Pierre Charles Le Monnier (; 23 November 1715 – 3 April 1799) was a French
astronomer
An astronomer is a scientist in the field of astronomy who focuses their studies on a specific question or field outside the scope of Earth. They observe astronomical objects such as stars, planets, moons, comets and galaxies – in either ...
. His name is sometimes given as Lemonnier.
Biography
Le Monnier was born in
Paris
Paris () is the capital and most populous city of France, with an estimated population of 2,165,423 residents in 2019 in an area of more than 105 km² (41 sq mi), making it the 30th most densely populated city in the world in 2020. Si ...
, where his father
Pierre (1675–1757), also an astronomer, was professor of philosophy at the college d'Harcourt.
His first recorded astronomical observation was made before he was sixteen, and the presentation of an elaborate lunar map resulted in his admission to the
French Academy of Sciences
The French Academy of Sciences (French: ''Académie des sciences'') is a learned society, founded in 1666 by Louis XIV at the suggestion of Jean-Baptiste Colbert, to encourage and protect the spirit of French scientific research. It was at ...
, on 21 April 1736, aged only 20. He was chosen in the same year to accompany
Pierre Louis Maupertuis
Pierre Louis Moreau de Maupertuis (; ; 1698 – 27 July 1759) was a French mathematician, philosopher and man of letters. He became the Director of the Académie des Sciences, and the first President of the Prussian Academy of Science, at the ...
and
Alexis Clairaut
Alexis Claude Clairaut (; 13 May 1713 – 17 May 1765) was a French mathematician, astronomer, and geophysicist. He was a prominent Newtonian whose work helped to establish the validity of the principles and results that Sir Isaac Newton had ou ...
on their
geodetical expedition for
measuring a meridian arc of approximately one
degree's length to
Torne Valley
The Torne, also known as the Tornio ( fi, Tornionjoki, sv, Torne älv, , se, Duortneseatnu, fit, Tornionväylä), is a river in northern Sweden and Finland. For approximately half of its length, it defines the border between these two countr ...
in
Lapland. In 1738, shortly after his return, he explained, in a memoir read before the Academy, the advantages of
John Flamsteed's mode of determining
right ascension
Right ascension (abbreviated RA; symbol ) is the angular distance of a particular point measured eastward along the celestial equator from the Sun at the March equinox to the ( hour circle of the) point in question above the earth.
When pair ...
s.
His persistent recommendation of
British methods and instruments contributed effectively to the reform of French practical astronomy, and constituted the most eminent of his services to science. He corresponded with
James Bradley, was the first to represent the effects of
nutation in the solar tables, and introduced, in 1741, the use of the transit-instrument at the
Paris Observatory
The Paris Observatory (french: Observatoire de Paris ), a research institution of the Paris Sciences et Lettres University, is the foremost astronomical observatory of France, and one of the largest astronomical centers in the world. Its histo ...
. He visited England in 1748, and, in company with the
Earl of Morton
The title Earl of Morton was created in the Peerage of Scotland in 1458 for James Douglas of Dalkeith. Along with it, the title Lord Aberdour was granted. This latter title is the courtesy title for the eldest son and heir to the Earl of Morton.
...
and
James Shore the optician, continued his journey to
Scotland
Scotland (, ) is a country that is part of the United Kingdom. Covering the northern third of the island of Great Britain, mainland Scotland has a border with England to the southeast and is otherwise surrounded by the Atlantic Ocean to ...
, where he observed the
annular eclipse of 25 July.
The liberality of King
Louis XV of France
Louis XV (15 February 1710 – 10 May 1774), known as Louis the Beloved (french: le Bien-Aimé), was King of France from 1 September 1715 until his death in 1774. He succeeded his great-grandfather Louis XIV at the age of five. Until he reache ...
, in whose favour Le Monnier stood high, furnished him with the means of procuring the best instruments, many made in Britain. Amongst the fruits of his industry may be mentioned a laborious investigation of the disturbances of
Jupiter
Jupiter is the fifth planet from the Sun and the largest in the Solar System. It is a gas giant with a mass more than two and a half times that of all the other planets in the Solar System combined, but slightly less than one-thousand ...
by
Saturn
Saturn is the sixth planet from the Sun and the second-largest in the Solar System, after Jupiter. It is a gas giant with an average radius of about nine and a half times that of Earth. It has only one-eighth the average density of Earth; h ...
