**Christian Huygens** He was a Dutch mathematician, physicist and astronomer, born in The Hague, The Netherlands, on April 14, 1629. He was the second of four children of the poet and diplomat Constantijn Huygens (1596-1687). He was a man of wide culture who also devoted himself to the sciences. From his father, Huygens received his first instruction in mathematics and mechanics at the age of thirteen, and from early on aroused interest and skill in both.

He became the most prestigious international scientist of his day. As a child, he met renowned intellectuals such as René Descartes and received an education in mathematics and physics at Leiden University, where he studied with Frans van Schooten, a former student of Descartes.

At the age of sixteen, Huygens entered Leyden University to study law and was soon transferred to Breda, where his father headed the new university, graduating two years later in law. In both places he continued his studies in mathematics, but only after graduating did he turn his attention to the study of the physical and mathematical sciences.

At seventeen, he communicated his first mathematical discovery to Mersene, who introduces it to Archimedes' works, and was soon in correspondence with the most important scientists in Europe. In 1651, at the age of 21, Huygens published his first mathematical works, the most important being the quadrature of the conic sections. In 1654, he made the best approximation, made at the time, of the circle area. Two years later he sends Van Schooten his work on probability calculus entitled * From ratiociniis in ludo aleae*.

Huygens soon became famous as a mathematician, and his main contributions were the infinitesimal analysis of the conics (1656), the surface calculation of a paraboloid revolution (1657) and, most importantly, the complementation of the studies by Pascal and Fermat on the theory of probability (1657).

Using a telescope of his own, he observed that Saturn was surrounded by rings (1659) and discovered the Orion Nebula. He later became interested in the accurate measurement of time, which led to his discovery of the pendulum as a clock regulator. About the influence of Mersenne acquired great interest for experiments with vacuum.

He researched the behavior of pure liquids, air resistance and polishing and lens assembly. In mechanics he spelled out the principle of centrifugal force and the remarkable law of the pendulum. This inventor is attributed the creations, among others, of the grandfather clock (1657) and the pressure gauge (1661).

In 1666 he moved to Paris, permanently weakening Leyden's group, which had fallen into decay since the death of Schooten (1660) and became a foreign member of the "young" Academie des Sciences (1666). In his research on the behavior of the pendulum he made a mathematical discovery considered of paramount importance: the involute cycloid theorem, published in his famous treatise Horologium oscillatorium (1673), a classic of scientific literature on circular and pendular motion, conservation of kinetic energy. and other mechanical studies.

He discovered the polarization of light (1678) and formulated the wave theory of light propagation in * Traité de la lumière* (1690) elaborating the famous principle of Huygens, in which he expounded his conception of light as a wave of energy propagating in space, a theory that would later be developed by Fresnel. This theory had its first arguments with Aristotle and later with Da Vince and Galileo.

Huygens died in his hometown (The Hague) on July 8, 1695.

Encyclopaedia Britannica, vol: 11, p.949, 1963; Great Books of the Western World, Encyclopaedia Britannica, Editor William Blake, Newton & Huygens, Vol.34, p. 547-548, 1952; Philip Cane, Giants of Science, Ediouro. * Photo taken from MacTutor History of Mathematics.