The True Story of a Lone
Genius Who Solved the Greatest Scientific Problem of His Time
Dava Sobel and William J. H. Andrewes
ISBN 0-8027-1344-0
Christmas 2003 from Viannah
Read: 2004 March 6 – March 20 (approx.)
Reviewed: 2004 April 20
I bought this book before it was illustrated, circa 1997, and still have it somewhere in my bottomless pile of books I need to read. When Viannah went to college at Franklin & Marshall in Lancaster, PA in fall 2003, one of the first four courses she took was Navigation and this was one of the required texts. It was so new that it was not even available in the college bookstore until we bought it during ParentÕs Weekend in October.
She tells me she read the first 13 chapters for the class. She then gave it to me for Christmas saying that I would probably get more out of it than she had.
This edition is greatly enhanced through the use of paintings or photographs (supplied by the co-author Andrewes to SobelÕs original text) illustrating virtually every key discussion, technology, or personality involved in the story.
The basic problem is that global surface navigation is inextricably tied to knowledge of time. Since the earth rotates about poles, it is fairly simple to find ÒlatitudeÓ which is a measure of the distance from the poles (actually, counted from the equator, that Ògreat circleÓ which lies between the poles). It is not easy to find ÒlongitudeÓ since itÕs value changes by one degree every four minutes throughout the day. One degree, at the equator is about 69 miles (60 nautical miles by definition) so that four minutes translates to a pretty hefty navigational error.
Before longitude could be determined from mobile platforms, the standard technique of navigation was to sail to the latitude of destination, then go east or west until the destination was sighted. This, too, had obvious problems, not the least of which were several forms of inefficiency. Sea-borne commerce, though crucial, was highly risky and highly speculative largely due to the rampant and random disasters that occurred owing to lack of a good handle on the quantity longitude.
The book begins with hair raising accounts of some of the more notorious of these disasters including those befalling Admiral Sir Clowdisley Shovell, who, along with his fleet was lost to a tragic and ironic navigation error and post captain George Anson who spent months and lost hundreds of crew trying, nearly in vain, to round Cape Horn and proceed beyond.
ÒDead ReckoningÓ indeed!
The admiralty had had enough. Parliament formed a ÒBoard of LongitudeÓ that offered a handsome prize to the inventor or investigator who could solve this problem.
Conventional wisdom of the day was represented by Isaac NewtonÕs view that the solution would be astronomical. It was necessary to know, to an accuracy of several seconds, the time at some reference longitude (such as, but not necessarily the prime meridian). Observation of some astronomical event and comparison to published tables would give some reference time which could then be compared to local observations of the sun or stars (giving Òlocal timeÓ) to find local longitude. Latitude would still be observed and computed as before, by measuring the altitude of known celestial objects at transit and comparing to known declinations.
Another approach would be to build a timekeeping instrument of sufficient accuracy to transfer time from a reference location, such as a homeport (where longitude was known) throughout a voyage through the return home. Most clocks of the day relied on pendulums, however, which did not work well at sea. Other escapements were known, but were much too temperature sensitive to maintain time within a minute or two over several weeks.
Without mechanical calculators and with only a sense of the ÒrightnessÓ of celestial mechanics, several ideas were tried, heroically, with various degrees success. Probably the best technique was to observe events at the moons of Jupiter. These could be predicted, tabulated, and catalogued years in advance and would give time measurements accurate to several seconds, as required. (A by-product of this technique was that the speed of light itself was finally quantified to one and a half significant digits by noting that the variations in the times of these events was largely due to differing distances between earth and Jupiter.) Other techniques involved measurement of the position of the moon or planets against the stars. The planets, however, donÕt move enough to give very good time precision and the moonÕs motion was problematic to calculate, predict, and tabulate. Further, it required allowance for parallax, that is, the fact that the moonÕs distance from the earth is not essentially infinite compared to the size of the earth. A competent navigator could, under appropriate conditions, take the necessary measurements and reduce the data in a space of three or four hours. Certainly an important, full time shipboard job!
