Kelvin, Lord

William Thomson was born on June 26, 1824, in Belfast, Northern Ireland, as the fourth child of James and Margaret Thomson. At that time his father was Professor of Mathematics at the Royal Academical Institution of Belfast. When Kelvin (although he only received his peerage in 1892, I’ll use this name retroactively) was six years old, his mother passed away, thereby leaving the home-education of the children to father James. Two years later (1832) professor James Thomson was offered the Chair of Mathematics at the University of Glasgow and the whole family relocated to Glasgow, Scotland. Kelvin proved himself such a prodigy that at the young age of ten he attended the University of Glasgow where he excelled in Mathematics and Physical Science.

In 1841 at age 17, he left Glasgow University and went to Cambridge where he completed his Mathematical Tripos (honours degree at Cambridge) in 1845 and became second wrangler, i.e. he was the second-highest-scoring student. Following a short trip to Paris, he accepted a post as College Lecturer in Mathematics at Cambridge. Although he was only 21, he had established himself with an impressive reputation for his knowledge and understanding of mathematical physics. In 1846 he was offered, and accepted, the Chair of Natural Philosophy at Glasgow University – where his father still held the Chair of Mathematics. Kelvin would hold this position for the next 53 years till he retired in 1899 at the age of 75.

Kelvin is obviously remembered for his 1848 invention of the absolute scale of temperature. Although he called this the “absolute scale”, it was renamed the Kelvin scale after his death. Kelvin explained that when the temperature of a gas is reduced, its atoms’ energy level is reduced also. When this energy level reaches zero – i.e. the atoms stop moving – the temperature cannot be lowered any further. The French physicist Jacques Charles had worked out that for every degree Celsius below zero of cooling of a gas its volume would be reduced by a factor 1/273.16. Kelvin showed that this would be true for any substance and defined -273.16°C as the absolute zero of temperature. This lowest possible temperature (0 °K) equates to -273.16°C in Celsius and to -459.69°F in Fahrenheit.

The trans-atlantic cable

Although the first submarine cable between France and England was laid in 1850, it was not until 1857 before an attempt was made to lay a cable across the Atlantic. The 2500 nautical miles of cable was manufactured in two halves by two different companies, resulting in the now classical blunder of one half being right-hand lay manufactured while the other half was done in left-hand lay. As this would obviously result in a slow untwisting once the cable halves had been joined, engineers had to come up with a solution to keep the splice tight. However, the 1857 attempt was unsuccessful.

A new attempt was made in 1858, but this cable failed after only 28 days. Kelvin, who had been roped in to assist with the project, realised that this was caused by the heavy current sent through the cable, as was the custom in landlines. His invention – the mirror galvanometer – enabled a tiny current to be sent across a long-distance deep-sea cable and to be visible to the operator at the other end. Thus Kelvin played a crucial part in the attempt of 1866 when an 1896 mile long cable was laid. Following this successful attempt, Kelvin was awarded a knighthood by Queen Victoria and became Sir William Thomson.

Where the cables of yesteryear were gutta-percha insulated copper wire inside a protective outer layer, modern cables are based on optical fibre. Without a reliable cable network spanning and interconnecting all continents, the internet of today would not be able to function.

Kelvin’s tide predictor, an analog computer

Kelvin was a keen yachtsman and he spent many hours on his sailing yacht Lalla Rookh. Hence it comes as no surprise that he took a great interest in the tides of the coastal waters of Scotland, not only as a yachtsman, but also because of his interest in the mathematical background in the calculations of tides. As he stated in his 1882 evening lecture to the British Association “I shall therefore define tides thus: Tides are motions of water on the earth, due to the attractions of the sun and of the moon,” but its exact behaviour on any spot on the coast is strongly affected by the shape of the coastline and the profile of the seabed. So, although the forces that cause and influence tides were well understood, one needed to collect data regarding the tides at a certain spot over a certain period of time and then use that data to calculate and predict future rise and fall of tides at that spot. Using a method, called “harmonic analysis”, the complex curve of the tidal gauge measurements was broken down into the separate curves representing the effect of time, moon, sun, etc. Or as Kelvin lectured: “The exceedingly complicated motion that we have in the tides is analysed into a series of simple harmonic motions in different periods and with different amplitudes or ranges; and these simple harmonic constituents added together give the complicated tides.” This work required substantial calculations to be done by a person employed for that specific purpose. Interestingly, Kelvin used the term “calculator” for this type of person.

He continues: “All the work hitherto done has been accomplished by laborious arithmetical calculation; but calculation of so methodical a kind that a machine ought to be found to do it.”

Using a system of pulleys, wires and dials, Kelvin designed a tide-predictor in 1876. The dials were used to set the oceanographic and astronomical data of the coastal harbour. The results were printed in curve format on a long strip of paper. On cranking its handle, the machine – an early analog computer – calculated and printed the harbour’s tide patterns for up to a year in only four hours. The machine proved the feasibility of replacing calculations performed by people with computations by a machine.

In 1892 Queen Victoria conferred a peerage on William Thomson and he assumed the title Baron Kelvin of Largs. “Kelvin” was derived from the river Kelvin which flows through the grounds of Glasgow University while “of Largs” referred to his country home Netherhall in the popular seaside town of Largs on the Firth of Clyde about 50 km from Glasgow. The title died with him as he left neither heirs nor close relatives.

Glasgow has honoured its famous son by naming the Kelvin Hall after him. It is a large exhibition centre, opened in 1927, used for arts and sport events. Apart from housing the Glasgow Museum of Transport it also has its own post office.

Kelvin died on December 17, 1907, while at home in Largs. He was buried with national honours one week later in Westminster Abbey, his grave being next to that of Sir Isaac Newton.

© Wobbe Vegter, 2007