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| Photo: Natasha Frost |
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| Thales, in an 18th-century engraving by F. Ramberg. Photo: Wellcome Images/Public Domain |
The year was 585 B.C., and
the Lydians and the Medes had been warring for half a decade in what we
now know as Turkey. No clear victory was in sight. Sometimes the
Lydians were on top, on other occasions, the Medes seemed to have
matters in hand. Once they even fought a battle in the dead of night.
But, in the sixth year of their war, as they brandished their arms on
the battlefield, something amazing happened. The skies began to darken.
The moon passed in front of the sun. The armies, astonished, lay down
their weapons—and called a truce.
This story comes to us via Herodotus, the Greek historian, who lived about a century after the fight. What’s perhaps more remarkable about this story is the line that follows it: “Thales of Miletus had foretold this loss of daylight to the Ionians, fixing it within the year in which the change did indeed happen.”
This story comes to us via Herodotus, the Greek historian, who lived about a century after the fight. What’s perhaps more remarkable about this story is the line that follows it: “Thales of Miletus had foretold this loss of daylight to the Ionians, fixing it within the year in which the change did indeed happen.”
The ancient philosopher Thales of Miletus
had no access to the scientific knowledge or equipment to successfully
predict a solar eclipse. As a result, this story has puzzled and divided
classicists and scientists for centuries. Was it preternaturally
sophisticated astronomy, a myth, or just a happy accident?
Researchers believe that the eclipse Herodotus describes over the battlefield is the one that took place
on May 28, 585 B.C. Its path ran from Nicaragua, over the Atlantic,
then across France and Italy—and, finally, Turkey. Thales’s home, the
ancient city of Miletus, on the Mediterranean coast, is just outside the
path of totality. He would have seen an impressive partial eclipse from
there. There are other eclipses around that time that are possible candidates, but none that would have plunged the Lydians and Medes into abrupt darkness in the way that Herodotus describes.
It is particularly strange, if the historian is to be taken at his word, that Thales predicted the year of the eclipse, rather than the exact date. In fact, wrote mathematician Dmitri Pachenko in the Journal for the History of Astronomy, “if one can predict an eclipse at all, one can predict it to the day.” Astronomy is an extremely precise science. If you know a major celestial event is coming, and where it will be visible, you’ll most likely have some precision about when it will take place. Thales, however, was at a marked disadvantage for making astronomical predictions. He didn’t know that the Earth is spherical—and seems to have thought of it as a flat disc, resting on water.
It is particularly strange, if the historian is to be taken at his word, that Thales predicted the year of the eclipse, rather than the exact date. In fact, wrote mathematician Dmitri Pachenko in the Journal for the History of Astronomy, “if one can predict an eclipse at all, one can predict it to the day.” Astronomy is an extremely precise science. If you know a major celestial event is coming, and where it will be visible, you’ll most likely have some precision about when it will take place. Thales, however, was at a marked disadvantage for making astronomical predictions. He didn’t know that the Earth is spherical—and seems to have thought of it as a flat disc, resting on water.
So how did he do it? A common suggestion is that Thales had coopted the
expertise of the ancient Babylonians. Their astronomers, based near
modern Baghdad, kept careful records of the sky, including how Venus,
Mercury, the Sun, and the Moon moved in the heavens. In 1063 B.C., their
records document
a total eclipse “that turned day into night.” These records led them to
discover what we now call the Saros cycle, which governs the recurrence
of eclipses. After three 223-month Saros series, eclipses do return to
the same geographic region, but they are a complicated way to make an
eclipse prediction. At any given moment, there are approximately 40
Saros cycles taking place at once, carrying on for over 1,000 years. As
old sets of cycles end, new ones begin. Understanding them enough to be
predictive, at the very least, requires the knowledge that the Earth is
round and accurate, detailed observations—not to mention accounting for
those missed eclipses that take place on cloudy days.
Thales did feats of mathematics that might have looked like magic to his
contemporaries, including calculating the height of the pyramids from
the length of their shadows. He was a legend. It’s possible, then, that
his famous prediction was, too. People so readily accepted his
claims—that magnets have souls because they make things move, that
earthquakes happen because the Earth is floating on water, that all
things are full of gods—that it wasn’t much of a stretch to believe he
could have predicted mysterious happenings in the sky.
Natasha Frost ends his article with the following: Thales did feats of mathematics that might have looked like magic to his
contemporaries, including calculating the height of the pyramids from
the length of their shadows. He was a legend. It’s possible, then, that
his famous prediction was, too. People so readily accepted his
claims—that magnets have souls because they make things move, that
earthquakes happen because the Earth is floating on water, that all
things are full of gods—that it wasn’t much of a stretch to believe he
could have predicted mysterious happenings in the sky.
Recommended Reading
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| The so-called Venus Tablet of Ammisaduqa, from ancient Mesopotamia, shows detailed astrological forecasts. Photo: Fae/CC BY 3.0 |
How to Predict an Eclipse Without a Computer by Natasha Frost.
"Some methods are easier than others."
Source: Atlas Obscura
