## John Couch Adams

**-**

## Adams, John Couch

# Adams, John Couch

(*b*. Laneast, Cornwall, England, 5 June 1819; *d*. Cambridge, England, 21 January 1892)

*astronomy, mathematics.*

John Couch Adams was born at Lidcot farm, seven miles from Launceston. He was the eldest son of Thomas Adams, a tenant farmer and a devout Wesleyan, and Tabitha Knill Grylls. The family circumstances were modest but respectable: Tabitha Adams’ cousin was the headmaster of a private school in Devonport, and in 1836 her adoptive mother left her some property and a small income which helped support John’s education.

Adams had his first schooling in a Laneast farmhouse. In 1827 he was tutored in calligraphy, Greek, and mathematics, but quickly outpaced his teacher. He developed an early interest in astronomy, inscribing a sundial on his window sill and observing solar altitudes with an instrument he built himself. In 1831 he was sent to his cousin’s academy, where he distinguished himself in classics, spending his spare time on astronomy and mathematics. Teaching himself, he finished the standard texts on conic sections, differential calculus, theory of numbers, theory of equations, and mechanics. Adams’ precocity convinced his parents that he should be sent to a university, and in October 1839 he sat for examinations at St. John’s College, Cambridge University, and won a sizarship. He went on to win the highest mathematical prizes in his college and took first prize in Greek testament every year that he was at Cambridge.

In July 1841, Adams, having read about the irregularities in the motion of the planet Uranus, decided to investigate them as soon as he had taken his degree. He graduated from Cambridge in 1843 as senior wrangler in the mathematical tripos and first Smith’s prizeman; shortly afterward he became a fellow and tutor of his college. At the beginning of the next long vacation he returned to Lidcot and began the longdeferred investigation of Uranus.

By October 1843 Adams had arrived at a solution of the inverse perturbation problem: given the mass of a body and its deviations from the path predicted for it by Newtonian mechanics, find the orbit and position of another body perturbing it through gravitational attraction. This problem required, among other procedures, the solution of ten simultaneous equations of condition for as many unknowns. Although Adam’s first result was approximate, it convinced him that the disturbances of Uranus were due to an undiscovered planet.

In February 1844, Adams applied through James Challis to the astronomer royal, Sir George Biddell Airy, for more exact data on Uranus. Using figures supplied by Airy, Adams computed values for the elliptic elements, mass, and heliocentric longitude of the hypothetical planet. He gave his results to Challis in September 1845, and after two unsuccessful attempts to present his work to Airy in person, he left a copy of it at the Royal Observatory on 21 October 1845. Although Airy wrote to Adams a few weeks later criticizing his paper, he did not institute a search for the planet until July 1846.

In the meantime a French astronomer, Urbain Jean Joseph Leverrier, independently published several papers on the theory of Uranus and reached the same conclusions as Adams had regarding an exterior planet. Although Leverrier began his investigation later, he pressed his case more aggressively, and on 23 September 1846 the perturbing body—Neptune—was discovered as a result of his efforts. Johann Gottfried Galle, an astronomer at the Berlin Observatory, found the planet less than one degree distant from the point where Leverrier predicted it would lie.

Leverrier was immediately showered with honors and congratulations. Adams’ earlier prediction, which agreed closely with Leverrier’s, was thus far unpublished. It was first publicized in a letter from Sir John Herschel to the London *Athenaeum* on 3 October 1846 and provoked a long and bitter controversy over priority of discovery. The two principals took little part in the feud, but the issue became a public sensation. It still seems remarkable that Airy suppressed Adams’ work for so long and that Adams was so reticent about pressing his claims. This behavior was, however, characteristic of Adams. The modesty that temporarily cost him some glory endeared him to colleagues and friends throughout his life.

The disparity between the credit accorded to Leverrier and that accorded to Adams was not made up for some years, but the two men met at Oxford in 1847 and became good friends. Adams was offered a knighthood by Queen Victoria in 1847 but declined it; the following year the Adams Prize, awarded biennially for the best essay in physics, mathematics, or astronomy, was instituted at Cambridge. The Royal Society gave Adams its highest award, the Copley Medal, in 1848.

In 1851 Adams was elected president of the Royal Astronomical Society and shortly afterward began to work on lunar theory. After much laborious calculation he finished new tables of the moon’s parallax which corrected several errors in lunar theory and gave more accurate positions. In the meantime, since he had not taken holy orders, his fellowship at St. John’s expired in 1852. He was elected a fellow of Pembroke College in 1853, and shortly afterward he presented to the Royal Society a remarkable paper on the secular acceleration of the moon’s mean motion. This quantity was thought to have been definitively investigated by Pierre Simon de Laplace in 1788, but Adams showed that Laplace’s solution was incorrect. In particular, Laplace had ignored a variation in solar eccentricity that introduces into the differential equations for the moon’s motion a series of additional terms. Adams calculated the second term of the series, on which the secular acceleration depends, as 3771/64*m ^{4}* the value computed from Laplace’s work was 2187/128 m

^{4}. The effect of the correction was to reduce the figure for the moon’s secular acceleration by about half, from 10″.58 to 5″.70.

