François Arago
Encyclopedia
François Jean Dominique Arago , known simply as François Arago (fʁɑ̃swa aʁaɡo; Catalan: Francesc Aragó, fɾənˈsɛsk əɾəˈɣo) (1786–1853), was a French mathematician
, physicist
, astronomer
and politician
.
, a small village near Perpignan
, in the département of Pyrénées-Orientales
, France, where his father held the position of Treasurer of the Mint. He was the eldest of four brothers. Jean (1788–1836) emigrated to North America and became a general in the Mexican
army. Jacques Étienne Victor
(1799–1855) took part in Louis de Freycinet
's exploring voyage in the Uranie from 1817 to 1821, and on his return to France devoted himself to his journalism and the drama. The fourth brother, Étienne Vincent de
(1802–1892), is said to have collaborated with Honoré de Balzac
in The Heiress of Birague, and from 1822 to 1847 wrote a great number of light dramatic pieces, mostly in collaboration.
Showing decided military tastes, François Arago was sent to the municipal college of Perpignan
, where he began to study mathematics
in preparation for the entrance examination of the École Polytechnique
. Within two years and a half he had mastered all the subjects prescribed for examination, and a great deal more, and, on going up for examination at Toulouse
, he astounded his examiner by his knowledge of J. L. Lagrange
.
Towards the close of 1803 Arago entered the École Polytechnique
, Paris, but apparently found the professors there incapable of imparting knowledge or maintaining discipline. The artillery
service was his ambition, and in 1804, through the advice and recommendation of Siméon Poisson, he received the appointment of secretary to the Paris Observatory
. He now became acquainted with Pierre-Simon Laplace
, and through his influence was commissioned, with Jean-Baptiste Biot
, to complete the meridian arc
measurements which had been begun by J. B. J. Delambre, and interrupted since the death of P. F. A. Méchain in 1804). Arago and Biot left Paris in 1806 and began operations along the mountains of Spain. Biot returned to Paris after they had determined the latitude of Formentera
, the southernmost point to which they were to carry the survey. Arago continued the work until 1809, his purpose being to measure a meridian arc
in order to determine the exact length of a metre.
After Biot's departure, the political ferment caused by the entrance of the French into Spain extended to the Balearic Islands
, and the population suspected Arago's movements and his lighting of fires on the top of Mount Galatzó (Catalan
: Mola de l'Esclop) as the activities of a spy for the invading army. Their reaction was such that he was obliged to give himself up for imprisonment in the fortress of Bellver in June 1808. On 28 July he escaped from the island in a fishing-boat, and after an adventurous voyage he reached Algiers
on 3 August. From there he obtained a passage in a vessel bound for Marseille
, but on 16 August, just as the vessel was nearing Marseille, it fell into the hands of a Spanish corsair
. With the rest the crew, Arago was taken to Roses, and imprisoned first in a windmill, and afterwards in a fortress, until the town fell into the hands of the French, when the prisoners were transferred to Palamos
.
After three months' imprisonment, Arago and the others were released on the demand of the dey
of Algiers, and again set sail for Marseille on 28 November, but then within sight of their port they were driven back by a northerly wind to Bougie
on the coast of Africa. Transport to Algiers by sea from this place would have occasioned a weary delay of three months; Arago, therefore, set out over land, guided by a Muslim priest, and reached it on Christmas Day. After six months in Algiers he once again, on 21 June 1809, set sail for Marseille, where he had to undergo a monotonous and inhospitable quarantine in the lazaretto
, before his difficulties were over. The first letter he received, while in the lazaretto, was from Alexander von Humboldt
; and this was the origin of a connection which, in Arago's words, lasted over forty years without a single cloud ever having troubled it.
at Paris. As a reward for his adventurous conduct in the cause of science, he was elected a member of the French Academy of Sciences
, at the remarkably early age of twenty-three, and before the close of 1809 he was chosen by the council of the École Polytechnique
to succeed Gaspard Monge
in the chair of analytical geometry. At the same time he was named by the emperor one of the astronomers of the Royal Observatory, which was accordingly his residence till his death, and it was in this capacity that he delivered his remarkably successful series of popular lectures in astronomy, which were continued from 1812 to 1845.
In 1816, along with Joseph Louis Gay-Lussac
, he started the Annales de chimie et de physique
, and in 1818 or 1819 he proceeded along with Biot to execute geodetic
operations on the coasts of France, England and Scotland. They measured the length of the seconds-pendulum at Leith
, Scotland, and in the Shetland Islands
, the results of the observations being published in 1821, along with those made in Spain. Arago was elected a member of the Bureau des Longitudes immediately afterwards, and contributed to each of its Annuals, for about twenty-two years, important scientific notices on astronomy and meteorology
and occasionally on civil engineering
, as well as interesting memoirs of members of the Academy.
Arago's earliest physical researches were on the pressure
of steam
at different temperatures, and the velocity
of sound, 1818 to 1822. His magnet
ic observations mostly took place from 1823 to 1826. He discovered rotatory magnetism, what has been called Arago's rotations
, and the fact that most bodies could be magnetized; these discoveries were completed and explained by Michael Faraday
.
Arago warmly supported Augustin-Jean Fresnel
's optical
theories, helping to confirm Fresnel's wave theory of light by observing what is now known as the spot of Arago
. The two philosophers conducted together those experiments on the polarization of light which led to the inference that the vibration
s of the luminiferous ether were transverse to the direction of motion
, and that polarization consisted of a resolution of rectilinear propagation
into components at right angles to each other. The subsequent invention of the polariscope and discovery of Rotary polarization
are due to Arago. He invented the first polarization filter in 1812.
