George Gabriel Stokes
1819 - 1903
Lucasian Professor of Mathematics, Cambridge
Sir George Gabriel Stokes, First Baronet, physicist and mathematician, was born on 13 August 1819 in Skreen, County Sligo, Ireland. He was the youngest of eight children born to the rector of Skreen, Gabriel Stokes (1762–1834), and Elizabeth Haughton, the daughter of John Haugton, the rector of Kilrea, County Londonderry. The family lineage on the Stokes side includes various rectors, mathematicians and physicians, including Gabriel Stokes, a renowned Irish engineer born in 1680 who authored a treatise on hydrostatics.
George Stokes was first formally educated at thirteen, in Dublin, and was sent to England for further schooling two years later. There he studied at Bristol College, and according to one of his obituary writers and colleagues, John William Strutt Rayleigh (Lord Rayleigh), he was deeply influenced by the mathematics master at the college, Francis Newman, brother to Cardinal Newman. At Bristol, Stokes studied a curriculum that included pure mathematics, Newton’s Principia, hydrostatics, optics and astronomy, all topics that Stokes would devote his career to later in life.
According to Lord Rayleigh, Stokes had been a tempestuous and, sometimes, violent child; his arrival in Bristol marked a turn toward placidity—a character trait that would remain with him throughout his life. As Stokes’s ship sailed to Bristol, it nearly overturned in stormy weather; his older brother, who had accompanied him, later told Rayleigh that Stokes had remained cool and collected throughout. From that point onward, the story goes, Stokes was known for his calmness and, even, timidity, often only giving one word responses like ‘yes’ or ‘no’ to questions that seemed to demand greater complexity. Yet, Rayleigh notes that when asked for his opinion directly, Stokes was known to give elaborate and loquacious accounts of his personal views.
Stokes matriculated at Pembroke College, Cambridge, in 1837, and never left. At Cambridge he not only immersed himself in the typical curriculum of the day, which focused on pure mathematics, Newtonian gravitational theory and the new undulatory theory of light, but Stokes’s contemporary biographer, David B. Wilson, also claims he was introduced to the theological works of William Paley, whose books, Evidences of Christianity and Moral Philosophy—imbued as they are with arguments from Design—later appear as themes in Stokes’s Gifford Lectures.
Stokes studied for the Cambridge Tripos examination in mathematics with tutor William Hopkins. He graduated Senior Wrangler in the exam (the top student in the class) and first Smith’s prizeman, both prestigious accolades. He was immediately offered a fellowship at Pembroke College upon completion of his studies, and he became the Lucasian Professor at Cambridge in 1849, a post previously held by Newton, and one which Stokes held until his death in 1903. At the time of his appointment to the Lucasian chair, Stokes took up teaching natural science and physics at the Government School of Mines in London to supplement his income.
From then on, his life became a hectic mélange of researching and publishing. Various colleagues later wrote there was almost no topic in physics which Stokes did not meddle with, publish on, or lecture in throughout his lifetime, the sole exception being electricity. In particular, Stokes focused on optics, friction in fluids, fluorescence (a phenomena he named and explained as the product of light whose wavelength had changed as a result of the substance it had been refracted from), planetary orbits and the ‘mysterious’ luminiferous ether, as Stokes called it. Stokes spent a great deal of his life researching the nature of this ether, which he ultimately concluded was analogous to a jelly-like substance pervading the entire universe. Like jelly, it was solid enough to transmit light rays through it (since the theory was that light rays could not travel in a vacuum), yet it was fluid enough to allow the planets to orbit through it. By the middle of the century, Stokes was a widely demanded lecturer.
Stokes wrote various papers commenting on, criticising, and developing ideas first proposed by French mathematicians such as Lagrange, Laplace, Fourier, Poisson and Cauchy. His interest led him to advocate changes to Cambridge’s Tripos exam system to include more continental mathematics. This focus led some colleagues to label him a mathematician of the French tradition. However, it is generally acknowledged the papers Stokes wrote on mathematical topics were deeply related to his physical experiments. Stokes argued mathematics was, and always would be, secondary to physical experimentation in terms of developing scientific knowledge. While math could help describe and formalize our observations, he claimed, it alone could not prove anything about the various phenomena we observe.
