Slide 1 of 21
Eclipse of the sun
Although they were once feared as an evil omen, solar eclipses have helped to shape human history — and a few solar eclipses, in particular, have helped to guide philosophers and scientists to a better understanding of the heavens and our true place in the universe.
Here is a countdown of 10 solar eclipses that changed science.
Ugarit Eclipse – Syria 1223 B.C.Slide 2 of 21
Ugarit Eclipse – Syria 1223 B.C.
Observations of solar eclipses made by astronomers in Mesopotamia more than 3,000 years ago are among the very earliest astronomical records. In fact, along with other observations gathered by the Babylonians, Assyrians and others in the ancient Middle East, they are the oldest scientific records of any sort whatsoever.
At the time, astrologers believed that solar eclipses, comets and other celestial events could affect human events here on Earth, especially the fates of kings and empires. But their observations for the sake of astrology also mark the earliest known steps taken by humankind on the road to modern science.
The earliest known solar eclipse observation recorded in the Middle East is the Ugarit Eclipse, which was inscribed in cuneiform script on a clay tablet discovered in the Syrian city of Ugarit in the 1940s.
According to a study published in the journal Nature in 1989, the text on the tablet describes a total solar eclipse that occurred on March 5 in 1223 B.C., when Ugarit was part of the Assyrian Empire.
The observation notes that the stars and the planet Mars were visible in the darkness caused by the eclipse: "On the day of the new moon, in the month of Hiyar, the Sun was put to shame, and went down in the daytime, with Mars in attendance."Slide 3 of 21
Anyang Eclipse – China 1302 B.C.Slide 4 of 21
Anyang Eclipse – China 1302 B.C.
For many years, the Ugarit tablet was thought to describe an eclipse that occurred in 1375 B.C., which would have made it the oldest known eclipse observation.
But since the Ugarit tablet is now thought to refer to 1223 B.C., an observation of the sun made in the city of Anyang in central China in 1302 B.C. is now thought to be the earliest surviving record of a solar eclipse.
It was written in an ancient Chinese script that was scratched onto a flat fragment of tortoise shell, one of thousands of archaeological relics from the period known as "oracle bones," from the later belief that they were magical and could help to foretell the future.
The observation notes that "three flames ate the sun, and big stars were seen," which researchers have interpreted as a description of a total eclipse with three bright streamers of gas in the solar corona, which only becomes visible during an eclipse.
In 1989, astronomers at NASA's Jet Propulsion Laboratory (JPL) used the Anyang observations and lunar eclipse observations from the same period to determine the exact date of the ancient eclipse as June 5, 1302 B.C.
The JPL researchers then used that information in a computer model to show that the Earth's rotation has slowed slightly, by 0.0047 seconds, since 1302 B.C., due to tidal friction — the drag on the spinning Earth caused by the gravitational tug of the moon on the outermost bulge of our planet.Slide 5 of 21
Thales’ Eclipse – Anatolia, 585 B.C.Slide 6 of 21
Thales’ Eclipse – Anatolia, 585 B.C.
According to the ancient Greek historian Herodotus, the philosopher, astronomer and mathematician Thales of Miletus predicted a solar eclipse that occurred over Asia Minor in the 6th century B.C.
While there is considerable doubt about the accuracy of the claim, modern astronomers calculate that, if it happened as Herodotus said, then it was probably an annular solar eclipse that was visible over the Middle East on May 28, 585 B.C.
Herodotus also reported that the eclipse took place during a battle beside the Halys River in Anatolia between the Medes and the Lydians, a battle since known to history as the "Battle of the Eclipse."
The sci-fi writer Isaac Asimov noted that this battle was therefore the earliest event in history for which there is an accurate date; while historians of science note that it would also have been the first scientific prediction of any sort of phenomena — at least the first one that actually came true.
Supporters of Thales argue that he could have predicted a likely date when a solar eclipse might occur by using the Saros Cycle, a roughly 18-year cycle in which the pattern of solar and lunar eclipses repeats almost exactly.
The earliest evidence for the use of the Saros Cycle is from Babylonia in around 500 B.C., but it may have been in use much earlier. And it's even possible that Thales may have travelled to Babylonia to learn it.Slide 7 of 21
Anaxagoras’ Eclipse – Greece, 478 B.C.Slide 8 of 21