The general idea of the experimental determination of the velocity of light in the manner subsequently effected by Hippolyte Fizeau
and Léon Foucault
was suggested by Arago in 1838, but his failing eyesight prevented his arranging the details or making the experiments.
Arago's fame as an experimenter and discoverer rests mainly on his contributions to magnetism and still more to optics
. He showed that a magnetic needle, made to oscillate over nonruginous surfaces, such as water, glass, copper, etc., falls more rapidly in the extent of its oscillations according as it is more or less approached to the surface. This discovery, which earned him the Copley Medal
of the Royal Society
in 1825, was followed by another, that a rotating plate of copper tends to communicate its motion to a magnetic needle suspended over it ("magnetism of rotation"). Arago is also fairly entitled to be regarded as having proved the long-suspected connexion between the aurora borealis and the variations of the magnetic elements. In 1828, he was elected a foreign member of the Royal Swedish Academy of Sciences
.
In optics, Arago not only made important optical discoveries on his own, but is credited with stimulating the genius of Jean-Augustin Fresnel, with whose history, as well as that of Etienne-Louis Malus
and Thomas Young
, this part of his life is closely interwoven.
Shortly after the beginning of the 19th century the labours of at least three philosophers were shaping the doctrine of the undulatory, or wave, theory of light. Fresnel's arguments in favour of that theory found little favour with Laplace, Poisson and Biot, the champions of the emission theory; but they were ardently espoused by Humboldt and by Arago, who had been appointed by the Academy to report on the paper. This was the foundation of an intimate friendship between Arago and Fresnel, and of a determination to carry on together further fundamental laws of the polarization of light known by their means. As a result of this work, Arago constructed a polariscope, which he used for some interesting observations on the polarization of the light of the sky. To him also is due the discovery of the power of rotatory polarization exhibited by quartz
.
Among Arago's many contributions to the support of the undulatory hypothesis, comes the experimentum crucis which he proposed to carry out for measuring directly the velocity of light in air and in water and glass. On the emission theory the velocity should be accelerated by an increase of density in the medium; on the wave theory, it should be retarded. In 1838 he communicated to the Academy the details of his apparatus, which utilized the relaying mirrors employed by Charles Wheatstone
in 1835 for measuring the velocity of the electric discharge; but owing to the great care required in the carrying out of the project, and to the interruption to his labours caused by the revolution of 1848, it was the spring of 1850 before he was ready to put his idea the test; and then his eyesight suddenly gave way. Before his death, however, the retardation of light in denser media was demonstrated by the experiments of H. L. Fizeau and B. L. Foucault, which, with improvements in detail, were based on the plan proposed by him.
In 1830, Arago, who always professed liberal opinions of the republican
type, was elected a member of the chamber of deputies for the Pyrénées-Orientales
département, and he employed his talents of eloquence and scientific knowledge in all questions connected with public education, the rewards of inventors, and the encouragement of the mechanical and practical sciences. Many of the most creditable national enterprises, dating from this period, are due to his advocacy – such as the reward to Louis-Jacques Daguerre for the invention of photography, the grant for the publication of the works of Fermat and Laplace
, the acquisition of the museum of Cluny, the development of railways and electric telegraphs, the improvement of the reneile.
In 1830 Arago also was appointed director of the Observatory, and as a member of the chamber of deputies he was able to obtain grants of money for rebuilding it in part, and for the addition of magnificent instruments. In the same year, too, he was chosen perpetual secretary of the Academy of Sciences, the place of J. B. J. Fourier. Arago threw himself into its service, and by his faculty of making friends he gained at once for it and for himself a worldwide reputation. As perpetual secretary it was his duty to pronounce historical éloges on deceased members; and for this duty his rapidity and facility of thought, and his happy piquancy of style, and his extensive knowledge peculiarly adapted him. He was elected a Foreign Honorary Member of the American Academy of Arts and Sciences
in 1832.
In 1834 Arago again visited Scotland
, to attend the meeting of the British Association
at Edinburgh
. From this time till 1848 he led a life of comparative quiet – although he continued to work within the Academy and the Observatory to produce a multitude of contributions to all departments of physical science – but on the fall of Louis-Philippe
he left his laboratory to join the Provisional Government (24 February 1848). He was entrusted with two important functions, that had never before been given to one person, viz. the ministry of marine and colonies (24 February 1848 – 11 May 1848) and ministry of war (5 April 1848 – 11 May 1848); in the former capacity he improved of rations in the navy and abolished flogging. He also abolished political oaths of all kinds, and, against an array of moneyed interests, succeeded in procuring the abolition of slavery
in the French colonies
.
On 10 May 1848, Arago was elected a member of the Executive Power Commission
, a governing body of the French Republic. He was made President of the Executive Power Commission (11 May 1848) and served in this capacity as provisional head of state until 24 June 1848, when collective resignation of the Commission was submitted to the National Constituent Assembly. At the beginning of May 1852, when the government of Louis Napoleon
required an oath of allegiance from all its functionaries, Arago peremptorily refused, and sent in his resignation of his post as astronomer at the Bureau des Longitudes. This, however, the prince president declined to accept, and made "an exception in favour of a savant whose works had thrown lustre on France, and whose existence the government would regret to embitter."
