George Biddell Airy
George Biddell Airy was born on July 27th, 1801 in the village of Alnwick in Northumberland, England. (Alnwick—pronounced ann-ick—is home to Alnwick Castle, which is featured in a number of Harry Potter films as Hogwarts School.) His father, William Airy, was a self-made man who rose through the ranks of the Excise Service until in 1813 he was dismissed from a fairly senior post for what appears to have been wrongful practices. To the impressionable young George his father’s dismissal, and the shame it brought on the Airy family, had a profound effect on his life which left him with an acute sense of public duty. A brilliant student, George Airy could easily have gained a scholarship that would have automatically led to a career in law and, ultimately, to a judgeship or a bishopric and all the power that goes with such senior positions. Instead he chose what was then the still largely amateur science of astronomy
Airy was of medium height and was said to be of strong constitution with many interests including scripture, poetry, history, geology, mathematics, optics, engineering and, of course, astronomy. He suffered from astigmatism - an eye problem resulting in blurred vision - and in 1825 developed a cylindrical lens to correct the defect. His method is still in use today.
Airy’s career began at Cambridge University when he was elected Lucasian Professor of Mathematics in 1826 and, two years later, he received the Plumian Professorship of Astronomy. With this latter position came the responsibility of the University’s astronomical observatory which subsequently proved to be invaluable experience.
The First in His Profession
The Oxford historian Dr. Allan Chapman considers Airy to have been Britain’s first truly professional astronomer. While it is certainly a fact that astronomers had been paid for their services many years before Airy came onto the scene, their salaries were very modest and most had to rely on landed wealth, strategic marriages or Holy Orders to provide them with enough income to live like gentlemen. When, at the age of only 34, the Government aske
d Airy to succeed John Pond to become the 7th Astronomer Royal he demanded, and received, a salary of 800 pounds Sterling ($2,700) - a staggering 68,540 pounds ($230,285) in today’s money and double the 400 pounds ($1,350) paid to his predecessor. For this remuneration - on par with a successful barrister - he was willing to surrender his entire professional time to his paymasters. For Airy, unlike previous Astronomers Royal, there were no financial problems to distract him from his duty.
Airy was undoubtedly a complex character. Certainly he was a workaholic, almost obsessed with facts and figures, but his intellectual brilliance was matched only by his shrewd practical judgment. Always cautious he was nonetheless ambitious though also modest. He was, of course, a pillar of the establishment: a solid member of Victorian middle class society. But he had no desire to accede to the House of Lords, unlike many of his scientific contemporaries.
Airy’s first task as Astronomer Royal was to reform the Royal Observatory at Greenwich, which operated under the auspices of the Admiralty. When the Observatory was founded in 1675 its role was to aid navigation at sea, mainly by promoting positional astronomy. It had subsequently evolved into a sort of gentlemen’s club and Airy set about making the Observatory more industrious by introducing an almost production line system of observation and analysis. This also involved the redesign of the Observatory’s entire instrumentation: a difficult and lengthy process but one which Airy achieved with his usual efficiency.
During the 46 years he served as Astronomer Royal - a record matched only by Nevil Maskelyne (1765-1811) - he embraced the new technologies of the industrial revolution to modernize practical astronomy in England and drag it into the realm of professionalism. By the mid-1850s Airy had succeeded in having Greenwich Mean Time transmitted across Britain through the newly established commercial telegraph network, bringing time distribution to the public at large.
The Mass of the Earth
Not all of Airy’s work was done at Greenwich though. In 1854 he descended almost a quarter of a mile into the bowels of the Earth at Harton Colliery, a coal mine in South Shields in an attempt to determine the mass of our planet. Maintaining contact with the surface through the electric telegraph, Airy recorded precisely the swing of a pendulum at the base of the shaft and compared it to another at the surface. From this simple experiment Airy estimated the overall density of the Earth as being nearly seven times that of water: somewhat higher than the currently accepted value. This led to an error in calculating the mass of the Earth by about 20%. However, the error was not entirely Airy’s fault. The scientists at that time had misinterpreted the nature of the rock at the colliery’s base and had provided Airy with an incorrect estimate of its density. He gave a talk on his experiments in South Shields on January 1, 1855 and later presented a paper to the Royal Institution.
