An outstanding discovery could change how we view the history of science. New research has suggested that ancient Babylonian astronomers used geometry to track the position of Jupiter in the sky, one and a half millennia before European thinkers developed the same approach.
Astroarchaeologist Dr. Mathieu Ossendrijver of Humboldt University discovered five cuneiform tablets (a type of ancient writing) with detailed calculations that predict how Jupiter would move across the sky. The tablets make reference to the trapezoid procedure, similar to what modern-day physics students use when calculating positions in a velocity-time graph. His findings were published in this week’s issue of Science.
“What is new about these tablets is that they mention geometrical figures,” Dr. Ossendrijver told IFLScience. “Two were already known in the 1950s but all of them are damaged, so they could not be read completely and it was not completely clear that they deal with Jupiter.”
There are over 450 tablets in the Babylonian astronomy corpus. Most of them detail the motion of the Moon and the Sun and are based on the Zodiac, which was invented in Babylonia around the 5th century B.C.E. The tablets in the study are the few describing Jupiter that were associated with Marduk, the patron god of Babylon.
“This is now totally clear because of a 5th tablet,” said Dr. Ossendrijver. “It is the key for the other tablets. What is described on this tablet is the velocity of Jupiter expressed in degrees per day.”
Tablet A gives a complete description of the velocity of Jupiter for more than a year. Ossendrijver/British Museum
The tablet contains the values of Jupiter’s daily displacement, connecting the trapezoid procedure to real astronomical data. The Babylonians knew that the apparent velocity of Jupiter in the sky is not constant, and they were able to make predictions using abstract geometry. The tablet gives a complete description of the velocity of Jupiter for more than a year.
“The Babylonians and also the Greeks observed that the planets don’t move at a constant speed; sometimes they slow down, they come to a stand still, they go backwards, they come to a standstill, and they move forward again,” added Dr. Ossendrijver. “They do a loop. The Babylonians observed it, described it, and modelled it in mathematical ways.”
In the 14th century, the same procedure was then redeveloped in Oxford and Paris, and it is at the very core of the calculus that was developed by Newton and Leibniz in the 17th century.
But while the Babylonians were very meticulous astronomers, there are no texts in which they appear to try to understand the peculiar motion of the planets in the sky, suggesting they didn’t know (or perhaps care) about what they were looking at with regards to Jupiter.
“They did not talk about why this happens,” said Dr. Ossendrijver. “We [now] know that this is because planets circle the Sun, and as the Earth overtakes Jupiter it creates this motion in the sky. It’s a projection effect.”