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Jean-Jacques d'Ortous de Mairan

Jean-Jacques d'Ortous de Mairan (26 November 1678 – 20 February 1771) was a French natural philosopher (physicist), born in the town of Béziers on 26 November 1678.[1] De Mairan lost his father, François d'Ortous, at age four and his mother twelve years later at age sixteen.[1] Over the course of his life, de Mairan was elected into numerous scientific societies and made key discoveries in a variety of fields including ancient texts and astronomy. His observations and experiments also inspired the beginning of what is now known as the study of biological circadian rhythms. At the age of 92, de Mairan died of pneumonia in Paris on 20 February 1771.

Jean-Jacques d'Ortous de Mairan

26 November 1678

Béziers, France

20 February 1771(1771-02-20) (aged 92)

Paris, France

University of Toulouse

Studies of circadian rhythm

Elected to the French Academy of Sciences, Fellow of the Royal Society, Foreign Member of the Royal Swedish Academy of Sciences

Geophysics, astronomy, chronobiology

Cardinal de Fleury, Louis XV, Prince of Conti, Duke of Orléans

Nicolas Malebranche

In 1719, De Mairan discussed the varying of light that causes cold in winter and heat in summer. He postulated that the sun's heating effect was related to the square of the sine of its elevation. He neglected the effects of atmosphere, admitting that he did not know how much the sun's heat would be absorbed by it. Two and a half years later, he presented a paper to the Academie Royale des Sciences in Paris: "Problem: the ratio of two degrees or quantities of sunlight seen through the atmosphere at two different known angular elevations being given, to find what part of the absolute light of the sun is intercepted by the atmosphere at any desired elevation." In this paper, de Mairan made a hypothesis based on mere observations, supposing that the ratio had been measured, even though it had not. The significance of de Mairan's work, although incorrect, led his protégé, Pierre Bouguer, to invent the photometer.[2]

obliquity

In 1729, de Mairan constructed an experiment showing the existence of a in plants, presumably originating from an endogenous clock (See 'Experiment on circadian rhythms in plants' below).

circadian rhythm

In 1731, he also observed a nebulosity around a near the Orion nebula. This was later designated M43 by Charles Messier.

star

In 1731, he published "Traite Physique et Historique De l'Aurore Boreale" (a short summary appeared in the [3]) in which he put up a novel hypothesis that the Northern Lights are caused by the Sun, as the interaction of the atmosphere with the zodiacal light. At the time, the aurorae were thought to be 'flames' caused by sulfurous effluvia emanating from the Earth.

Philosophical Transactions

Scientific societies and recognition[edit]

In 1718, de Mairan was inducted into the Académie Royale des Sciences.[1] The Cardinal de Fleury and the Count of Maurepas selected Mairan to replace Bernard le Bovier de Fontenelle as "Secrétaire perpétuel" of the Académie in 1740, a position he accepted only for 3 years, and thus duly resigned in 1743.[1] De Mairan also served as the Académie's assistant director and later director intermittently between 1721 and 1760.[1] Eventually, de Mairan was appointed editor of the Journal des sçavans, a science periodical, by Chancellor d'Aguesseau.[1] Also, in 1735, de Mairan was elected a Fellow of the Royal Society and in 1769, a Foreign Member of the Royal Swedish Academy of Sciences as well as to the Russian Academy (St. Petersburg) in 1718.[1] De Mairan was also a member of the Royal Societies of London, Edinburgh, and Uppsala; the Institute of Bologna,[1] and the Academy of Rouen.[12] With Jean Bouillet and Antoine Portalon, he founded his own scientific society in his hometown of Béziers, named the Académie de Béziers, around 1723.[1]

Dissertation sur les variations du barometre (Bordeaux, 1715) (Essays on barometric variations)

(Bordeaux, 1716) (Essay on the ice)

Dissertation sur la glace

(Bordeaux, 1717) (Dissertation on the cause of light phosphates and noctilucence or nightly light)

Dissertation sur la cause de la lumiere des phosphores et des noctiluques

(1728) (Essay on the estimation of the measures of acting forces on the body)

Dissertation sur l'estimation et la mesure des forces motrices des corps

Lettre de m. de Mairan a Madame. Sur la question des forces vives (1741) (Letter to Mme Chatelet on the Question of Living Forces), one side of a with Émilie du Châtelet on forces vives.

public debate

Beyond astronomical and circadian observations, de Mairan actively worked in several other fields of physics including "heat, light, sound, motion, the shape of the Earth, and the aurora".[1]


The following is an abbreviated list of publications (with their English translations) organised by Dr. Robert A. Hatch at the University of Florida:[13][14]


He also published mathematical works.

Galileo project entry

SEDS Biography

At the dawn of chronobiology

Biological Clocks — Garden Variety Experiments

Clock Classics: It all started with the plants

Ellen McNiven Hine (1996): Jean-Jacques Dortous de Mairan and the Geneva connection: Scientific networking in the eighteenth century (The Voltaire Foundation)