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Why are there 360 degrees in a circle?

Dear Cecil:

Why are there 360 degrees in a circle?

Listener, NPR

Cecil replies:

My assistant, little Ed, got this question the other day on a radio talk show and predictably had no clue. However, from long experience we have learned that when in doubt, blame it on the Babylonians. Sure enough, when we looked up “degree” in our Oxford English Dictionary, we read, “this division of the circle is very ancient, and appears to have been originally applied to the circle of the Zodiac, a degree being the space or distance travelled by the sun each day according to ancient Babylonian and Egyptian computation, just as a sign represented the space passed through in a month.”

But wait, you say. The year has 365 days, not 360. We seem to be five degrees short.

Well, yeah. Standards of scientific measurement in those days were a little more relaxed. Three hundred sixty was also readily divisible into thirds, fourths, fifths, sixths, etc. — no small advantage. You think you would have enjoyed trigonometry more if the number of degrees in a right angle had been 91.25?

Cecil Adams

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