Maybe they were moonlighting …

In contrast to his last article, John Frewen-Lord takes a look this week at some of the activities of seven famous people who later had SI units of measurement named after them.

It is well known that many measurement units of the International System (SI) are named after prominent scientists and others in the scientific community who contributed to the area of scientific knowledge to which the unit relates. What is less well known is that many of these had alternative careers – in fact, these alternative careers might well have been their main occupation and source of income, and their scientific endeavours were secondary or supplementary to their main work in life.

The following shows some of these occupations that had little to do with the SI units that bear their names:

Sir Isaac Newton: Newton, after whom the SI unit of force is named, is regarded as one of the most influential scientists of all time, and is of course most famous for establishing the laws of motion and gravitation and for inventing calculus. What is not often realised is that Newton also was in charge of the Royal Mint. In 1717, Newton, formerly Warden and now Master of the Mint, unofficially moved the Pound Sterling on to the Gold Standard from Silver. It was for his work at the Mint that Newton received his knighthood and it was there that he spent his final years, dying at the ripe old age of 84.

James Watt: While we often (erroneously) think of James Watt as the inventor of the steam engine, this was not his initial career direction. He started out as an instrument maker, producing scales, rulers, compasses, quadrants and the like, even telescopes, eventually teaming up with a business partner, John Craig. In fact, Watt, after whom the SI unit of power is named, had some of his astronomical instruments installed in the McFarlane Observatory at the University of Glasgow. It was not until he sold this business to an employee after Craig had died that he turned his attention to improving (but not actually inventing) the steam engine, patenting the condensing steam engine in 1765. During this work, Watt started to establish some of the early principles of thermodynamics. He did devise a unit of power – the horsepower, about 750 W.

Blaise Pascal: Pascal, born in Clermont-Ferrand, France, is famous for his work involving pressure and vacuum, especially the study of fluid dynamics. For this reason, the SI unit of pressure is named after him. But Pascal is also famous for inventing the world’s first calculating machine, in 1642, and went on to manufacture a considerable quantity of such machines, each one improving on the one before. He also dabbled in many other fields – mathematics, the probability theory that to this day underpins modern economics, social sciences, philosophy and theology, which resulted in some studies espousing his somewhat controversial religious beliefs. He must have been a very busy man, for he died at the relatively young age of 39.

William Thomson (aka 1^st Baron Kelvin): Thomson started out as a physicist and then moved into electrical studies. Becoming Baron Kelvin in 1892, and after whom the temperature unit the kelvin is named, he could look back on a very varied career. His early work at the University of Glasgow involved the mathematical analysis of electricity in the 1840s. As an electric telegraph engineer and inventor, his work made possible the first functioning transatlantic telegraph, for which he was knighted by Queen Victoria. Best known for accurately measuring absolute zero (-273.15 °C), he was also Professor of Natural Philosophy for over 50 years at University of Glasgow. Just to round out his many and varied activities, Thomson also acted as vice-chairman of the board at the British operation of Eastman Kodak, a position he was still holding upon his death in 1907 at age 83.

James Prescott Joule: In spite of a last name that sounds distinctly French, Joule was born in Salford, in greater Manchester. The son of a wealthy brewer, the young James Prescott became manager of the family brewery – his already keen interest in science (especially electricity) was nothing more than a hobby at this point in his life, and relegated to his spare time. It was, however, the necessity of improving the efficiency of the brewery that led Joule, after whom the SI unit of energy or work is named, into the realm of physics involving electricity, energy, work and heat. Joule slowly became ever more obsessed in analysing the varying effects of heat, and how it could be measured in terms of a mechanical equivalent, such that he started to take less and less interest in the running of the brewery, and instead concentrated on producing ever more scientific papers and theories. In 1841, he established the relationship between electrical current through a wire and its heat loss, later known as Joule’s law.

Michael Faraday: Lending his name to the SI unit of electrical capacitance, the farad, Michael Faraday was actually a chemist, not a physicist. His discoveries include that of benzene in 1825, while he is also credited with inventing the Bunsen burner. His work in chemistry resulted in his becoming Fullerian Professor of Chemistry at the Royal Institution in London. Additionally he served as deacon for his church, an offshoot of the Church of Scotland. It appears that Faraday transferred his attentions to electricity after discovering the laws of electrolysis during his chemistry work.

Charles-Augustin de Coulomb: Like many of his contemporaries noted above, Coulomb, after whom the SI unit of electrical charge is named, seemed to discover his famous law as an incidental consequence of his main areas of interest. Although he was a physicist, his work encompassed a huge variety of subjects – philosophy, language, literature, mathematics, astronomy, chemistry and botany, all of which he studied at Collège Mazarin in Paris. Adding to this breadth of expertise was his work in civil and structural engineering (his name is one of 72 inscribed on the Eiffel Tower), soil mechanics and geotechnical engineering, positions that he was employed in for over twenty years. He gradually turned his attentions into studying electricity, and it was his work on electrical forces that resulted in Coulomb’s Law. While in Paris in the 1790s, he took part in the French revolutionary government’s determination of weights and measures – the only one of these eminent scientists to actually be directly involved in that field.

There were, of course, other scientists, for example Volta, Ampère, Gray (another Briton, although not as well known as the five discussed above) and Tesla, whose careers were almost completely dedicated to the work that gave rise to the SI units named after them, that is the volt, amp, gray and tesla.

In this brief article, we have omitted eight or so other scientists distinguished by eponymous SI units. Perhaps readers may wish to comment on their achievements and careers. Were any of them moonlighters too?

There aren’t many areas in the field of metrology that might give rise to new SI units. Anyone moonlighting at present in the hope of seeing their name appear against a unit in the next edition of the Système Internationale brochure is likely to be disappointed, but who knows?