◀ ▲ ▶History / 18th-century / Person: Arago, Dominique François Jean

Person: Arago, Dominique François Jean

François Arago was an important French mathematician and politician. He made important discoveries on the corpuscular theory of light.

Mathematical Profile (Excerpt):

• Jean Arago (1788-1836) emigrated to North America and had a military career; Jacques Étienne Victor Arago (1799-1855) took part in the voyage of l'Uranie led by Louis de Freycinet to conduct magnetic and oceanographic researches in the Pacific; and Étienne Vincent de Arago (1802-1892) was an author and dramatist.
• At first François Arago showed an interest in a military career and it was with this in mind that he was educated at the Municipal College of Perpignan where he came to love mathematics.
• This friend introduced Arago to Poisson who was five years older than Arago and had been appointed at an assistant professor at the École Polytechnique in the year before Arago entered the school.
• Arago and Poisson became friends, not really behaving as student and teacher.
• Despite being taught by some of the leading mathematicians in the world, Arago did not find their abilities to teach come anywhere close to their abilities for research.
• In 1805 Poisson was able to offer Arago a task of far more importance than one would have expected a young student to be asked to undertake.
• He asked Arago to help in measuring the meridian.
• Laplace asked Poisson to find someone who would continue the work, and Poisson proposed his young friend Arago.
• The challenge was a daunting one, and Arago took some time to make a decision.
• On 3 September 1806 Arago and Biot set out for Spain.
• Biot and Arago must have looked extremely suspicious; two Frenchmen with sophisticated measuring instruments working on Spanish territory.
• Biot fled back to France but Arago remained on Mallorca, disguised as a Spaniard, trying to complete his measurements which he had recorded in a logbook.
• Arago managed to persuade the commander of the prison that he was a scientist, not a spy, and the commander agreed to give Arago a chance to escape.
• The boat on which Arago was sailing was captured while on its way to France by a Spanish warship and he was back in captivity again.
• Arago was held in a Spanish prison in Roses but after only a short spell the Spanish decided to send their prisoners to Palamos since the French armies were advancing through Spain.
• However Arago was lucky and, having been recognised by the authorities, was released an put on another boat for Marseille on 28 November.
• It was not to be, however, for again Arago failed to reach his homeland.
• A new local leader in Algiers was opposed to the French and Arago found himself in prison waiting to be shipped off to a penal colony.
• However the French consul again came to his rescue and, on 21 June 1809, Arago was put, for the third time, on a ship bound for Marseille.
• Arago knew roughly what the velocities should be, so he knew that the effect he was looking for was well within what he should be able to detect.
• Arago made observations of stars on 19 and 27 March 1810.
• How did Arago explain the puzzling results?
• In 1813 Arago began to give popular lectures on astronomy.
• Arago was also active in other ways.
• This government established universal manhood suffrage in France, a cause championed by Arago.
• Arago made early discoveries on the corpuscular theory of light in 1811.
• However difficulties with the experiment meant that Arago was not in a position to try his experiment until 1850.
• Successful results were obtained by Fizeau and Léon Foucault before Arago died.
• Arago carried out further experiments of this type and demonstrated several effects which led Faraday later to explain them as induction.
• It appears that Arago was the first person to construct an electromagnet.
• Working with Biot, Arago made measurements of arc length on the Earth which led to the standardisation of the metric system of lengths.
• Although many have criticised Arago for his part in this dispute, particularly for his efforts to get the new planet named Le Verrier, one has to feel that he did the right thing in championing his own student who had made the discovery following his advice.
• Other contributions made by Arago include work on the polarization of light, investigations of the solar corona and chromosphere, and measurements of the diameters of the planets.
• Leaders in various field were required to swear allegiance and Arago held two such positions, as Director of the Observatory and as secretary of the Academy of Sciences.
• Arago, a staunch republican, refused to swear allegiance.
• Arago was honoured with the award of the Royal Society Copley Medal in 1825 and the Rumford Medal in 1850.
• The Academy of Sciences inaugurated the Arago Medal in 1893.

Born 26 February 1786, Estagel, Roussillon, France. Died 2 October 1853, Paris, France.

View full biography at MacTutor

Tags relevant for this person:

Astronomy, Physics

Thank you to the contributors under CC BY-SA 4.0!

Github:

non-Github:

@J-J-O'Connor

@E-F-Robertson

References

Adapted from other CC BY-SA 4.0 Sources:

1. O’Connor, John J; Robertson, Edmund F: MacTutor History of Mathematics Archive