L'Aigle

The 1803 shower of stones in Normandy that finally convinced scientists rocks really do fall from the sky.

Key facts

Type

Ordinary chondrite (L6)

Fell or found

Fell (witnessed)

Year

1803 (26 April)

Country

France

Mass

about 37 kg recovered, in some 3,000 stones

Official name

L'Aigle

Today it seems obvious that rocks fall from space. A little over two centuries ago it did not. Most scholars of the 18th century dismissed tales of stones falling from the sky as superstition, the misunderstandings of country folk who had perhaps seen lightning strike an ordinary rock. A remarkable shower of stones near the town of L'Aigle in Normandy, on 26 April 1803, did more than any other event to change their minds.

The scientific background

By 1803 the tide was already turning. In 1794 the German physicist Ernst Chladni had published a book arguing that fireballs and fallen stones were genuine objects from space. In 1802 the chemist Edward Howard, working with the mineralogist Jacques-Louis de Bournon, showed that stones said to have fallen in different countries shared unusual features, including grains of metal containing nickel, unlike ordinary rocks. Earlier reported falls, such as a shower of stones near Siena in Italy in 1794, had already stirred debate. Yet many scientists, especially in France, remained unconvinced.

A shower of stones

Around one o'clock in the afternoon, people in and around L'Aigle saw a fireball and heard a series of explosions like cannon fire, followed by a rattling hiss. Stones began to fall over the farms and villages, some still warm. Thousands of them came down, and around 3,000 were eventually collected, with a total weight of about 37 kilograms. The largest weighed around 9 kilograms.

Biot investigates

The French government's Minister of the Interior sent a young physicist, Jean-Baptiste Biot, to investigate. Biot worked like a detective. He interviewed dozens of witnesses of all kinds, from villagers to local officials, and compared their accounts. He examined the stones, noting that they were completely unlike any rock in the local geology but very similar to stones from other reported falls. And he carefully mapped where they had been found, showing that they lay within an oval area roughly 10 kilometres long and 4 kilometres wide.

His report to the French Institute, the country's leading scientific body, combined physical evidence with consistent eyewitness testimony from many independent people. It was hard to argue with, and after L'Aigle the scientific community broadly accepted that stones really do fall from the sky. The modern science of meteoritics, the study of meteorites, grew from that acceptance.

What the stones are

L'Aigle is an L6 ordinary chondrite. Ordinary chondrites are the most common meteorites that fall to Earth. 'L' stands for low iron, one of the three main groups of ordinary chondrites, and '6' shows that the rock was strongly heated inside its parent asteroid, so its chondrules, the small rounded grains typical of chondrites, are partly blurred. The stones have the thin black fusion crust that forms when a meteorite's surface melts as it plunges through the air.

Why it matters

Biot's oval map was one of the first descriptions of what is now called a strewn field, the area over which fragments of a single meteoroid land. Strewn fields are typically elongated, with the heaviest fragments travelling furthest along the direction of flight, a pattern still used by meteorite hunters today to plan their searches.

Perhaps most importantly, L'Aigle shows how science changes its mind. The reports of ordinary people had been right all along; what scientists needed was careful, systematic evidence. Biot went on to become a famous physicist, remembered especially for his work on magnetism and light, but his investigation in Normandy remains one of the turning points in our understanding of the cosmos. Historians of science still point to his report as a model of how to weigh human testimony alongside physical evidence, and stones from L'Aigle are treasured in museum collections, especially in Paris.

Did you know?

See more

L'Aigle in the catalogue