassins of Alamut. Thanks largely to Thompson, I now know that those authors' claims are invalid, and I deleted the discussion from my book.


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