As part of his experimental drive, Stokes helped to set up the Cavendish laboratory in the mid 1880s. The lab aimed at directing more of Cambridge’s bright young minds to experimental issues in physics, rather than solely pure mathematics. Stokes declined to take up leadership of the new laboratory, telling his friends he was too old to take on new experimental projects. As a result, the laboratory, started in 1884, was first run by J. J. Thomson (who went on to develop a theory of atomic structure with Ernest Rutherford).
Stokes was often considered the authority on questions of optics, in particular the functioning of the eye and the refraction of light waves in the eye’s structures. Yet, he never ended up writing a final treatise on the subject, though his colleagues long expected one from him. His personal friend and lifelong colleague, Sir William Thomson, or Lord Kelvin (the physicist who created the Kelvin scale of temperature), lamented that Stokes’s various administrative duties had taken up too much of his time, and had restrained him from publishing the treatise and other works. Those duties were great, indeed. To mention only a few, Stokes was secretary of the Royal Society of London for thirty years prior to being its president for five, he represented Cambridge University as a parliamentarian at Westminster from 1887 to 1891, and he was the president of the Victoria Institute (created in 1865 to explore the relationship between religion and science) from 1886 to 1903.
Yet, although his opus on optics never came to fruition, Stokes did not fail to publish copious amounts on various intriguing topics throughout his lifetime. In the early 1840s he calculated the maximum height of various massive waves in the ocean; in 1849 he wrote two papers on variable gravitation on the Earth’s surface, which is said to have reformed the science of geodesy. While it was known that the force of gravity differed depending on where a person was on Earth, Stokes claimed that this was not dependent upon the interior composition of the Earth, which had been assumed to be the case up until then. About the same time, he published a paper on the internal friction of fluids (viscosity). Stokes calculated the effect of friction on a swinging pendulum; he also determined why clouds hang in the air as they do. He claimed that every falling object hits a terminal velocity when the pull of gravity downwards is offset by the friction the body experiences with the air. Because water droplets are so tiny, their fall to the Earth is offset by the friction of the air around them; thus, clouds are suspended water particles. It was this work on the friction internal to fluids which led Stokes to his conclusion that the luminiferous ether was jelly-like in nature. In later years Stokes also provided answers to questions such as: why are sounds harder hear when we stand upwind? How it is that sound vibrations travel from a vibrating body to surrounding gas? And, what is the nature of Röntgen rays (also called X-rays)?
Throughout, Stokes remained deeply religious. Just over a decade before he died, Stokes delivered his Gifford Lectures, published under the title Natural Theology. But his religiosity did not initially save him from loneliness and despair. Following his engagement to Mary Robinson, daughter of Dr. Romney Robinson, astronomer of Armagh, Stokes wrote a fifty-seven-page letter to his betrothed expressing regret for what he felt was his inability to love passionately due to the nature of his scientific life. He wrote that he hoped she could save him from the dreary loneliness of his duties. Just a few weeks prior to the wedding, he wrote again offering Mary the chance to renege on the engagement if she liked: ‘It is right that you should even now draw back, nor heed though I should go to the grave a thinking machine unenlivened and uncheered and unwarmed by the happiness of domestic affection.’ They did marry, however, producing five children—two of whom died in childhood and one of whom, a physician, died at thirty. Stokes’s final years were spent living with his daughter, Isabella Lucy, who wrote a laudatory memoir of her father following his death. Stokes died on 1 February, 1903, and was buried four days later in Mill Road cemetery, Cambridge.
Stokes’s major publications include: Mathematical and Physical Papers, 5 vols. (1880–1905); On Light: delivered at Aberdeen University: Burnett Lectures (1887); Natural Theology, 2 vols. (1891, 1893); ‘The Annual Address of the Victoria Institute: The Perception of Light’ (1895); Röntgen Rays: Memoirs by Röntgen (1899); Memoir and Scientific Correspondence of the Late Sir George Gabriel Stokes (1907).
University of Edinburgh