This paper caused a sharp scientific controversy, marked by angry chauvinism on the part of several French astronomers. Their attacks stimulated a number of independent investigations of the subject, all of which confirmed Adams’ result. The matter was definitely settled in his favor by 1861, but not without hard feelings.

In 1858 Adams occupied the chair of mathematics at the University of St. Andrews, vacating it the following year to accept the appointment as Lowndean professor of astronomy and geometry at Cambridge. In 1861 he succeeded James Challis as director of the Cambridge Observatory, and in 1863, when he was forty-four, he married Eliza Bruce of Dublin. In 1866 the Royal Astronomical society awarded Adams a gold medal for his work on lunar theory.

The brilliant Leonid meteor shower of November 1866 stimulated Adams to investigate the elements of the Leonid system. By dividing the orbit into small segments, he calculated an analysis of perturbations for the meteor group, resulting in improved values for its period and elements. This work provided another demonstration of Adams’ extraordinary ability to manipulate equations of great length and complexity without error.

In 1870 the Cambridge Observatory acquired a Simms transit circle. In order to exploit it fully, Adams undertook—a rarity for him—the direction of a program of observational astronomy. The circle was used to map a zone lying between 25° and 30° of north declination for the *Astronomische Gesellschaft* program. This work was first published in 1897.

In 1874 Adams was elected to a second term as president of the Royal Astronomical Society. His scientific interest at this time turned to mathematics. Like Euler and Gauss, Adams enjoyed the calculation of exact values for mathematical constants. In 1877 he published thirty-one Bernoullian numbers, thus doubling the known number. With sixty-two Bernoullian numbers available, he decided to compute a definitive value of Euler’s constant; this required the calculation of certain logarithms to 273 decimal places. Using these terms, Adams extended Euler’s constant to 263 decimal places. This result was published in the *Proceedings* of the Royal Society in 1878; in the same year Adams published expressions for the products of two Legendrian coefficients and for the integral of the product of three.

Adams was a fervent admirer of Isaac Newton. In 1872, when Lord Portsmouth presented Newton’s scientific papers to Cambridge University, Adams willingly undertook to arrange and catalog those dealing with mathematics. He was also an omnivorous reader in other fields, especially botany, history, and fiction. He usually kept a novel at hand when working on long mathematical problems.

In retrospect Adams’ many mathematical and astronomical achievements pale in comparison to his analysis of the orbit of Uranus and his prediction of the existence and position of Neptune at the age of twenty-four. Much of his later work has been superseded, but as the co-discoverer of Neptune he occupies a special, undiminished place in the history of science.

## BIBLIOGRAPHY

I. Originasl Works. Works by Adams include MSS on the perturbations of Uranus, 1841–1846, St. John’s College Library, Cambridge, England; *Lectures on the Lunar Theory* (Cambridge, England, 1900); and William Grylls Adams, ed., *The Scientific Papers of John Couch Adams*, 2 vols. (Cambridge, England, 1896–1900).

II. Secondary Literature. See Morton Grosser, *The Discovery of Neptune* (Cambridge, Mass., 1962); Urbain Jean Joseph Leverrier, MS of the memoir “Recherches sur le mouvement de la planète Herschel (dite Uranus),” in the library of the Paris Observatory; W. M. Smart, “John Couch Adams and the Discovery of Neptune,” in *Occasional Notes of the Royal Astronomical Society* (London), **2** (1947), 33–88.

Morton Grosser

## John Couch Adams

# John Couch Adams

**1819-1892**

**English Astronomer**

John Couch Adams was born to a farming family in rural Landeast, Cornwall. His mathematical abilities were evident at an early age, impressing teachers and earning him a scholarship at St. John's College, Cambridge. Graduating in 1843 with high marks, he had already become interested in the problem of Uranus's orbit, which varied from what was predicted using the laws developed by Johannes Kepler (1571-1630) and Isaac Newton (1642-1727). Studying these discrepancies, Adams determined that there must be an additional, then undiscovered, planet beyond Uranus. This meant that when the unconfirmed planet was ahead of Uranus in its orbit, it would pull on Uranus, speeding it up in its orbit. Similarly, when Uranus pulled ahead of this planet, it would be slowed in its orbit. These were the discrepancies Adams and others had noted. The alternative, that Kepler's and Newton's laws were incorrect, was not conceivable since they worked so well for other planets.

Adams's study of the problem involved writing and solving sets of equations with up to 27 unknown terms, a laborious and difficult task. In order to solve this problem, Adams assumed the new planet was at twice the distance from the sun as Uranus (we now know this to be an incorrect assumption as Neptune lies at only about half again the distance from the sun as Uranus). He solved many of the equations and developed a detailed conceptual understanding of the problem in his head, later writing everything down.

Completing his calculations in October, 1845, Adams tried several times to meet with Sir George Airy (1801-1892), one of reigning English astronomers at that time. After several unsuccessful attempts to meet directly with Airy (he neglected to make an appointment, then returned during their meal), Adams left his work for review. Airy, not convinced of the accuracy of Adams's assumption regarding the new planet's distance, wrote Adams to question this but did not receive a response. Meanwhile, papers published by French astronomer Urbain Jean Joseph Leverrier (1811-1877) convinced both English and German astronomers to search for Neptune, which was discovered by Johann Gottfried Galle (1812-1910) in September, 1846.