The “Pit and the Pendulum” experiment was commemorated in 1992 when the then Astronomer Royal, Prof. Arnold Wolfendale of Durham University, unveiled a plaque as a tribute to Airy. Paid for by Harton Rotary Club in South Shields after the idea was put to them by Dr. David Turnbull, a Vice-President of the Newcastle Astronomical Society. It proved impossible to site the plaque at the exact location of the experiment, as the old colliery is now covered by a housing estate. Instead the plaque has been placed at nearby South Tyneside General Hospital. A further plaque was erected in 2003 at his birthplace, 3 Grosvenor Terrace.
The Astronomical Unit
One of the most fundamental measurements in astronomy is the astronomical unit: the distance between the Sun and the Earth (about 150 million km or 93 million miles). The distance had been estimated by the German astronomer Johann Franz Encke (1791-1865) as being 95 million miles and, towards the end of the 19th century Airy attempted to improve on Encke’s measurement by organizing vast expeditions to the antipodes in December 1874 and 1882 to observe the transit of the planet Venus across the disk of the Sun—something that Capt. James Cook had previously done for the first time in 1768-71. By timing how long it took for Venus to cross the Sun, Airy could work out the value of the astronomical unit. However in this he failed for, like the Earth, Venus also has a distorting atmosphere which makes accurate observation impossible.
The greatest criticism of Airy was undoubtedly his refusal to search for the “missing” planet predicted to exist by the English mathematician John Couch Adams. Airy maintained that such research should be left to universities and private observatories. The Royal Observatory, he insisted, was there to monitor the constants of the Universe and it was not his duty to waste public funds on what might be nothing more than a wild-goose chase. He passed the search on to Challis at Cambridge, but it was J.G.Galle at Berlin Observatory who finally discovered the planet Neptune in 1846. Airy’s decision outraged many of Britain’s scientific and political leaders who saw a British discovery fall to the Germans. But Airy was convinced that he had done his duty in not getting Greenwich involved in the search.
Unlike many astronomers of his time, Airy was a great popularizer. His talks, usually illustrated by his wife, were always well attended and on one occasion attracted some 700 members of the public.
In a country gripped by the industrial revolution he was often called upon by Parliament, in his capacity as General Scientific Consultant to Her Majesty’s Government, to give his considered opinion on technological standards, to offer advice to engineers and to design new instruments. He was, in his day, one of the most brilliant and innovative scientists in the world, although he considered Charles Babbage’s invention of an analytical engine – the first mechanical computer – to be “worthless”. He received numerous honours including the Presidency of the Royal Society—then, as now, the world’s foremost scientific organization. And, on several occasions he served as President of the Royal Astronomical Society. During his long and distinguished career he published some 518 papers covering such a diverse range of subjects as magnetic storms, bridge building and problems associated with laying cables on the floor of the Atlantic Ocean.
Airy declined the offer of a Knighthood on three occasions but relented in 1872. Sir George Airy’s work in astronomy is matched by his research in Earth sciences. He developed a theory of isostasy in which the world’s continents float around the globe, sinking and rising as they do so. And his investigation of earthquakes led to the Airy Phase which describes how shock waves behave.
Airy retired from the post of Astronomer Royal in 1881. Apart from defining more clearly the role of the Royal Greenwich Observatory, he also instigated meteorological and geomagnetic measurements hoping to improve navigation and public health. Navigation was of prime concern to Airy, because of the Observatory’s roots, and he conducted a number of experiments aboard the Rainbow and the Ironsides in order to gain a better understanding of how magnetic compasses were influence by the metallic hulls of ships, though it was some 50 years later, in 1889, before the Royal and Merchant Navies adopted his mechanical system of compensation. Airy died, in Greenwich, on 2nd January 1892 and was buried at Playford in Suffolk.
- Sir George Biddell Airy image http://www.archive.org/details/popularsciencemo03newy
- Dr Allan Chapman: Sir George Biddell Airy: Britain’s First Professional Astronomer http://www.brlsi.org/proceed04/lecture200311b.htm
- Relative values of the pound Sterling and the US$ from the Economic History Association http://eh.net/hmit/
- George Biddell Airy short biography: http://www.nndb.com/people/766/000096478/
- Royal Greenwich Observatory http://www.nmm.ac.uk/places/royal-observatory/