Guest Post by Willis Eschenbach
I’m sure many people know this, but a “great circle” is a circle that goes clear around the entire globe, and whose center is at the center of the globe. A “meridian”, on the other hand, is a great circle that passes through the poles. Lines of longitude are meridians, for example, while the Equator is a great circle. And the “Prime Meridian” is the line of longitude that goes through both poles .. and right through the Greenwich Observatory.
On the other side of the planet from where I am now, the Prime Meridian is called the “International Date Line”. Inter alia, it runs through the island of Taveuni. And I’ve stood there in Taveuni astride the Date Line, with one foot in yesterday and one foot in today.
So it was with great satisfaction that I was able to do the same on…