How Scientists Identified the Oldest Known Solar Eclipse … Using the Bible

The Old Testament certainly features its share of miracles, from burning bushes to humans transforming into pillars of salt. But among the Bible’s clearly mythological moments are some that aren’t as clear cut. Consider the striking verses from Joshua 10:12, when the Hebrew leader Joshua brings the Israelites into battle in Canaan: “And he said in the sight of Israel, ‘O sun, stand still at Gibeon, And O moon in the valley of Aijalon.’ So the sun stood still, and the moon stopped, Until the nation avenged themselves of their enemies.”

For physicist Sir Colin Humphreys and astrophysicist Graeme Waddington, this passage suggested something more than fantasy or hyperbole. “If these words are describing a real observation,” they speculate in a new paper, published in Astrophysics and Geosciences, “then a major astronomical event was being reported.” And if a solar eclipse did indeed take place on October 30, 1207 BC—as they conclude in their paper—that would have important repercussions for the fields of astronomy, Egyptology and Biblical history.

But how do two physicists go about testing an event that’s only obliquely referred to in an ancient text? Solving the multidisciplinary mystery required a foray into ancient Hebrew, a rethinking of Egypt’s royal history, and some complex calculations about the Earth’s rotation.

The investigation began with the translation of the Hebrew word “dôm.” In English versions of the Bible, it’s usually translated as “stopped,” as in the sun “stopped moving.” When discussing the word with Alan Millard, a professor of Hebrew and ancient Semitic languages, Humphreys pondered whether it could actually mean the sun “stopped shining”—which might suggest an eclipse.

In fact, another linguist named Robert Wilson had come to the same conclusion nearly 100 years earlier. And while previous scientists had attempted to find solar eclipses for that period and failed, they’d never thought to look for an annular eclipse, which occurs when the moon only partially covers the sun, leaving a ring of light visible at the edges. “That convinced me that ‘eclipse’ was the right translation,” Humphreys says.

Just to be safe, Humphreys looked for corroboration that the Israelites really were in Canaan during the time of a supposed eclipse. He cross-referenced the Old Testament with an Egyptian text: the Merneptah Stele, a giant stone inscription produced under the Egyptian pharaoh Merneptah. It’s also believed to be the earliest textual reference to Israel. Scholars think the final few lines of hieroglyphics refer to a battle with the Israelites in Canaan.

The final task was potentially the most difficult: calculating the exact timing of the eclipse. That would necessitate a bit of geologic and astronomical detective work.

“Going back in the past, you have to take into account that the Earth was rotating faster than it is now,” Humphreys says. There are myriad factors that play into Earth’s rotational speed gradually decreasing, but three big ones are tidal friction (resistance from water moving around the planet), Earth’s distance from the moon (that’s right, the moon is drifting away from us, like a dog on a stretchy leash), and the shape of the Earth. When ice sheets stretched across the northern hemisphere, Earth was a different shape, so it spun differently. All of these variables have to be factored into any equation that attempts to predict a past eclipse.

“It gets harder [to calculate] the further back you go,” says Lauri Jetsu, an astrophysicist at the University of Helsinki who previously wrote a paper on how ancient Egyptians used a binary star system to create calendars but wasn’t involved in the new research. But, Jetsu adds, if Waddington and Humphreys successfully pinpointed the date for this eclipse with a small enough margin of error, that means we have a data point on the speed of Earth’s rotation that goes back in time further than anything else ever has before.

Scientists still don’t have a definitive list of all the variables affecting Earth’s rotational speed, says John Dvorak, a geophysicist and the author of Mask of the Sun: The Science, History and Forgotten Lore of Eclipses. If the new findings are proven correct, this paper could add one more piece of crucial data. “The paper surprised me, but I shouldn’t be surprised.” Dvorak says. “It’s a reminder that even the ancient study of eclipses changes with time.”

Indeed, humans have been looking to the sky for answers and omens for thousands of years. The Babylonians created rituals for eclipses, while ancient Indian astronomers interpreted the disappearing sun as a sign that the gods were in trouble, reports Maya Wei-Haas for Smithsonian.com. And although the Egyptians didn’t leave any records of eclipses, that doesn’t mean they didn’t observe them.

“The Egyptians worshipped some of the planets and the stars as gods,” Jetsu says. “They used legends to describe celestial phenomenon, they would not have described them directly.”

Eclipses have also shaped human events, says Duncan Steel, author of Eclipse: The Celestial Phenomenon That Changed the Course of History. “Historically, they have been pivotal in deciding battles,” including the 585BC eclipse that stopped a battle between the Medes and the Lydians; Greek philosopher Thales had predicted the appearance of the eclipse, and when darkness did fall, the warring sides viewed it as an omen and hurried to come to a peaceful agreement.

The research by Humphreys and Waddington clearly adds to the field of astronomy. Perhaps more remarkably, it also provides new data for the fields of Egyptology and Hebrew studies. “I think modern translations of the Bible really should say the sun was eclipsed,” Humphreys says. “And I think this should alter history and Egyptology textbooks.”

The changes to Egyptian history that Humphreys suggest have to do with the ruling period of each pharaoh, including Merneptah, during whose reign the Merneptah Stele was carved. Merneptah was the son of Rameses the Great, one of Egypt’s most famous pharaohs, and there’s been considerable debate over the years about when Rameses was in power. With the combination of a date from the solar eclipse, and the carving of the Stele, Humphreys and Waddington have proposed years for the pharaohs’ reigns that narrow the accuracy down to plus or minus one year. They argue Rameses the Great ruled from 1276 to 1210 BC, while Merneptah was in power from 1210 to 1200 BC.

Humphreys recognizes that he isn’t a Biblical scholar, an astrophysicist or an Egyptologist. Yet he argues that being a scientific outsider and drawing on the knowledge of insiders can actually open up new avenues of inquiry. In the past he’s written about using astronomical observations to date the crucifixion of Jesus Christ and to explain the star of Bethlehem that appears in the Bible as a marker of Jesus’s birthplace.

Given the far-ranging cultural and scientific significance of the events he’s looking into, he does anticipate some pushback to this latest finding. That doesn’t mean he has any intention to stop investigating.

“In ancient writings, the Bible or Egyptian writing, you do get records of strange events in the sky. The first thing to do is assume these are genuine records and study them,” Humphreys says. “You shouldn’t jump to saying it’s a myth without first looking into it.” 

Lorraine Boissoneault | | READ MORE

Lorraine Boissoneault is a contributing writer to SmithsonianMag.com covering history and archaeology. She has previously written for The Atlantic, Salon, Nautilus and others. She is also the author of The Last Voyageurs: Retracing La Salle's Journey Across America. Website: http://www.lboissoneault.com/