George Gabriel Stokes

George Stokes
File:Gstokes.jpg Sir George Gabriel Stokes, 1st Baronet
Born	13 August 1819 Skreen, County Sligo, Ireland
Died	1 February 1903 Cambridge, England
Residence	England
Nationality	Irish
Field	Mathematician and physicist
Institutions	University of Cambridge
Alma mater	University of Cambridge
Academic advisor	William Hopkins
Notable students	;
Known for	Stokes' law Stokes' theorem Stokes line Stokes relations Stokes shift
Notable prizes	Rumford Medal (1852) Copley Medal (1893)
Religious stance	Evangelical protestant
Stokes did not have a doctorate, however William Hopkins is considered to be his equivalent mentor.

Sir George Gabriel Stokes, 1st Baronet (13 August 1819–1 February 1903) was an Irish mathematician and physicist, who made important contributions to fluid dynamics, optics, and mathematical physics. Stokes had strong religious convictions, and sided with the creationists in the debate over the validity of Charles Darwin's theory of evolution.

Life

George Gabriel Stokes was the youngest of eight children of the Reverend Gabriel Stokes, rector of Skreen, County Sligo, and Elizabeth Haughton. Stokes was raised in an evangelical Protestant home. This, perhaps, was influential in his later siding with creationists against Charles Darwin's emerging theory of evolution at the end of the 19th century.

Education

Stokes's childhood home, to which he often returned in later years, was near the water, and some speculate that it was his exposure to the sea in his early years that later gave rise to Stokes's research on waves and fluid flow. Stokes was first tutored by a church clerk, but at the age of 13 was sent to a school in Dublin for a more formal course of education. Stokes's father died in 1834, but his mother secured the financing to send him to Bristol College. His mathematics teacher there was Francis Newman, the brother of Cardinal Newman.

In 1837, Stokes transferred as an undergraduate to Pembroke College at the University of Cambridge, where his brother William, breaking with the family tradition of attending Trinity, had studied. On graduating as senior wrangler and first Smith's prizeman in 1841, Stokes was elected to a fellowship at the college.

Research and discovery

Stokes published his first paper in 1843, "On some cases of fluid motion," and expanded on this theme in a subsequent paper in 1845. In 1849, be became Lucasian Professor at Cambridge, where he lectured on hydrostatics and optics. The next year, he published a paper on the relationship of internal friction of air and the motion of a pendulum. In 1851, Stokes was elected to membership in the Royal Academy. He won the society's Rumford Medal a year later for his paper on the refrangibility of light.

Stokes became a secretary for the Royal Society in 1854, a post he would hold for many decades before becoming president of the society in the 1880s. Around this time, he also accepted a chair at the School of Mines in London. In 1857, he married Mary Susannah Robinson, the daughter of an astronomer. His marriage prevented him from continuing at Pembroke, according to the rules of that institution. The rule regarding celebacy was later revoked, and 12 years later, Stokes was reinstated.

During their courtship, Stokes is said to have written Mary Susannah a letter of concern, as his habit was to work into the early morning hours on physics and mathematics problem, and he wondered if this kind of effort would be consistent with a happy family life. After their marriage, the Stokeses moved to Lensfield Cottage, where Stokes set up a small makeshift laboratory. The cottage would serve as Stokes' residence for the remainder of his life.

The famous physicist William Thomson, Lord Kelvin, who was a close associate of Stokes, had discovered the somewhat obscure work of George Green, who died in 1841, and managed to expand upon one of Green's theorems, proving it in three dimensions. Stokes is said to have posed the proof of Kelvin's theorem as an examination question, and it henceforth became known as "Stokes's theorem."

The massive administrative tasks that Stokes undertook brought forth calls from his closest colleagues, such as Lord Kelvin, to find a position where he could devote more of his time to research. He paid little heed to these kind reproaches. Most of his time was taken up in adminstrative work and teaching. As he had pledged, once entrusted with the Lucasian chair, to devote his time to assist any unversity student who needed help, many investigators later depended on his feedback in shaping their research.

Later life

In 1886, Stokes, who was a religious man throughout his life, was appointed president of the Victoria Institute, which explored the relationship between religious doctrine and the findings of science. Stokes held this position until his death. Stokes was a religious man, and his faith often affected even his professional decisions. He sided with Lord Kelvin and other scientists of his day in their critical view of Charles Darwin's theory of evolution.

Sir George Stokes, who was made a baronet in 1889, further served his university by representing it in parliament from 1887 to 1892 as one of the two members for the Cambridge University. During a portion of this period, from 1885 to 1890, Stokes also served as president of the Royal Society. Thus, being at the same time Lucasian professor, he united in himself three offices which had only once before been held by one man, Sir Isaac Newton, who, however, did not hold all three simultaneously.

Stokes died February 1, 1903 in Cambridge. He was buried in the Mill Road cemetery.

