George Biddell Airy

Born in Alnwick, George Biddell Airy is one of only two people to have been elected Astronomer Royal four times and he achieved this after a brilliant early career as a mathematician at Cambridge University. He also became a skilled engineer in the field of astronomical instruments. He was five times president of the Royal Astronomical Society and for two years president of the highly prestigious Royal Society. In all he published 518 academic papers.

One of Airy's most well known contributions to science was establishing the definitive prime meridian at Greenwich in 1854, which is the basis for longitude calculations. This is the reference line for Greenwich Mean Time, or GMT, which is used to set the time across the world.

He also established inequalities in the orbital patterns of the Moon, the Earth and of Venus which led to corrections being made in Solar Tables which show relative positions of the planets. His work on calculating the polar and equatorial radii of the Earth is still used by Ordnance Survey today. He argued for a more realistic view of the size of distant stars and their deceptive outer aura which could lead to exaggeration of their size. This was named the Airy disc.

Although he left the region when young, two links back to the North East appeared later in his life. When working at the Cambridge Observatory in 1833, the Duke of Northumberland gifted the institution a fine object glass of 12 inch aperture which Airy installed. Later, in 1854 at Harton Colliery in South Shields, he carried out an important experiment which enabled him to establish the most accurate value (up to that point in time) of the mean density of the Earth.  He achieved this by measuring gravity at the top and bottom of the mine, using a pendulum experiment. Although we now know his value was too high, this was one of many notable achievements during his lifetime.