On this day in history: Foundation stone of Royal Greenwich Observatory laid, 1675

On 4th March 1675, King Charles II issued a royal warrant appointing John Flamsteed as his 'astronomical observator' - a position later known as Astronomer Royal. The warrant detailed his dual role to further scientific knowledge by 'rectifieing the Tables of the motions of the Heavens, and the places of the fixed stars' and to improve British trade by working 'out the so much desired Longitude of places for the perfecting the Art of Navigation' for which Flamsteed received an annual salary of one-hundred pounds. To aid him in these tasks, the king issued another royal warrant in July of that year commissioning an observatory to be built.

The site chosen for this, the first purpose built scientific building in England, was on a hill in the royal park at Greenwich, then a town outside London. Robert Hooke started work on a design for the observatory, possibly consulting Christopher Wren with whom he collaborated on several projects (and who is identified as the designer of the observatory in some accounts). On 10th August 1675, work was ready to begin and Flamsteed laid the foundation stone for the observatory.

Successive, royal astronomers used this building, later known as Flamsteed House, as the point from which they measured the longitude (distance east or west in degrees) of various places. In the nineteenth-century, an international convention agreed that the building should mark the Prime Meridian, that is zero degrees longitude. The Royal Observatory also became the 'home' of Greenwich Mean Time, initially the standard time for all British naval ships, and later the standard by which all clocks were set with variations according to time-zone.

The Royal Observatory is now a World Heritage Site administered by the National Maritime Museum.

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