, complicated by dropsy, he resigned his post as astronomer rather than take the oath of allegiance
. Napoleon III
gave directions that the old man should be in no way disturbed, and should be left free to say and do what he liked. In the summer of 1853 Arago was advised by his physicians to try the effect of his native air, and he accordingly set out to the eastern Pyrenees
, but it was ineffective and he died in Paris. His grave is at the famous cemetery Père Lachaise in Paris.
Craters on Mars
and the Moon
, and a ring of Neptune
, are named after Arago, as well as the study association for Applied Physics at the University of Twente. His name is one of the 72 names inscribed on the Eiffel Tower.
Arago's works were published after his death under the direction J. A. Barral, in 17 vols., 8vo, 1854–1862; also separately his Astronomie populaire, in 4 vols.; Notices biographiques, in 3 vols.; Indices scientifiques, in 5 vols.; Voyages scientifiques, in 1 vol.; Grimoires scientifiques, in 2 vols.; Mélanges, in I vol.; and Tables analytiques et documents importants (with portrait), in 1 vol.
English translations of the following portions of Arago's works have appeared:
Mathematician
A mathematician is a person whose primary area of study is the field of mathematics. Mathematicians are concerned with quantity, structure, space, and change....
, physicist
Physicist
A physicist is a scientist who studies or practices physics. Physicists study a wide range of physical phenomena in many branches of physics spanning all length scales: from sub-atomic particles of which all ordinary matter is made to the behavior of the material Universe as a whole...
, astronomer
Astronomer
An astronomer is a scientist who studies celestial bodies such as planets, stars and galaxies.Historically, astronomy was more concerned with the classification and description of phenomena in the sky, while astrophysics attempted to explain these phenomena and the differences between them using...
and politician
Politician
A politician, political leader, or political figure is an individual who is involved in influencing public policy and decision making...
.
Early life and work
Arago was born at EstagelEstagel
Estagel is a commune in the Pyrénées-Orientales department in southern France.-References:*...
, a small village near Perpignan
Perpignan
-Sport:Perpignan is a rugby stronghold: their rugby union side, USA Perpignan, is a regular competitor in the Heineken Cup and seven times champion of the Top 14 , while their rugby league side plays in the engage Super League under the name Catalans Dragons.-Culture:Since 2004, every year in the...
, in the département of Pyrénées-Orientales
Pyrénées-Orientales
Pyrénées-Orientales is a department of southern France adjacent to the northern Spanish frontier and the Mediterranean Sea. It also surrounds the tiny Spanish enclave of Llívia, and thus has two distinct borders with Spain.- History :...
, France, where his father held the position of Treasurer of the Mint. He was the eldest of four brothers. Jean (1788–1836) emigrated to North America and became a general in the Mexican
Mexico
The United Mexican States , commonly known as Mexico , is a federal constitutional republic in North America. It is bordered on the north by the United States; on the south and west by the Pacific Ocean; on the southeast by Guatemala, Belize, and the Caribbean Sea; and on the east by the Gulf of...
army. Jacques Étienne Victor
Jacques Arago
Jacques Étienne Victor Arago was a French writer, artist and explorer, author of a Voyage Round the World.-Biography:...
(1799–1855) took part in Louis de Freycinet
Louis de Freycinet
Louis Claude de Saulces de Freycinet was a French navigator. He circumnavigated the earth, and was one of the first to produce a comprehensive map of the coastline of Australia.-Biography:...
's exploring voyage in the Uranie from 1817 to 1821, and on his return to France devoted himself to his journalism and the drama. The fourth brother, Étienne Vincent de
Étienne Arago
Étienne Arago was a French writer and politician, and co-founder of the newspaper Le Figaro.-Early life:Arago was born in Perpignan, the youngest of the four Arago brothers...
(1802–1892), is said to have collaborated with Honoré de Balzac
Honoré de Balzac
Honoré de Balzac was a French novelist and playwright. His magnum opus was a sequence of short stories and novels collectively entitled La Comédie humaine, which presents a panorama of French life in the years after the 1815 fall of Napoleon....
in The Heiress of Birague, and from 1822 to 1847 wrote a great number of light dramatic pieces, mostly in collaboration.
Showing decided military tastes, François Arago was sent to the municipal college of Perpignan
Perpignan
-Sport:Perpignan is a rugby stronghold: their rugby union side, USA Perpignan, is a regular competitor in the Heineken Cup and seven times champion of the Top 14 , while their rugby league side plays in the engage Super League under the name Catalans Dragons.-Culture:Since 2004, every year in the...
, where he began to study mathematics
Mathematics
Mathematics is the study of quantity, space, structure, and change. Mathematicians seek out patterns and formulate new conjectures. Mathematicians resolve the truth or falsity of conjectures by mathematical proofs, which are arguments sufficient to convince other mathematicians of their validity...
in preparation for the entrance examination of the École Polytechnique
École Polytechnique
The École Polytechnique is a state-run institution of higher education and research in Palaiseau, Essonne, France, near Paris. Polytechnique is renowned for its four year undergraduate/graduate Master's program...
. Within two years and a half he had mastered all the subjects prescribed for examination, and a great deal more, and, on going up for examination at Toulouse
Toulouse
Toulouse is a city in the Haute-Garonne department in southwestern FranceIt lies on the banks of the River Garonne, 590 km away from Paris and half-way between the Atlantic Ocean and the Mediterranean Sea...
