The Prime Meridian

Which part of London is best known throughout the world? The obvious answers I suppose would be Westminster or Buckingham Palace or perhaps its Big Ben or maybe Tower Bridge.

Looking at my street map it struck me that it is probably Greenwich, the home of the Prime Meridian (zero degrees Longitude).

People may not even know where Greenwich is but they may well have heard of GMT (Greenwich Mean Time) or have seen Longitude marked on a map. The divisions between the Eastern and Western Hemispheres are not particularly marked, certainly you don't tend to group countries by their relationship to the Prime Meridian in the way that you do with the Equator i.e. Northern and Southern Hemisphere. However, the Prime Meridian remains essential for navigation and time keeping (UTC or Coordinated Universal Time remains for all practical purposes the same as GMT).

However, the choice of Greenwich as the Prime Meridian was not supported by everyone, in particular, France.

It was recognised that one meridian had to be chosen for the purposes of standardising Longitude and time measurement. In October 1884 The International Meridian Conference was held in Washington DC where it was decided to adopt Greenwich as the Prime Meridian. One of the main factors in that decision was that a substantial proportion of the world's shipping (and their charts) was already using Greenwich as the Prime Meridian. The Canadian delegate, Sanford Fleming, showed that 72% of shipping was using Greenwich whilst the other 28% were relying any one of ten different meridians. The dominance of Greenwich is, most likely, a reflection of the dominance of Britain in merchant shipping at the time. In the 19th Century, Britain, because of the British Empire, was the single largest sea trading nation in the world. Unsurprisingly, British ships would use the London based meridian as their reference point.

There is a meridian running through Paris and France abstained from voting for Greenwich in the Final Act Resolutions of the International Meridian Conference in 1884. France tried to link the selection of Greenwich to the adoption of the metric system by Britain something which, despite continuing efforts, no one has yet forced Britain to do. France did not immediately recognise the Greenwich Meridian and it was not until 1911 that legislation was passed in France adopting the Greenwich Meridian.

So every time you use a map reference, a satellite navigation device or cross a time zone you linking back both to a small part of South East London and to a larger part of international history and politics.