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360 Degrees in a Circle

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Date: 06/09/98 at 19:49:49
From: Jennifer Dial
Subject: History of the 360 Degrees

I have asked a middle school math instructor the following question:

When studying angles, we are taught that a complete rotation is 360
degrees. (90 degrees and you've turned one-quarter, 180 degrees
and you've turned halfway and so on.) Why or what is the history of
360 degrees? Why not isn't it something like 500 degrees for a
complete rotation (where 125 degrees is a one-quarter turn, and
so on.)

He wasn't certain about the history but speculated that is had to do
with the earth's rotation around the sun (close to 365 days). Can you
provide any background / history?

Thanks!
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Date: 06/09/98 at 21:43:04
From: Doctor Gary
Subject: Re: History of the 360 Degrees

I recall a fairly bitter dispute about the history on the sci-math
newsgroup about three years ago, but I think the following fable is
worth knowing.

In ancient times, it made perfect sense to equate timekeeping with
circles. Days and years were similar to travelling around a circle
because patterns (sunrise/sunset or the seasons) would recur.

Early timekeepers noticed that the pattern of seasons we've come to
know as a year could be broken up into twelve comings and goings of
the moon.  These "moon things" (say it very, very fast, and it sounds
a bit like "months"), three to a season, could be broken into roughly
thirty comings and goings of the sun.

Be grateful for our anscestors' imprecision. 360 has a lot more
integral factors than 365 and a quarter.

Historical or not, I like an explanation of how our measure of time,
both within years and within days, came to be based on 12 (months in a
year, and hours both before and after noon).

-Doctor Gary,  The Math Forum
Check out our web site! http://mathforum.org/dr.math/
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Associated Topics:
Elementary Math History/Biography
Middle School History/Biography

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