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Longitude : Harrison's clock
Dava Sobel’s book “Longitude” is an entertaining and informative tale of the work of John Harrison, inventor of the chronometer, and its relevance to solving the worldwide problem of accurately calculating ‘Longitude’.
Sobel’s story also provides a wonderful illustration of three key ideas around the invention of new technology.
Firstly, the dramatic shift in thinking "From Nature to Machine" as a reflection of the shift from the Agricultural Age to the Industrial Age.
Secondly, Sobel highlights 'The Impossibility of Invention'.
Thirdly, we map Harrison's process as 'The Path of Innovation'.
Before we look at these three key ideas, let’s start with an overview of the significance of the ‘Longitude’ problem.
Background
Today when we look at a globe of our planet, we may notice the artificial lines that trace its surface, the lines of latitude running parallel to the equator and the lines of longitude that arc between the poles. For those of us that travel by armchair or commercial airlines, these lines will have no meaning and limited value. They neither inspire us or enhance our journey in any way.
For the pilots of our planes and the computer navigation systems, these lines are the key to getting from A to B, from London to New York, from Sydney to Nairobi.
For the great explorers of the last millennium, who effectively left their countries behind to literally travel to uncharted waters, these directional lines were crucial to either finding a new land or losing track of one’s place on the planet. In some cases, navigational error cost numerous lives as ships ran aground, sources of food and water were missed, cargoes were lost and opportunities to claim new territories were wasted.
Sobel cites the inglorious example of the British Navy and the loss of two thousand men as four British warships sank upon the rocks of the Scilly Isles in the fog one night in 1707. Their failure to accurately chart their longitude and therefore know their precise location was the cause of their demise.
Loss of life was one thing, economic loss was another. The loss of ships, merchants, cargo and treasures unsettled empires to such an extent, the British Parliament in 1714 established the Longitude Act and a healthy prize to prompt a solution. Other countries and regions such as Spain, France, the Netherlands and Tuscany also offered prizes. Calculating Longitude was considered to be a key competitive advantage in owning the seas and the treasures it could provide. The Longitude problem had existed for centuries and now the race was hotting up to find a solution.
Calculating latitude was a relatively easy task. This could be accomplished through measuring the length of the day, the height of the sun or in reference to known stars seen in the night sky. Columbus’ famous voyage to America was simply plotted as ‘sailing the parallel’ directly east.
The measurement of longitude meridians was a different matter and was totally reliant on the measurement of time. The key to knowing your longitude was to know the exact time in known places of known longitude. The time difference was then calculated into a geographical location. Errors in the measurement of time were multiplied into errors in the measure of your location.
At the time, clocks were not suited to the task because they simply weren’t accurate enough or stable enough to counter the swaying decks on a ship in the ocean. More importantly, clocks had not been designed to counter variations in temperature that effected the components and the accuracy of the timepiece.
Today, we have the luxury of being able to buy a wristwatch for less than $10 that loses less than a second each month. In contrast, in the mid 1500’s, the best available timepieces were only accurate to within 15 minutes per day. This would be considered completely unacceptable today and it was hardly suitable either for a long ocean voyage that required days of extrapolation of minutes and seconds to determine the longitudinal location.
Furthermore, the design of these clocks were based upon the pendulum which was made them even less suited to the rolling deck of a sailing ship.
To put it in context, solving the ‘Longitude’ problem had been such a concern for such a significant period of time that it was considered to be a holy grail, akin to developing a perpetual motion machine. For many, a solution was considered impossible. Sobel describes the problem as the great technological question of the time, comparable in today’s terms to finding a cure for cancer.
In solving the problem of longitude, this was considered by some to have been the key advantage that enabled the British to create their worldwide Empire.
Further Articles in the Longitude series
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