Contributions to science

The motion of fluids

His first published papers, which appeared in 1842 and 1843, were on the steady motion of incompressible fluids and some cases of fluid motion. These were followed in 1845 by one on the friction of fluids in motion and the equilibrium and motion of elastic solids, and in 1850 by another on the effects of the internal friction of fluids on the motion of pendulums. To the theory of sound he made several contributions, including a discussion of the effect of wind on the intensity of sound and an explanation of how the intensity is influenced by the nature of the gas in which the sound is produced. These inquiries together put the science of hydrodynamics on a new footing, and provided a key not only to the explanation of many natural phenomena, such as the suspension of clouds in air, and the subsidence of ripples and waves in water, but also to the solution of practical problems, such as the flow of water in rivers and channels, and the skin resistance of ships. His work on fluid motion and viscosity led to his calculating the terminal velocity for a sphere falling in a viscous medium. This became known as Stokes' law. Later the CGS unit of viscosity was named a Stokes after his work.

The Navier-Stokes equation gets its name from Stokes and Claude Navier, who in 1822 published the equations of motion of an incompressible fluid. In his 1845 paper, Stokes improved on Navier's analysis by inserting a different explanation for the internal friction of fluids, making the derivation of the equation more credible. The equation shows how forces acting both upon and within a fluid determine velocity at different points in the fluid.

Properties of light

Perhaps his best-known researches are those which deal with the wave theory of light. His optical work began at an early period in his scientific career. His first papers on the aberration of light appeared in 1845 and 1846, and were followed in 1848 by one on the theory of certain bands seen in the spectrum. In 1849 he published a long paper on the dynamical theory of diffraction, in which he showed that the plane of polarization must be perpendicular to the direction of propagation. Two years later he discussed the colors of thick plates.

In 1852, in his famous paper on the change of wavelength of light, he described the phenomenon of fluorescence, as exhibited by fluorspar and uranium glass, materials which he viewed as having the power to convert invisible ultra-violet radiation into radiation of longer wavelengths that are visible. The Stokes shift, which describes this conversion, is named in Stokes' honor. A mechanical model, illustrating the dynamical principle of Stokes' explanation was shown. The offshoot of this, Stokes line, is the basis of Raman scattering. In 1883, during a lecture at the Royal Institution, Lord Kelvin said he had heard an account of it from Stokes many years before, and had repeatedly but vainly begged him to publish it.

In the same year, 1852, Stokes published a paper on the composition and resolution of streams of polarized light from different sources, and in 1853 an investigation of the metallic reflection exhibited by certain non-metallic substances. About 1860 he was engaged in an inquiry on the intensity of light reflected from, or transmitted through, a pile of plates; and in 1862 he prepared for the British Association a valuable report on double refraction, which marks a period in the history of the subject in England. A paper on the long spectrum of the electric light bears the same date, and was followed by an inquiry into the absorption spectrum of blood.

The identification of organic bodies by their optical properties was treated in 1864; and later, in conjunction with the Rev. William Vernon Harcourt, he investigated the relation between the chemical composition and the optical properties of various glasses, with reference to the conditions of transparency and the improvement of achromatic telescopes. A still later paper connected with the construction of optical instruments discussed the theoretical limits to the aperture of microscope objectives.

Fluorescence

In the early 1850s, Stokes began experimenting with filtered light. He passed sunlight through a blue-tinted glass, and then shone the beam through a solution of quinone, which has a yellow color. When the blue light reached the quinone solution, it produced a strong yellow illumination. Stokes tried the same experiment with the solutions of different compounds, but found that only some showed an illumination of a color different from that of the original light beam. Stokes named this effect fluorescence.

Spectroscopy

Stokes's published work by no means represents the whole of his services in the advancement of science. Many of his discoveries were not published, or at least were only touched upon in the course of his oral lectures. An excellent example is his work in the theory of spectroscopy. In his presidential address to the British Association in 1871, Lord Kelvin (Sir William Thomson, as he was then) stated his belief that the application of the prismatic analysis of light to solar and stellar chemistry had never been suggested directly or indirectly by anyone else when Stokes taught it to him in Cambridge some time prior to the summer of 1852, and he set forth the conclusions, theoretical and practical, which he learnt from Stokes at that time, and which he afterwards gave regularly in his public lectures at Glasgow. These statements, containing as they do the physical basis on which spectroscopy rests, and the way in which it is applicable to the identification of substances existing in the sun and stars, make it appear that Stokes anticipated Kirchhoff by at least seven or eight years. Stokes, however, in a letter published some years after the delivery of this address, stated that he had failed to take one essential step in the argument—not perceiving that emission of light of definite wavelength not merely permitted, but necessitated, absorption of light of the same wavelength. He modestly disclaimed "any part of Kirchhoff's admirable discovery," adding that he felt some of his friends had been over-zealous in his cause. It must be said, however, that English men of science have not accepted this disclaimer in all its fullness, and still attribute to Stokes the credit of having first enunciated the fundamental principles of spectroscopy.

