Who Invented the Computer? Lord Kelvin

Who Invented the Computer? This is the third installment in our ongoing series.

Churchill referred proudly to the British as an "Island race," and for good reason as they are completely reliant on the sea for transportation, commerce and defense. Indeed, until the advent of air travel and the building of the Channel Tunnel (more colloquially called the Chunnel), marine transport was the only way to reach Britain.

With the sea being so important, the Brits did their best to master it. Their notable maritime achievements include the world's first dry-dock (in 1496), its first wet dock (in 1715), and the Marine Chronometer to determine a ship's longitude at sea (in 1761).

Seafaring Englishmen even perfected the screw propeller design used to this day on maritime vessels everywhere. Even in 2020, the Brits have a fascination with the sea. If you include historical ships, there are nearly 300 maritime museums in Britain.

A Beautiful Mind

One Brit in particular, William Thomson (1824-1907) had an oversized positive impact on shipping, benefiting not only the British, but the entire world. Thomson is widely regarded as one of the 19th century's most eminent scientists.

During his lifetime, he published more than 650 scientific papers and made contributions to the fields of electricity, geophysics, thermodynamics and telegraphy. In 1866, Queen Victoria knighted him for his work on the transatlantic telegraph project, officially making him "Sir William."

If one title is good in Britain, then two are better. In 1890, Thomson was raised to the peerage for his most notable accomplishment: determining the correct value for the temperature of absolute zero (-459.67 degree Fahrenheit).

Henceforth, he would be known as "Lord Kelvin of Largs." (Largs being the name of his town and Kelvin the river next to his laboratory.) Absolute temperature measurements are still stated in "kelvins" in his honor.

Thomson's contribution to shipping — and ultimately to the development of computing — came in 1873 when he designed and built the world's first tide prediction machine. The machine was a special-purpose mechanical analog computational device that predicted the ebb and flow of sea tides and the irregular variations in their height. This was not an insignificant invention.

Much Ado About Tides

French astronomer Francois Arago called studying tides the "tomb of human curiosity." By that he meant it was an onerous and often frustrating endeavor requiring hour-by-hour observations of tides in a port. These measurements would be recorded preferably over at least a year, and the precise level of tides hand-calculated and published.

Prior to Thomson's invention, mariners everywhere relied on these tables to determine the best time to enter or leave a port. Unfortunately, hand-calculated tidal tables are inefficient and error prone, which often caused ships to have to wait to unload or take on cargo, or worse, find themselves caught in an ebb tide and eventually run aground.

The expansion of commercial shipping lines in the 19th century, increased the demand for quick and accurate tidal information.

Thomson's device consisted of a series of pulleys and wheels, each representing a different "constant" that influenced the tide in a certain port or region. For example: the largest wheel represented the Moon's gravitational pull on the Earth, others represented the distance of the Moon from the Earth, the gravitational pull of the Sun, the effects of shallow water and undersea shelves, and even coastal drift.

The constants were analyses of existing sets of measurements regularly conducted at British ports and then programmed into the machine.

When operating, each differently sized wheel rotated at a different speed. As the wheels turned around together, a thin tape of pure nickel travelled across them, measuring and summing up their movements to predict the tidal height and the precise times of high and low tides at a specific location.

The tide predictor also simultaneously graphed the predicted tides on a chart located at the bottom of the machine. So accurate was Thomson's machine that it could predict tides from hour-to-hour or day-to-day for a year or more.

A Rising Tide of Prediction

The tide predicting machine was a boon to British shipping and before long other nations were asking for their tides to be predicted as well. During the next five decades, improvements would be made on Thomson's design creating larger and faster tide predicting machines that improved shipping times worldwide and helped reduce the cost of ocean-transported goods.

The most famous predictor machine was built by Arthur Thomas Doodson in 1929. A more powerful model, Doodson's device could, over 30 days, calculate a year's worth of tidal levels for a particular port and could do this a couple of years in advance.

The most famous tidal prognostication to come from Doodson's machine was its use in assisting the Allied landings in Europe on D-Day at the height of World War II. To avoid disaster, it was essential that the troop transports hit the beaches at the most opportune low tide.

Interestingly, individuals who operated tide predicting machines were initially referred to as "computers." (Indeed, the word "computer" was widely used to describe human mathematicians acting in many different roles before it became commonly and primarily applied to machines.)

Tide prediction machines remained in widespread use until the early 1970s, eventually made obsolete by digital electronic computers capable of calculating tides in a fraction of a second (and with even greater accuracy).

For a machine that had such an impact on shipping, surprisingly few were ever built. No one is certain exactly how many were constructed, but historical consensus puts the number somewhere between 25 and 36. Many are accounted for and on display in museums around the world, and most of those are still in working order.

The Doodson model is currently on display at the National Oceanography Center in Southampton, England. To read an excellent inventory of tide predicting machines with photos and descriptions, click here.

Note: Lord Kelvin also has a key role in our next installment, in which we learn about the impact of the tidal prediction machine on the development of the differential analyzer.