George Gabriel Stokes was born on 13 August 1819 inSkreen, Ireland, the youngest son of the Reverend Gabriel Stokes (died 1834), a clergyman in theChurch of Ireland who served as Rector of Skreen, and Elizabeth Haughton, daughter of the Reverend John Haughton. His home life was strongly influenced by his father'sevangelical Protestantism; three of his brothers entered the Church, of whom the most eminent wasJohn Stokes, who becameArchdeacon of Armagh.[4] Alongside a lifelong commitment to his Protestant faith, his childhood in Skreen had a strong influence on his later decision to pursuefluid dynamics as a research area.[5] His daughter, Isabella Humphreys, wrote that her father "told me that he was nearly carried away by one of these great waves when bathing as a boy off the coast of Sligo, and this first attracted his attention to waves".[6]
John and George were always close, and George lived with John while attending school inDublin. Of all his family, he was closest to his sister, Elizabeth. Their mother was remembered in the family as "beautiful but very stern". In 1837, after attending schools in Skreen, Dublin, andBristol, Stokes matriculated atPembroke College, Cambridge. In 1841, he graduated asSenior Wrangler andSmith's Prizeman, achievements that earned him election as a Fellow of the College that year.[7]
In accordance with the college statutes, Stokes had to resign from his fellowship when he married in 1857. Twelve years later, under new statutes, he was re-elected to the fellowship and retained that place until 1902, when he was elected Master of Pembroke College. He died the following year on 1 February at the age of 83,[8] and was buried atMill Road Cemetery inCambridge. There is also a memorial to him in the north aisle atWestminster Abbey.[9]
In 1849, Stokes was appointedLucasian Professor of Mathematics at theUniversity of Cambridge, a position he held until his death in 1903. On 1 June 1899, the golden jubilee of this appointment was celebrated there in a ceremony attended by numerous delegates from European and American universities. A commemorative gold medal was presented to Stokes by the Chancellor of the University, and marble busts of Stokes byHamo Thornycroft were formally offered to Pembroke College and to the university byLord Kelvin. At 54 years, Stokes' tenure as Lucasian Professor was the longest in history.
Stokes, who was made abaronet in 1889, further served his university by representing it in parliament from 1887 to 1892 as one of the two members for theCambridge University constituency. From 1885 to 1890, he was also President of theRoyal Society, of which he had been one of the secretaries since 1854. As he was also Lucasian Professor at this time, he was the first person to hold all three positions simultaneously;Isaac Newton held the same three, although not at the same time.[8]
Stokes was the oldest of the trio of natural philosophers,James Clerk Maxwell andLord Kelvin being the other two, who especially contributed to the fame of the Cambridge school ofmathematical physics in the middle of the 19th century.
Stokes' original work began about 1840, and is distinguished for its quantity and 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.[10]
In scope, Stokes' work covered a wide range of physical inquiry but, asMarie Alfred Cornu remarked in hisRede Lecture of 1899,[11] the greater part of it was concerned with waves and the transformations imposed on them during their passage through various media.[12]
Stokes's first published papers, which appeared in 1842 and 1843, were on the steady motion of incompressiblefluids and some cases of fluid motion.[13][14] These were followed in 1845 by one on the friction of fluids in motion and the equilibrium and motion of elastic solids,[15] and in 1850 by another on the effects of the internal friction of fluids on the motion ofpendulums.[16] To the theory of sound he made several contributions, including a discussion of the effect of wind on the intensity of sound[17] and an explanation of how the intensity is influenced by the nature of the gas in which the sound is produced.[18] These inquiries together put the science offluid dynamics on a new footing, and provided a key not only to the explanation of many natural phenomena, such as the suspension of clouds in the 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.[12]
Creeping flow past a sphere:streamlines and forces.
