Origin of 360 Degrees and 365 Days



name         Daniel
status       other
grade        other
location     NY

Question -   If the earth takes 365 days to complete a cycle and 
fulfill a circle/year, why are there only 360 degrees in a circle?

Also if the earth rotates counter-clockwise, how does the sun rise 
in the east? I am having trouble visualizing this.

I would really appreciate your insight!
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Daniel,

It is coincidence that there are 360 degrees in a circle and 365 1/4 
days a year.

In the Old Babylonian period, there was a unit of time corresponding 
to the "barleycorn."  In Sumerian, one barleycorn (called se) was 
1/180 of a shekel.  In late Babylonian astronomical texts, it was 1/6 
of a finger.  Since 1 finger was 1/12 or a degree, we have 1 degree = 
72 barleycorns and 15 degrees = 1080 barleycorns.  So why are we 
worried about 15 degrees?  That is the amount of arc length the sun 
travels in the sky in one hour, where one hour is 1/24 of a day.  It 
was convenient to divide the day into 12 daylight and 12 night time 
parts.  At 15 degrees per hour, and 24 hours per day, this would give 
360 degrees of rotation per day.  From this, it is an easy jump to 
360 degrees in a circle.

If you look into Biblical texts,you will find that hours were broken 
up into 1080 parts (we now divide our hours into 3600 seconds) 
corresponding to these barleycorns.  The relationship of 1 finger = 6 
barleycorns is well known in Arabic, Syriac, and Sanskrit astronomy.

Some scholars claim that 1080 (and 360) were used because these 
numbers are easily divisible by so many numbers (notably 7 
excepted).  There does not seem to be great evidence for this.

An expert on the History of Mathematics, which involves some of the 
ancient astronomy was Professor Otto Neugebauer of Brown 
University.  I am guessing his work in this area was done in the mid 1900's.

As for counterclockwise rotation of Earth, this is only if your frame 
of reference is looking down from the North Pole.  Indeed, this would 
necessitate the sun rising in the east.  Spin a basketball 
counterclockwise as you look down on the axis of rotation.  Have a 
light illuminating it from only one side.  East is the direction a 
point moves from the ball's shadow into light.

---Nathan A. Unterman
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