Let's face it: The Babylonians got it right when they developed the base-60 system. It was applied to the sixth of a circle (one sixtieth of this being a degree) and the hour, of which we still use the first and second minutes. Third minutes (sixtieths of second minutes) are not in common use, although I would note that the third minute of an hour is the period of U.S. power main standard 60 Hz alternating current. Coincidence?
The arc minute is so convenient for expressing human visual acuity because the value of the latter is coincidentally close to 1 arc minute. For practical calculations at small angles arc minutes and arc seconds are best converted to radians, the arc second being approximately 5 microradians, the arc minute about 17 milliradians. And, of course, the angular diameter of the sun is approximately 10 milliradians.
Gordon At 10:55 AM 2/15/00 -0700, Jim_Cobb wrote:
The radian is a natural measure of angle, but I would suppose everyone subscribing to this list uses degrees, minutes, and seconds. For example, I haven't seen any of the recent discussion about human visual acuity conducted in terms of radians.
Gordon Uber [EMAIL PROTECTED] San Diego, California USA Webmaster: Clocks and Time: http://www.ubr.com/clocks
