George Airy

George Airy was born in Alnwick in 1801. His birthplace is identified by the blue plaque on the wall of number five, Grosvenor Terrace.

After leaving Alnwick in 1805 George attended Colchester Royal Grammar School. It was recorded that he was “an introverted but not shy child” and “even for the time and especially for his circumstances, a young snob”, but that “he overcame some of the dislike of his schoolmates by his great skill and inventiveness in the construction of peashooters and other such devices”. At school, he was particularly noted for his memory. In one examination he is supposed to have repeated over two thousand lines of Latin verse!

From Colchester, in 1819, he went to Trinity College, Cambridge, where his career as a mathematician and astronomer was launched. By 1828 he was Director of the newly established Cambridge Observatory, where, in 1833, he was able to design a mounting for a fine twelve-inch telescope that had been presented by the Duke of Northumberland. In its day, this telescope, known as the Northumberland Telescope, was one of the largest in the world. It is still in place at Cambridge, and although it is no longer employed for scientific work, it is still regularly used for observations by the University Astronomical Society and members of the public.

In 1830, he carried out calculations to determine the difference between the diameter of the earth at the equator and at the pole, effectively working out how non-spherical the earth actually is. This might seem a bit academic, but it is fundamental to accurate mapping. Despite more accurate measurements becoming available, his ‘Airy geoid’ measurements are still used today by the Ordnance Survey. Known as the OSGB36 projection, this more accurately reflects the local situation in the UK.

In 1835 Airy was appointed as Astronomer Royal. He took over the Greenwich Observatory at a time when it was, in his words’ “in a queer state”, after years of neglect. He worked energetically to get things in order, getting new equipment installed and formalising the astronomical observations. By 1859, the organisation was unrecognisable, with a wide range of new instruments being available to the staff.

One of Airy’s most lasting legacies was the establishment of the prime meridian at Greenwich, though this was, to some extent, an accidental circumstance. The prime meridian depended on the installation of a transit circle, a telescope that could only move in a north-south direction. The Greenwich meridian had moved a number of times as new transit circle telescopes had been installed in different positions around the Greenwich site, but it was Airy’s transit circle that, in 1851, established the UK’s prime meridian. In 1884, at the International Meridian Conference in Washington DC, despite vigorous attempts by the French to have Paris as the prime meridian, the Greenwich meridian, and in consequence Airy’s transit circle, was adopted as the Prime Meridian of the world.

On the moon, there is a crater named Airy, while on Mars there are two craters bearing his name, one sitting within the other. The smaller of these, called Airy-0, defines the prime meridian of that planet, the equivalent of our Greenwich meridian.

Airy was not confined to work at Greenwich. In 1854, he undertook experiments at the Harton Pit near South Shields, to determine the average density of the earth so enabling its weight to be determined. And his legacy was not just about astronomy. The Airy Stress Function is still used by engineers to determine stress and strain in structures.

Airy retired in 1881 and lived the rest of his life close to Greenwich Park, passing away in 1892 at the age of 90.

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