Ancient Babylonians living almost 4,000 years ago could have predicted Monday's total solar eclipse.
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In fact the ancient Babylonians were the fathers of modern astronomy. They could track and predict the relative movements of the sun and moon, and even those of the Solar System planets that they recognized, Venus and Mercury.
How exactly could peoples living thousands of years ago who hadn't even discovered iron yet, predict a solar eclipse today?
Absent computer technology, they did it the old-fashioned way: by keeping records over generations, and noticing patterns. And doing math. Cuneiform tablets found in Babylonia and Uruk show they could predict the position of celestial bodies using advanced geometric techniques that westerners had thought were invented in 14th-century Europe.
The ancient Babylonians meticulously mapped the stars over 3,000 years ago, and recorded each and every celestial event, including the motions of the planets they could see – and the eclipses of the sun and moon. They wrote their findings in cuneiform on clay tablets, some of which were found in the city of Ugarit.
Some archaeologists suspect astronomical observations began much earlier, possibly with the first known Mesopotamian civilization in the early Bronze Age: the Sumerians, because some of the star names in the Babylonian list of stars are in Sumerian. Alternatively, some think the original sky-gazers were the Elamites, a mysterious ancient people who destroyed the Sumerian capital and rule in round 1750 B.C.E.
We can be sure that the Babylonians realized cyclicity was involved in cosmic phenomena like eclipses, and began predicting solar and lunar eclipses based on the so-called Saros cycle of 223 synodic months, which is 18 years and 11.3 days and a bit. And that is how they could have, with decent accuracy, predict today's eclipse.
The gods are peeved
Despite noting the periodicity, and therefore the predictability of eclipses, the ancients persisted in associating them with the wrath of their uneven-tempered gods.
Why the gods should be predictable about eclipses and nothing else has never been explained.
So, despite their periodicity, the ancient civilizations also believed that eclipses, particularly of the moon, might portend evil, such as the imminent death of a king. Thus being able to predict the date actually gave the Mesopotamian kings of yore an elegant solution: they could abdicate briefly, handing the reins to some unfortunate who would then, fitly, be killed. Alexander the Great is believed to have sacrificed just a substitute king named for an eclipse to save his own skin, not that it helped him achieve long life.
Another unwitting achievement of the moon-sun juxtaposition in space was to end a war between Medes and Lydians in Turkey on May 28. 585 B.C.E. Both the parties assumed the gods were displeased, even though the eclipse seems to have been predicted by the Greek genius Thales of Miletus, according to the historian Herodotus.
Thales is thought to be the first westerner to predict an eclipse, but neither he nor the Babylonians were thought to understand how eclipses happen.
Earliest records and a mystery
The earliest known Babylonian record of a solar eclipse dates to May 3, 1375 B.C.E. but there could of course be previous ones. The record famously included the sun's disappearance on July 31, 1063 B.C.E. and some 61 eclipses altogether.
There is even a cuneiform tablet recording Halley's Comet passing by the planet in 164 B.C.E.
The Babylonian knowledge would reach the peoples around them. Assyrian observers in Nineveh recorded an eclipse on June 15, 763 B.C.E., almost 2,800 years ago, which became known as the "Assyrian eclipse" (Pur-Sagal). Some scribe of the time wrote a single sentence: "Pur-Sagal of Guzana, revolt in the city of Assur. In the month Simanu an eclipse of the sun took place."
One might think that based on the fear of eclipse and evil portents, the sun's disappearance led the terrified people to revolt against the king of the time, Ashur-Dan the Third, but it seems the unrest was more a function of poverty and plague. By the way, if the jury's out on anything in this regard, it's which eclipse the Assyrian one was: some scholars argue they were referring to the sun's disappearance on June 24, 791 B.C.E.
Fascinatingly, some scholars suggest that the ancient Babylonian stargazers could (and did) predict solar eclipses that weren't even visible from Babylon.
Either way, their knowledge would continue on with the peoples around them and following them, including the ancient Egyptians, Greeks and Jews, and later, Islamic astronomers as well.
Meanwhile, at the bottom of the sea
The ancient Greeks, or at least one of them, might not have needed the Babylonians' charts and records any more to predict eclipses. In the year 1907 sponge divers off the Greek coast found a congealed lump of corroded metal, that turned out to be a computer made of bronze dating back more than 2,000 years.
Dubbed the Antikythera Mechanism, the device consists of multi-layered meshing bronze gears (some think, up to 50 of them!) and was made some time from 220 B.C.E. to 60 B.C.E.
The degree of precision metalwork – the largest gear is only 5.5 inches in diameter but has 224 teeth – and of miniaturization astounded the modern world. Its calculator could add, multiply, divide and subtract. It could align the number of lunar months with years and show the positions of the sun and the moon, corrected for orbital anomalies, along the zodiac.
Naturally, it could predict eclipses. Yet even then, with the absolute ability to remove the mystery from solar motions, the ancients persisted in believing the gods were involved, and that they were signaling something. Some people still do.