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.

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.

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.

[9] 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.

Although his measurements were superseded by more accurate radius figures (such as those used for GRS 80 and WGS84) his Airy geoid (strictly a reference ellipsoid, OSGB36) is still used by Great Britain's Ordnance Survey for mapping of England, Scotland and Wales because it better fits the local sea level (about 80 cm below world average).

The cause of this he did not long seek in vain; thirteen times the mean motion of Venus is so nearly equal to eight times that of Earth that the difference amounts to only a small fraction of Earth's mean motion, and from the fact that the term depending on this difference, although very small in itself, receives in the integration of the differential equations a multiplier of about 2,200,000, Airy was led to infer the existence of a sensible inequality extending over 240 years (Phil.

Tycho Brahe and Giovanni Battista Riccioli pointed out that the lack of stellar parallax detectable at the time entailed that stars were a huge distance away.

In June 1835 Airy was appointed Astronomer Royal in succession to John Pond, and began his long career at the national observatory which constitutes his chief title to fame.

At the end of 1850 the great transit circle of 203 mm (8.0 in) aperture and 3.5 metres (11 feet 6 inches) focal length was erected, and is still the principal instrument of its class at the observatory.

The mounting in 1859 of an equatorial of 330 mm (13 in) aperture evoked the comment in his journal for that year, "There is not now a single person employed or instrument used in the observatory which was there in Mr Pond's time"; and the transformation was completed by the inauguration of spectroscopic work in 1868 and of the photographic registration of sunspots in 1873.

[8] The formidable undertaking of reducing the accumulated planetary observations made at Greenwich from 1750 to 1830 was already in progress under Airy's supervision when he became Astronomer Royal.

Shortly afterwards he undertook the further laborious task of reducing the enormous mass of observations of the moon made at Greenwich during the same period under the direction, successively, of James Bradley, Nathaniel Bliss, Nevil Maskelyne and John Pond, to defray the expense of which a large sum of money was allotted by the Treasury.

As a result, no fewer than 8,000 lunar observations were rescued from oblivion, and were, in 1846, placed at the disposal of astronomers in such a form that they could be used directly for comparison with the theory and for the improvement of the tables of the moon's motion.

[8] For this work Airy received in 1848 a testimonial from the Royal Astronomical Society, and it at once led to the discovery by Peter Andreas Hansen of two new inequalities in the moon's motion.

In June 1846, Airy started corresponding with French astronomer Urbain Le Verrier over the latter's prediction that irregularities in the motion of Uranus were due to a so-far unobserved body.

Aware that Cambridge Astronomer John Couch Adams had suggested that he had made similar predictions, on 9 July Airy urged James Challis to undertake a systematic search in the hope of securing the triumph of discovery for Britain.

Ultimately, a rival search in Berlin by Johann Gottfried Galle, instigated by Le Verrier, won the race for priority.

[19] Using a water-filled telescope, in 1871 Airy looked for a change in stellar aberration through the refracting water due to the aether drag hypothesis.

In 1872 Airy conceived the idea of treating the lunar theory in a new way, and at the age of seventy-one he embarked on the prodigious toil which this scheme entailed.

It consisted essentially in the adoption of Charles-Eugène Delaunay's final numerical expressions for longitude, latitude, and parallax, with a symbolic term attached to each number, the value of which was to be determined by substitution in the equations of motion.

[8] In this mode of treating the question the order of the terms is numerical, and though the amount of labour is such as might well have deterred a younger man, yet the details were easy, and a great part of it might be entrusted to "a mere computer".

[21] This technique, sometimes called the Airy stress function method, can be used to find solutions to many two-dimensional problems in solid mechanics (see Wikiversity).

Airy was consulted about wind speeds and pressures likely to be encountered on the proposed Forth suspension bridge being designed by Thomas Bouch for the North British Railway in the late 1870s.

He thought that pressures no greater than about 10 pounds per square foot (500 pascals) could be expected, a comment Bouch took to mean also applied to the first Tay railway bridge then being built.