Jacques d'Allonville

Jacques Eugène d'Allonville de Louville (14 July 1671 – 10 September 1732) was a French astronomer and mathematician. He also went by the name of Chevalier de Louville (Knight of Louville).

Biography

Louville's father (1628–1707) was the lord of Louville. His mother (1646–1704) was born a Vaultier de Moyencourt. His older brother named Charles Auguste was known for his role with Philip V of Spain and was a member of the family who had a higher social rank.

Early life

Being the youngest son, Jacques Louville was destined to the church (the other choices were a military career or another path which would not offend his elders) We know in his youth two remarkable things happened:

When he was questioned about the tonsure at age 7, he attended the ceremony and firmly declared that he would not be ecclesiastic.
At the age of 12, he read Les Elements d'Euclid translated by Dennis Henrion without a guide and this was a turning point for him in his life.

Military career

Louville was the youngest in the French Royal Navy. He fought in the Battle of La Hougue in 1692. He became an army captain at the end of 1700. His older brother Charles Auguste who served with Philip V, brought him there. He was nominated to be a brigadier and his services were recognised with a pension. When he returned to France, he resumed his service. He became a prisoner of war in 1708 at the Battle of Oudenarde and was held for two years. Once he was released he became Colonel of the Dragons of The Queen army and was paid by the king. He later found peace in returning to the study of astronomy. He cut the ties with the army and against the wishes of his family, he returned his officer certificate and renounced his appointments.

Scientific career

He devoted his time to mathematics and the principle of astronomy. Louville went to Marseille in 1713 or 1714, to measure the height of the pole needed to properly tie his observations of the stars to the observations of Pythéas (a Greek astronomer and explorer), made 2000 years ago. In 1715 Louville went to London to observe a total solar eclipse assisting Edmund Halley in the remarkable phenomenon. The men saw on the dark surface of the moon jets of light that lasted for an instant and passed. They resembled flashes (fulminations). In 1717 he situated himself in Carré a mile from Orléans. He had been a member of the Academy of Sciences since 1714 and the Academy had a residency obligation. The situation was not a regular occurrence. But Louville promised to communicate to the school annually, kept his promise and continued to study the sky in Oréans.

Personality

Fontenelle who did not fail to make the connection with the child refusing the tonsure, was an independent minded man, nor misanthrope, nor austere, but generous with his time. If one arrived early for dinner he did not mind, he read a book from his library or he would take a walk. “He was a perfect stoic and kept to himself, and didn't show anything on the outside; good friend however, unofficial, generous, but those kind on the outside often compensate for the most part. Or at least are very forward. He was very taciturn, even when there was a question on mathematics and he spoke, it was not to parade his knowledge, but to communicate to those the serious matter. The scholar who speaks only to instruct others, and as far as they want to be educated is a grace; Instead of speaking to flaunt knowledge, It can be amazing if one listens." (Fontonelle)

Contributions

Louville concluded in his measurements taken during his stay in Marseille ( watching the same stars that Pythéas had observed in the same city five centuries ago and those of other astronomers for century's had also observed) that the tilt on the axis of earth was not constant all the time. Voltaire was the witness after the other enlargement of time scales given by the work of Louville.

"This astronomer in 1714 went to Marseille to observe the eclipse as it had been set by Pythéas approximately 2000 years before ; he found in less than 20 minutes , it is to say in 2000 years, the eclipse, according to him it was approaching the equator by 3 degrees ( its assumed). Besides the movements he knew the sun would have another movement where it would turn on itself from one pole to another. This finding showed that in 23000 years the sun will be directed towards the equator and that in 2 million years all the climates around the world under the torrid zones and under the glacier zones will change” (Voltaire)

Louvilles thesis explained mathematically by Euler, and accepted today, had a considerable echo but he was still challenged by other scientists. The Hire and Riccioli were reluctant. The observations from ancient Greeks, Arab-Muslim, ancient Chinese and the west search to add ideas.

The crater Louville on the Moon is named after him.

References

"Library and Archive". Royal Society. Retrieved 3 December 2014.

1732. Académie des Sciences. Archives, vol 3529., p. 131–136.

Notes

Bibliography

Observations sur l'obliquité de l'écliptique, 1714
Nouvelles tables du soleil, 1720
Nouvelle méthode de calculer les éclipses, 1724
Remarques sur la question des forces vives, 1721–28.