Jacques Babinet
Encyclopedia
France
The French Republic , The French Republic , The French Republic , (commonly known as France , is a unitary semi-presidential republic in Western Europe with several overseas territories and islands located on other continents and in the Indian, Pacific, and Atlantic oceans. Metropolitan France...
physicist
Physics
Physics is a natural science that involves the study of matter and its motion through spacetime, along with related concepts such as energy and force. More broadly, it is the general analysis of nature, conducted in order to understand how the universe behaves.Physics is one of the oldest academic...
, mathematician, and astronomer who is best known for his contributions to optics
Optics
Optics is the branch of physics which involves the behavior and properties of light, including its interactions with matter and the construction of instruments that use or detect it. Optics usually describes the behavior of visible, ultraviolet, and infrared light...
.
Babinet started his studies at the Lycée Napoléon, but was persuaded to abandon a legal education for the pursuit of science. A graduate of the École Polytechnique
École Polytechnique
The École Polytechnique is a state-run institution of higher education and research in Palaiseau, Essonne, France, near Paris. Polytechnique is renowned for its four year undergraduate/graduate Master's program...
, which he left in 1812 for the Military School at Metz
Metz
Metz is a city in the northeast of France located at the confluence of the Moselle and the Seille rivers.Metz is the capital of the Lorraine region and prefecture of the Moselle department. Located near the tripoint along the junction of France, Germany, and Luxembourg, Metz forms a central place...
, he was later a professor at the Sorbonne
Sorbonne
The Sorbonne is an edifice of the Latin Quarter, in Paris, France, which has been the historical house of the former University of Paris...
and at the Collège de France
Collège de France
The Collège de France is a higher education and research establishment located in Paris, France, in the 5th arrondissement, or Latin Quarter, across the street from the historical campus of La Sorbonne at the intersection of Rue Saint-Jacques and Rue des Écoles...
. In 1840, he was elected as a member of the Académie Royale des Sciences
French Academy of Sciences
The French Academy of Sciences is a learned society, founded in 1666 by Louis XIV at the suggestion of Jean-Baptiste Colbert, to encourage and protect the spirit of French scientific research...
. He was also an astronomer of the Bureau des Longitudes
Bureau des Longitudes
The Bureau des Longitudes is a French scientific institution, founded by decree of 25 June 1795 and charged with the improvement of nautical navigation, standardisation of time-keeping, geodesy and astronomical observation. During the 19th century, it was responsible for synchronizing clocks...
.
Among Babinet's accomplishments are the 1827 standardization of the Ångström
Ångström
The angstrom or ångström, is a unit of length equal to 1/10,000,000,000 of a meter . Its symbol is the Swedish letter Å....
unit for measuring light using the red Cadmium line's wavelength, and the principle (Babinet's principle
Babinet's principle
In physics, Babinet's principle is a theorem concerning diffraction that states that the diffraction pattern from an opaque body is identical to that from a hole of the same size and shape except for the overall forward beam intensity.-Explanation:...
) that similar diffraction patterns are produced by two complementary screens. He was the first to suggest using wavelengths of light to standardise measurements. His idea was first used between 1960 and 1983, when a meter was defined as a wavelength
Wavelength
In physics, the wavelength of a sinusoidal wave is the spatial period of the wave—the distance over which the wave's shape repeats.It is usually determined by considering the distance between consecutive corresponding points of the same phase, such as crests, troughs, or zero crossings, and is a...
of light from krypton
Krypton
Krypton is a chemical element with the symbol Kr and atomic number 36. It is a member of Group 18 and Period 4 elements. A colorless, odorless, tasteless noble gas, krypton occurs in trace amounts in the atmosphere, is isolated by fractionally distilling liquified air, and is often used with other...
gas.
Babinet was interested in the optical properties of minerals throughout his career. He designed and created many scientific instruments utilized to determine crystalline structure and polarization properties, including the polariscope and an optical goniometer to measure refractive indices. The Babinet compensator, an accessory useful in polarized light microscopy
Microscopy
Microscopy is the technical field of using microscopes to view samples and objects that cannot be seen with the unaided eye...
, was built with twin, opposed quartz wedges having mutually perpendicular crystallographic axes, and is still widely employed in microscopy. This design avoids the problems inherent in the basic quartz wedge, where the zero reading coincides with the thin end of the wedge, which is often lost when grinding the plate during manufacture.
Expanding his fascination of diffraction to meteorology
Meteorology
Meteorology is the interdisciplinary scientific study of the atmosphere. Studies in the field stretch back millennia, though significant progress in meteorology did not occur until the 18th century. The 19th century saw breakthroughs occur after observing networks developed across several countries...
, Babinet spent a significant amount of time in the study of rainbow optics. His astronomical research focused on Mercury's
Mercury (planet)
Mercury is the innermost and smallest planet in the Solar System, orbiting the Sun once every 87.969 Earth days. The orbit of Mercury has the highest eccentricity of all the Solar System planets, and it has the smallest axial tilt. It completes three rotations about its axis for every two orbits...
mass and the Earth's magnetism, while his inventions included valve improvements for air pumps and a hygrometer
Hygrometer
A hygrometer is an instrument used for measuring the moisture content in the environmental air, or humidity. Most measurement devices usually rely on measurements of some other quantity such as temperature, pressure, mass or a mechanical or electrical change in a substance as moisture is absorbed...
. In geography
Geography
Geography is the science that studies the lands, features, inhabitants, and phenomena of Earth. A literal translation would be "to describe or write about the Earth". The first person to use the word "geography" was Eratosthenes...
and hydrogeomorphology, the Baer-Babinet Law helps to explain and predict directionality in the course of rivers. Babinet's cartography
Cartography
Cartography is the study and practice of making maps. Combining science, aesthetics, and technique, cartography builds on the premise that reality can be modeled in ways that communicate spatial information effectively.The fundamental problems of traditional cartography are to:*Set the map's...
work includes homalographic projections where the parallels are rectilinear and meridian lines are elliptical.
In addition to his brilliant lectures on meteorology and optics research, Babinet was also a great promoter of science, an amusing and clever lecturer, and a brilliant, entertaining and prolific author of popular scientific articles. Unlike the majority of his contemporaries, Babinet was beloved by many for his kindly and charitable nature.