Jacques d'Allonville facts for kids

Jacques Eugène d'Allonville de Louville (born July 14, 1671 – died September 10, 1732) was a French astronomer and mathematician. He was also known as the Chevalier de Louville, which means 'Knight of Louville'.

Early Life and Choices

Jacques Louville came from an important family. His father was the lord of Louville. As the youngest son, it was expected that Jacques would join the Catholic Church.

However, when he was only seven years old, Jacques made a clear choice. He attended a special ceremony for joining the church, but he firmly said he would not become a Priest. This showed he had a strong will, even at a young age.

Military Adventures

Instead of the church, Louville chose a military career. He joined the French Royal Navy when he was very young. He fought in a big sea battle called the Battle of La Hougue in 1692.

Later, he became an army captain. His older brother, Charles Auguste, helped him join the army of King Philip V. Louville was recognized for his service and received a special payment.

He returned to France and continued his military duties. In 1708, he was captured during the Battle of Oudenarde and was a prisoner for two years. After being released, he became a Colonel in the Queen's army. But his passion for science was growing. He decided to leave the army, even though his family disagreed. He gave up his military titles to focus on his studies.

A Life in Science

After leaving the military, Louville dedicated his time to mathematics and astronomy. He became a member of the French Academy of Sciences in 1714.

In 1713 or 1714, Louville traveled to Marseille. He wanted to measure the height of the pole star from that city. He compared his observations to those made by Pythéas, an ancient Greek astronomer, about 2,000 years earlier. This was important for understanding how the Earth and stars move over long periods.

In 1715, Louville went to London to observe a total solar eclipse. He worked with a famous astronomer named Edmund Halley. During the eclipse, they saw quick flashes of light on the dark surface of the Moon. These flashes were very interesting to them.

Even though he was a member of the Academy of Sciences, Louville preferred to study the sky from his home in Carré, near Orléans. He promised to share his findings with the Academy every year, and he kept his promise.

Important Discoveries

Louville made a very important discovery based on his measurements in Marseille. By comparing his observations of stars with those from Pythéas and other astronomers over centuries, he realized something amazing. He concluded that the tilt of the Earth's axis is not always the same. It changes very slowly over time.

This idea was a big deal because it meant that climates on Earth could change over millions of years. The famous writer Voltaire even wrote about Louville's findings, saying: "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)."

Voltaire also mentioned that this finding showed how climates could change over vast periods. Louville's idea was later explained mathematically by another great scientist, Euler, and is accepted by scientists today.

To honor his contributions to astronomy, a crater on the Moon is named after him: Louville.

See also

• List of French astronomers