, the results of which were employed and confirmed by
Euler
Leonhard Euler ( , ; 15 April 170718 September 1783) was a Swiss mathematician, physicist, astronomer, geographer, logician and engineer who founded the studies of graph theory and topology and made pioneering and influential discoveries in ...
in his prize essay of 1748; a series of lunar observations extending over fifty years; some interesting researches in
terrestrial magnetism and
atmospheric electricity, in the latter of which he detected a regular diurnal period; and the determination of the places of a great number of stars, including at least twelve separate observations of
Uranus
Uranus is the seventh planet from the Sun. Its name is a reference to the Greek god of the sky, Uranus ( Caelus), who, according to Greek mythology, was the great-grandfather of Ares (Mars), grandfather of Zeus (Jupiter) and father of ...
, between 1750 and its discovery as a planet. In his lectures at the
Collège de France
The Collège de France (), formerly known as the ''Collège Royal'' or as the ''Collège impérial'' founded in 1530 by François I, is a higher education and research establishment ('' grand établissement'') in France. It is located in Paris n ...
he first publicly expounded the analytical theory of
gravitation
In physics, gravity () is a fundamental interaction which causes mutual attraction between all things with mass or energy. Gravity is, by far, the weakest of the four fundamental interactions, approximately 1038 times weaker than the stron ...
, and his timely patronage secured the services of
J. J. Lalande for astronomy.
Le Monnier's temper and hasty speech resulted in many arguments and grudges. He fell out with Lalande "during an entire revolution of the moon's nodes". His career was ended by
paralysis
Paralysis (also known as plegia) is a loss of motor function in one or more muscles. Paralysis can also be accompanied by a loss of feeling (sensory loss) in the affected area if there is sensory damage. In the United States, roughly 1 in 5 ...
late in 1791, and a repetition of the stroke terminated his life. He died at Héril near
Bayeux
Bayeux () is a commune in the Calvados department in Normandy in northwestern France.
Bayeux is the home of the Bayeux Tapestry, which depicts the events leading up to the Norman conquest of England. It is also known as the first major tow ...
. By his marriage with Mademoiselle de Cussy he left three daughters, one of whom became the wife of
J. L. Lagrange.
Le Monnier was admitted on 5 April 1739 to the
Royal Society
The Royal Society, formally The Royal Society of London for Improving Natural Knowledge, is a learned society and the United Kingdom's national academy of sciences. The society fulfils a number of roles: promoting science and its benefits, re ...
,
[The Royal Society]
Lists of Fellows of the Royal Society 1660 – 2007
URL. Retrieved 19 February 2010. and was one of the 144 original members of the Institute.
On 29 January 1745 he also became a member of the
Prussian Academy of Sciences
The Royal Prussian Academy of Sciences (german: Königlich-Preußische Akademie der Wissenschaften) was an academy established in Berlin, Germany on 11 July 1700, four years after the Prussian Academy of Arts, or "Arts Academy," to which "Berlin ...
.
[Berlin-Brandenburgische Akademie der Wissenschaften]
Mitglieder der Vorgänger-Akademien
URL. Retrieved 19 February 2010.
The crater
Le Monnier on the
Moon
The Moon is Earth's only natural satellite. It is the fifth largest satellite in the Solar System and the largest and most massive relative to its parent planet, with a diameter about one-quarter that of Earth (comparable to the width of ...
is named after him.
Works
*''Histoire céleste'' (1741)
*''Théorie des comètes'' (1743, a translation, with additions of Halley's ''Synopsis'')
*''Institutions astronomiques'' (1746, an improved translation of
John Keill's textbook)
*''Nouveau zodiaque'' (1755)
*''Observations de la lune, du soleil, et des étoiles fixes'' (1751–1775)
*''Lois du magnétisme'' (1776–1778)
References
;Attribution
*
External links
{{DEFAULTSORT:Le Monnier, Pierre
1715 births
1799 deaths
Scientists from Paris
18th-century French astronomers
Members of the French Academy of Sciences
Fellows of the Royal Society
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