Early Greek scholars adopted the Babylonian practice of dividing the 12 signs of the zodiac into 30 equal parts. The choice of 30 probably reflects the observation that it takes roughly 30 days for the sun to pass through each sign, and the division of a circle into 360 parts can probably be traced to the fact that there are about 360 days in a year. If so, the Corinthian starting line is evidence of an early use of the degree as a unit of angular measurement among the Greeks. References Rorres, C., and D.G. Romano. 1997. Finding the center of a circular starting line in an ancient Greek stadium.
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Ivars Peterson is the mathematics and physics writer and on-line editor at Science News. A Mathematical Safari by Ivars Peterson.