, he astounded his examiner by his knowledge of J. L. Lagrange
Joseph Louis Lagrange
Joseph-Louis Lagrange , born Giuseppe Lodovico Lagrangia, was a mathematician and astronomer, who was born in Turin, Piedmont, lived part of his life in Prussia and part in France, making significant contributions to all fields of analysis, to number theory, and to classical and celestial mechanics...
.
Towards the close of 1803 Arago entered the École Polytechnique
École Polytechnique
The École Polytechnique is a state-run institution of higher education and research in Palaiseau, Essonne, France, near Paris. Polytechnique is renowned for its four year undergraduate/graduate Master's program...
, Paris, but apparently found the professors there incapable of imparting knowledge or maintaining discipline. The artillery
Artillery
Originally applied to any group of infantry primarily armed with projectile weapons, artillery has over time become limited in meaning to refer only to those engines of war that operate by projection of munitions far beyond the range of effect of personal weapons...
service was his ambition, and in 1804, through the advice and recommendation of Siméon Poisson, he received the appointment of secretary to the Paris Observatory
Paris Observatory
The Paris Observatory is the foremost astronomical observatory of France, and one of the largest astronomical centres in the world...
. He now became acquainted with Pierre-Simon Laplace
Pierre-Simon Laplace
Pierre-Simon, marquis de Laplace was a French mathematician and astronomer whose work was pivotal to the development of mathematical astronomy and statistics. He summarized and extended the work of his predecessors in his five volume Mécanique Céleste...
, and through his influence was commissioned, with Jean-Baptiste Biot
Jean-Baptiste Biot
Jean-Baptiste Biot was a French physicist, astronomer, and mathematician who established the reality of meteorites, made an early balloon flight, and studied the polarization of light.- Biography :...
, to complete the meridian arc
Meridian arc
In geodesy, a meridian arc measurement is a highly accurate determination of the distance between two points with the same longitude. Two or more such determinations at different locations then specify the shape of the reference ellipsoid which best approximates the shape of the geoid. This...
measurements which had been begun by J. B. J. Delambre, and interrupted since the death of P. F. A. Méchain in 1804). Arago and Biot left Paris in 1806 and began operations along the mountains of Spain. Biot returned to Paris after they had determined the latitude of Formentera
Formentera
Formentera is the smaller and more southerly island of the Pine Islands group , which belongs to the Balearic Islands autonomous community .-Geography:...
, the southernmost point to which they were to carry the survey. Arago continued the work until 1809, his purpose being to measure a meridian arc
Arc (geometry)
In geometry, an arc is a closed segment of a differentiable curve in the two-dimensional plane; for example, a circular arc is a segment of the circumference of a circle...
in order to determine the exact length of a metre.
After Biot's departure, the political ferment caused by the entrance of the French into Spain extended to the Balearic Islands
Balearic Islands
The Balearic Islands are an archipelago of Spain in the western Mediterranean Sea, near the eastern coast of the Iberian Peninsula.The four largest islands are: Majorca, Minorca, Ibiza and Formentera. The archipelago forms an autonomous community and a province of Spain with Palma as the capital...
, and the population suspected Arago's movements and his lighting of fires on the top of Mount Galatzó (Catalan
Catalan language
Catalan is a Romance language, the national and only official language of Andorra and a co-official language in the Spanish autonomous communities of Catalonia, the Balearic Islands and Valencian Community, where it is known as Valencian , as well as in the city of Alghero, on the Italian island...
: Mola de l'Esclop) as the activities of a spy for the invading army. Their reaction was such that he was obliged to give himself up for imprisonment in the fortress of Bellver in June 1808. On 28 July he escaped from the island in a fishing-boat, and after an adventurous voyage he reached Algiers
Algiers
' is the capital and largest city of Algeria. According to the 1998 census, the population of the city proper was 1,519,570 and that of the urban agglomeration was 2,135,630. In 2009, the population was about 3,500,000...
on 3 August. From there he obtained a passage in a vessel bound for Marseille
Marseille
Marseille , known in antiquity as Massalia , is the second largest city in France, after Paris, with a population of 852,395 within its administrative limits on a land area of . The urban area of Marseille extends beyond the city limits with a population of over 1,420,000 on an area of...
, but on 16 August, just as the vessel was nearing Marseille, it fell into the hands of a Spanish corsair
Privateer
A privateer is a private person or ship authorized by a government by letters of marque to attack foreign shipping during wartime. Privateering was a way of mobilizing armed ships and sailors without having to spend public money or commit naval officers...
. With the rest the crew, Arago was taken to Roses, and imprisoned first in a windmill, and afterwards in a fortress, until the town fell into the hands of the French, when the prisoners were transferred to Palamos
Palamós
Palamós is a town and municipality in the Mediterranean Costa Brava, located in the comarca of Baix Empordà, in the province of Girona, Catalonia, Spain....
.
After three months' imprisonment, Arago and the others were released on the demand of the dey
Dey
Dey was the title given to the rulers of the Regency of Algiers and Tripoli under the Ottoman Empire from 1671 onwards...
of Algiers, and again set sail for Marseille on 28 November, but then within sight of their port they were driven back by a northerly wind to Bougie
Béjaïa
Béjaïa, Vgaiet or Bejaya is a Mediterranean port city on the Gulf of Béjaïa in Algeria; it is the capital of Béjaïa Province, Kabylia. Under French rule, it was formerly known under various European names, such as Budschaja in German, Bugia in Italian, and Bougie...
on the coast of Africa. Transport to Algiers by sea from this place would have occasioned a weary delay of three months; Arago, therefore, set out over land, guided by a Muslim priest, and reached it on Christmas Day. After six months in Algiers he once again, on 21 June 1809, set sail for Marseille, where he had to undergo a monotonous and inhospitable quarantine in the lazaretto
Lazaretto
A lazaretto or lazaret is a quarantine station for maritime travellers. Lazarets can be ships permanently at anchor, isolated islands, or mainland buildings. Until 1908, lazarets were also used for disinfecting postal items, usually by fumigation...
