A prime meridian is a meridian, i.e. a line of longitude, at which longitude is defined to be 0°. A prime meridian and its opposite in a 360°-system, the 180th meridian (at 180° longitude), form a great circle.
This great circle divides the sphere, e.g. the Earth, into two hemispheres. If one uses directions of East and West from a defined prime meridian, then they can be called Eastern Hemisphere and Western Hemisphere.
An international conference in 1884 decided the prime meridian passes through the Royal Observatory, Greenwich in southeast London, United Kingdom, known simply as the prime meridian but also sometimes referred to as the International Meridian or Greenwich meridian.
Read more about Prime Meridian: General Concept, Earth, Other Planetary Bodies
Famous quotes containing the words prime and/or meridian:
“One wants in a Prime Minister a good many things, but not very great things. He should be clever but need not be a genius; he should be conscientious but by no means strait-laced; he should be cautious but never timid, bold but never venturesome; he should have a good digestion, genial manners, and, above all, a thick skin.”
—Anthony Trollope (1815–1882)
“I knew that my vocation was found. I had received the call, and having done so, I was sure my work would be assigned me. Of some things we feel quite certain. Inside there is a click, a kind of bell that strikes, when the hands of our destiny meet at the meridian hour.”
—Amelia E. Barr (1831–1919)