Thursday, August 21, 2008
Greenwich, England, lies upon the Prime Meridian
The Prime Meridian and the opposite 180th meridian (at 180° longitude), which the International Date Line generally follows, form a great circle that divides the Earth into the Eastern and Western Hemispheres.
Unlike the parallels of latitude, which are defined by the rotational axis of the Earth (the poles being 90° and the Equator 0°), the Prime Meridian is arbitrary. By international convention, the modern Prime Meridian is one passing through Greenwich, London, United Kingdom, known as the International Meridian or Greenwich Meridian.