Louis Victor Pierre Raymond de Broglie | Biography

Louis Victor Pierre Raymond de Broglie, a twentieth century French theoretical physicist, established the foundations for wave mechanics, and as a result for much of modern physics. The principle underlying wave mechanics is that matter has both the characteristics of particles and waves, and the particular characteristic that is observed will depend on how the observation is made. These ideas fundamentally changed the way physicists view the world, and earned Louis de Broglie the 1929 Nobel Prize for physics.

Louis de Broglie was the youngest of five children. His early education was obtained at home. Born to Duc Victor and Pauline d'Armaille Broglie on August 15, 1892 in Dieppe, France, the young physicist-to-be was second in line to his elder (by 17 years) brother Maurice to inherit the titles of French Duc and German Prinz as the result of his family's past service to French and Austrian monarchies.

By the late nineteenth century, the de Broglie family had been supplying France with soldiers, diplomats, and politicians for centuries. Expected to follow in the family's traditional paths, elder brother Maurice was earmarked at an early age for a career as a diplomat or military officer. And so, with his paternal grandfather's consent, the young Maurice prepared for a naval career.

But by 1898, bolstered by further academic coursework, Maurice de Broglie had become increasingly interested in scientific work, and he approached his grandfather with the idea of resigning his naval commission and taking up a career in physics instead. Predictably, his grandfather would have none of it. The old man reportedly told de Broglie that science was like an old lady, content with the attentions of old men, and was an unsuitable career for a de Broglie.

As a compromise, Maurice set up a laboratory in one the rooms on the family estate, and meanwhile returned to his commission in the navy where he distinguished himself with scientific work. In 1904, after his grandfather's death, he took a military furlough, and eventually resigned his commission in 1908. At the same time, Maurice arranged for the younger Louis to study at the Lycée Janson de Sailly in Paris. Maurice, meanwhile, continued his studies in physics at the Collège de France, where he completed a thesis under the noted physicist, Paul Langevin.

In 1909, younger brother Louis graduated from the Sorbonne with baccalaureate degrees in philosophy and mathematics. But before settling on a career in physics, he also considered the fields of ancient history, paleography, and law. His decision to pursue scientific work was largely influenced by the writings of the French theoretical physicist, Jules Henri Poincaré.

Maurice, had already by this time begun experimental research on X-rays and radioactivity. In 1912, with the discovery by Laue and the Braggs that X-rays could produce diffraction patterns, Maurice suddenly began looking at X-ray spectra, which was to be the field of his greatest discoveries. His first achievement was to develop a crystal rotation method for X-ray analysis. Maurice was now in an ideal position to encourage his younger brother's budding interest in atomic theory. And in 1913, Louis obtained his diploma from the University of Paris' Faculté des Sciences.

During World War I, the de Broglies' scientific pursuits were put aside while Louis served in the French army, and Maurice in the navy. Louis' wartime service was spent with the French Engineers at the wireless (a field in which his brother had already distinguished himself) station under the Eiffel Tower. In 1919, after six years of army service, Louis once again took up scientific work, this time in his brother's laboratory.

It was at this time that Louis began to look at a problem that had long been baffling the scientific community: why does light sometimes show the properties of particles, and at other time, the properties of waves? Based on work performed in his brother's laboratory, Louis wrote a doctoral thesis entitled "Investigations into the Quantum Theory," which he submitted to the Sorbonne in 1924.

Louis' thesis was that all elements of matter, including negatively charged electrons, behave as both as particles and waves, but that it is only at the atomic level that the wave characteristics show up. At ordinary dimensions, where the billiard-ball, i.e., particulate, properties of matter are observed. Louis argued that the wave and particle properties were actually one and the same; which one was observed depended only on the way the observation was made.

Louis' theory had the effect of making classical Newtonian mechanics a special case (e.g., one that applied to the everyday world) of a more general view of matter that included atomic effects. Louis argued that all matter has waves associated with it; the only reason that these waves are not usually observed is that they are very small compared to the dimensions of objects usually encountered. To formally express these ideas, he developed a mathematical formula, which is now known as the wave equation.

Because Louis' professors at the Sorbonne did not consider themselves competent to evaluate his thesis, they asked him to send a copy of his thesis to Albert Einstein. Einstein immediately recognized the significance of de Broglie's theory. Another early investigator in the field of quantum mechanics, Erwin Schrödinger, later based his own theory of wave mechanics on Louis' work.

De Broglie's theory remained unproven, however, until experiments by American and English physicists demonstrated conclusively that electrons can indeed be bent like waves. Other experiments followed demonstrating that protons, atoms, and molecules behave similarly. These discoveries paved the way for the invention of the electron microscope much later on.

In 1927, Louis attended the seventh Solvay Conference where the leading atomic physicists continued the debate about wave mechanics. At the conference, such theorists as Werner Heisenberg, Niels Bohr, and Max Born argued that matter waves provided only statistical information about the position of a particle (probabilistic theory), and nothing about the exact position. But Einstein, Louis de Broglie, and Schrödinger, being unwilling to believe that matter can act in a random way, supported the view that the waves determined exact positions and left nothing to chance (deterministic theory).

Unable to counter certain objections to his deterministic view of waves, Louis abandoned it, and thereafter taught his students probabilistic theory. In 1928, he accepted an appointment as professor of theoretical physics at the University of Paris' Faculty of Science. Despite his academic career, he established no significant record of guiding research students.

In 1929, the 37-year-old Louis was awarded the Nobel Prize for physics in recognition of his work on wave mechanics. In 1933, he moved to the Henri Poincaré Institute, where he was to remain for the next 29 years. While at the Institute, he established a center for the study of modern physical theories. Also in 1933, he was elected to the Académie of Sciences; he was later to use his influence as an academician to point out the harmful effects of nuclear explosions. In 1943, he established a center for applied mechanics at the Institute. A year later, he was elected to the Académie Francaise. In 1945, both he and his brother were appointed to the French High Commission of Atomic Energy.

Louis de Broglie was the author of over twenty books. His writings frequently dealt with the practical side of physics, and addressed such topics as cybernetics, atomic energy, particle accelerators, and optics.

With the death of his older brother in 1960, Louis inherited the title of titles of French duke and German prince. He died at the age of 95 on March 19, 1987, without ever having resolved all of the ambiguities of wave-particle duality.