Bob Moler's Ephemeris Blog

Veteran’s Day, Thursday, November 11th.  The sun will rise at 7:33.  It’ll be up for 9 hours and 45 minutes, setting at 5:18.   The moon, 2 days before first quarter, will set at 10:22 this evening.

Check out the moon tonight.  The Greeks were able to use it to make two great discoveries.  First they knew that lunar eclipses were caused by the moon entering the earth’s shadow.   That wasn’t the discovery, the discovery was that the edge of the earth’s shadow was always circular.  The only object that casts a circular shadow no matter what its orientation is a sphere.  So the Greeks knew the earth was round long before the birth of Christ.  They were also able to determine the distance of the moon via eclipses as 60 earth radii, which is within the moon’s actual distance range.  It was in the 3rd century B.C. that Eratosthenes determined the circumference of the earth to provide an actual distance scale to the moon.

* Times, as always are for the Traverse City/Interlochen area of Michigan.