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The life of François

Dominique François Jean Arago was born on 26 February 1786 in Estagel, a small town in the eastern part of the Pyrenees. His father was treasurer of the local department. When he was nine years old, his parents moved to Perpignan, where he was classically educated.

One day, he met the chief of a technical department. Because this chief was still pretty young, Arago asked him how he had managed to obtain the epaulet at such a young age. The man referred him to l’Ecole Politechnique in Toulouse. Arago immediately quit his literary classes and committed to mathematics.

On his own, he read the works of Euler, Lagrange and Laplace, and when he turned sixteen, he passed the matriculation for l’École Polytechnique to everybody’s great surprise. Less than a year later, he became secretary of the observatory of Paris, l’Observatoire, where he met Laplace and Biot. He discussed the importance of extending the meridian southward with them. Laplace instructed him to determine the ten millionth part of one quadrant of the Paris meridian as accurately as possible. This distance had been accepted as the unit of length, one metre, by the National Convention. Measuring an entire quadrant is quite a job, so they decided to measure the distance Dunkirk-Formentera, a quarter of the quadrant. Delambre had been measuring up until Barcelona.

In 1806, Biot and Arago left for Spain, to continue Delambre’s measurements. When they were almost finished, Biot went back to Paris, while Arago performed the last measurements. During that period, French armies invaded Spain, and Arago was suspected of spying and was captured by the Spaniards. He managed to escape the prison of Palma and started his adventurous journey.

In 1809, he returned to Paris with the data. Shortly after his return, in appreciation of his work, he was named member of the Académie des Sciences. At the same time, he became a teacher in analytical geometry at the École Polytechnique and astronomer at the Observatoire.

Arago soon became very loved by his pupils. As an astronomer, he gave popular lectures to great success. Together with Gay-Lussac, he started a scientific journal with the goal to emphasise the balance between research and applications.

In 1830, he became politically active. As a leftist republican, he expounded on education, freedom of speech and the application of scientific knowledge in technology. He was also named secretary of the Académie des Sciences for life, succeeding Fourier. Four years later, he received the highest academical honour at the University of Edinburgh.

His political career reached its climax in 1848, when he was appointed Minister of War and Marine. During his tenure, he repealed corporal punishments in France and slavery in the colonies. After the June Days uprising, he retired from politics. Because of his frail health, he was able to perform fewer and fewer experiments.

As mentioned, he has been praised many times as a scientist, mostly due to his clear reporting. Examples of his research in the fields of physics and astronomy are the photometric determination of the brightness of the moon and stars, and research on the effect of astronomical refraction on observations.

His favourite areas were optics and magnetism. He discovered the phenomenon of rotation magnetism, which was later explained by Faraday. He helped Fresnel with his theories on the wave character of light and got the Arago spot named after him because of that. Together with Fresnel and Humboldt, he also discovered polarisation and applied the concept to the construction of the polarimeter, which could weakly observe it. He discovered the rotation of the polarisation caused by quartz.

The pinnacle of his experimental work would be Arago’s measurements in comparing the velocity of light in air, glass and water. By the particle theory, light speed should increase, while the wave theory predicted reduction. Because of his political obligations during the revolution and his worsening eyesight later on, he did not manage to complete the research. However, he did live to see measurements by Fizeau and Foucault (performed on devices designed by Arago) lead to results in favour of wave theory.

Arago in the 20th century

From 1893 until 1942, a bronze statue of Dominique François Jean Arago was located at the place where the Paris meridian crosses the Boulevard Arago. It stood close to the observatory, l’Observatoire, but was, like many other statues in Paris, melted down during World War II. Only the pedestal remained.

The Arago Association, a dignified company of retired astronomers, hoped that the statue would return, but it had unfortunately been turned into a German cannon. To keep the memory of François Arago alive, the Ministry of Cultural Affairs asked four artists for a plan. A design by Dutch artist Jan Dibbets, an imaginary monument in the form of an imaginary line, the prime meridian of Paris, was chosen.

Jan Dibbets was born in the Netherlands in 1941, he lives and works in Amsterdam. He is part of the generation of conceptual artists (in the late 60s / start of the 70s). Exhibitions of his work have taken place in many large contemporary art museums in the world. The imaginary monument was carried out in the form of a trajectory through Paris of 135 bronze medallions with a cross section of 12 cm. On the medallions is the name Arago and an N and S pointing at the North and South respectively. The medallions are placed on the prime meridian of Paris, which was crucial in determining the universal hour up until 1884. The pedestal of the molten statue forms the centre of the twelve-kilometer-long object. It took surveyors weeks to determine the exact place of the meridian, and the measurements from 1806 were corrected. It turned out that the southern aiming point, la Mire du Sud, was actually 40 metres off originally. The 135 medallions are spaced apart randomly in the streets, pavements, observatory, the Louvre museum and close to all kinds of other famous monuments. In the end, 300 medallions were made, as the Public Works breaking up the Parisian streets every three years on average will undoubtedly cause some to vanish.

This monument for Arago is a new type of memorial, never shown before. It was inaugurated on 14 November 1994 in the meridian hall in the observatory of Paris. The project is in accordance with recurring themes in Jan Dibbet’s work: displacement, a piecewise division of spaces and the balance between what you see up close (a medallion with Arago’s name on it) and from afar (a trajectory forming the prime meridian of Paris)

Craters on the moon and Mars and a ring of Neptune were named after Dominique François Jean Arago, and so was our beautiful association!