, before his difficulties were over. The first letter he received, while in the lazaretto, was from Alexander von Humboldt
Alexander von Humboldt
Friedrich Wilhelm Heinrich Alexander Freiherr von Humboldt was a German naturalist and explorer, and the younger brother of the Prussian minister, philosopher and linguist Wilhelm von Humboldt...
; and this was the origin of a connection which, in Arago's words, lasted over forty years without a single cloud ever having troubled it.
Scientific studies
Arago had succeeded in preserving the records of his survey; and his first act on his return home was to deposit them in the Bureau des LongitudesBureau des Longitudes
The Bureau des Longitudes is a French scientific institution, founded by decree of 25 June 1795 and charged with the improvement of nautical navigation, standardisation of time-keeping, geodesy and astronomical observation. During the 19th century, it was responsible for synchronizing clocks...
at Paris. As a reward for his adventurous conduct in the cause of science, he was elected a member of the French Academy of Sciences
French Academy of Sciences
The French Academy of 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...
, at the remarkably early age of twenty-three, and before the close of 1809 he was chosen by the council of the École Polytechnique
École Polytechnique
The École Polytechnique is a state-run institution of higher education and research in Palaiseau, Essonne, France, near Paris. Polytechnique is renowned for its four year undergraduate/graduate Master's program...
to succeed Gaspard Monge
Gaspard Monge
Gaspard Monge, Comte de Péluse was a French mathematician, revolutionary, and was inventor of descriptive geometry. During the French Revolution, he was involved in the complete reorganization of the educational system, founding the École Polytechnique...
in the chair of analytical geometry. At the same time he was named by the emperor one of the astronomers of the Royal Observatory, which was accordingly his residence till his death, and it was in this capacity that he delivered his remarkably successful series of popular lectures in astronomy, which were continued from 1812 to 1845.
In 1816, along with Joseph Louis Gay-Lussac
Joseph Louis Gay-Lussac
- External links :* from the American Chemical Society* from the Encyclopædia Britannica, 10th Edition * , Paris...
, he started the Annales de chimie et de physique
Annales de chimie et de physique
Annales de chimie et de physique is a scientific journal that was founded in Paris, France, in 1789 under the title Annales de chimie. One of the early editors was the French chemist Antoine Lavoisier. In 1815, it became the Annales de chimie et de physique, and was published under that name for...
, and in 1818 or 1819 he proceeded along with Biot to execute geodetic
Geodesy
Geodesy , also named geodetics, a branch of earth sciences, is the scientific discipline that deals with the measurement and representation of the Earth, including its gravitational field, in a three-dimensional time-varying space. Geodesists also study geodynamical phenomena such as crustal...
operations on the coasts of France, England and Scotland. They measured the length of the seconds-pendulum at Leith
Leith
-South Leith v. North Leith:Up until the late 16th century Leith , comprised two separate towns on either side of the river....
, Scotland, and in the Shetland Islands
Shetland Islands
Shetland is a subarctic archipelago of Scotland that lies north and east of mainland Great Britain. The islands lie some to the northeast of Orkney and southeast of the Faroe Islands and form part of the division between the Atlantic Ocean to the west and the North Sea to the east. The total...
, the results of the observations being published in 1821, along with those made in Spain. Arago was elected a member of the Bureau des Longitudes immediately afterwards, and contributed to each of its Annuals, for about twenty-two years, important scientific notices on astronomy and meteorology
Meteorology
Meteorology is the interdisciplinary scientific study of the atmosphere. Studies in the field stretch back millennia, though significant progress in meteorology did not occur until the 18th century. The 19th century saw breakthroughs occur after observing networks developed across several countries...
and occasionally on civil engineering
Civil engineering
Civil engineering is a professional engineering discipline that deals with the design, construction, and maintenance of the physical and naturally built environment, including works like roads, bridges, canals, dams, and buildings...
, as well as interesting memoirs of members of the Academy.
Arago's earliest physical researches were on the pressure
Pressure
Pressure is the force per unit area applied in a direction perpendicular to the surface of an object. Gauge pressure is the pressure relative to the local atmospheric or ambient pressure.- Definition :...
of steam
Steam
Steam is the technical term for water vapor, the gaseous phase of water, which is formed when water boils. In common language it is often used to refer to the visible mist of water droplets formed as this water vapor condenses in the presence of cooler air...
at different temperatures, and the velocity
Velocity
In physics, velocity is speed in a given direction. Speed describes only how fast an object is moving, whereas velocity gives both the speed and direction of the object's motion. To have a constant velocity, an object must have a constant speed and motion in a constant direction. Constant ...
of sound, 1818 to 1822. His magnet
Magnet
A magnet is a material or object that produces a magnetic field. This magnetic field is invisible but is responsible for the most notable property of a magnet: a force that pulls on other ferromagnetic materials, such as iron, and attracts or repels other magnets.A permanent magnet is an object...
ic observations mostly took place from 1823 to 1826. He discovered rotatory magnetism, what has been called Arago's rotations
Arago's rotations
Arago's rotations is an observable phenomena effect discovered by François Arago in 1824. In the effect, as a copper disc is rotated in its own plane, and if a magnetic needle be freely suspended on a pivot over the disc, the needle will rotate with the disc. If on the other hand the needle is...
