William Thomson – 100 years beyond absolute zero

William Thomson (1824-1907)

Today marks the 100th anniversary of the passing of William Thomson, aka the 1st Baron Kelvin.

Thomson (1824–1907) was a distinguished Scottish physicist, engineer and entrepreneur, and is known today for the temperature scale named after him.

When you hear of the term “absolute zero”, this is zero Kelvin (0 K), which is equivalent to –273.15°C. It is the temperature at which atoms have no kinetic energy, and everything becomes absolutely still. It is physically impossible to cool matter to absolute zero.

As well as thermodynamics, Thomson worked on electrical standards, and developed the Kelvin balance used for the precise specification of the ampere, the standard unit of electric current.

Thomson’s thermodynamic calculation of the age of the Earth proved to be wrong, but it was carried out before the development of nuclear physics, and the realisation that much of the planet’s internal heat comes from the radioactive decay of unstable isotopes. The calculated age of 20–40 million years was still four orders of magnitude greater than that derived from the bible. But ignoring the complaints of religious fundamentalists, the major problem with Thomson’s estimate was that it contradicted Charles Darwin’s evolutionary theory, and Charles Lyell’s ideas about gradual geological change.

Notable gaffes include the pronouncement that “Heavier-than-air flying machines are impossible.”, made just eight years before Orville and Wright’s maiden flight in 1903. Thomson also predicted that “Radio has no future.” My home WiFi router is named KelvinNet, in honour of the canny Scot.