I totally enjoyed listening to this audio book. Dava Sobel always researches her books well, and they exude a love of science that I share. This particular book takes us through a history of astronomy, navigation, and clockmaking. It focuses mainly on John Harrison's effort to imagine a mechanical solution to the longitude problem: a clock that would keep precise time at sea, something no clock had ever been able to do on land. After listening, I spent time searching the internet to get a glimpse of the clocks themselves. Check Youtube to find lots of great stories about the clocks.

3.5 stars

For a very short book—175 pages of text, and they’re small pages—this little work of history packs in a decent amount of information. It’s about the centuries-long quest to discover an accurate way of measuring longitude at sea, and particularly the 18th century British solutions.

With the right instruments and calculations, latitude is fairly easy to determine from the position of the sun and stars; people have been doing that for millennia. Longitude is much harder, because everyone at the same latitude sees the same sun and stars, just at different times of day. Essentially, the earth is a giant clock—so, without satellites, how to figure where on it you are, especially at sea without landmarks? For centuries, thinkers have understood that the answer was measuring time, and eventually two possible solutions emerged. One was observing a celestial event (Galileo chose the eclipses of the moons of Jupiter) and comparing the local time at which it occurs to the time calculated in an almanac at which it will occur at some known location. The other was comparing your local time, determined through the angle of the sun, to the time at some known location, from which you can calculate the degree of difference between the two places. Unfortunately, up through the 18th century, there were no sufficiently accurate instruments to use either of these methods at sea, resulting in great loss of life when navigators didn’t know where they were. (Not helped, in the British fleet, by an apparent rule prohibiting common seamen from keeping tabs on the navigation themselves. One brave soul came forward with his calculations in an attempt to avert a disaster and was promptly hanged for mutiny, his warning ignored; the fleet then foundered and most of the crew died.)

The book summarizes the situation and the journey of 18th century clockmaker John Harrison to building timepieces that could keep sufficiently accurate time (despite the jostling, temperature and humidity changes, etc., that had doomed prior sea clocks) to allow ships to find their way. It’s readable and interesting, and I certainly learned a lot about early clocks and watches and the mathematics of navigation, as well as some fun tidbits on a variety of other topics. There’s also a lot about the jostling for position among the various men who wanted to claim credit (and a large financial reward) for solving the longitude problem.

On the other hand, the book is quite brief, and the author seems overly enamored of Harrison, though she doesn’t actually refer to him as a “lone genius” as stated in the subtitle (he seems to have collaborated as much as anyone else at the time, when there was less apparent need for lab assistants than today). It seems odd that she never addresses what appears to me the reason most people won’t have heard of Harrison: in the sciences we tend to lionize those who came up with big ideas, rather than the hands-on technicians who made them work. And Harrison was an instrument maker, very much a hands-on technician; his wasn’t a conceptual breakthrough but a technical one.

Overall, a perfectly adequate book, though not to my mind a remarkable one. But if you’re interested, it’s worth taking a look as it certainly won’t take long to read.

An amazing book.

An amazing book following the attempts to solve the longitudinal navigation problems. The author’s research covered several hundred years of partial success and many failures. Especially interesting was the English contest for solving the problem. An amazing man, John Harrison, worked tirelessly to conquer the problem. The trials of Harrison, and the jealously of others in his attempts made for a good story.. This genius is credited with producing the first marine machine to accurately calculate longitude. Then he reduced his machine to a marine watch. He made numerous chronometers and many of them may be seen in the Royal Observatory and other places in England.

Well written and documented with bibliography .

Fascinating. I love reading tales of ships and pirates, and yet I never knew how hard the problem of "longitude" was to solve. Makes you appreciate the feat of sailing in the Golden Age even more.

This is a non-fiction book, which describes why knowing longitude is so important for sea voyages, multiple ways its correct and precise estimation was suggested and finally a life and struggle of John Harrison, the inventor of chronometer. I read it as a part of monthly reading for October 2022 at Non Fiction Book Club group.

The book starts with a calamity: in 1707, the Scillies became unmarked tombstones for two thousand of British troops because in the fog they went significantly off course and ran onto the ground. There are a few more examples of how ships lost their way and wrecked or lost crew to scurvy because they were unable to get their own coordinates. Moreover, it turns out that despite the oceans are vast, it was easy to ambush ships because most followed narrow routes to avoid confusion. So, in 1714 Parliamentary committee assembled to respond to its challenge, with such prominent experts as Sir Isaac Newton, by then a grand old man of seventy-two, and his friend Edmond Halley (one of the famous comet). It was assumed that the solution is in the stellar clocks – e.g. following moons of Jupiter or the movement of the Moon over the star sky to find out the precise time. Mechanical clocks were disregarded because back then a clock running fast/late by 15 minutes daily was assumed quite accurate. Moreover, the movement of a ship, and differences in temperature and humidity led even precise clocks to significant errors.

One of the interesting solutions was presented by William Whiston and Humphrey Ditton, mathematicians and friends. The idea was that sounds might serve as a signal to seamen. Cannon reports or other very loud noises, intentionally sounded at certain times from known reference points, could fill the oceans with audible landmarks. If enough signal boats, therefore, were stationed at strategic points from sea to sea, sailors could gauge their distance from these stationary gun ships by comparing the known time of the expected signal to the actual shipboard time when the signal was heard. Then Whiston hit on the idea of combining sound and light. If the proposed signal guns were loaded with cannon shells that shot more than a mile high into the air, and exploded there, sailors could time the delay between seeing the fireball and hearing its big bang. A well-timed bomb, exploding 6,440 feet in the air (the limit of available technology), could be seen from a distance of 100 miles. Therefore, a new breed of fleet must be dispatched and anchored at 600-mile intervals in the oceans shooting cannons in the air.

