Babylonians tracked Jupiter with fancy math, tablet reveals

For a text that may rewrite the history of mathematics, it looks rather sloppy. The brown clay tablet, which could fit in the palm of your hand, is scrawled with hasty, highly abbreviated cuneiform characters. And, according to science historian Mathieu Ossendrijver, it proves that the ancient Babylonians used a complex geometrical model that looks like a rudimentary form of integral calculus to calculate the path of Jupiter. Scientists previously thought this mathematical technique was invented in medieval Europe. “It sounds minute for a layperson, but this geometry is of a very special kind that is not found anywhere else, for instance, in ancient Greek astronomy,” Ossendrijver said. “It is an application in astronomy that was totally new. Thus far everybody thought Babylonian scholars only computed with numbers.” A sophisticated invention: The tablet has long been in the collection at the British Museum in London, and it was likely created in Babylon (located in modern-day Iraq) between 350 and 50 B.C. Ossendrijver recently deciphered the text, and he described his discovery in an article that’s featured on the cover of the journal Science this week. From his office at Humboldt University here in Berlin, which is decorated with posters of both the Ishtar Gate and the Antikythera mechanism (thought to be the world’s oldest known computer), he explained that the tablet plots the apparent decreasing velocity of Jupiter from the planet’s first appearance along the horizon, to 60 days later, and then 120 days later. If drawn on a graph, this relationship is represented in the shape of two conjoined trapezoids. The area of each trapezoid describes Jupiter’s total displacement (measured in degrees) along the ecliptic, or the path of the sun. “It’s not an actual trapezoid that describes the shape of a field, or some configuration of the planets in space,” Ossendrijver told Live Science. “It’s a configuration in a mathematical space. It’s a highly abstract application.” Ancient Greek mathematicians and astronomers were using geometry around the same time, but only to make calculations involving real, 3D space, such as using circles torepresent the orbits of planets around Earth. Students of math might take it for granted today, but the abstract use of geometry was, until now, unheard of at the time. “Anyone who has studied physics or a little bit of math is familiar with making graphs — plotting one quantity against time — but actually this had to be invented once,” Ossendrijver said. Current textbooks on the history of math say this invention took place around A.D. 1350. In the mid-14th century, mathematicians at Merton College in England who were referred to as the “Oxford Calculators,” and another scholar collaborating with them in Paris, were interested in understanding the velocity and displacement of an object over time. They came up with the Merton mean speed theorem, which holds that the distance a uniformly accelerating body travels in a given interval of time is the same distance it would travel if it were moving at a constant velocity (with that constant velocity being the average of the accelerating body’s initial and final velocity). But the mean speed theorem now seems to be a reinvention of a lost model; about 1,400 years earlier, it seems the Babylonians had their own technique to make calculations based on this principle. “When I looked at the text, I was immediately convinced,” said Jens Høyrup, an expert in Babylonian mathematics at Roskilde University in Denmark, who was not involved in the new study. “There are words that indisputably point to geometric understanding — not a geometric model of how the planets move, but a geometric technique to make some arithmetic calculations.”

Fascinating!!  To see a photo of this clay tablet, and read the rest of this article, click on the text above.    🙂

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