Stokes' work on fluid motion andviscosity led to his calculating the terminal velocity for a sphere falling in a viscous medium. This became known asStokes' law. He derived an expression for the frictional force (also calleddrag force) exerted on spherical objects with very smallReynolds numbers.[19]
Stokes' work is the basis of the falling sphereviscometer, in which the fluid is stationary in a vertical glass tube. A sphere of known size and density is allowed to descend through the liquid. If correctly selected, it reachesterminal velocity, which can be measured by the time it takes to pass two marks on the tube. Electronic sensing can be used for opaque fluids. Knowing the terminal velocity, the size and density of the sphere, and the density of the liquid, Stokes' law can be used to calculate the viscosity of the fluid. A series of steelball bearings of different diameters is normally used in the classic experiment to improve the accuracy of the calculation. The school experiment usesglycerine as the fluid, and the technique is used industrially to check the viscosity of fluids used in processes.[citation needed]
The same theory explains why small water droplets (or ice crystals) can remain suspended in air (as clouds) until they grow to a critical size and start falling as rain (or snow andhail). Similar use of the equation can be made in the settlement of fine particles in water or other fluids.[citation needed]
Perhaps Stokes' best-known researches are those which deal with the wave theory of light. Hisoptical work began at an early period in his scientific career. His first papers on theaberration of light appeared in 1845 and 1846,[20][21] and were followed in 1848 by one on the theory of certain bands seen in thespectrum.[22][12]
In 1849, Stokes published a long paper on the dynamical theory ofdiffraction, in which he showed that the plane ofpolarisation must be perpendicular to the direction of propagation.[23] Two years later, he discussed the colours of thick plates.[24][12]
Stokes also investigatedGeorge Airy's mathematical description ofrainbows.[25] Airy's findings involved an integral that was awkward to evaluate. Stokes expressed the integral as adivergent series, which were little understood. However, by cleverly truncating the series (i.e., ignoring all except the first few terms of the series), He obtained an accurate approximation to the integral that was far easier to evaluate than the integral itself.[26] Stokes' research on asymptotic series led to fundamental insights about such series.[27]
In 1852, in his famous paper on the change ofwavelength of light, he described the phenomenon offluorescence, as exhibited byfluorspar anduranium glass, materials which he viewed as having the power to convert invisibleultra-violet radiation into radiation of longer wavelengths that are visible.[28] TheStokes shift, which describes this conversion, is named in Stokes's honour. A mechanical model, illustrating the dynamical principle of Stokes's explanation was shown. The offshoot of this,Stokes line, is the basis ofRaman scattering. In 1883, during a lecture at theRoyal 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.[29]
A calcite crystal laid upon a paper with some letters showing the double refraction
In the same year, 1852, there appeared the paper on the composition and resolution of streams of polarised light from different sources,[30] and in 1853 an investigation of the metallicreflection exhibited by certain non-metallic substances.[31] The research was to highlight the phenomenon oflight polarisation. About 1860 he was engaged in an inquiry on the intensity of light reflected from, or transmitted through, a pile of plates;[32] and in 1862 he prepared for theBritish Association a valuable report ondouble refraction,[12] a phenomenon where certain crystals show different refractive indices along different axes.[33] Perhaps the best known crystal isIceland spar, transparentcalcite crystals.
A paper on the long spectrum of the electric light bears the same date,[34] and was followed by an inquiry into theabsorption spectrum of blood.[12][35]
The chemical identification oforganic bodies by their optical properties was treated in 1864;[36] 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 oftransparency and the improvement ofachromatictelescopes.[37] A still later paper connected with the construction of optical instruments discussed the theoretical limits to the aperture of microscope objectives.[38][12]
In 1849, Stokes invented theStokes lens to detectastigmatism.[39] It is a lens combination consisting of equal but opposite powercylindrical lenses attached together in such a way so that the lenses can be rotated relative to one another.[40]
In other areas of physics may be mentioned his paper on theconduction of heat incrystals (1851)[41] and his inquiries in connection withCrookes radiometer;[42] his explanation of the light border frequently noticed in photographs just outside the outline of a dark body seen against the sky (1882);[43] and, still later, his theory of thex-rays, which he suggested might be transverse waves travelling as innumerable solitary waves, not in regular trains.[44] Two long papers published in 1849 – one on attractions andClairaut's theorem,[45] and the other on the variation ofgravity at the surface of the Earth (1849) –Stokes's gravity formula[46]—also demand notice, as do his mathematical memoirs on the critical values of sums of periodic series (1847)[47] and on the numerical calculation of a class of definiteintegrals andinfinite series (1850)[48] and his discussion of adifferential equation relating to the breaking of railway bridges (1849),[49][12] research related to his evidence given to theRoyal Commission on the Use of Iron in Railway structures after theDee Bridge disaster of 1847.
Many of Stokes's discoveries were not published, or were only touched upon in the course of his oral lectures. One such example is his work in the theory ofspectroscopy.[12]
Lord Kelvin
In his presidential address to theBritish Association in 1871,Lord Kelvin 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 at Cambridge University 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 atGlasgow.[50]
Kirchhoff
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 anticipatedGustav 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.[51] It must be said, however, that English scientists have not accepted this disclaimer in all its fullness, and still attribute to Stokes the credit of having first enunciated the fundamental principles ofspectroscopy.[12]
In another way, too, 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 with 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.[12]
Stokes was involved in several investigations into railway accidents, especially theDee Bridge disaster inChester in May 1847, and he served as a member of the subsequent Royal Commission into the use of cast iron in railway structures. He contributed to the calculation of the forces exerted by moving engines on bridges. The bridge failed because a cast iron beam was used to support the loads of passing trains.Cast iron isbrittle intension orbending, and many other similar bridges had to be demolished or reinforced.
