Track Jupiter's Path Like An Ancient Babylonian : The Two-Way Clay tablets show that Babylonian astronomers tracked planets using a method that was thought to be invented 1,400 years later. In a way, scientists say, the ancient techniques were "very modern."

Track Jupiter's Path Like An Ancient Babylonian

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Babylonians - they're just like us, or at least more like us than first thought. The Babylonians lived in what is now Iraq. They were obsessed with trying to predict the future by watching the stars and planets. And a startling discovery shows that their astronomers used a surprisingly modern technique. Here's NPR's Nell Greenfieldboyce.

NELL GREENFIELDBOYCE, BYLINE: Oh, the Babylonians - they seem like such ancient history. But Mathieu Ossendrijver says no. When you count a 60-second minute or a 60-minute hour, you are acting a little Babylonian, and you know astrology.

MATHIEU OSSENDRIJVER: With horoscopes and with the zodiacal signs, the 12 signs, that was invented in Babylonia.

GREENFIELDBOYCE: Ossendrijver works at Humboldt University in Berlin. He has a PhD in astrophysics, but he doesn't study the stars. Instead, he spends his days poring over crumbling clay tablets. They're covered with the tiny scrawls of long-dead Babylonian priests. Ossendrijver specializes in a few-hundred tablets that deal with the hardcore mathematics of Babylonian astronomy. They're filled with numbers and arithmetic, except there are four mysterious tablets that are different.

OSSENDRIJVER: Nobody understood what they are about, including me. I didn't know it until very recently.

GREENFIELDBOYCE: These tablets talk about a shape - a rectangle with a slanted top, a trapezoid. The tablets don't have an actual drawing. They just talk about the trapezoid's sides and its area and dividing the area into parts. What exactly were the ancient astronomers doing here? Last year, Ossendrijver made a breakthrough.

OSSENDRIJVER: I found, so to speak, the key to understanding these weird texts that deal with trapezoids.

GREENFIELDBOYCE: The key was another clay tablet. This one describes how the planet Jupiter moves across the sky. He noticed that the numbers on this tablet matched the numbers on those strange trapezoid tablets.

OSSENDRIJVER: So that was, like, the a-ha moment. It was, like, oh.

GREENFIELDBOYCE: He realized that the Babylonian astronomers were using the tools of geometry to deal with a very abstract concept - how the velocity of Jupiter changes over time. Now, historians knew that Babylonians used geometry to work with physical objects like a plot of land or a building, but this is way more sophisticated. It's a very modern method, one that historians had thought was invented some 14 centuries later in the Middle Ages in Europe. Ossendrijver describes his discovery in the journal Science, and it's wowed scholars like Alexander Jones at New York University's Institute for the Study of the Ancient World.

ALEXANDER JONES: I'm quite surprised. I'm not surprised that this is coming out of Babylonian because these sort of astronomer scribes of the last five centuries B.C. or so really were amazing.

GREENFIELDBOYCE: He says they developed a slew of new techniques for astronomy. Of course, these priests wanted to track Jupiter to understand the will of their god Marduk in order to do things like predict future grain harvests. But still, they had the insight to see that the same math used for working with mundane stuff like land could be applied to the motions of celestial objects.

JONES: They're, in a way, like modern scientists. In a way, they're very different. But they're still coming up with very, you know - things that we can recognize as being like what we value as mathematics and science.

GREENFIELDBOYCE: Nell Greenfieldboyce, NPR News.

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