Dava Sobel writes books about science and its greatest heroes. These include John Harrison, Copernicus, Harvard’s women astronomers, and Galileo. Her book Galileo’s Daughter was short-listed for the Pulitzer Prize. Longitude, released in 1995, won several awards and inspired a film and TV series. An illustrated version of Longitude was issued in 1998.

A woodworker by trade, John Harrison was born in 1693 and took an early interest in physics and engineering. In 1727 he accepted Parliament’s challenge of inventing a solution to the problem of finding longitude to within half a degree. A self-taught clockmaker, Harrison constructed five precision clocks, known as H-1 through H-5, which were accurate enough to pin down a ship’s longitude to within half a degree. The pride Harrison took in his work is evident not only in the decades he devoted to it, but also in the fact that he declined an early offer of the prize money because he was dissatisfied with his results.

In vying for Parliament’s prize, Harrison faced stiff competition from astronomers, especially the directors of the Greenwich Royal Observatory, whose celestial method of determining longitude threatened to bypass all of Harrison’s efforts. There was an element of class prejudice and intellectual snobbishness to the Board of Longitude’s treatment of Harrison; he came from a family of tradesmen rather than the gentry or professional classes, and his more mechanistic work wasn’t considered scientific in the same sense as more abstract fields like astronomy.