THERE IS nothing quite like the delicious pleasure of a good book. Dava Sobel's Longitude has it all: an enthralling story, lovely language, a handsome production. It tells the story of what was once a most important problem. It is a book that we all should read.
Science is full of great stories, yet they are seldom told - popularisers prefer to tell us about "the ideas that changed the world" - which is a pity, for it denies the fact that science is just like any other human activity, conducted by people with passions and prejudices.
And what a story Sobel (an award winning science journalist and former New York Times reporter) has chosen to tell. There are goodies and baddies, an (almost) happy ending and, that vital narrative ingredient, the lone individual fighting the establishment.
Today, when global positioning systems can locate us with pinpoint accuracy, it is hard to imagine what the world was like 300 years ago. Then, "discovering the longitude" was considered to be impossible, on a par with perpetual motion.
Navigators could always use the sky to determine their latitude, since these lines (e.g. the equator) are defined by the Sun's behaviour. But lines of longitude are political constructs and one's position east or west could not be so easily reckoned.
The great navigators reached their destination by happenstance or because, like Columbus, they "sailed the parallel" (or line of latitude). Others were less lucky: the need to stick to known shipping lanes delivered many into the hands of pirates; poorly reckoned longitudes could mean a missed land fall (and the dreaded scurvy) or destruction on an unexpected one.
In October 1707 the English navy lost 2,000 men on the Scilly Isles after Admiral Shovell misgauged their position. It would be nice to think that, as he died, the admiral regretted hanging the insubordinate young seaman who, having kept his own careful log, courageously challenged those who reckoned the fleet to be safely off the Brittany coast.
This disaster in particular prompted the English government to establish a Board of Longitude and, in 1714, it offered £20,000 - a king's ransom - for a solution to the greatest problem of the day.
Since the sky can be compass, clock and calendar, most scientists sought an astronomical solution. They studied (and some promised) the sun, moon and stars, and computed complex tables of astronomical positions.
John Harrison took a different approach. If sailors could compare the time on board ship with the time at home, they could compute the distance travelled. But that required a timepiece accurate to a few seconds a day, and capable of enduring the rigours of long voyages.
Harrison set out to build such a timepiece, and Sobel here brings the story to life: his patience and obsession (his third chronometer took 19 years to build); his ill treatment by the board (ruled hay astronomers who championed their own system is disputed old age (the prize was never awarded).
In Sobel's hands even the timepieces are characters, and rightly so, for they are works of art and were as famous then as the captains they sailed with on trial voyages (Cook and Bligh, among others).
Along the way, Sobel finds time to relate other developments (like the measurements of the speed of light), and introduce other personalities (Galileo and Newton, among the many). And, throughout, she follows the politics of breakthrough and progress: did Nevil Maskelyne, astronomer royal, really mistreat Harrison's clocks?
The legacy of these 18th century events are with us today:
Harrison's innovations are still used in mechanical clocks; Maskelyne defined Greenwich as the place where East meets West.
This is a history worth knowing, one that touches anyone who travels, who uses a watch. This wonderful "brief history of time" is a slim volume, but a fine tribute to a man who changed the world.