> Mark Gingrich wrote: > Indeed. And here's a curious bit of related trivia: If you > start due east from *any* latitude and travel a great circle > route -- i.e. "straight" -- a distance of one quarter of the > Earth's circumference, you *always* end up on the equator. > > This also works from the North and South Pole, if you allow > the convenient fiction that all directions are considered east > from the poles. >
It's easy to see why this works. Put your finger on any spot on the globe. Rotate the globe so that point is directly in front of you. Draw or imagine the great circle that goes through that point and the point directly opposite on the earth in the other hemisphere. Now you see that the tangent to this great circle is horizontal at the point of interest, i.e. due east and west. And you can see that it is 1/4 of a circle to the equator. --------------------------------------------------- https://lists.uni-koeln.de/mailman/listinfo/sundial
