George Hadley (February 12,1685 – June 28,1768) was an
EnglishEngland is a country that is part of the United Kingdom. It shares land borders with Scotland to the north and Wales to the west; the Irish Sea is to the north west, the Celtic Sea to the south west and the North Sea to the east, with the English Channel to the south separating it from continental...
lawyerA lawyer, according to Black's Law Dictionary, is "a person learned in the law; as an attorney, counsel or solicitor; a person licensed to practice law." Law is the system of rules of conduct established by the sovereign government of a society to correct wrongs, maintain stability, and deliver...
and amateur meteorologist who proposed the atmospheric mechanism by which the
Trade WindThe trade winds are the prevailing pattern of easterly surface winds found in the tropics near the Earth's equator. The trade winds blow predominantly from the northeast in the Northern Hemisphere and from the southeast in the Southern Hemisphere...
s 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[]London is the capital of England and the United Kingdom. It has been a major settlement for two millennia, and the history of London goes back to its founding by the Romans, when it was named Londinium. London's core, the ancient City of London, the 'square mile', retains its medieval boundaries...
, England to Katherine FitzJames and George Hadley.
George Hadley (February 12,1685 – June 28,1768) was an
EnglishEngland is a country that is part of the United Kingdom. It shares land borders with Scotland to the north and Wales to the west; the Irish Sea is to the north west, the Celtic Sea to the south west and the North Sea to the east, with the English Channel to the south separating it from continental...
lawyerA lawyer, according to Black's Law Dictionary, is "a person learned in the law; as an attorney, counsel or solicitor; a person licensed to practice law." Law is the system of rules of conduct established by the sovereign government of a society to correct wrongs, maintain stability, and deliver...
and amateur meteorologist who proposed the atmospheric mechanism by which the
Trade WindThe trade winds are the prevailing pattern of easterly surface winds found in the tropics near the Earth's equator. The trade winds blow predominantly from the northeast in the Northern Hemisphere and from the southeast in the Southern Hemisphere...
s 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[]London is the capital of England and the United Kingdom. It has been a major settlement for two millennia, and the history of London goes back to its founding by the Romans, when it was named Londinium. London's core, the ancient City of London, the 'square mile', retains its medieval boundaries...
, England to Katherine FitzJames and George Hadley. He had an unremarkable childhood, and was eclipsed in his early years by his older brother
JohnJohn Hadley was an English mathematician, inventor of the octant and precursor to the sextant around 1730....
, the inventor of the
octantThe octant, also called reflecting quadrant, is a measuring instrument used primarily in navigation. It is a type of reflecting instrument.-Etymology:...
(a precursor to the
sextantA sextant is an instrument generally used to measure the altitude of a celestial object above the horizon. Making this measurement is known as sighting the object, shooting the object, or taking a sight. The angle, and the time when it was measured, can be used to calculate a position line on a...
). With John and his brother, Henry, George had constructed effective
Newtonian telescopeThe Newtonian telescope is a type of reflecting telescope invented by the British scientist Sir Isaac Newton , using a concave primary mirror and a flat diagonal secondary mirror. Newton’s first reflecting telescope was completed in 1668 and is the earliest known functional reflecting telescope...
s.
In 1686,
Edmond HalleyEdmond Halley FRS was an English astronomer, geophysicist, mathematician, meteorologist, and physicist, who is best known for computing the orbit of Halley's comet, which is named for him.- Biography and career :...
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's theory, published in 1735, remained unknown, but it was rediscovered independently several times. Among the rediscoverers was
John DaltonJohn Dalton FRS was an English chemist, meteorologist and physicist. He is best known for his pioneering work in the development of modern atomic theory, and his research into colour blindness .-Early life:John Dalton was born into a Quaker family at Eaglesfield, near Cockermouth in Cumberland,...
, who later learned 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 Halley'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
momentumIn classical mechanics, momentum is the product of the mass and velocity of an object . For more accurate measures of momentum, see the section "modern definitions of momentum" on this page...
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 was elected a Royal Fellow in 1745 and died in 1768. The
Hadley Centre for Climate Prediction and ResearchThe Met Office Hadley Centre for Climate Change — named in honour of George Hadley — is part of, and based at the headquarters of the Met Office in Exeter...
, within the UK
Met OfficeThe Met Office , is the United Kingdom's national weather service, and a trading fund of the Ministry of Defence. Part of the Met Office headquarters at Exeter in Devon is the Met Office College, which handles the training for internal personnel and many forecasters from around the world...
, is named in his honour. A
craterIn the broadest sense, the term impact crater can be applied to any depression, natural or manmade, resulting from the high velocity impact of a projectile with a larger body...
on
MarsMars is the fourth planet from the Sun in the Solar System. The planet is named after Mars, the Roman god of war. It is also referred to as the "Red Planet" because of its reddish appearance, due to iron oxide prevalent on its surface....
was also named after him.
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