The main problem with all astronomical techniques, however, was that they depended on sufficient observing weather and, to some extent, enough calm to make good measurements. While the Òmoons of JupiterÓ method was used to set up simple observatories along coastlines everywhere and to improve mapmaking precision by an order of magnitude, the technique was practically worthless at sea.
Once the huge money was offered, there were many quack methods proposed such as setting semaphore relay stations at anchor all over the oceans or treating injured dogs remotely using some magical cloth, then synchronizing clocks to the dogÕs actions.
Many thought that a suitable, sea-worthy clock would also be out of the question, but this did not deter self-taught mechanical genius William Harrison and a few others who were working on the problems of clocks. Even big household and business clocks of his day were not very accurate until HarrisonÕs Ògridiron,Ó bearings, cleaning and calibrating techniques, and other methods were understood and adopted. The gridiron, in particular was the ingenious construction of a pendulum from two metals with different coefficients of expansion such that the pendulum produced would be insensitive to temperature variations to first order. This also worked with flywheels and other escapements.
HarrisonÕs story is, alas, more political than technical. Many celebrated breakthroughs have been made by those not within conventional wisdom (Galileo, Copernicus, Lindbergh, Wright) and Harrison was within this crowd. The Board of Longitude changed membership several times throughout its existence, but it was never more than mildly supportive of any clock making schemes. Nonetheless, they were often impressed enough with HarrisonÕs work to advance him considerable sums of money to live and work on while he perfected various iterations of his designs, some of which took many years. At the end of his personal journey, the Board was more hostile than average, however. Not only did they confiscate all his works and documentation as if they owned them due to all the cash advances given, but they abused and neglected the instruments. Only in the 20th century was any restoration done to these historic pieces. Some of them are unsalvageable.
HarrisonÕs son accompanied the H-4, an intricate clock that looked and operated similarly to a large pocket watch, on a couple of Atlantic crossing voyages in which the prize should have been won, sealed, and awarded, but his arch nemesis, Nevil Maskelyne, Astronomer Royale for decades and a proponent of the Òlunar method,Ó stalled and demurred Harrison on technicalities while giving awards to competing methods less well proven or useful.
Finally King George III (the same king who lost the AmericaÕs to the colonist revolutionaries) got involved, and after a long interview with Harrison declared that justice would be done. Not only this, but he took an interest in the timepieces himself and was involved in the daily monitoring of them at his personal observatory.
In the end, several techniques for finding longitude from shipboard could have met the prize criteria. The timepieces could have been used to bridge periods of bad weather while the astronomical ones could have been used to resynchronize the timepieces at opportune moments. Timepieces, however, coupled with the octant and then the sextant, made sea navigation safer and more profitable by orders of magnitude until the dawn of the radio and satellite eras.
Today, it is ironic that the way we navigate is a mechanical solution and it has astronomical components. Ordinary citizens with under a hundred dollars can obtain Global Positioning System receivers. These receive signals from GPS satellites, in any weather conditions, and use them to automatically triangulate. From the perspective of the receiver, the satellites are ÒastronomicalÓ, that is, in the heavens, but the system would not work were it not for the ultra accurate atomic clocks employed aboard each satellite. User knowledge of position and time is only as good as the accuracy of those clocks, converted through the speed of light to distance. State of the art today is real time positioning to a few meters accuracy (much better using certain assistance), and time to well under a microsecond.
I vaguely remember reading some complaining about the Harrison-biased tone that Sobel appears to take in this book. Perhaps it is true or perhaps we are hearing grumblings from modern partisans of ancient rivalries in these high stakes contests. I donÕt have problems with the narrative myself. It is much higher quality than other works IÕve read recently. This is a professionally written, illustrated, and produced work of value.
(Today, we offer prizes for flying to the edge of space without government help, and we wait for a winner this very year (2004). The stakes are higher than anyone knows, probably also the risks.)
So, as can be seen from this write up, I probably did get more out of the book than Viannah did. This is because I knew more about it going in and am intrinsically interested. IÕm glad, however, that she took the class and got anything out of it herself.