On this day in history : 13th October 1884 – Greenwich is chosen as the universal time meridian of longitude – upon which standard times throughout the world are calculated….

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Greenwich Clock with standard measurements – image credit : Alvesgaspar CC BY-SA 3.0

A geographical meridian is the dividing line of an imaginary circle on the Earth’s surface encompassing the North and South Poles, connected by points of equal longitude…. The meridian is the North to South line and is selected as the zero reference line to make observations of an astronomical nature, enabling the ability to produce an accurate map of the sky by comparing observations from the same meridian…. The Royal Observatory in Greenwich is the place where East meets West at Longitude 0 degrees…. Just as the Equator divides the Northern and Southern Hemispheres, the Greenwich line divides East to West and from it every place on Earth is measured in distance either to the east or west of the line….

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In 1884 the Greenwich line became the reference for mean time…. Before this nearly all the towns and cities of the world kept their own local times….there was no ‘international’ common ground – or even for that matter ‘national’ – as to when the day should officially begin and end…. In fact, it was so unregulated even the humble hour had no determined accepted length….greenwich mean time

So, why Greenwich? There were two main reasons why it was chosen…. Firstly the USA was already using Greenwich for its own national time zone system…. Secondly, during the late 1800s over 70% of the world’s commerce used sea charts that were based on the Greenwich Meridian…. To most, it made sense – as it benefitted the majority of organisations and people…. Obviously it is impossible to please everybody….

41 delegates from 25 nations met in Washington DC for the ‘International Meridian Conference’ to decide the matter…. When put to the vote Greenwich won 22-1 against…. There were two abstentions – France and Brazil….

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Royal Observatory, Greenwich – Image credit : Timitrius via Flickr

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