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Prince Louis-Victor Pierre Raymond de Broglie
(1892-1987)
French physicist best known for his research on quantum theory and
for his discovery of the wave nature of electrons. He was awarded the
1929 Nobel Prize for Physics.
Early life.
Broglie was the second son of a member of the French nobility. From
the Broglie family, whose name is taken from a small town in Normandy,
have come high-ranking soldiers, politicians, and diplomats since the
17th century. In choosing science as a profession, Louis de Broglie
broke with family tradition, as had his brother Maurice (from whom,
after his death, Louis inherited the title of duc). Maurice, who was
also a physicist and made notable contributions to the experimental
study of the atomic nucleus, kept a well-equipped laboratory in the
family mansion in Paris. Louis occasionally joined his brother in his
work, but it was the purely conceptual side of physics that attracted
him. He described himself as "having much more the state of mind
of a pure theoretician than that of an experimenter or engineer, loving
especially the general and philosophical view. . . ." He was brought
into one of his few contacts with the technical aspects of physics during
World War I, when he saw army service in a radio station in the Eiffel
Tower.
Broglie's interest in what he called the "mysteries" of atomic
physics--namely, unsolved conceptual problems of the science--was aroused
when he learned from his brother about the work of the German physicists
Max Planck and Albert Einstein, but the decision to take up the profession
of physicist was long in coming. He began at 18 to study theoretical
physics at the Sorbonne, but he was also earning his degree in history
(1909), thus moving along the family path toward a career in the diplomatic
service. After a period of severe conflict, he declined the research
project in French history that he had been assigned and chose for his
doctoral thesis a subject in physics.
Theory of electron waves.
In this thesis (1924) Broglie developed his revolutionary theory of
electron waves, which he had published earlier in scientific journals.
(See de Broglie wave.) The notion that matter on the atomic scale might
have the properties of a wave was rooted in a proposal Einstein had
made 20 years before. Einstein had suggested that light of short wavelengths
might under some conditions be observed to behave as if it were composed
of particles, an idea that was confirmed in 1923. The dual nature of
light, however, was just beginning to gain scientific acceptance when
Broglie extended the idea of such a duality to matter. (See wave-particle
duality.)
Broglie's proposal answered a question that had been raised by calculations
of the motion of electrons within the atom. Experiments had indicated
that the electron must move around a nucleus and that, for reasons then
obscure, there are restrictions on its motion. Broglie's idea of an
electron with the properties of a wave offered an explanation of the
restricted motion. A wave confined within boundaries imposed by the
nuclear charge would be restricted in shape and, thus, in motion, for
any wave shape that did not fit within the atomic boundaries would interfere
with itself and be canceled out. In 1923, when Broglie put forward this
idea, there was no experimental evidence whatsoever that the electron,
the corpuscular properties of which were well established by experiment,
might under some conditions behave as if it were radiant energy. Broglie's
suggestion, his one major contribution to physics, thus constituted
a triumph of intuition.
The first publications of Broglie's idea of "matter waves"
had drawn little attention from other physicists, but a copy of his
doctoral thesis chanced to reach Einstein, whose response was enthusiastic.
Einstein stressed the importance of Broglie's work both explicitly and
by building further on it. In this way the Austrian physicist Erwin
Schrodinger learned of the hypothetical waves, and on the basis of the
idea, he constructed a mathematical system, wave mechanics, that has
become an essential tool of physics. Not until 1927, however, did Clinton
Davisson and Lester Germer in the United States and George Thomson in
Scotland find the first experimental evidence of the electron's wave
nature.
Later career and writings.
After receiving his doctorate, Broglie remained at the Sorbonne, becoming
in 1928 professor of theoretical physics at the newly founded Henri
Poincare Institute, where he taught until his retirement in 1962. He
also acted, after 1945, as an adviser to the French Atomic Energy Commissariat.
In addition to winning the Nobel Prize for Physics, Broglie received,
in 1952, the Kalinga Prize, awarded by the United Nations Economic and
Social Council, in recognition of his writings on science for the general
public. He was a foreign member of the British Royal Society, a member
of the French Academy of Sciences, and, like several of his forebears,
a member of the Academie Francaise.
Broglie's keen interest in the philosophical implications of modern
physics found expression in addresses, articles, and books. The central
question for him was whether the statistical considerations that are
fundamental to atomic physics reflect an ignorance of underlying causes
or whether they express all that there is to be known; the latter would
be the case if, as some believe, the act of measuring affects, and is
inseparable from, what is measured. For about three decades after his
work of 1923, Broglie held the view that underlying causes could not
be delineated in a final sense, but, with the passing of time, he returned
to his earlier belief that the statistical theories hide "a completely
determined and ascertainable reality behind variables which elude our
experimental techniques."
BIBLIOGRAPHY.
Translations of Broglie's popular writings include Matter and Light:
The New Physics (1939, reissued 1955), The Revolution in Physics (1953,
reissued 1969), Physics and Microphysics (1955, reissued 1966), and
New Perspectives in Physics (1962). William C. Price, Seymour S. Chissick,
and Tom Ravensdale (eds.), Wave Mechanics: The First Fifty Years (1973),
includes an article by Broglie. An account of his work may be found
in Barbara Lovett Cline, The Questioners: Physicists and the Quantum
Theory (1965).
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