Darwin, Sir George Howard

(1845-1912), mathematician and geophysicist

by David Kushner

© Oxford University Press 2004 All rights reserved

Darwin, Sir George Howard (1845-1912), mathematician and geophysicist, was born on 9 July 1845 at Down House, Downe, Kent, the fifth child (the third of seven to survive childhood) of Charles Robert Darwin (1809-1882), the naturalist, and his wife, Emma Wedgwood (1808-1896), granddaughter of the potter Josiah Wedgwood of Etruria.

Education
George Darwin was reared in a scientific environment and his earliest education was at his father's side. In 1856 he was sent to the nearby Clapham grammar school owned and directed by the Revd Charles Pritchard FRS, later Savilian professor of astronomy at Oxford. There, among the Airys, Herschels, and Hamiltons, he studied mathematics and science at a level higher than that found at the public schools. At that time the young Darwin exhibited no profound aptitude for mathematics but, as might be expected, he took an interest in natural history, especially in the study of lepidoptera.

In both 1863 and 1864 Darwin failed to gain entrance scholarships at Cambridge, but he matriculated at Trinity College in 1864. There he became friends with the Balfour brothers, Arthur, Frank, and Gerald, and with J. W. Strutt (later Lord Rayleigh). He also quickly joined Fletcher Moulton (later a lord justice of appeal) and William Christie (later astronomer royal) in the mathematics classes of E. J. Routh, the most successful coach of his generation. These studies paid handsome dividends, for in 1866 Darwin won a foundation scholarship at Trinity, and in 1868 he was placed second wrangler in the tripos and won the second Smith's prize, both behind Moulton. Later that autumn he was elected a fellow of Trinity.

Although offered the mathematical mastership at Eton, Darwin decided to make the law his profession, and he studied in London from 1869 to 1872. He was called to the bar in 1874 but never practised, for it was during those years that he developed (apparently inherited) symptoms of serious digestive troubles that would ail him for the rest of his life. He took cures at Malvern, Homburg, and Cannes, but to no avail. The bouts of illness apparently persuaded him to give up the legal profession, and he settled back at Trinity in October 1873, gradually turning to scientific pursuits.

Geodesy
Darwin's first major scientific paper, 'On the influence of geological changes on the earth's axis of rotation', was read before the Royal Society in 1876 and published the following year (Philosophical Transactions, 167, 1877, 271-312). Darwin was animated by recent speculations of geologists that great changes in the obliquity of the ecliptic and in the positions of the earth's poles could explain glacial periods. He proved analytically that 'thus throughout geological history the obliquity of the ecliptic must have remained sensibly constant' (ibid., 303). However, he did find that changes of position of the earth's axis of symmetry due to geological deformations were possible, although limited, for large-scale deformations could produce a geographical displacement of the pole of at most 1° to 3°. Nevertheless, because Darwin thought that the earth exhibited plasticity by making rough readjustments to a figure of equilibrium, perhaps through earthquakes, he suggested that the pole might actually have wandered up to some 10° or 15°. Since Darwin had proved that the obliquity of the ecliptic itself could not have shifted, here he had found a way to explain the geologists' problem of the glacial epoch: the glacial period may only appear to have been a period of great cold, for, if the north pole were in Greenland, then Europe and much of North America would have been glaciated. But he backed off, modestly, but rhetorically, asking: 'If, then, geologists are right in supposing that where the continents now stand they have always stood, would it not be almost necessary to give up any hypothesis which involved a very wide excursion of the poles?' (ibid., 305).

This paper was reviewed for the Royal Society by William Thomson. Soon afterwards, in the spring of 1877, Thomson invited Darwin to Glasgow to discuss the issues. That dialogue profoundly altered Darwin's life. It was the beginning of a very intimate friendship between Darwin and Sir William and Lady Thomson, the Thomsons later becoming the godparents of Darwin's first son. Given the traditional portrayal of the confrontational relationship between Thomson and Charles Darwin concerning the age of the earth and its impact on the theory of natural selection, George's position is all the more surprising.

That discussion, and many similar ones, convinced Darwin to investigate the geophysical history of the earth. In particular he determined that if he treated the earth as a viscous body, instead of as an elastic one as Thomson had done--mathematicians and astronomers heretofore had only treated it as rigid--then an analysis of tidal reactions, especially of the frictional resistance to the tides, might prove illuminating. Consequently Darwin was the first to find that Thomson's own path breaking work on the strain of an incompressible elastic sphere could be adapted to the flow of an incompressible viscous fluid, he was the first to treat the earth as a wholly viscous body, and he was the first to develop a theory of viscous tides in the body of the earth.

