Marin Mersenne

French theologian, philosopher, and mathematician; b. 8 September, 1588, near Oizé (now Department of Sarthe); d. 1 September, 1648 at Paris.  Marin Mersenne was perhaps the most brilliant and the most unknown men of the 16th and 17th centuries. Born of peasant parents near Oizé, Maine (present day Sarthe, France). He was educated at Le Mans and at the Jesuit College of La Flèche,  where a lifelong friendship with Descartes, his fellow student, originated. On 17 July 1611, he joined the Minim Friars at Nigeon near Paris and, after studying theology and Hebrew in Paris, was ordained a priest in 1613. Between 1614 and 1618, he taught theology and philosophy at Nevers, but he returned to Paris and settled at the  Minim convent of L’Annonciade in 1619, where he lived for the rest of his life. 

There he studied mathematics and music. By 1626, he held weekly scientific discussions in the convent and met with other kindred spirits such as René Descartes, Étienne Pascal, Pierre Petit, Gilles de Roberval, Thomas Hobbes, and Nicolas-Claude Fabri de Peiresc. 

His first publications were theological and polemical studies against Atheism and Scepticism, but later, Mersenne devoted his time almost exclusively to science, making personal experimental researches, and publishing a number of works on mathematical sciences. 

His most remarkable personal trait was his ability to maintain close personal friendships with men who genuinely hated each other’s scientific ideas. In 1635 he set up the informal Académie Parisienne (Academia Parisiensis) which had nearly 140 correspondents including astronomers and philosophers as well as mathematicians. His network was the precursor of the of the Royal Society in London, founded in 1660, twelve years after Mersenne’s death  and the Parisian Académie des sciences established by Jean-Baptiste Colbert in 1666. The stimulus he gave to other writers in many fields — by posing problems, transmitting objections, supplying information, brokering contacts, prompting publication or indeed organizing it himself — was absolutely invaluable.

His chief merit was the encouragement which he gave to scientists of his time, the interest he took in their work, and the stimulating influence of his suggestions and questions. Gassendi and Galileo were among his friends; but, above all, Mersenne is known today as Descartes's friend and adviser. In fact, when Descartes began to lead a free and dissipated life, it was Mersenne who brought him back to more serious pursuits and directed him toward philosophy. In Paris, Mersenne was Descartes's assiduous correspondent, auxiliary, and representative, as well as his constant defender. The numerous and vehement attacks against the "Meditations" seem, for a moment, to have aroused Mersenne's suspicions; but Descartes's answers to his critics gave him full satisfaction as to his friend's orthodoxy and sincere Christian spirit.

Mersenne’s correspondance network of Europe’s top scientists, put him in communication with Giovanni Doni, Constantijn Huygens, Galileo Galilei, and other scholars in Italy, England and the Dutch Republic. He was a staunch defender of Galileo, assisting him in translations of some of his mechanical works, and spreading his discoveries throughout Europe. He disagreed with the views of skepticism, the idea that the world is completely unknowable. Instead, he asserted that knowledge should freely advance through experiment and observation, frequently chiding scholars for not including accurate experimental data in their paperr, while insisting that hypotheses are, at best, probable explanations. He argued that true physics could only be descriptive and strenuously fought the Rosicrucian ideas of the day. 

In mathematics, he discovered what are now known as Mersenne Primes. In astronomy, he discovered the telephoto effect, and was the first to establish both the two-mirror telescope and the afocal telescope, along with the beam compressor that is useful in many multiple-mirror scopes today. He demonstrated how to correct spherical aberration. His work on the pendulum was superior to even Galileo’s. 

But, it is his book, L’Harmonie universelle, that is his most influential work. It is one of the earliest comprehensive works on music theory, touching on a wide range of musical concepts, and especially the mathematical relationships involved in music. The work contains the earliest formulation of what has become known as Mersenne’s laws, which describe the frequency of oscillation of a stretched string.  For this work, he is known as the Father of Acoustics.


Mersenne's works are: "Quæstiones celeberrimæ in Genesim" (Paris, 1623), against Atheists and Deists; a part only has been published, the rest being still in manuscript, as also a "Commentary on St. Matthew's Gospel"; "L'impiété des déistes et des plus subtils libertins découverte et réfutée par raisons de théologie et de philosophie" (Paris, 1624); "La vérité des sciences contre les sceptiques et les pyrrhoniens" (Paris, 1625); "Questions theólogiques, physiques, morales et mathématiques" (Paris, 1634); "Questions inouïes, ou récréations des savants" (Paris, 1634); Les mécaniques de Galilée" (Paris, 1634), a translation from the Italian; "Harmonie universelle, contenant la théorie et la pratique de la musique" (Paris, 1936-7); "Nouvelles découvertes de Galilée", and "Nouvelles pensées de Galilée sur les mécaniques" (Paris, 1639), both translations; "Cogitata physico-mathematica" (Paris, 1644); "Euclidis elementorum libri, Apollonii Pergæ conica, Sereni de sectione coni, etc." (Paris, 1626), selections and translations of ancient mathematicians, published again later with notes and additions under the title, "Universæ geometriæ mixtæque mathematicæ synopsis" (Paris, 1644).


Mersenne asked that, after his death, an autopsy be made on his body, so as to serve to the last the interests of science.