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August 15, 2020, 5:22 pm UTC    
January 13, 2020 05:46AM
Ossendrijver and Winkler have published a paper which analyses text found on Ostracon written in Demotic script and dated to circa 50 - 100 CE. In it, they find evidence of the Egyptian astronomers leveraging a Babylonian method to calculate the position of Mercury. A summary of their paper can be found here:


One of the things that fascinated me was that this demotic script contains the symbols for degrees:

Ossendrijver and Winkler, p 392
Degrees are called ** (1.5); ** (2.4); ** (2.14), swsw (Winkler 2009: 368 n. 28). The reading of one star is s( j)w (Erichsen 1954: 413); evidence that two stars are to be read as swsw is provided by some of the astrological papyri from the Tebtunis Temple Library, which contain phonetic writings of the word, e.g. P.Carlsb. 71 (unpubl.): swsw “You always calculate from the twentieth degree of Libra .....” The same manuscript also contains a similar sentence with the writing of the same word, which dem- onstrates that we are dealing with the identical term in all instances. Another instance derives from a transcribed passage in the astrological text preserved on P.Carlsb. 66 (Chauveau 1994: 104), but note that the author translates swsw erroneously as “day” instead of “degree.”
The term is not found in any earlier stage of the Egyptian language and does not appear explicitly in Coptic.

I recalled from my analyses of the Westcar Papyrus that Lull and Belmonte documented an asterism of the two stars. In Table 6.1, Belmonte proposes that the “Pair of Stars” which he has transliterated as “sb3wy” are identified as Castor and Pollux. Lull accepts Belmote’s hypothesis. Investigating further, I wondered whether there could be any relationship between this asterism of a pair of stars and the two stars from the much later Demotic script.

According to Edberg:
the Galactic Latitude of Castor is +22.4792 degrees,
the Galactic Latitude of Pollux is +23.4063 degrees.

According to SkySafari 6 Plus for iOS:
the Galactic Latitude of Castor is +22 degrees 28 minutes 45 seconds
the Galactic Latitude of Pollux is +23 degrees 24 minutes 23 seconds

These both turn out to be the same when calculated out to decimal degrees. The difference in galactic latitude from 1 degree calculates a little under 4 minutes or in decimal degrees they are 0.92722 degrees apart in galactic latitude which is quite close to one degree apart, allowing for observation error. Galactic Latitude can be calculated from ground-based observations but is a spherical co-ordinate system centred on the sun:


Could this be a case of winning a galactic lottery or could the Egyptians have known about the degree further back in time?

[1] Mathieu Ossendrijver, Andreas Winkler, 2018, Chaldeans on the Nile: Two Egyptian Astronomical Procedure Texts with Babylonian Systems A1 and A2 for Mercury, in: C. J. Crisostomo, E. A. Escobar, T. Tanaka, N. Veldhuis (eds.), The Scaffolding of Our Thoughts: Essays on Assyriology and the History of Science in Honor of Francesca Rochberg, Leiden: Brill, 382–419.
[2] Lull and Belmonte, The Constellations of Ancient Egypt, accessed from [www.iac.es]
[3] Stephen J Edberg, Jet Propulsion Laboratory, California Institute of Technology, Studies of a Population of Stars: Mapping the Positions of Stars, accessed from [pumas.nasa.gov]
[4] SkySafari Plus 6 for iOS - Object information for Castor and Pollux
Subject Author Posted

Evidence of Egyptian use of degrees in astronomy

engbren January 13, 2020 05:46AM

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