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360 Degrees in a Circle


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!


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/   
    
Associated Topics:
Elementary Math History/Biography
Middle School History/Biography

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