Latitude is measured by your position north or south of the equator but what about longitude? How is your east or west position defined? Discover all about the quest to establish longitude and why it was important, the men behind its discovery, and the establishment of the Prime Meridian at Greenwich.

18 Dec 2015
Samuel Pepys and the Royal Observatory
Curator of the Royal Observatory, Louise Devoy, looks at Samuel Pepys's links to our site here in Greenwich.
What is longitude?
Find out what longitude is and what makes it so hard to measure
What made the search for longitude so important?
Why did most of the great European powers offer huge rewards for a way to determine longitude at sea?
Longitude found: Nevil Maskelyne and the lunar method
Find out how the celebrated Astronomer Royal helped to solve the longitude problem
Longitude found - the story of Harrison's Clocks
Who was John Harrison, and how did his clocks help to solve the problem of finding longitude at sea?
Robert Hooke: the man who knew everything
Neither the smallest nor the largest objects in the known Universe escaped the brilliant Hooke’s attention.
The magnetic Mr. Halley
Discover the work of Edmond Halley, the pioneering astronomer and mathematician
The Astronomer Royal
The Astronomer Royal is the best-known and most prestigious post in astronomy with illustrious forebears such as Flamsteed and Halley
Traditional ways to determine a ship’s position
How did ships know where they were before seamen could get an accurate reading of their east/west location?
Projectors, pranks and perpetual motion
From the satirical to the serious, the quest for longitude provoked a wealth of responses, some more worthy of attention than others.