Ancient Babylonian Astronomers Tracked Jupiter

The discovery of a clay tablet dating back at least 2,000 years has revealed that the ancient Babylonian astronomers were keeping track of Jupiter in the night sky.

The tablet, just a few inches tall and wide, showcases a form of “pre-calculus” that could be used to describe the motion of Jupiter across the sky in relation to the stars. Dated roughly between 350 BCE and 50 BCE, the tablet’s mathematics predate the European model by around 1,500 years, making the find a “truly astonishing” one, according to Mathieu Ossendrijver.

Professor Ossendrijver, from Berlin’s Humboldt University, is the lead author on a new research study describing the discovery of the tablet. In an interview with the New York Times, he says that the thoroughly modern concept of graphing velocity over time is clearly at play on the ancient clay; additionally, four other tablets with mathematical calculations on them clearly show that the Babylonian mathematicians and astronomers at the time understood how to read such a graph, with the area under its curve representing distance traveled.

The idea that Babylonians had a strong grasp of math isn’t anything new – the ancient city-state, which was located south of what is today Baghdad, Iraq, was an epicenter of science and culture. There’s evidence that mathematicians living within the city between 1800 BCE and 1600 BCE would have known how to perform moderately complex calculations such as finding the area of a trapezoid and how to split one in half into two equal parts. Most of this knowledge would have been used for everyday needs such as calculating the size of a particular parcel of land, yet some tablets surviving from this time period and earlier indicate that these math equations were applied to astronomy as well.

The existence of these tablets has been known about since the 1950s, though it was a mystery as to what these calculations had been used for. Even Professor Ossendrijver, who discovered additional ones himself, was left in the dark, until he saw a photograph of yet another tablet in London’s British Museum with identical calculations – one that mentioned the planet Jupiter. Upon visiting the museum and examining the tablet in person, it became obvious that the trapezoid calculations had been used by ancient Babylonians to determine the distance Jupiter traveled over the course of 60 days.

Professor Ossendrijver says he’s unsure as to why these calculations were used in this way, as the concept of making plots of something against time would have been an abstract one. Even the ancient Greeks didn’t engage in such behavior, the scientist added, though the mathematics used would be “utterly familiar” to any living mathematician or physicist.

Whether the fourteenth century French and English scholars that developed these calculations did so independently of the Babylonians, or if they had access to some lost or unknown texts referencing the 1500-year-old tablets, is a mystery.

The research study, published recently in the journal Science and including images of the clay tablet, can be found here

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