George Biddell Airy

British astronomer

• Born: July 27, 1801
• Birthplace: Alnwick, Northumberland, England
• Died: January 2, 1892
• Place of death: Greenwich, England

Airy’s inventive genius was in the fields of optics, engineering, and computational methods. His most practical inventions included the optical method for correcting astigmatism in eyes and a method for compensating a compass on a metal ship.

Primary fields: Mechanical engineering; optics; physics

Primary inventions: Astigmatism-correcting lenses; compass compensation

Early Life

George Biddell Airy (EH-ree) was born into a family that could trace its origins back to the fourteenth century. His father, William, was a tax collector in Northumberland and his mother, Ann, was the daughter of a farmer in Suffolk. George was their first of four children. In 1802, William was appointed to Hereford, where his children attended elementary schools. George was a diffident child who was more popular with his teachers than with his peers, and he excelled at mathematics and writing. His father’s transfer to Essex in 1810 made it possible for George to enter a more complete school at Sir Isaac’s Walk, where he studied geography, orthography, and mathematics. George also read extensively among his father’s books and committed to memory a prodigious amount of poetry. It was in reading his father’s encyclopedia that he developed a fascination with technical matters, especially engineering, shipbuilding, astronomy, optics, and navigation.

Attending more advanced schools, Airy soon attained proficiency in Greek and Latin, as well as mathematics, chemistry, and physics. His uncle, George Biddell, recognized his potential and persuaded his father to send him to college. Airy was subsequently examined by scholars from Trinity College, Cambridge, and his performance easily paved the way to admission.

He entered Cambridge University in 1819 and graduated in 1823 after an exceptional academic career that included high distinction in his studies and several important early investigations and inventions, including designs for achromatic telescopes and experiments for the design of a mechanical computer. Upon graduation, he was appointed a fellow of Trinity College, a position of considerable responsibility involving teaching and research. While a fellow, he developed new mathematical methods for treating the motions of celestial bodies.

Life’s Work

Airy’s many publications and the quality of his lectures led to his promotion to the prestigious position of Lucasion Professor of Mathematics at the age of twenty-five. Continuing his rapid rise in academia, he was named Plumian Professor of Astronomy and Natural Philosophy and director of the Cambridge observatory in 1828, only two years later. The work that Airy did in expanding the observatory and its productivity brought him much favorable recognition. His fundamental investigations of planetary orbits, especially the rhythmic relationships of Earth’s and Venus’s orbits (called planetary inequalities), and his work in optical theory brought such honors as the Copley Medal and the Royal Astronomical Society’s Gold Medal. As an inventor and innovator, his work at Cambridge involved the design and building of an impressive observatory, one that was far more effective than the small facility he found when he took over as director.

In 1835, Airy began a new life as astronomer royal and director of the Royal Greenwich Observatory. Reluctantly giving up his Cambridge professorship, Airy moved his family to London and took up residence in the observatory. During Airy’s remarkably long tenure at Greenwich, he accomplished a great deal, much of it related to astronomy, but also much concerned with the observatory’s mandate of improving the means of accurate celestial navigation at sea. As was his habit, Airy approached all tasks with his penchant for precision and orderliness, as well as for mathematical representation of practical problems whenever it was possible. He was basically a theoretician, but he became an inventor or designer whenever it became necessary to achieve a particular goal.

An indication of Airy’s range of interests and his inventive nature occurred in 1838, when he was asked to help solve the problem of the failure of magnetic compasses installed on iron ships, which were coming into use to replace wooden vessels. He investigated the problem theoretically and then experimented with a design of compensating magnets placed on the ship in appropriate places. The method was tested on the iron ship Rainbow, with Airy working on board the ship as it maneuvered in the Thames River near Deptford. The result was a perfect correction, allowing a subsequent voyage across the English Channel to Antwerp, with the compass performing excellently.

One of the major projects at Greenwich after Airy became the director was the design of a new kind of celestial position-measuring telescope, called the altazimuth telescope, which he designed in 1844. This new instrument permitted measurement of the position of the Moon precisely at any sky position. The determination of the Moon’s position was needed for navigation, which was of great commercial and military importance to Great Britain. In the following year, he invented another type of telescope, called the reflex zenith tube, with which precise star positions could be determined at nearly any position in the sky.

