Arago, Francois

Dominic Francois Jean Arago was born on February 26, 1786 in Estagel , near Perpignan .

At the age of 18, Arago entered the Polytechnic School , and in 1806 he received the position of secretary in the Bureau of Longitude . In this position, he continued with Jean-Baptiste Bio and the Spanish commissars Sche and Rodriguez the measurement of the meridian in the space from Barcelona to the island of Formentera , begun by Delambre and Meschen, and was in Mallorca just at the time when the rebellion against Spain began Napoleon . There Arago was arrested and spent several months in custody at the Belver citadel near Palma . After being released, he tried to cross to Algeria in order to sail from there to Marseille on an Algerian ship, but the ship was captured by a Spanish cruiser , and Arago was taken to Fort Rosas . Finally, at the request of the Algerian dey, he was released and again tried to return to Marseille, but a storm arose near the harbor itself and the ship Arago washed ashore to the Sardinian coast, from where, however, he managed to get to Algeria. But the former dei was already killed, and the new ruler put Arago on the list of slaves and used him as an interpreter on the ships of corsairs . Only in 1809, at the repeated request of the French consul , Arago received freedom and finally reached Marseille, barely escaping the persecution of the English frigate . Despite all the adventures, Arago managed to preserve the results of his observations, which he presented in the work “Recueil d'observations géodésiques, astronomiques et physiques”. Shortly afterwards, at the age of only 23 years old, he was elected to the Academy of Sciences in the vacant Lalanda place and was appointed Napoleon I as a professor at the Polytechnic School.

In 1812, he was born the son of Francois Victor Emmanuel , a future diplomat, Minister of Justice and Minister of the Interior of France ^[6] .

At the Polytechnic School, Arago taught until 1831 mathematical analysis in geodesy . Later, he was mainly engaged in astronomy, physics (especially the polarization of light, galvanism and magnetism ), meteorology and physical geography .

Foreign member of the Bavarian Academy of Sciences (1843) ^[7] .

The merits of Arago in various fields of science are enormous. Possessing a penetrating mind and extraordinary observation, he introduced new things into each of the sections he was engaged in. So, for example, living in solitude at his geodesic stations in Spain, he noticed that his vision penetrated freely to the seabed dotted with pitfalls, and this simple observation led him to interesting studies about the ratio of light reflected from the surface of the water at sharp angles, to the light coming straight from the seabed. Having learned this relationship, he applied it to the discovery of pitfalls by means of a tourmaline plate cut parallel to the axis of double refraction.

Arago made a number of discoveries that significantly advanced science. The most fruitful period of his activity was the time from 1811 to 1824. During these thirteen years of Arago:

1. He discovered the polarization of the scattered light of the sky.
2. He made precise observations on the movement of colored stripes originating from the meeting of two rays, of which one passes through a thin transparent plate.
3. He experimentally confirmed the existence of a bright spot in the center of the geometric shadow of an opaque object ( Poisson-Arago spot ), which was one of the decisive proofs of the correctness of the diffraction theory developed by Fresnel .
4. The first noticed that iron filings are attracted by the conductor of electricity in the experience of Oersted
5. He was the first to pass an electric current in a spiral with an arrow embedded in it, which was magnetized by both discharging a Leiden can and the current of the Volta column .
6. Established a connection between auroras and magnetic storms.
7. While in Greenwich , I noticed the so-called rotation magnetism - the action of a rotating metal plate on a magnetic needle.

Observing with Humboldt in 1825 the power of magnetism through the swings of the tilt arrow, he pointed out to his colleague that the swings of the arrow quickly cease when there are metallic or non-metallic bodies near it. He applied this observation to the explanation of phenomena during the rotation of ice or glass circles above a magnetic arrow, which is at rest.

Until the end of his life, Arago did not stop making extremely important and useful discoveries. So, having discovered color polarization, he invented a polariscope , photometer , cyanometer and many other useful instruments for studying optical phenomena. He successfully applied his observations on color polarization to the study of light, atmosphere, and the sun and discovered the so-called “midpoint of polarization” (the point at which polarization is invisible). Arago applied the interference of light to explain the glitter of stars; this theory is given by Humboldt in the 4th volume of his "Travels to Equinox Countries".

When in 1835, Wheatstone , exploring the speed of electricity and light, built a witty device from rotating mirrors, Arago quickly realized that the speed of light could be determined with such a device, and presented in 1838 a plan of new experiments. The mechanic Breguet was engaged in the manufacture of these devices, but there were many difficulties, and only in 1850 he was able to achieve satisfactory results, but by this time Arago had very weak eyesight, so that he could not begin to experiment. At a meeting of the Institute on April 29, 1850, he openly stated: "I am forced to limit myself to only setting out the problem and pointing out the correct ways to solve it." Two talented physicists - Fizeau and Foucault - were not slow to take advantage of his valuable instructions, determined the speed of light in the atmosphere, and in their reports to the Academy of Sciences, the first in 1850 and the second in 1851, gave a solid foundation to the theory of light, refuting the existing hypothesis of expiration. Numerous discoveries and works of Arago are set forth in his writings, which are divided by Humboldt into 5 parts: astronomical (Especially known among them is "Comprehensible Astronomy", or the presentation of public astronomical lectures of Arago from 1812 to 1845, translated into Russian), as well as works in optics , electromagnetism , meteorology and physical geography .

