Greenwich - the Royal Observatory

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The Royal Observatory, founded in 1675.

It was meant to find astronomical methods for the solution of the ’longitude problem’: how could a ship determine its position at sea? the latitude could be accurately determined by estimating the height of the sun, but the lack of proper ways to calculate the longitude caused numerous shipwrecks.

The solution was eventually found in the 18^th century by other methods - an accurate clock, Harrison’s timekeeper, that could give the difference between local time at sea and Greenwich time, thus showing the number of time zones separating the local position from the prime meridian. It took Harrison several decades to find the solution.

Greenwich - the Royal Observatory

[click on the picture to enlarge it]