Other research

In other departments of physics may be mentioned his paper on the conduction of heat in crystals (1851) and his inquiries in connection with Crookes radiometer; his explanation of the light border frequently noticed in photographs just outside the outline of a dark body seen against the sky (1883); and, still later, his theory of the x-rays, which he suggested might be transverse waves travelling as innumerable solitary waves, not in regular trains. Two long papers published in 1840—one on attractions and Clairaut's theorem, and the other on the variation of gravity at the surface of the earth—also demand notice, as do his mathematical memoirs on the critical values of sums of periodic series (1847) and on the numerical calculation of a class of definite integrals and infinite series (1850) and his discussion of a differential equation relating to the breaking of railway bridges (1849).

Legacy

Stokes was the oldest of the trio of natural philosophers, James Clerk Maxwell and Lord Kelvin being the other two, who especially contributed to the fame of the Cambridge school of mathematical physics in the middle of the 19th century. His original work began about 1840, and from that date onwards the great extent of his output was only less remarkable than the brilliance of its quality. The Royal Society's catalogue of scientific, papers gives the titles of over a hundred memoirs by him published down to 1883. Some of these are only brief notes, others are short controversial or corrective statements, but many are long and elaborate treatises.

Stokes did much for the progress of mathematical physics. Soon after he was elected to the Lucasian chair he announced that he regarded it as part of his professional duties to help any member of the university in difficulties he might encounter in his mathematical studies, and the assistance rendered was so real that pupils were glad to consult him, even after they had become colleagues, on mathematical and physical problems in which they found themselves at a loss. Then during the thirty years he acted as secretary of the Royal Society he exercised an enormous if inconspicuous influence on the advancement of mathematical and physical science, not only directly by his own investigations, but indirectly by suggesting problems for inquiry and inciting men to attack them, and by his readiness to give encouragement and help.

Stokes's contribution to fluid dynamics is memorialized in the equations that bear his name. His devotion to teaching and to the institutions that encourage the pursuit of science showed him to be a man who was aware of a broader picture of the needs of his time.

List of Stokes eponyms

• Stokes' law, in fluid dynamics
• Stokes radius in biochemistry
• Stokes' theorem, in differential geometry
• Stokes line, in Raman scattering
• Stokes relations, relating the phase of light reflected from a non-absorbing boundary
• Stokes shift, in fluorescence
• Navier-Stokes equations, in fluid dynamics
• Stokes (unit), a unit of viscosity
• Stokes parameters and Stokes vector, used to quantify the polarisation of electromagnetic waves
• Campbell-Stokes recorder, an instrument for recording sunshine improved by Stokes, and still widely used today
• Stokes (lunar crater)
• Stokes (crater on Mars)

Honors

In addition to the honors mentioned above:

• From the Royal Society, of which he became a fellow in 1851, he received the Rumford Medal in 1852 in recognition of his inquiries into the wavelength of light, and later, in 1893, the Copley Medal.
• In 1869 he presided over the Exeter meeting of the British Association.
• From 1883 to 1885 he was Burnett lecturer at Aberdeen, his lectures on light, which were published in 1884–1887, dealing with its nature, its use as a means of investigation, and its beneficial effects.
• In 1889 he was made a baronet.
• In 1891, as Gifford lecturer, he published a volume on Natural Theology.
• His academic distinctions included honorary degrees from many universities, together with membership of the Prussian Order Pour le Mérite.

Published works

Sir George Stokes's mathematical and physical papers (see external links) were published in a collected form in five volumes; the first three (Cambridge, 1880, 1883, and 1901) under his own editorship, and the two last (Cambridge, 1904 and 1905) under that of Sir Joseph Larmor, who also selected and arranged the Memoir and Scientific Correspondence of Stokes published at Cambridge in 1907.

See also

• Fluid
• Fluorescence
• Sound
• Viscosity

References

ISBN links support NWE through referral fees

• Pieribone, Vincent, and David F. Gruber. 2005. Aglow in the dark: the revolutionary science of biofluorescence. Cambridge, Mass: Belknap Press of Harvard University Press. ISBN 0674019210.
• McCartney, Mark and Andrew Whitaker. 2003. Physicists of Ireland: Passion and Precision. Phila.: IOP Publishing. ISBN: 0750308664.
• Wilson, David B., 1987. Kelvin and Stokes A Comparative Study in Victorian Physics. ISBN 0852745265.
• Stokes, George Gabriel, William Thomson. 1990. The Correspondence Between Sir George Gabriel Stokes and Sir William Thomson, Baron Kelvin of Largs. New York: Cambridge University Press. ISBN 0521328314.

External links

• John J. O'Connor and Edmund F. Robertson. George Gabriel Stokes at the MacTutor archive
• Biography on Dublin City University Web site
• Mathematical and physical papers volume 1 and volume 2 from the Internet Archive
• Life and work of Stokes

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• This article incorporates text from the Encyclopædia Britannica Eleventh Edition, a publication now in the public domain.

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Honorary Titles
Preceded by: Joshua King	Lucasian Professor at Cambridge University 1849–1903	Succeeded by: Sir Joseph Larmor
Preceded by: Thomas Henry Huxley	President of the Royal Society 1885–1890	Succeeded by: The Lord Kelvin

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