He appeared as an expert witness at theTay Bridge disaster, where he gave evidence about the effects of wind loads on the bridge. The centre section of the bridge (known as the High Girders) was completely destroyed during a storm on 28 December 1879, while an express train was in the section, and everyone aboard died (more than 75 victims). The Board of Inquiry listened to manyexpert witnesses, and concluded that the bridge was "badly designed, badly built and badly maintained".[52]
As a result of his evidence, he was appointed a member of the subsequentRoyal Commission into the effect of wind pressure on structures. The effects of high winds on large structures had been neglected at that time, and the commission conducted a series of measurements across Britain to gain an appreciation of wind speeds during storms, and the pressures they exerted on exposed surfaces.
Stokes generally held conservative religious values and beliefs. In 1886, he became president of theVictoria Institute, which had been founded to defend evangelical Christian principles against challenges from the new sciences, especially theDarwinian theory of biologicalevolution. He gave the 1891Gifford lecture onnatural theology.[53][54] He was also the vice-president of theBritish and Foreign Bible Society and was actively involved in doctrinal debates concerning missionary work.[55] However, although his religious views were mostly orthodox, he was unusual among Victorian evangelicals in rejecting eternal punishment in hell, and instead was a proponent ofChristian conditionalism.[56]
As President of the Victoria Institute, Stokes wrote:"We all admit that the book of Nature and the book of Revelation come alike from God, and that consequently there can be no real discrepancy between the two if rightly interpreted. The provisions of Science and Revelation are, for the most part, so distinct that there is little chance of collision. But if an apparent discrepancy should arise, we have no right on principle, to exclude either in favour of the other. For however firmly convinced we may be of the truth of revelation, we must admit our liability to err as to the extent or interpretation of what is revealed; and however strong the scientific evidence in favour of a theory may be, we must remember that we are dealing with evidence which, in its nature, is probable only, and it is conceivable that wider scientific knowledge might lead us to alter our opinion".[57]
On 4 July 1857, Stokes married Mary Susanna Robinson, the only daughter of Irish astronomerThomas Romney Robinson, atSt Patrick's Cathedral inArmagh. They had five children: Arthur Romney, who inherited theStokes Baronetcy; Susanna Elizabeth, who died in infancy; Isabella Lucy (Mrs Laurence Humphry), who contributed the personal memoir of her father in "Memoir and Scientific Correspondence of the Late George Gabriel Stokes, Bart"; Dr William George Gabriel, physician, a troubled man who committed suicide aged 30 while temporarily insane; and Dora Susanna, who died in infancy. His male line and hence his baronetcy have since become extinct.
1883–1885: Burnett Lecturer at theUniversity of Aberdeen; his lectures on light, which were published in 1884–1887, dealt with its nature, its use as a means of investigation, and its beneficial effects.[12]
1909: the Stokes Society atPembroke College, Cambridge, was founded as an academic hub for undergraduate scientists across the University. It remains active as of 2023.[66]
1964: the lunar craterStokes was named in his honor.[67]
1973: the Martian craterStokes was named in his honor.[68]
July 2017:Dublin City University named a building after Stokes in recognition of his contributions to physics and mathematics[69]
Stokes' 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 SirJoseph Larmor, who also selected and arranged theMemoir and Scientific Correspondence of Stokes published at Cambridge in 1907.[70]
Volumes I-V ofMathematical and Physical Papers (1880-1905)
Title page to Volume I ofMathematical and Physical Papers (1880)
Table of contents to Volume I ofMathematical and Physical Papers (1880)
First page of Volume I ofMathematical and Physical Papers (1880)
^Baldwin, Melinda (2014). "Tyndall and Stokes: Correspondence, Referee Reports, and the Physical Sciences in Victorian Britain".The Age of Scientific Naturalism: John Tyndall and His Contemporaries:171–186.
^Larmor, Joseph, ed. (1907).Memoir and Scientific Correspondence of the late Sir George Gabriel Stokes Volume 1. Cambridge: Cambridge University Press. p. 31.
^Stokes, G.G. (1858)."On the effect of wind on the intensity of sound".Report of the Twenty-seventh Meeting of the British Association for the Advancement of Science; held at Dublin in August and September 1857: Notices and Abstracts of Miscellaneous Communications to the Sections. Report of the ... Meeting of the British Association for the Advancement of Science (1833). London, England: John Murray. pp. 22–23.
^Thomson, William (2 February 1883)."The size of atoms".Notices of the Proceedings at the Meetings of the Members of the Royal Institution, with Abstracts of the Discourses.10:185–213. ;see pp. 207–208.
^Stokes, G. G. (1863)."Report on double refraction".Report of the Thirty-second Meeting of the British Association for the Advancement of Science; held at Cambridge in October 1862. London, England: John Murray. pp. 253–282.
