Marie Alfred Cornu, French physicist and academic (b. 1842)

Marie Alfred Cornu, born on 6 March 1841 and passing away on 12 April 1902, was an eminent French physicist whose work left a lasting imprint on several branches of science. Though his full given name was Marie Alfred, he is almost universally known and referred to, particularly within French academic and scientific circles, as Alfred Cornu. This common abbreviation reflects how deeply his individual contributions resonated, allowing his surname to stand prominently alongside his most recognized given name.

A Life Dedicated to Precision and Discovery

Hailing from Orléans, France, Alfred Cornu embarked on a distinguished academic career that saw him excel in various fields of experimental physics. After his rigorous education at the prestigious École Polytechnique, where he later became a professor of physics in 1867, and subsequently at the École Nationale Supérieure des Mines, Cornu's scientific endeavors were characterized by an unwavering commitment to accuracy and innovation.

One of his most significant contributions involved the precise determination of the speed of light. Building upon the foundational work of earlier physicists like Hippolyte Fizeau and Léon Foucault, Cornu meticulously refined the experimental methods, particularly Foucault's rotating mirror technique. His careful measurements, conducted between 1872 and 1876, yielded results that were among the most accurate of his time, significantly reducing the margin of error and providing crucial data for astronomical calculations and the understanding of electromagnetic theory.

Beyond the speed of light, Cornu's intellectual curiosity led him to explore numerous other areas. He conducted important research in optics, contributing to the understanding of interference and diffraction phenomena. His work extended to the study of the elasticity of solids, where he developed methods for precise measurement. Cornu was also a pioneer in spectroscopy, examining the ultraviolet spectrum and its applications. His dedication to experimental accuracy even saw him participate in expeditions to photograph solar eclipses, pushing the boundaries of astrophysical observation.

His profound impact on physics was recognized by his peers. He was elected a member of the French Academy of Sciences in 1878, received the Rumford Medal from the Royal Society of London in 1899, and held various prestigious positions throughout his career, cementing his legacy as a leading scientific figure of his era.

The Cornu Spiral: A Lasting Graphical Tool

While often associated with his experimental work, Alfred Cornu's name also lives on through a specific mathematical and graphical tool in optics: the Cornu spiral. This elegant curve is a parametric plot of the Fresnel integrals, providing a visual representation that greatly simplifies calculations and understanding of diffraction patterns, particularly at the edges of shadows (Fresnel diffraction). Though primarily a mathematical construct, its practical utility in optics firmly links it to his broader contributions to the field.

Frequently Asked Questions about Alfred Cornu

What was Alfred Cornu primarily known for?

Alfred Cornu is most renowned for his highly precise experimental determination of the speed of light, refining earlier methods and contributing significantly to one of the fundamental constants in physics.

Why is he often referred to as "Alfred Cornu" instead of "Marie Alfred Cornu"?

While his full given name was Marie Alfred, it was a common cultural practice in France, particularly for men with multiple given names, to be publicly known and referred to by one of them, typically the one they themselves preferred or that became most associated with their public persona. In his case, "Alfred Cornu" became his universally recognized appellation.

What is the Cornu spiral?

The Cornu spiral is a graphical representation used in optics, particularly in the study of Fresnel diffraction. It plots the real and imaginary parts of the Fresnel integrals, offering a visual and intuitive way to calculate and understand the intensity of light in diffraction patterns.

What other areas of physics did Cornu contribute to?

Beyond the speed of light, Alfred Cornu made significant contributions to optics (interference, diffraction, spectroscopy of the ultraviolet spectrum), the elasticity of solids, and even pioneering work in astrophysical photography during solar eclipses.

When and where did Alfred Cornu live?

Alfred Cornu was a French physicist born on 6 March 1841 in Orléans, France, and he passed away on 12 April 1902.