February 12, 1685|
|Died||June 28, 1768(aged 83)|
|Occupation||Lawyer, amateur meteorologist|
George Hadley (February 12, 1685 – June 28, 1768) was an English lawyer and amateur meteorologist who proposed the atmospheric mechanism by which the Trade Winds are sustained. As a key factor in ensuring that European sailing vessels reached North American shores, understanding the Trade Winds was becoming a matter of great importance at the time. Hadley was intrigued by the fact that winds which should by all rights have blown straight north had a pronounced westerly flow, and it was this mystery he set out to solve.
Hadley was born in London, England to Katherine FitzJames and George Hadley. He had an unremarkable childhood, and was eclipsed in his early years by his older brother John Hadley (1682–1744), the inventor of the octant (a precursor to the sextant). With John and his brother, Henry, George had constructed effective Newtonian telescopes.
George Hadley entered Pembroke College, Oxford, on 30 May 1700, and on 13 August 1701 became a member of Lincoln's Inn, where his father purchased chambers for him. He was called to the bar on 1 July 1709. He remained more interested in mechanical and physical studies than in legal work.
In 1686, Edmond Halley proposed his theory attempting to explain the Trade Winds. Halley's theory remained the most widely known internationally almost to the beginning of the 19th century.
Hadley was elected a fellow of the Royal Society on 20 February 1735, and on 22 May that year published a short paper in Philosophical Transactions (vol. 39, 1735, 58–62) giving his own explanation of the Trade Winds. His theory, remained unknown, but it was independently created several times. Among the later creators was John Dalton, who later eventually became aware of Hadley's priority. During the second half of the 19th century the theory gradually became known as "Hadley's principle".
In retrospect the crucial step forward was the recognition that the Earth's rotation plays a role in the direction taken by air mass that moves relative to the Earth. That element had been missing in Hadley's proposal.
Later, in the second half of the 19th century, Hadley's theory was shown to be deficient in several respects. Hadley's theory is based on an assumption that when air mass travels from one latitude to another its linear momentum is conserved. However, since the air mass is at all times in a state of circumnavigating the Earth axis, it is in fact the angular momentum that is conserved. When using the correct angular momentum conservation in calculations the predicted effect is twice as large as when the erroneous conservation of linear momentum is used. The fact that Hadley's principle is a deficient theory is not known to all people who should know; it can still be found in popular books and popular websites.
Hadley succeeded William Derham in the post of interpreter of the meteorological diaries sent to the Royal Society from observers around the world, mainly in Britain and Scandinavia. He tried to correlate the data in the different temperature and pressure scales then in use. He attempted to deduce general patterns that emerged over time and twice he published an account of the results in Philosophical Transactions.
Hadley never married. In later life he left London and lived for a while at East Barnet with a nephew, most likely his brother John Hadley's son John. Most of his later years were spent at Flitton, Bedfordshire, where another nephew, Hadley Cox (d. 1782), son of his sister Elizabeth, was vicar.
Hadley died at Flitton on 28 June 1768 aged 83 years, and was buried in the chancel of Flitton church.
The Hadley Centre for Climate Research and Prediction, within the UK Met Office, was named in his honour and subsequently renamed due to the unfortunate acronym. A crater on Mars was also named after him.
- Dictionary of National Biography
- Anders Persson, 'Hadley's Principle: Understanding and Misunderstanding the Trade Winds', History of Meteorology 3 (2006) (PDF-file 244 KB)
- Anita McConnell, ‘Hadley, George (1685–1768)’, Oxford Dictionary of National Biography, Oxford University Press, Sept 2004; online edn, Jan 2008 accessed 8 Feb 2010
- George Hadley, “Concerning the cause of the general trade winds,” Philosophical Transactions, vol. 39 (1735).