Today we took a river cruise on the Thames, and under the Tower Bridge, to Greenwhic in Greater London. After a quick jaunt through the Maritime Museum, we went up to the Royal Observatory to stand on the Prime meridan, the line of latitude that divides the western and eastern hemispheres. The Greenwhich time also provides the GMT (or Greenwhich Mean Time) for the U.K. In the Museum we did some research about the history of the trouble of cartographers comming up with a way to determine latitude and longitude. Eratosthenes (ca. 275-194 B.C.) devised a system similar to meridians and parallels, but Hipparchus (ca. 190-126 B.C.) related astronomical measurements to the determination of climata, or latitudinal positions. He was the first to use a formalized system of longitude and latitude in which the meridian and parallel circles were each divided into 360 degrees, each degree into 60 minutes, and each minute into 60 seconds. I did not realize the history was so extensive, and this is just a tibit, of a system we take advantage of today.