, and the fact that most bodies could be magnetized; these discoveries were completed and explained by Michael Faraday
Michael Faraday
Michael Faraday, FRS was an English chemist and physicist who contributed to the fields of electromagnetism and electrochemistry....
.
Arago warmly supported Augustin-Jean Fresnel
Augustin-Jean Fresnel
Augustin-Jean Fresnel , was a French engineer who contributed significantly to the establishment of the theory of wave optics. Fresnel studied the behaviour of light both theoretically and experimentally....
's optical
Optics
Optics is the branch of physics which involves the behavior and properties of light, including its interactions with matter and the construction of instruments that use or detect it. Optics usually describes the behavior of visible, ultraviolet, and infrared light...
theories, helping to confirm Fresnel's wave theory of light by observing what is now known as the spot of Arago
Arago spot
In optics, an Arago spot, Fresnel bright spot, or Poisson spot is a bright point that appears at the center of a circular object's shadow due to Fresnel diffraction...
. The two philosophers conducted together those experiments on the polarization of light which led to the inference that the vibration
Oscillation
Oscillation is the repetitive variation, typically in time, of some measure about a central value or between two or more different states. Familiar examples include a swinging pendulum and AC power. The term vibration is sometimes used more narrowly to mean a mechanical oscillation but sometimes...
s of the luminiferous ether were transverse to the direction of motion
Motion (physics)
In physics, motion is a change in position of an object with respect to time. Change in action is the result of an unbalanced force. Motion is typically described in terms of velocity, acceleration, displacement and time . An object's velocity cannot change unless it is acted upon by a force, as...
, and that polarization consisted of a resolution of rectilinear propagation
Rectilinear propagation
Rectilinear propagation is a wave property which states that waves propagate in straight lines. This property applies to both transverse and longitudinal waves. Even though a wave front may be bent the individual waves are moving in straight lines...
into components at right angles to each other. The subsequent invention of the polariscope and discovery of Rotary polarization
Rotary polarization
Rotary polarization is an optical phenomenon occurring in certain crystalline materials. The vibrational direction of light passing through such a crystal is rotated so that it varies in a circular manner. The amount of polarization rotation depends on the thickness of the crystal...
are due to Arago. He invented the first polarization filter in 1812.
The general idea of the experimental determination of the velocity of light in the manner subsequently effected by Hippolyte Fizeau
Hippolyte Fizeau
Armand Hippolyte Louis Fizeau was a French physicist.-Biography:Fizeau was born in Paris. His earliest work was concerned with improvements in photographic processes. Following suggestions by François Arago, Léon Foucault and Fizeau collaborated in a series of investigations on the interference of...
and Léon Foucault
Léon Foucault
Jean Bernard Léon Foucault was a French physicist best known for the invention of the Foucault pendulum, a device demonstrating the effect of the Earth's rotation...
was suggested by Arago in 1838, but his failing eyesight prevented his arranging the details or making the experiments.
Optics
Optics is the branch of physics which involves the behavior and properties of light, including its interactions with matter and the construction of instruments that use or detect it. Optics usually describes the behavior of visible, ultraviolet, and infrared light...
. He showed that a magnetic needle, made to oscillate over nonruginous surfaces, such as water, glass, copper, etc., falls more rapidly in the extent of its oscillations according as it is more or less approached to the surface. This discovery, which earned him the Copley Medal
Copley Medal
The Copley Medal is an award given by the Royal Society of London for "outstanding achievements in research in any branch of science, and alternates between the physical sciences and the biological sciences"...
of the Royal Society
Royal Society
The Royal Society of London for Improving Natural Knowledge, known simply as the Royal Society, is a learned society for science, and is possibly the oldest such society in existence. Founded in November 1660, it was granted a Royal Charter by King Charles II as the "Royal Society of London"...
in 1825, was followed by another, that a rotating plate of copper tends to communicate its motion to a magnetic needle suspended over it ("magnetism of rotation"). Arago is also fairly entitled to be regarded as having proved the long-suspected connexion between the aurora borealis and the variations of the magnetic elements. In 1828, he was elected a foreign member of the Royal Swedish Academy of Sciences
Royal Swedish Academy of Sciences
The Royal Swedish Academy of Sciences or Kungliga Vetenskapsakademien is one of the Royal Academies of Sweden. The Academy is an independent, non-governmental scientific organization which acts to promote the sciences, primarily the natural sciences and mathematics.The Academy was founded on 2...
.
In optics, Arago not only made important optical discoveries on his own, but is credited with stimulating the genius of Jean-Augustin Fresnel, with whose history, as well as that of Etienne-Louis Malus
Étienne-Louis Malus
- External links :...
and Thomas Young
Thomas Young (scientist)
Thomas Young was an English polymath. He is famous for having partly deciphered Egyptian hieroglyphics before Jean-François Champollion eventually expanded on his work...
, this part of his life is closely interwoven.
