The Thumbnail Book Reviews
by John Q McDonald --- 8 September 1998
by Dava Sobel
His name was John Harrison, and the problem was the determination of longitude at sea. Ocean-going voyages were hazardous when the sailors couldn't accurately determine where they were. Latitude was relatively easy to determine from the stars, but longitude required accurate knowledge of the time at a fixed reference point. Today, that fixed point is the Greenwich Meridian, and the time is variously referred to as Universal Time, Greenwich Mean Time or Zulu time. This book is about the race to find an accurate method for determining longitude, after the British government offered a huge monetary prize for the first to succeed. Astronomers were determined to find longitude by the stars and planets, but the measurements had to be more accurate than any ever taken. Harrison took a technical approach to the problem, inventing the most accurate clocks of his day. Sobel tells this story in an enormously engaging manner. The book is hard to put down. She tells of the hazards of inaccurate longitude and bizarre methods once proposed to find it. We learn of the intrigues between favored astronomers at Greenwich, and Harrison's difficulty in getting his five clocks accepted. As a result of this race, the speed of light was accurately determined, as were the distances to the Moon, Sun and Jupiter, the size of that massive planet as well, and the marine chronometer came into being. The book is excellent, but at times the chronology becomes difficult to follow. The reader may also be left wanting for further historical or technical details beyond this popularly written work.
Also by Sobel: [Galileo's Daughter]
[Other History and Biography books]