Sir George Biddell Airy (; 27 July 1801 – 2 January 1892) was an English mathematician and astronomer, as well as the Lucasian Professor of Mathematics from 1826 to 1828 and the seventh Astronomer Royal from 1835 to 1881. His many achievements include work on planetary orbits, measuring the mean density of the Earth, a method of solution of two-dimensional problems in solid mechanics and, in his role as Astronomer Royal, establishing Greenwich as the location of the prime meridian.
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Biography
Airy was born at Alnwick in Northumberland, one of a long line of Airys who traced their descent back to a family of the same name residing at Kentmere, in Westmorland, in the 14th century. The branch to which he belonged, having suffered in the English Civil War, moved to Lincolnshire and became farmers. Airy was educated first at elementary schools in Hereford, and afterwards at Colchester Royal Grammar School. An introverted child, Airy gained popularity with his schoolmates through his great skill in the construction of peashooters.
From the age of 13, Airy stayed frequently with his uncle, Arthur Biddell at Playford, Suffolk. Biddell introduced Airy to his friend Thomas Clarkson, the slave trade abolitionist who lived at Playford Hall. Clarkson had an MA in mathematics from Cambridge, and examined Airy in classics and then subsequently arranged for him to be examined by a Fellow from Trinity College, Cambridge on his knowledge of mathematics. As a result, he entered Trinity in 1819, as a sizar, meaning that he paid a reduced fee but essentially worked as a servant to make good the fee reduction. Here he had a brilliant career, and seems to have been almost immediately recognised as the leading man of his year. In 1822 he was elected scholar of Trinity, and in the following year he graduated as senior wrangler and obtained first Smith's Prize. On 1 October 1824 he was elected fellow of Trinity, and in December 1826 was appointed Lucasian professor of mathematics in succession to Thomas Turton. This chair he held for little more than a year, being elected in February 1828 Plumian professor of astronomy and director of the new Cambridge Observatory. In 1836 he was elected a Fellow of the Royal Society and in 1840, a foreign member of the Royal Swedish Academy of Sciences. In 1859 he became foreign member of the Royal Netherlands Academy of Arts and Sciences.
Research
Some idea of his activity as a writer on mathematical and physical subjects during these early years may be gathered from the fact that previous to this appointment he had contributed three important memoirs to the Philosophical Transactions of the Royal Society, and eight to the Cambridge Philosophical Society. At the Cambridge Observatory Airy soon showed his power of organisation. The only telescope in the establishment when he took charge was the transit instrument, and to this he vigorously devoted himself. By the adoption of a regular system of work, and a careful plan of reduction, he was able to keep his observations up to date, and published them annually with a punctuality which astonished his contemporaries. Before long a mural circle was installed, and regular observations were instituted with it in 1833. In the same year the Duke of Northumberland presented the Cambridge observatory with a fine object-glass of 12-inch aperture, which was mounted according to Airy's designs and under his superintendence, although construction was not completed until after he moved to Greenwich in 1835.
Airy's writings during this time are divided between mathematical physics and astronomy. The former are for the most part concerned with questions relating to the theory of light arising out of his professorial lectures, among which may be specially mentioned his paper On the Diffraction of an Object-Glass with Circular Aperture, and his enunciation of the complete theory of the rainbow. In 1831 the Copley Medal of the Royal Society was awarded to him for these researches. Of his astronomical writings during this period the most important are his investigation of the mass of Jupiter, his report to the British Association on the progress of astronomy during the 19th century, and his work On an Inequality of Long Period in the Motions of the Earth and Venus.
One of the sections of his able and instructive report was devoted to "A Comparison of the Progress of Astronomy in England with that in other Countries", very much to the disadvantage of England. This reproach was subsequently to a great extent removed by his own labours.
One of the most remarkable of Airy's researches was his determination of the mean density of the Earth. In 1826, the idea occurred to him of attacking this problem by means of pendulum experiments at the top and bottom of a deep mine. His first attempt, made in the same year, at the Dolcoath mine in Cornwall, failed in consequence of an accident to one of the pendulums. A second attempt in 1828 was defeated by a flooding of the mine, and many years elapsed before another opportunity presented itself. The experiments eventually took place at the Harton pit near South Shields in northern England in 1854. Their immediate result was to show that gravity at the bottom of the mine exceeded that at the top by 1/19286 of its amount, the depth being 383 m (1,257 ft). From this he was led to the final value of Earth's specific density of 6.566. This value, although considerably in excess of that previously found by different methods, was held by Airy, from the care and completeness with which the observations were carried out and discussed, to be "entitled to compete with the others on, at least, equal terms." The currently accepted value for Earth's density is 5.5153 g/cm3.
Private life
In July 1824, Airy met Richarda Smith (1804–1875), "a great beauty", on a walking tour of Derbyshire. He later wrote, "Our eyes met ... and my fate was sealed ... I felt irresistibly that we must be united," and Airy proposed two days later. Richarda's father, the Revd Richard Smith, felt that Airy lacked the financial resources to marry his daughter. Only in 1830, with Airy established in his Cambridge position, was permission for the marriage granted.
The Airys had nine children, the first three of whom died young.
Elizabeth Airy (born 1833) died of consumption (tuberculosis) in 1852.
The eldest child to survive to adulthood was Wilfrid (1836–1925), who designed and engineered "Colonel" George Tomline's Orwell Park Observatory. Wilfrid's daughter was the artist Anna Airy. Anna's mother died shortly after she was born, and she was raised by her maiden aunts Christabel and Annot (see below).
George Airy's son Hubert Airy (1838–1903) was a doctor, and a pioneer in the study of migraine. Airy himself suffered from this condition.
The Airys' eldest daughter, Hilda (1840–1916), married the mathematician Edward Routh in 1864.
Christabel (1842–1917) died unmarried, as did the next sister Annot (1843–1924).
The Airys' youngest child was Osmund (1845–1929).
Airy was knighted on 17 June 1872.
Airy retired in 1881, living with his two unmarried daughters at Croom's Hill near Greenwich. In 1891, he suffered a fall and an internal injury. He survived the consequential surgery only a few days. His wealth at death was £27,713, equivalent to £3,746,548.49 in 2021. Airy and his wife and three pre-deceased children are buried at St. Mary's Church in Playford, Suffolk. A cottage owned by Airy still stands, adjacent to the church and now in private hands.
Legacy and honours
Elected president of the Royal Astronomical Society four times, for a total of seven years (1835–37, 1849–51, 1853–55, 1863–64). No other person has been president more than four times (a record he shares with Francis Baily).
Foreign Honorary Member of the American Academy of Arts and Sciences (1832)
Elected to Honorary membership of the Manchester Literary and Philosophical Society 1843.
The Martian crater Airy is named for him. Within that crater lies another smaller crater called Airy-0 whose location defines the prime meridian of that planet, as does the location of Airy's 1850 telescope for Earth.
winner of the Lalande Prize for astronomy from the French Academy of Sciences, 1834
Elected as a member of the American Philosophical Society in 1879.
There is also a lunar crater Airy named in his honour.
Airy wave theory is the linear theory for the propagation of gravity waves on the surface of a fluid.
The Airy functions Ai(x) and Bi(x) and the differential equation they arise from are named in his honour, as well as the Airy disc and Airy points.
Honorary Fellow of the Institution of Engineering and Technology.