The distinguished members of the Academie Royale des Sciences gathered at Faubourg St Jacques in Paris at the summer solstice in 1667. With pomp and ceremony they made observations of the sky with the aim of "locating" the proposed Observatory of Paris. They established a meridian through its centre, a line which was to become the official meridian of Paris, and in due course, they hoped, the prime meridian of the entire world. But this latter ambition was never realised.
At that time, and indeed for many years thereafter, longitude was a haphazard concept. Sailors would quote their location, in so far as they could know it, as being so many degrees and minutes east or west of a particular spot - perhaps the port they had just left, or their destination, or some conspicuous landmark on the way like the Scilly Isles or Finisterre.
But in the middle of the 18th century a certain order crept into these affairs that was to thwart the academie's ambitions. In 1766, Nevil Maskelyne began to publish the Nautical Almanac and Astronomical Ephemeris , which contained the astronomical tables needed by mariners to calculate their longitude.
Naturally enough, Maskelyne, being Astronomer Royal, chose Greenwich Observatory near London as his base, and all co-ordinates to be derived from the tables had the observatory as their point of reference.
The Nautical Almanac became for sailors worldwide an essential handbook. Greenwich thus became a universal reference point, and longitude everywhere was calculated as being as east or west of there. Likewise, cartographers mapping newly discovered regions recorded longitude in these terrae incognitae with respect to Greenwich.
Towards the end of the 19th century it became desirable to adopt an international standard, and a special international meridian conference of 25 countries was convened in Washington D.C. in 1884. Strong political pressure was exerted in favour of a prime meridian through the Observatory of Paris, and also in favour of one through the centre of Berlin.
But on October 11th, 1884, 116 years ago today, delegates voted in favour of the commonly accepted practice of the day; the meridian of the Greenwich Transit Telescope was declared to be the prime meridian of the globe from which all longitudes should now be measured. And so it has remained.
A logical outcome of this decision was the Zonal System of Standard Times, based on Greenwich Mean Time. Germany adapted quickly, in 1893, but for many years France avoided all reference to GMT for official purposes, and referred instead to "Paris Mean Time retarded by nine minutes and 21 seconds". But 27 years afterwards, in 1911, the Paris Observatory finally conceded its defeat.