Tue 1 Mar 2011 20:44
Wind: Light, variable
Weather: Mostly sunny, warm.
Not a lot happening, waiting for the crown for my broken tooth to be made, should be finished on Thursday. Meanwhile doing some maintenance and reading up on the archaic art of celestial navigation:
Why 360 degrees in a circle?
If you were an early astronomer you would have noticed that the stars
rotate counterclockwise (ccw) about Polaris at the rate of seemingly once per
day. And that as the year moved on the constellation's position would slowly
crank around as well, once per year ccw. The planets were mysterious and
thought to be gods as they roamed around the night sky, only going through
certain constellations named the zodiac (in the ecliptic plane). You would have
noticed that after ¼ of a year had passed, or ~ 90 days, that the constellation
had turned ccw about ¼ of a circle. It would have seemed that the angle of
rotation per day was 1/90 of a quarter circle. A degree could be thought of as
a heavenly angular unit, which is quite a coincidence with the Babylonian base
60 number system which established the angle of an equilateral triangle as 60º.
The Egyptians had divided the day into 24 hours, and the
Mesopotamians further divided the hour into 60 minutes, 60 seconds per
minute. It is easy to see the analogy between angle and clock time, since the
angle was further divided into 60 arcminutes per degree, and 60 arcseconds per
arcminute. An arcminute of a great circle on the surface of our planet defined
the unit of distance; a nautical mile, which = 1.15 statute miles. By the way,
mile comes from the Latin milia for 1000 double paces of a Roman soldier.
From "Celestial Navigation in a Teacup" by Rodger E. Farley.
How very interesting, don't you think?
All is well.