Study of tides
Darwin began to develop the consequences of this line of thought in his seminal paper, 'On the precession of a viscous spheroid, and on the remote history of the earth' (Philosophical Transactions, 170, 1879, 447-538). The paper is ostensibly an investigation of how the rotation of a homogeneous viscous spheroid is altered by the tides raised in it by external disturbing bodies. But it is really about tides in the earth's body caused by the moon and sun and the reaction of such tides on the moon, for, indeed, it was Darwin's desire to fathom the physical history of the earth that led him to apply his mathematical talents along this vein in the first place.

Darwin analysed the tidal friction due to bodily tides in the earth. The result was the development of his theory of the tidal evolution of the earth-moon system, resulting from the effects of tidal retardation. If the earth is now being retarded and the moon receding, then in the remote past the earth must have been rotating much more swiftly and the moon must have been much closer. Darwin calculated that a minimum of 57 million years ago (he believed the actual lapse of time was magnitudes greater) the day would have been 6 hours 45 minutes, the month would have been about 1 day 14 hours, the obliquity would have been 9° less, and the moon's distance from the earth would have been 36,000 miles. Darwin did not believe this whole process had to be pre-geological, and he saw much to aid the geologist: the change in obliquity could affect climate, the trade winds would be augmented and the ocean currents affected, the shorter days and nights would lead to more violent storms, and the higher and more frequent tides would increase oceanic denudation.

From dynamical principles, it is clear that as long as the day and month are not equal, tidal friction must act, and Darwin was determined to find the initial condition of the earth and moon. Using the principle of the conservation of moment of momentum, Darwin altered his analysis to find a day-month equal to 5 hours 36 minutes, but this was a position of dynamically unstable equilibrium, for if the month were ever less than the day, then the moon would fall into the earth. Since the moon exists, something caused the equilibrium to tip in the other direction. At first, Darwin suggested that the contraction of the earth as a cooling body may have been the deciding circumstance. But with a day-month of 5 hours 36 minutes, only 6000 miles separated the surfaces of the two bodies. This clearly indicated to Darwin a rupture into at least two bodies of a primeval planet rotating in about 5 hours. Darwin hypothesized that the resonance of the enormous solar tides with the gravitational oscillation of an inhomogeneous earth could rupture the primeval planet. Thus was born Darwin's fission theory of the genesis of the moon, a theory largely accepted for the next fifty years.

Mathematician
This initial series of papers catapulted Darwin into the scientific elite. In 1879 he was elected a fellow of the Royal Society, and by the mid-1880s he was well on his way to becoming a central figure of the scientific aristocracy of late Victorian and Edwardian Britain. In 1883 he succeeded James Challis as Plumian professor of astronomy and experimental philosophy at Cambridge and won the Telford medal of the Institution of Civil Engineers. On 22 July 1884 he married Maud du Puy (1861-1947) of Philadelphia; in the same year he was awarded the royal medal, which he jokingly referred to as a wedding present. The couple soon moved into Newnham Grange (later Darwin College), Cambridge. Their four children included the artist Gwen Raverat (1885-1957) and the physicist Sir Charles Galton Darwin (1887-1962).

As his eminence grew, so did Darwin's scientific responsibilities. He spent significant amounts of time on committee and government work. His work on oceanic tidal theory, through which he became the government clearing-house for the organization and reduction of tidal observations throughout the British empire, led to his being recognized as the world's leading authority on the tides. In turn, he wrote the standard reference articles (for example, 'Tides', in the Encyclopaedia Britannica), assisted foreign governments, and developed a tide predictor and a tidal abacus. His book, The Tides and Kindred Phenomena in the Solar System (1898)--a semipopular account of nearly the whole compass of his scientific work, based on the Lowell lectures he gave at Boston in 1897--became a scientific bestseller and was translated into German, Hungarian, Spanish, Italian, and other languages. In addition Darwin was an influential member of the Seismological Congress and the meteorological council to the Royal Society.

