James Thomson's Birthday

James Thomson was born February 16, 1822 in Belfast Ireland, he was the first son of James and Margaret Thomson. His mother, Margaret Gardner Thomson died in 1830 so his father James raised their seven children alone. In 1832 his father took up the Chair of Mathematics at Glasgow University and two years later at the age of twelve James and his younger brother William began studying at the university. James graduated in 1839 and began his apprenticeship as a civil engineer but do to health reasons decided he was not cut out for the hard physical labor common to civil engineers of the day. So beginning around 1843 he devoted himself to inventing machines and theoretical studies making many contributions to physics and engineering. He was living in Belfast when in 1857 he became Professor of Civil Engineering at Queen’s College. He stayed in Belfast until 1873 when he accepted the Glasgow University Regius Chair in Civil Engineering. He remained at the University of Glasgow until 1889 and died May 8, 1892.

While James Thomson had many achievements including helping his brother William (Lord Kelvin) he caught my eye because of the radian. The term radian was used in print for the first time by James on June 5, 1873 in examination questions he wrote at Queen’s College. He also helped spread the adoption of this unit of measurement in consultations with other scientists and engineers. (See A History of Mathematics By Florian Cajori, page 484) He is also credited with the invention of the non-SI unit the poundal.

The radian is the SI derived unit of measurement for a plane angle. Most people are more familiar with degrees for measuring angles however, the radian is extremely important because it encapsulates the value of PI. PI, the ratio of a circle’s circumference to its diameter is an irrational real number that can create a mess in formulas when degrees are used for the angle measurement.

So, lets raise a glass and toast James Thomson, MA, DSc, LLD, FRS for being a giant on who’s shoulders we can all stand!

References and further reading:
Dictionary of Ulster Biography
Who, Where and When: The History & Constitution of the University of Glasgow [pdf]
His father
1911 Encyclopedia Britannica
1911 Encyclopedia Britannica

The radian
Angle measurement
Radian Measure
A History of Mathematics By Florian Cajori
Origin of Radians