Shortly after the beginning of the 19th century the labours of at least three philosophers were shaping the doctrine of the undulatory, or wave, theory of light. Fresnel's arguments in favour of that theory found little favour with Laplace, Poisson and Biot, the champions of the emission theory; but they were ardently espoused by Humboldt and by Arago, who had been appointed by the Academy to report on the paper. This was the foundation of an intimate friendship between Arago and Fresnel, and of a determination to carry on together further fundamental laws of the polarization of light known by their means. As a result of this work, Arago constructed a polariscope, which he used for some interesting observations on the polarization of the light of the sky. To him also is due the discovery of the power of rotatory polarization exhibited by quartz
Quartz
Quartz is the second-most-abundant mineral in the Earth's continental crust, after feldspar. It is made up of a continuous framework of SiO4 silicon–oxygen tetrahedra, with each oxygen being shared between two tetrahedra, giving an overall formula SiO2. There are many different varieties of quartz,...
.
Among Arago's many contributions to the support of the undulatory hypothesis, comes the experimentum crucis which he proposed to carry out for measuring directly the velocity of light in air and in water and glass. On the emission theory the velocity should be accelerated by an increase of density in the medium; on the wave theory, it should be retarded. In 1838 he communicated to the Academy the details of his apparatus, which utilized the relaying mirrors employed by Charles Wheatstone
Charles Wheatstone
Sir Charles Wheatstone FRS , was an English scientist and inventor of many scientific breakthroughs of the Victorian era, including the English concertina, the stereoscope , and the Playfair cipher...
in 1835 for measuring the velocity of the electric discharge; but owing to the great care required in the carrying out of the project, and to the interruption to his labours caused by the revolution of 1848, it was the spring of 1850 before he was ready to put his idea the test; and then his eyesight suddenly gave way. Before his death, however, the retardation of light in denser media was demonstrated by the experiments of H. L. Fizeau and B. L. Foucault, which, with improvements in detail, were based on the plan proposed by him.
Politics and legacy
Republicanism
Republicanism is the ideology of governing a nation as a republic, where the head of state is appointed by means other than heredity, often elections. The exact meaning of republicanism varies depending on the cultural and historical context...
type, was elected a member of the chamber of deputies for the Pyrénées-Orientales
Pyrénées-Orientales
Pyrénées-Orientales is a department of southern France adjacent to the northern Spanish frontier and the Mediterranean Sea. It also surrounds the tiny Spanish enclave of Llívia, and thus has two distinct borders with Spain.- History :...
département, and he employed his talents of eloquence and scientific knowledge in all questions connected with public education, the rewards of inventors, and the encouragement of the mechanical and practical sciences. Many of the most creditable national enterprises, dating from this period, are due to his advocacy – such as the reward to Louis-Jacques Daguerre for the invention of photography, the grant for the publication of the works of Fermat and Laplace
Pierre-Simon Laplace
Pierre-Simon, marquis de Laplace was a French mathematician and astronomer whose work was pivotal to the development of mathematical astronomy and statistics. He summarized and extended the work of his predecessors in his five volume Mécanique Céleste...
, the acquisition of the museum of Cluny, the development of railways and electric telegraphs, the improvement of the reneile.
In 1830 Arago also was appointed director of the Observatory, and as a member of the chamber of deputies he was able to obtain grants of money for rebuilding it in part, and for the addition of magnificent instruments. In the same year, too, he was chosen perpetual secretary of the Academy of Sciences, the place of J. B. J. Fourier. Arago threw himself into its service, and by his faculty of making friends he gained at once for it and for himself a worldwide reputation. As perpetual secretary it was his duty to pronounce historical éloges on deceased members; and for this duty his rapidity and facility of thought, and his happy piquancy of style, and his extensive knowledge peculiarly adapted him. He was elected a Foreign Honorary Member of the American Academy of Arts and Sciences
American Academy of Arts and Sciences
The American Academy of Arts and Sciences is an independent policy research center that conducts multidisciplinary studies of complex and emerging problems. The Academy’s elected members are leaders in the academic disciplines, the arts, business, and public affairs.James Bowdoin, John Adams, and...
in 1832.
In 1834 Arago again visited Scotland
Scotland
Scotland is a country that is part of the United Kingdom. Occupying the northern third of the island of Great Britain, it shares a border with England to the south and is bounded by the North Sea to the east, the Atlantic Ocean to the north and west, and the North Channel and Irish Sea to the...
, to attend the meeting of the British Association
British Association for the Advancement of Science
frame|right|"The BA" logoThe British Association for the Advancement of Science or the British Science Association, formerly known as the BA, is a learned society with the object of promoting science, directing general attention to scientific matters, and facilitating interaction between...
at Edinburgh
Edinburgh
Edinburgh is the capital city of Scotland, the second largest city in Scotland, and the eighth most populous in the United Kingdom. The City of Edinburgh Council governs one of Scotland's 32 local government council areas. The council area includes urban Edinburgh and a rural area...