There was some discussion regarding allocation of credit for Neptune's discovery. Adams performed the calculations first, but they were not published and eventually led to nothing. Leverrier, second to calculate Neptune's position, did publish his calculations, but Galle was the first to actually see Neptune. Ultimately all three men shared credit for this discovery.

Following the discovery of Neptune, Adams was recognized in Britain as a brilliant astronomer and was awarded a Fellowship at St. John's. Offered a knighthood at one point by Queen Victoria, he refused, fearing he did not have the financial resources needed for the life style demanded of a knight. He did accept an appointment as Lowndean Professor of Astronomy and Geometry at Cambridge and, in 1861, was appointed director of the Cambridge Observatory. Although elected president of the Royal Astronomical Society twice, he turned down the post of Astronomer Royal when Airy retired. He also found time to marry; in 1863 he wed Eliza Bruce.

Throughout his life Adams remained sincere, modest, and self-effacing, in spite of his mathematical and scientific genius. After his death in 1892, he was memorialized with a tablet at Westminster Abbey, near that of Sir Isaac Newton. Adams is currently regarded as the greatest English astronomer and mathematician since Newton.

**P. ANDREW KARAM**

## John Couch Adams

# John Couch Adams

The English mathematical astronomer John Couch Adams (1819-1892) was a principal figure in the discovery of the planet Neptune.

Born at Laneast, Cornwall, on June 5, 1819, to a farm family of modest station, John Couch Adams early demonstrated a remarkable capacity for mathematics. He was admitted to Cambridge University on a scholarship in the fall of 1839, and when he graduated in 1843 he was appointed to the faculty, spending virtually the rest of his life there.

The chain of events in which Adams figured so prominently began long before his birth. In 1781 William Herschel had discovered the planet Uranus. From then on, astronomers had sought to account for the movement of Uranus according to the rules which governed the motions of the other planets. By Adams's day it was apparent that their attempts had failed. Although a new orbit had been computed as late as 1820, the refractory planet was already departing from its predicted path by about 1 minute of arc. Although such a small angle is almost inconceivable by the layperson (it is the angle subtended by a nickel at a distance of 100 yards), it represented an intolerable error for 19th-century astronomy.

## Finding the Unknown Planet, Neptune

Adams's initial attack on Uranus, begun upon his graduation in 1843, lasted 2 1/2 years. Like earlier efforts, it was based on the law of universal gravitation, according to which the planet describes an essentially elliptical orbit around the sun with slight deviations caused by the attractions of other planets. Adams premised his work on the assumption that the computations of previous mathematicians had been spoiled by an unknown planet, whose actions on Uranus they necessarily failed to take into account. In September 1845 he presented his result to the director of the Cambridge observatory, indicating the approximate spot in the sky where the unknown planet should be found.

So unprecedented was Adams's prediction that no one knew how to treat it. Not until June 1846, when U.J.J. Leverrier in France published a similar result, did the English decide to drop their observational commitments and undertake the extensive search program to locate the planet. As was to appear later, they actually charted the planet on August 4 and 12 among the thousands of observations made. Before they could analyze all the data, however, the planet was discovered at Berlin on September 23 from the computations of Leverrier. Although Adams officially lost the honor of the discovery, the merit of his work was recognized, and his scientific reputation was established.

During the remaining 45 years of his life, he made important contributions to celestial mechanics and received many honors. He died in Cambridge on Jan. 21, 1892.

## Further Reading

Adams's professional work is republished in *The Scientific Papers of John Couch Adams* (2 vols., 1896-1900). There is no biography. Two accounts of Adams's greatest achievement are Sir Harold Spencer Jones, *John Couch Adams and the Discovery of Neptune* (1947), and Morton Grosser's highly readable *The Discovery of Neptune* (1962). □

## Adams, John Couch

John Couch Adams, 1819–92, English astronomer, grad. St. John's College, Cambridge, 1843. By mathematical calculation based on irregularities in the motion of Uranus, he predicted the position of the then unknown planet Neptune. Because of delay in England in making a telescopic search for the planet, the credit for the discovery went to a Frenchman, Leverrier. In 1858, Adams became professor of mathematics at St. Andrews Univ., but he soon returned to Cambridge, to occupy the Lowndean chair of astronomy and geometry until his death. From 1861 he was also director of the university observatory, preferring this post to that of astronomer royal, which was offered to him in 1881. He made valuable studies of the moon's motions, of the Leonids in the great meteor shower of 1866, and of terrestrial magnetism. His collected papers, edited by his brother, were published (1896–1900) at Cambridge.

## Adams, John Couch

**Adams, John Couch** (1819–92) British astronomer. Noting that Uranus' observed path was not in agreement with its calculated orbit, Adams believed that the discrepancies could be accounted for by the gravitational influence of an undiscovered planet. Neptune, as it was subsequently called, was discovered near a position predicted by Urbain Leverrier.