A Prime Mover at Greenwich
August 13, 2015
Tourists who enjoy standing at the Greenwich meridian in England, where they can watch their smart phones and tablets register 0° longitude, will have to move over a bit now. A group of navigation experts have moved the prime meridian 335 feet (102 meters) east from the original location that was established more than 130 years ago. Mapmakers view Earth as a huge ball that is divided into 360 equal slices. The lines marking the slices on the outside of the ball are called meridians. The meridians, which run from the North Pole to the South Pole along the surface of Earth, are used to measure longitude, or the position east or west from a particular point. The Greenwich meridian has been designated 0° longitude since 1884. In that year, an international conference decided that the meridian, which passed through the United Kingdom’s Royal Greenwich Observatory, would be the world’s prime meridian, the starting point from which the other meridians are numbered.
Scientists called geodesists use surveying techniques to measure the distances and directions between points on Earth’s surface. In the past, they calculated the elevation, latitude, and longitude of thousands of places on Earth using telescopes and other surveying equipment. However, the methods and equipment used to measure Earth’s surface have advanced a great deal since 1884. Today, geodesists make measurements using laser beams and the Global Positioning System (GPS), which uses satellites to precisely measure grid coordinates at any point on the Earth’s surface, often within 1 centimeter (3/8 inch). New measurements with this precise technology now place the prime meridian a short walk east of its historical location.
The site of the Royal Greenwich Observatory remains popular with tourists because of its key role in the development of methods needed for navigation. The observatory was founded in 1675 by Charles II of England. In the mid-1900′s, the Royal Greenwich Observatory moved its operations from Greenwich to Herstmonceux Castle in Sussex to avoid interference from London lights. Operations were moved to Cambridge in 1990, and then the observatory was closed in 1998. But the original Greenwich site has remained the location of the prime meridian ever since. Scientists behind the new measurements, however, are recommending that a new marker be installed in the correct location for the actual geographic prime meridian.
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