In 1806, Arago accurately measured the Paris meridian , defined in 1718 by Jacques Cassini . This meridian was until 1884 the zero meridian . It passes through the Paris Observatory and is indicated throughout Paris with the help of columns, as well as special marks ( bronze Arago medallions in honor of the famous physicist) on pavements , sidewalks and buildings, including the Louvre . In addition, Arago published the first comprehensive work in the world scientific literature on ball lightning , summarizing his 30 observations of eyewitnesses, which laid the foundation for the study of this natural phenomenon.

Arago was the first to announce the creation of photography by reading a report on the work of Daguerre and Nieps on January 7, 1839 at a meeting of the French Academy of Sciences . He also contributed to the purchase of the invention by the French government, which made daguerreotype public domain ^[8] . His name is included in the list of the greatest scientists of France , placed on the ground floor of the Eiffel Tower .

Involved in the discovery of Neptune - participated in scientific correspondence with leading scientists on the problem of perturbations of the orbit of the planet Uranus ; in the summer of 1845, as the director of the Paris Observatory and the head of French astronomy of that time, he turned to U. J. J. Le Verrier , offering to tackle the “Uranus problem” and to make a mathematical analysis of the motion of Uranus. The phrase Arago about Neptune “a planet open at the tip of a pen ” became winged.

In honor of Arago, the asteroid (1005) Arago , discovered in 1923, and the Arago crater on the Moon are named .

Of considerable interest is his autobiography , in which Arago shows himself to be perfectly honest, impartial, solid man and a citizen, as he really was, according to the testimony of his contemporary biographers . Arago published many articles in Mémoires, Comptes rendus, and Annales de chimie et de physique, which he published with Gay-Lussac , more than 80 articles in which he published, and since 1824 Arago published a series of popular essays in the Annuaire des longitudes, some of which were translated into other languages ​​more than once and was also published with Eloges and his other articles in the Barrale edition of Arago's works (Oeuvres, 17 volumes, Paris, 1854 -1862; German translation of Hankel, with the introduction of A. Humboldt, 16 volumes, Leipzig, 1854-1860). His works are distinguished by a clear statement of the most difficult scientific questions.

Arago also played an important role in politics. He was at one time one of the most popular people in France. In 1831 he was elected as a member of the Chamber of Deputies by the electoral college in Perpignan, where he joined the extreme “left” republican opposition. Having joined the Provisional Government after the February Revolution of 1848 , Arago simultaneously performed duties in the military and naval ministries and at the same time was a member of the executive commission. As a statesman, Arago firmly defended the main points of the state system against socialist movements and showed determination in suppressing the June uprising . Following this, he participated in the National Assembly, with the rank of member of the Military Committee. After the coup on December 2, 1851, Arago took the place of director of the observatory , despite the fact that he refused to take the oath of office to the new government of Napoleon III, from which he was released. He died in Paris on October 2, 1853. The opening of the monument to Arago in Perpignan took place on September 21, 1879.

From the works of Arago published in Russian by Khotinsky : “Thunder and Lightning” (St. Petersburg, 1859), “Common Astronomy” (St. Petersburg, 1861, 4 volumes), “Historical Note on Steam Engines” (St. Petersburg, 1861) , “Selected Articles from Notes on Scientific Subjects” (2 volumes, St. Petersburg, 1866), “Biographies of famous astronomers, physicists and geometers” (St. Petersburg, 3 volumes translated and supplemented by D. Perevoshchikov).

• Kolchinsky I.G., Korsun A.A., Rodriguez M.G. Astronomers: A Biographical Reference. - 2nd ed., Revised. and additional .. - Kiev: Naukova Dumka, 1986. - 512 p.
• Hramov Yu. A. Arago Dominic Francois // Physicists: Biographical Reference / Ed. A.I. Akhiezer . - Ed. 2nd, rev. and add. - M .: Nauka , 1983 .-- S. 18. - 400 p. - 200,000 copies. (per.)
• 100 years of photography. Daguerre, Nieps, Talbot . - M .: "Goskinoizdat", 1938. - 62 p.

• Arago Dominic Francois // Brockhaus and Efron Encyclopedic Dictionary : in 86 volumes (82 volumes and 4 additional). - SPb. , 1890-1907.
• Profile of Dominic-Francois-Jean Arago on the official website of the RAS