Astrologer Suidas, Astronomer Halley, and other stargazers…

Picture P60Ho and Hi, the Drunk Astronomers

“Here lie the bodies of Ho and Hi,

Whose fate, though sad, was visible;

Being slain because they could not spy

Th’ eclipse which was invisible…”

The story of Ho and Hi may be a real or fiction since its author is unknown. However, it refers to the Solar Eclipse of 2136 BC or 2159 BC: the royal astronomers Ho and Hi were drunk and failed to predict the eclipse, so that the people did not prepare to drive away the dragon which caused the eclipse. The astronomers lost their heads… There are different ways to become famous.

Maybe after a couple of centuries your name will be mentioned much more often than during your lifetime. How many people had heard about a man named Suidas in ancient Byzantium? But now anyone can read in Wikipedia that… Historically speaking, the word Saros derives from the Babylonian term “sar” which is an interval of 3600 years. But it was never used as an eclipse period until English astronomer Edmund Halley adopted it in 1691. According to R. H. van Gent, Halley “…extracted it from the lexicon of the 11th-century Byzantine scholar Suidas who in turn linked it to a not–quite–clear 223–month Babylonian eclipse period mentioned by Pliny the Elder…”

Historically speaking, solar eclipses have been a great subject to ponder at all times. Ancient Astrologers believed and modern Astronomers confirm that when two eclipses are separated by a period of one Saros (each 18 years plus 9–11 days), they share a very similar geometry: the two eclipses occur at the same node with the Moon at nearly the same distance from Earth and at the same time of year… That is why modern Astronomers think that the Saros is useful for organizing eclipses into families or series while Astrologers prefer considering the Saros as an iterative cycle. This explains the difference in the numbering of eclipses in Astronomy and Astrology.

In Astronomy each series typically lasts 12 to 13 centuries and contains 70 and more eclipses, the summary of Saros series you can find, for example, here https://eclipse.gsfc.nasa.gov/SEsaros/SEsaros0-180.html as we can see they use a simple sequential numbering.

In Astrology one Saros cycle is based on 18–year period and includes about 40 Solar Eclipses numbered 1N … 19S and since the geometry of one Saros series is the same when an old series comes to the end, a new one just replaces it in the cycle.

Interestingly that while Astrologers think over how the eclipses can affect people, Astronomers just love to give them very poetic nicknames

02–Oct–480 BC Xerxes’ Eclipse “…while he was offering sacrifice to know if he should march out against the Persian, the sun was suddenly darkened in mid sky” – Herodotus, History, IX, 10

05–Aug–1766 Captain Cook’s Eclipse

17–Apr–1912 The “Titanic” Eclipse

and of course 21–Aug–2017 upcoming The Great Total Eclipse through USA

In case of interest you may find the list of the Great Eclipses in NASA https://eclipse.gsfc.nasa.gov/SEhistory/SEhistory.html

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