Antoine Joseph Bernard Brunhes (3 July 1867 – 10 May 1910) was a

French French may refer to: * Something of, from, or related to France ** French language, which originated in France ** French people, a nation and ethnic group ** French cuisine, cooking traditions and practices Arts and media * The French (band), ...

geophysicist Geophysics () is a subject of natural science concerned with the physical processes and properties of Earth and its surrounding space environment, and the use of quantitative methods for their analysis. Geophysicists conduct investigations acros ...

known for his pioneering work in

paleomagnetism Paleomagnetism (occasionally palaeomagnetism) is the study of prehistoric Earth's magnetic fields recorded in rocks, sediment, or archeological materials. Geophysicists who specialize in paleomagnetism are called ''paleomagnetists.'' Certain ...

, in particular, his 1906 discovery of

geomagnetic reversal A geomagnetic reversal is a change in the Earth's Dipole magnet, dipole magnetic field such that the positions of magnetic north and magnetic south are interchanged (not to be confused with North Pole, geographic north and South Pole, geograp ...

. The current period of normal polarity, ''Brunhes Chron'', and the

Brunhes–Matuyama reversal The Brunhes–Matuyama reversal, named after Bernard Brunhes and Motonori Matuyama, was a geologic event, approximately 781,000 years ago, when the Earth's magnetic field last underwent reversal. Estimations vary as to the abruptness of the reve ...

are named for him. Brunhes was educated at the

École Normale Supérieure École or Ecole may refer to: * an elementary school in the French educational stages normally followed by Secondary education in France, secondary education establishments (collège and lycée) * École (river), a tributary of the Seine flowing i ...

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, from which he graduated as an '' agrégé'' qualified in

physics Physics is the scientific study of matter, its Elementary particle, fundamental constituents, its motion and behavior through space and time, and the related entities of energy and force. "Physical science is that department of knowledge whi ...

. Appointed at

Université Lille Nord de France The Community of Universities and Institutions (COMUE) Lille Nord de France (formerly Université Lille Nord de France) was a French Groups of Universities and Institutions ( COMUE) spread over multiple campuses and centered in Lille (North - Hau ...

, he taught physics and electrical engineering at

École centrale de Lille École or Ecole may refer to: * an elementary school in the French educational stages normally followed by secondary education establishments (collège and lycée) * École (river), a tributary of the Seine flowing in région Île-de-France * Éco ...

from 1893 to 1895. In November 1900, he was appointed as head of the

Puy-de-Dôme Puy-de-Dôme (; or ''lo Puèi Domat'') is a department in the Auvergne-Rhône-Alpes region in the centre of France. In 2021, it had a population of 662,285.Auvergne Auvergne (; ; or ) is a cultural region in central France. As of 2016 Auvergne is no longer an administrative division of France. It is generally regarded as conterminous with the land area of the historical Province of Auvergne, which was dis ...

region of

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, where he worked until his death in 1910. It was during his time at the observatory that he made the crucial observation that led to his discovery of geomagnetic reversal. In 1905, he found that rocks in an ancient lava flow at Pontfarin in the commune of

Cézens Cézens is a commune in the Cantal department in south-central France. Population See also *Communes of the Cantal department The following is a list of the 246 Communes of France, communes of the Cantal Departments of France, departme ...

(part of the

Cantal Cantal (; or ) is a rural Departments of France, department in the Auvergne-Rhône-Alpes Regions of France, region of France, with its Prefectures in France, prefecture in Aurillac. Its other principal towns are Saint-Flour, Cantal, Saint-Flou ...

département In the administrative divisions of France, the department (, ) is one of the three levels of government under the national level (" territorial collectivities"), between the administrative regions and the communes. There are a total of 101 ...

'') were magnetised in a direction almost opposite to that of the present-day

magnetic field A magnetic field (sometimes called B-field) is a physical field that describes the magnetic influence on moving electric charges, electric currents, and magnetic materials. A moving charge in a magnetic field experiences a force perpendicular ...

. From this, he deduced that the

magnetic North Pole The north magnetic pole, also known as the magnetic north pole, is a point on the surface of Earth's Northern Hemisphere at which the planet's magnetic field points vertically downward (in other words, if a magnetic compass needle is allowed t ...

of the time was close to the current geographical

South Pole The South Pole, also known as the Geographic South Pole or Terrestrial South Pole, is the point in the Southern Hemisphere where the Earth's rotation, Earth's axis of rotation meets its surface. It is called the True South Pole to distinguish ...

, which could only have happened if the magnetic field of the Earth had been reversed at some point in the past. He was correct, though it took another 50 years before his theory was fully accepted by the scientific community.

References

*
Bernard Brunhes, Directeur de l’Observatoire du Puy-de-Dôme (1900–1910)
, Observatoire de Physique du Globe de Clermont-Fd. {{DEFAULTSORT:Brunhes, Bernard 1867 births 1910 deaths École Normale Supérieure alumni French geophysicists Scientists from Toulouse