. From this time till 1848 he led a life of comparative quiet – although he continued to work within the Academy and the Observatory to produce a multitude of contributions to all departments of physical science – but on the fall of Louis-Philippe
Louis-Philippe of France
Louis Philippe I was King of the French from 1830 to 1848 in what was known as the July Monarchy. His father was a duke who supported the French Revolution but was nevertheless guillotined. Louis Philippe fled France as a young man and spent 21 years in exile, including considerable time in the...
he left his laboratory to join the Provisional Government (24 February 1848). He was entrusted with two important functions, that had never before been given to one person, viz. the ministry of marine and colonies (24 February 1848 – 11 May 1848) and ministry of war (5 April 1848 – 11 May 1848); in the former capacity he improved of rations in the navy and abolished flogging. He also abolished political oaths of all kinds, and, against an array of moneyed interests, succeeded in procuring the abolition of slavery
Abolition of slavery timeline
Abolition of slavery occurred as abolition in specific countries, abolition of the trade in slaves and abolition throughout empires. Each of these steps was usually the result of a separate law or action.-Ancient times:...
in the French colonies
French Colonies
"French Colonies" is the name used by philatelists to refer to the postage stamps issued by France for use in the parts of the French colonial empire that did not have stamps of their own...
.
On 10 May 1848, Arago was elected a member of the Executive Power Commission
French Executive Commission (1848)
The Executive Commission of the French Republic was a short-lived body and jointly head of state of France during the Second Republic. All members were equal and served together as co-heads of state.The Commission acted as head of state from May 10 to June 24, 1848, between governments of...
, a governing body of the French Republic. He was made President of the Executive Power Commission (11 May 1848) and served in this capacity as provisional head of state until 24 June 1848, when collective resignation of the Commission was submitted to the National Constituent Assembly. At the beginning of May 1852, when the government of Louis Napoleon
Napoleon III of France
Louis-Napoléon Bonaparte was the President of the French Second Republic and as Napoleon III, the ruler of the Second French Empire. He was the nephew and heir of Napoleon I, christened as Charles Louis Napoléon Bonaparte...
required an oath of allegiance from all its functionaries, Arago peremptorily refused, and sent in his resignation of his post as astronomer at the Bureau des Longitudes. This, however, the prince president declined to accept, and made "an exception in favour of a savant whose works had thrown lustre on France, and whose existence the government would regret to embitter."
Last years
Arago remained a consistent republican to the end, and after the coup d'état of 1852, though suffering first from diabetes, then from Bright's diseaseBright's disease
Bright's disease is a historical classification of kidney diseases that would be described in modern medicine as acute or chronic nephritis. The term is no longer used, as diseases are now classified according to their more fully understood causes....
, complicated by dropsy, he resigned his post as astronomer rather than take the oath of allegiance
Oath of allegiance
An oath of allegiance is an oath whereby a subject or citizen acknowledges a duty of allegiance and swears loyalty to monarch or country. In republics, modern oaths specify allegiance to the country's constitution. For example, officials in the United States, a republic, take an oath of office that...
. Napoleon III
Napoleon III of France
Louis-Napoléon Bonaparte was the President of the French Second Republic and as Napoleon III, the ruler of the Second French Empire. He was the nephew and heir of Napoleon I, christened as Charles Louis Napoléon Bonaparte...
gave directions that the old man should be in no way disturbed, and should be left free to say and do what he liked. In the summer of 1853 Arago was advised by his physicians to try the effect of his native air, and he accordingly set out to the eastern Pyrenees
Pyrenees
The Pyrenees is a range of mountains in southwest Europe that forms a natural border between France and Spain...
, but it was ineffective and he died in Paris. His grave is at the famous cemetery Père Lachaise in Paris.
Craters on Mars
Mars
Mars is the fourth planet from the Sun in the Solar System. The planet is named after the Roman god of war, Mars. It is often described as the "Red Planet", as the iron oxide prevalent on its surface gives it a reddish appearance...
and the Moon
Arago (lunar crater)
Arago is a lunar impact crater located in the western part of the Mare Tranquillitatis. To the southwest lies the crater Manners, and beyond are Dionysius and the Ritter–Sabine crater pair. To the southeast is the large Lamont formation that has been submerged by the mare.The rim of Arago has a...
, and a ring of Neptune
Rings of Neptune
The rings of Neptune consist primarily of five principal rings predicted in 1984 by André Brahic and imaged in 1989 by the Voyager 2 spacecraft...
, are named after Arago, as well as the study association for Applied Physics at the University of Twente. His name is one of the 72 names inscribed on the Eiffel Tower.
Publications
English translations of the following portions of Arago's works have appeared:
- Treatise on Comets, by C. Gold, C.B. (London, 1833); also translated Smyth and Grant (London, 1861)
- Euloge of James Watt, by Muirhead (London, 1839); also translated, with notes, by Brougham
- Popular Lectures on Astronomy, by Walter Kelly and Rev. L. Tomlinson (London, 1854); also translated by Dr W. H. Smyth and Prof. R. Grant, 2 vols. (London, 1855)
- Arago's Autography, translated by the Rev. Baden Powell (London, 1855, 58)
- Arago's Meteorological Essays, with introduction by Humboldt, translated under the supervision of Colonel Sabine (London, 1855)
- Arago's Biographies of Scientific Men, translated by Smyth, Powell and Grant, 8vo (London, 1857)
External links
- Arago in the 1911 Encyclopædia Britannica – the original source for almost all of this page's content
- Obituary Monthly Notices of the Royal Astronomical Society, 1854, volume 14, page 102
- The 0 meridian in Paris misused in The Da Vinci Code is in fact an art project by the Dutch artist Jan DibbetsJan DibbetsJan Dibbets , is a Dutch conceptual artist.In 1994, he was commissioned by the Arago Association to create a memorial to the French astronomer François Arago, known as Hommage à Arago...
(1941) made in 1987 as a tribute to the astronomer François Arago (1786–1853) - S.V. Arago The study association (Dutch) at the University of Twente is named after François Arago.