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prime meridian

noun
1.
the meridian running through Greenwich, England, from which longitude east and west is reckoned.
Origin
1860-1865
1860-65
Dictionary.com Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2014.
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British Dictionary definitions for prime meridian

prime meridian

noun
1.
the 0° meridian from which the other meridians or lines of longitude are calculated, usually taken to pass through Greenwich
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition
© William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins
Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012
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prime meridian in Science
prime meridian
  (prīm)   
The meridian with a longitude of 0°, adopted officially in 1884 as a reference line from which longitude east and west are measured and as a basis for standardized time zones. It passes through Greenwich, England, the site of the Royal Greenwich Observatory, which was founded in 1675 and which closed except as a museum in 1998. The prime meridian, together with its opposite meridian having a longitude of 180°, divide the Earth roughly into the Eastern and Western Hemispheres, with those portions of the British Isles, Europe, and Africa that lie west of the prime meridian, considered for practical purposes as belonging to the Eastern Hemisphere. See illustration at time zone.
The American Heritage® Science Dictionary
Copyright © 2002. Published by Houghton Mifflin. All rights reserved.
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prime meridian in Culture

prime meridian definition


The meridian at zero degrees longitude. All longitude is measured relative to the prime meridian, which passes through Greenwich, England.

The American Heritage® New Dictionary of Cultural Literacy, Third Edition
Copyright © 2005 by Houghton Mifflin Company.
Published by Houghton Mifflin Company. All rights reserved.
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Encyclopedia Article for prime meridian

Greenwich meridian

imaginary line used to indicate 0 longitude that passes through Greenwich, a borough of London, and terminates at the North and South poles. An international conference held in Washington, D.C., in 1884 designated "the meridian passing through the centre of the transit instrument at the Observatory of Greenwich as the initial meridian for longitude." The observatory (renamed the Royal Greenwich Observatory) was moved to Hailsham, East Sussex, during the 1950s, but the original site continues to serve as the location for 0 longitude.

Learn more about Greenwich meridian with a free trial on Britannica.com
Encyclopedia Britannica, 2008. Encyclopedia Britannica Online.
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