Among the various nonastronomical projects that occupied Airy’s inventive mind was a measurement of Earth’s mean density, achieved in 1845 by measuring the pull of gravity at the surface and at the bottom of a mine using pendulums. Although the first experiments failed because of various disasters (including fires and floods), success was eventually achieved.

The year 1845 was also notable for what Airy did not do. The young Cambridge mathematician John Couch Adams had calculated a position for a hypothetical new planet beyond Uranus, having analyzed perturbations on the orbit of Uranus. Although various historians differ on the details of what happened next, it is probable that Airy’s curt dismissal of Adams’s work when it was brought to him resulted in discouragement and inactivity. In the meantime, the French astronomer Urbain Le Verrier made similar calculations, transmitted them to Johann Galle in Germany, who immediately pointed his telescope in the indicated direction and discovered the new planet, eventually named Neptune. Airy’s role in losing the distinction for Adams and for England resulted in something of a scandal. His autobiography states, “I was abused most savagely both by English and French.”

Neptune was not the only mistake that Airy has become known for. In the early 1870’s, he was asked by Thomas Bouch to evaluate the pressures that would be encountered by the Tay Bridge, a 2.25-mile-long railroad bridge that spanned the Firth of Tay near Dundee in Scotland. Airy used his new mathematical treatment of physical mechanics and concluded that the design should be able to withstand ten pounds per square inch. Bouch used that as a guide in the design, and the bridge was completed on September 26, 1877. During a violent winter storm on December 28, 1879, the bridge collapsed, taking a train and over seventy lives with it. Airy’s contribution was only a small part of the reasons for the disaster, but his involvement nevertheless tended to tarnish his reputation, in spite of the many very positive achievements of his long life.

Impact

Few scientists have wielded as much power and influence for such a long period of time as Airy, who was astronomer royal of England for forty-six years. During his tenure, the Royal Greenwich Observatory became a major center for astronomical activity, especially with regard to stellar and planetary positions and issues of time. The world’s prime meridian, from where all longitudes are reckoned, was established under Airy’s directorship of the Royal Greenwich Observatory, and its exact position was established by the location of the Airy Transit Circle. The world’s time, known as Greenwich mean time, was similarly established by that instrument, designed by Airy.

Airy was a brilliant mathematician, but he also had interests in other scientific fields, especially those in which his mathematical talents could be useful. His was an inventive mind, and he often turned his attention to practical matters, inventing new instruments and techniques and even doing such things as embarking on ships to test his ideas and his inventions. His colleagues would probably have said that his greatest impact was his insistence on the orderly and scientifically based approach to the solution of problems. He kept careful and complete notes about everything he did (which is why he could write an exhaustive autobiography), and his inventions and new designs were thoroughly documented through the stepwise approach he took to solving the problems that they were intended to solve.

Bibliography

Airy, G. B. Mathematical Tracts on Physical Astronomy. Cambridge, England: J. Smith, 1826. Airy’s first major book, which remained a standard text on the subject for many decades. It has been reprinted several times, and students can still gain some useful insight by reference to it.

Airy, George Biddell. Autobiography of Sir George Biddell Airy. Charleston, S.C.: Biblio Bazaar, 2006. This autobiography covers Airy’s life from birth to 1871, with additions to the time of his death added by his son, Wilfrid Airy, who also wrote an excellent summary of the document. The text is a mix of descriptions of official documents and activities and a diary of more personal events in the author’s life.

Gould, B. A. “George Biddell Airy.” Astronomical Journal 11, no. 252 (1892): 96. A short announcement of Airy’s death and a well-spoken account of his achievements written by the editor of the journal.

Jones, Harold Spencer. The Royal Observatory, Greenwich. London: Longmans, 1946. This brief account of the observatory was written by the tenth astronomer royal during his directorship.

National Maritime Museum. A Guide to the Royal Observatory, Greenwich. London: Author, 2000. This booklet offers an up-to-date description of the observatory, its activities, and its history, including the long directorship of Sir George Airy. A well-written work that includes excellent illustrations of the observatory and its instruments.

“Sir George Biddell Airy.” In Encyclopaedia Britannica. Cambridge, England: Cambridge University Press, 1911. The famous 1911 edition of the Britannica includes a definitive article covering Airy’s life and accomplishments.