Darwin's theory of tidal evolution also led to three other important series of papers containing some of his most significant and sophisticated mathematical work. In the first of these series the changes in the earth-moon system led him to consider what the figure of the earth must have been in past times, and this in turn led him later to consider the whole theory to the second order of small quantities. By the 1890s Darwin was considered Britain's leading geodesist, and he urged his country's membership in the International Geodetic Association, of which he later became vice-president. In the second series Darwin considered the initial conditions of stability of a primeval planet preceding rupture. These studies of the figures of equilibrium of rotating fluid masses brought Darwin into a close relationship with Henri Poincaré. Darwin's researches elucidated the pear shaped figure of equilibrium Poincaré had shown to exist. In the third series Darwin began by attempting to discover how a Laplacian ring could coalesce into a planet but was quickly diverted to a study of periodic orbits. In these papers, also involving the work of Poincaré as well as of the American astronomer G. W. Hill, Darwin calculated numerous classes of orbits by a complex numerical procedure, and, even more importantly, attempted to determine their stability.

Darwin's researches laid the groundwork for the startling growth of the geophysical sciences. If this period saw the emergence of geophysics in Britain, then the following half-century saw the discipline's consolidation into a vibrant and vital aspect of twentieth-century science. Geophysicists of the second and third generations knew well the guiding influence of Darwin. Sir Harold Jeffreys paid his tribute by dedicating the first great classic in the field, The Earth (1924), to the memory of Sir George Howard Darwin, 'Father of Modern Geophysics and Cosmogony'.

Physically, Darwin was of average height but slight in build. His personality was marked by a childlike naivety and unassuming modesty. A romantic streak suffused his interests and activities. He keenly loved heraldry, history, and travel and was fluent in several languages and odd dialects. Although traditional in morals, Darwin was delighted by the new consumer technologies. For example, he made sure his family was among the first in Cambridge to ride bicycles with pneumatic tyres and to become connected to the telephone system. He was an avid tennis player in his younger days, and he took up archery late in his life, joined the Royal Toxophilite Society and even won the Norton cup and medal in 1912.

By the end of his career Darwin had been honoured with numerous presidencies, vice-presidencies, medals, and memberships in the leading scientific societies of the world. In 1911 he was awarded the Copley medal of the Royal Society, the country's highest scientific distinction. Darwin was particularly pleased at being made a knight commander of the Bath in 1905 after his successful presidency of the British Association for the Advancement of Science on its tour of south Africa following the Second South African War, and by Cambridge University Press's decision to publish his collected Scientific Papers (5 vols., 1907-16).

Darwin died at Newnham Grange on 7 December 1912 of cancer of the pancreas and was buried at Trumpington. He was survived by his wife and their four children.

DAVID KUSHNER

Sources  
D. Kushner, 'The emergence of geophysics in nineteenth century Britain', PhD diss., University of Princeton, 1990
D. Kushner, 'Sir George Darwin and a British school of geophysics', Osiris, 2nd ser., 8 (1993), 196-223
F. Darwin, 'Memoir of Sir George Darwin', in G. H. Darwin, Scientific papers, 5 (1916), ix-xxxiii
G. Raverat, Period piece (1952)
S. S. H. [S. S. Hough], PRS, 89A (1913-14), i-xi
F. J. M. S. [F. J. M. Stratton], Monthly Notices of the Royal Astronomical Society, 73 (1912-13), 204-10
E. W. Brown, 'The scientific work of Sir George Darwin', in G. H. Darwin, Scientific papers, 5 (1916), xxxiv-lv
M. E. Keynes, A house by the river: Newnham Grange to Darwin College (1976)
d. cert.

Archives  
CUL, corresp. and papers |  CUL, corresp. and papers relating to Cambridge University
CUL, corresp. with Lord Kelvin
CUL, corresp. with H. Middleton
CUL, letters to Sir George Stokes
King's AC Cam., letters to Oscar Browning
NA Scot., corresp. with Arthur Balfour
priv. coll., letters to Sir Norman Moore
RAS, letters to Royal Astronomical Society
RGS, letters to Sir David Gill
RGS, corresp. and papers relating to International Geodetic Conference
U. Glas. L., corresp. with Lord Kelvin and Lady Kelvin
UCL, corresp. with Sir Francis Galton
UCL, letters to Karl Pearson

Likenesses  
M. Gertler, oils, 1912, NPG
Elliott & Fry, cabinet photograph, NPG
D. Pertz, watercolour (after G. Raverat), Trinity Cam.
G. Raverat, pen-and-ink drawing (after photograph, 1883), repro. in Raverat, Period piece
G. Raverat, watercolour, NPG [see illus.]
photograph, repro. in P. E. B. Jourdain, 'Sir George Darwin: a biographical sketch', The Open Court (April 1913), frontispiece

Wealth at death  
£47,108 12s. 9d.: probate, 21 Feb 1913, CGPLA Eng. & Wales


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