## John Adams

astronomer
mathematician
scientist
professor of astronomy

June 5, 1819
(age 72)
Laneast, Launceston, Cornwall, United Kingdom of Great Britain and Ireland

While still an under-graduate he happened to read of certain unexplained irregularities in the motion of the planet Uranus, and determined to investi-gate them as soon as possible, with a view to ascertaining whether they might not be due to the action of a remote undiscovered planet.
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.
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.
He left at Greenwich Observatory, for the information of Sir George Airy, the astronomer-royal, a similar document, still preserved among the archives.
Adams, who thought the query unessential, did not reply, and Airy for some months took no steps to verify by telescopic search the results of the young mathematician's investigation.
Unaware of Adams's work, he attempted a like inquiry, and on the 16t of June 1846, in a second memoir, gave the position, but not the mass or orbit, of the disturbing body whose existence was presumed.
The longitude he assigned differed by only ie from that predicted by Adams in the document which Airy possessed.
Herschel, at the ensuing meeting of the British Association early in September, ventured accordingly to predict that a new planet would shortly be discovered.
Meanwhile Airy had in July suggested to Challis that the planet should be sought for with the Cambridge equa-torial.
The search was begun by a laborious method at the end of the month.
On the 4th and 12 th of August, as afterwards appeared, the planet was actually observed; but owing to the want of a proper star-map it was not then recognized as planet-ary.
Leverrier, still ignorant of these occurrences, presented on the 316t of August 1846 a third memoir, giving for the first time the mass and orbit of the new body.
He communicated his results by letter to Dr Galle, of the Berlin Observatory, who at once examined the suggested region of the heavens.
On the 23rd of September he detected near the predicted place a small star unrecorded in the map, and next evening found that it had a proper motion.
No doubt remained that " Leverrier's planet " had been discovered.
On the announcement of the fact, Herschel and Challis made known that Adams had already calculated the planet's elements and position.
Airy then at length published an account of the circumstances, and Adams's memoir was printed as an appendix to the Nautical Almanac.
As the indisputable facts became known, the world recognized that the two astronomers had in-dependently solved the problem of Uranus, and ascribed to each equal glory.
The new planet, at first called Leverrier by F. Arago, received by general consent the neutral name of Neptune.
Its mathematical prediction was not only an unsurpassed intellectual feat; it showed also that Newton's law of gravitation, which Airy had almost called in question, prevailed even to the utmost bounds of the solar system.
The honour of knighthood was offered to Adams when Queen Victoria visited Cambridge in 1847; but then, as on a subsequent occasion, his modesty led him to decline it.
His lay fellowship at St John's College came to an end in 1852, and the existing statutes did not permit of his re-election.
But Pembroke College, which possessed greater freedom, elected him in the following year to a lay fellowship, and this he held for the rest of his life.
Two years later he succeeded Challis as director of the Observatory, where he resided until his death. Although Adams's researches on Neptune were those which attracted widest notice, the work he subsequently performed in relation to gravitational astronomy and terrestrial magnetism was not less remarkable.
Several of his most striking contribu-tions to knowledge originated in the discovery of errors or fallacies in the work of his great predecessors in astronomy.
Thus in 1852 he published new and accurate tables of the moon's parallax.
In the following year his memoir on the secular acceleration of the moon's mean motion partially invalidated Laplace's famous explanation, which had held its place unchallenged for sixty years.
At first, Leverrier, Plana and other foreign astronomers controverted Adams's result; but its soundness was ultimately established, and its fundamental importance to this branch of celestial theory has only developed further with time.
The great meteor shower of 1866 turned his attention to the Leonids, whose probable path and period had already been discussed by Professor H. A. Newton.
Using a powerful and elaborate analysis, Adams ascertained that this cluster of meteors, which belongs to the solar system, traverses an elon-gated ellipse in 33 years, and is subject to definite perturbations from the larger planets, Jupiter, Saturn and Uranus.
These results were published in 1867.
Ten years later, when Mr. G. W. Hill of Washington expounded a new and beautiful method for dealing with the problem of the lunar motions, Adams briefly announced his own unpublished work in the same field, which, following a parallel course had confirmed and supplemented Hill's.
The determination of the constants in Gauss's theory of terrestrial magnetism occupied him at intervals for over forty years.
The calculations involved great labour, and were not published during his lifetime.
Numerical computation of this kind might almost be described as his pastime.
The value of the constant known as Euler's, and the Bernoullian numbers up to the 62nd, he worked out to an unimagined degree of accuracy.
For Newton and his writings he had a boundless admiration; many of his papers, indeed, bear the cast of Newton's thought.
An inter-national committee was formed for the purpose of erecting a monument to his memory in Westminster Abbey; and there, in May 1895, a portrait medallion, by Albert Bruce Joy, was placed near the grave of Newton, and adjoining the memorials of Darwin and of Joule.
Herkomer's portrait is in Pembroke College; and Mogford's, painted in 1851, is in the combination room of St John's.
Another bust, taken in his youth, belongs to the Royal Astronomical Society.
(1900), edited by William Grylls Adams and Ralph Allen Sampson, with a memoir by Dr J. W. L. Glaisher, were published by the Cambridge University Press.
The first volume contains his previously published writings; the second those left in manuscript, including the substance of his lectures on the Lunar Theory.
A description of them by Professor Sampson was inserted in the Memoirs of the Royal Astronomical Society .
Adams calculated the second term of the series, on which the secular acceleration depends, as 3771/64m4 the value computed from Laplace’s work was 2187/128 m4.
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.
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.
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.