Among his many scientific achievements, George Stokes, from Co Sligo, coined the term fluorescence, writes John Moore
As a tribute to one of Ireland's greatest 19th-century physicists, George Gabriel Stokes, the Royal Irish Academy last week held a centenary conference to celebrate his life and works. Ten scientists from the US, UK, Denmark and Ireland spoke about on Stokes, discussing his enormous contribution to science and mathematics.
Stokes, who was born in 1819 and died in 1903, was never fully recognised in Ireland. Yet he occupied the chair of mathematics once held by Sir Isaac Newton and now held by Stephen Hawking, so the academy's tribute is well and truly deserved.
The son of a Church of Ireland rector, Stokes was born in Skreen, Co Sligo, on August 13th, 1819. He received his early education in Sligo and Dublin before being sent to England, where he entered Pembroke College in Cambridge as an undergraduate in 1837.
After he graduated in 1841 as senior wrangler - that is, placed first in mathematics in the whole university - Pembroke recognised his extraordinary talent and immediately gave him a fellowship.
Much of Stokes's extensive reputation was gained early in his academic career, through work on the theory of viscous fluids from 1845 to 1850. He systematically and independently derived the equations of motion for the internal friction of fluids and deduced further equations of motion for the behaviour of waves in elastic solids.
His now famous Stokes' law, which determines the movement of a body through viscous fluids of various densities, formed the basis for solving an important experiment involving the charge on the electron, performed by the American physicist Robert Millikan between 1909 and 1913.
"He had an amazing dedication to his subject," says Prof Alastair Wood of the school of mathematical sciences at Dublin City University, who is writing a biography of Stokes and gave one of the academy's talks about Stokes's family background, early life and education. "He was extremely seriously minded, a man of few words, and his colleagues all seemed to warm to him, particularly his great friend for 40 years, Lord Kelvin, who at his graveside oration said that his heart was in the grave with Stokes."
Stokes's theoretical and experimental investigations over the following years covered a wide variety of physics. His papers show how he tailored pure mathematics to his needs in solving them. In 1852, for example, he received the Rumford Medal for the first explanation of fluorescence - a term he coined. He later used it to study ultraviolet spectra.
In the same year, while analysing elliptically polarised light, he produced one of his most important contributions to mathematics, called the Stokes parameters.
"In modern atomic and optical physics, the Stokes parameters' description is still the standard way to describe the light emitted in an experiment," says Dr Nils Andersen of the Niels Bohr Institute at the University of Copenhagen, who also spoke at the conference.
Stokes's influence can still be seen in modern textbooks of mathematics, physics and engineering, where we find the Stokes theorem, Stokes phenomenon, Stokes line, Stokes conjecture and Navier-Stokes equations.
One of the main reasons why Stokes isn't generally known is that he spent most of his life and produced most of his work outside Ireland. He maintained family links, however, regularly visiting his brother, John Whitley, in Co Tyrone, his sister, Elizabeth Mary, in Malahide, Dublin, and his father-in-law, Dr Romney Robinson of Armagh Observatory, until Stokes's death in 1903. He was buried in Cambridge.