Writing a blog post about Sir Isaac Newton is a rather daunting task for the non-expert like myself. What can you say about the great man that hasn’t been said before many many times? But it would be almost impossible to have a blog about the 18th century quest for Longitude without mentioning Isaac Newton.

By the early 18th century, Isaac Newton was the most respected scientific thinker in Britain. He was the leading witness and advisor to Parliament during debates on the longitude problem. As President of the Royal Society of London from 1703, Newton became a Commissioner of Longitude under the Act of 1714, and corresponded widely on proposals for finding longitude at sea. For example, this beautifully written manuscript is a handbook for finding longitude by the lunar-distance method.

This beautifully written manuscript is a handbook for finding longitude by the lunar-distance method. Robert Wright sent copies of his book to the Commissioners of Longitude. This is the copy given to Sir Isaac Newton.  National Maritime Museum, Greenwich: NVT/5 This beautifully written manuscript is a handbook for finding longitude by the lunar-distance method. Robert Wright sent copies of his book to the Commissioners of Longitude. This is the copy given to Sir Isaac Newton.National Maritime Museum, Greenwich: NVT/5

Newton’s Philosophiae Naturalis Principia Mathematica is one of the most important scientific books ever published. It describes the motions of the Solar System using mathematics. On display in Ships, Clocks & Stars, we have John Flamsteed’s own personal copy. In March 1675, Charles II signed a royal warrant that appointed John Flamsteed (1646–1719) as his ‘astronomical observator’. The King charged him ‘to apply himself with the most exact Care and Diligence to the rectifying the Tables of the Motions of the Heavens, and the places of the fixed Stars’ to help solve the longitude problem.

The Royal Observatory from Crooms Hill unknown English artist, about 1696 The Royal Observatory from Crooms Hillunknown English artist, about 1696

 

Newton understood that one of the greatest problems with the lunar distance method was to understand the complex motion of the Moon. He failed to solve this despite grappling with it in three editions of Principia. Isaac Newton died on March 31, 1727, before an official meeting of the Commissioners of Longitude could take place, and he didn’t live to see the huge breakthroughs in two of the methods he had originally proposed to parliament in his testimony: timekeepers and the lunar distance method. John Harrison didn’t start work on H1 until 1728.

In the 1740s the German map-maker, Tobias Mayer, began exploring ways to make maps more accurate. He specifically looked at how to improve lunar observations, as the Moon’s position was used to determine geographical longitudes. Initially he began to map the Moon’s surface and then turned his attention to its complex, irregular movements. Using the theoretical work of Newton and others, and accurate observations made at Greenwich, he devised a series of tables that predicted the Moon’s positions, succeeding where Newton had failed. Mayer’s work provided the breakthrough needed to make finding longitude by lunar distances possible.