This scheme was untenable on a lot of points, but it was one of the more reasonable ones. However, there was no need for it for a self-taught English clockmaker John Harrison, a mechanical genius who devoted his life to the quest for portable precision timekeeping. He accomplished what Newton had feared was impossible: He invented a clock that would carry the true time from the home port, like an eternal flame, to any remote corner of the world. However, due to his own desire to create a perfect chronometer and to machinations of opponents, who favored a stellar clock approach, his first contraption sailed in 1736 on a trial voyage to Lisbon aboard H.M.S. Centurion but he received his prize for solving the problem only in 1773.

A great book with a lot of interesting facts and awesome storytelling.

I first read this book when it was published in the mid-1990s and have just re-read it to add more depth to my knowledge of ancient maps. It is an excellent book to read in conjunction with A History of the World in Twelve Maps, especially for those seeking to understand why so many pre-18C regional and global maps misrepresented distances and relative sizes--it was the longitude problem.

While a position's latitude can be identified by anyone who understands that at the equator the sun, moon and planets pass almost directly overhead (with the Tropic of Cancer marking the extent of the sun's travels north, and the Tropic of Capricorn the sun's travels south), because "the zero-degree parallel of latitude is fixed by the laws of nature" (p. 4), longitudinal positions are far more difficult. Latitude is read by noting the length of the day or the height of the sun above the horizon. Longitude, however, is "tempered by time. To learn one's longitude at sea, one needs to know what time it is aboard ship and also the time at the home port or another place of known longitude--at that very same moment" (p. 4). This was no easy task on sailing ships in the days of pendulum clocks and hour glasses and why the problem of longitude was resolved earlier for land maps than those representing oceans and continents. The concept of latitude and longitude (a virtual net thrown over the world) was already known by Ptolemy's time (2C AD) who wrote his Geography listing 8,000 sites by their latitude and longitude. Whether maps accompanied this list or not is still debated by scholars, for the oldest map known based on Ptolemy's list dates back only to 1478.

This short but fact-filled work covers the fascinating story of mankind's attempts to resolve the longitude problem...that was to save countless maritime lives and demand adjustments to virtually every known map of the time. An afternoon's or evening's read and the knowledge can be yours, too.

A great book to read with an intelligent pre-teen with a globe (or even a tennis ball and felt-tip pen) at hand.

Appropriately short. Not great, but held my attention enough.

I'm so frustrated. It's nuts to me that someone would write the history of how clocks solved the longitude problem without actually explaining how the clocks worked or what hurdles they overcame. I understand it's highly technical, but the author writes how they were moved to tears seeing the clocks after years of studying how they work and how they were built - I don't think a simplified, accessible explanation is out of reach, and I think it's fair to expect it from this story, even if it is advertised as a brief history of a clockmaker. Maybe they didn't learn it well enough to teach it, but then I don't know why everyone else seems to enjoy this book.

I'm off to go learn more about clocks.

This is probably my third time reading this book, and I find it deeply satisfying every time. It is not particularly entertaining - in the sense of story told, but it is very informational, and unfolds in an order that I can understand. And that's generally a big ask. I am easily confused.

Here is why we have watches, timepieces carried on our persons, and that tick-tick-tick that runs every day of our lives. Here is a tool that can determine to the inch where we are on the planet at any given moment. If that is not magic, what is????

If you are interested in the whys and hows in life, this is a basic one. You might enjoy this read.

A great little read - I was inspired to read this one after being lucky enough to see the longitude exhibit and the Harrison clocks at the Greenwich Observatory a couple of years ago (only just got around to reading the book).

It's a great story and very well told - I mistakenly thought this was going to be a dramatisation / fictionalisation of the story - but it's not, it sticks purely to the historical facts.

Very well written and constructed - for anyone with even the vaguest of interest in the subject or even if you haven't - the determination, dedication, strive for perfection by John Harris and the political intrigue / subterfuge surrounding the Longitude Board / Royal Astronomers and the Longitude Prize is fascinating - it's just a great story and well worth a read.

Sobel ranks right up there with Mark Kurlansky for writing detailed, fascinating accounts of historical technology. Calculating longitude had bedeviled mariners for centuries. To do so required an extremely accurate timepiece.

John Harrison thought he could solve the problem. The book is a nice combination of science and biography. It reminded me of another similar work Noble Obsession Charles Goodyear, Thomas Hancock, and the Race to Unlock the Greatest Industrial Secret of the Nineteenth Century which details Goodyear's lifelong attempts to discover the secrets of vulcanization.

The search for an answer was given a push when Parliament offered a huge prize for anyone who could find a way to calculate longitude accurately. A big problem was figuring out a way to overcome errors induced by humidity causing the pendulum to swell or cold making it contract. Both these effects would through off its balance inducing time-keeping errors.

I have to admit admiring the tenacity and single-mindedness with which both Goodyear and Harrison attacked innumerable problems, never giving up. It's a shame that both had to overcome non-technical personal, social, and political problems to reap any rewards for their efforts.