Louis Leprince-Ringuet, an expert in cosmic rays and a great French scientific figure, died on 23 December 2000, a few months before his 100th birthday.
Leprince-Ringuet was born on 27 March 1901 in Alès, a mining town in southern France. In 1920, he graduated from Ecole Polytechnique in Paris and completed his engineering studies, specializing in telecommunications, at the French telecommunication school Ecole Supérieure d’Electricité in Paris before beginning, in 1925, a career as an engineer laying and servicing submarine cables.
In 1929, he decided to switch fully to conducting research in the laboratory of Maurice de Broglie, the brother of Louis de Broglie. The lab’s main activity was shifting from x rays to nuclear physics, and Leprince-Ringuet started to develop the relevant instrumentation. He received his doctorate in physics from the University of Paris and soon collaborated with Pierre Auger’s group on cosmic-ray studies in the high mountains, happy, as he said, to “leave for the open skies after work carried on in a basement.”
In 1933, Leprince-Ringuet joined Auger on a ship sailing from Hamburg, Germany, to Buenos Aires, Argentina, with 100 particle detectors onboard. At that time, the nature of cosmic rays was unknown. Charged particles, unlike gamma rays, are deflected by Earth’s magnetic field, which varies with latitude. Auger and Leprince-Ringuet hoped, therefore, that studying the variation of cosmic-ray intensity with latitude would reveal what cosmic rays consisted of. The experiment favored particles and was Leprince-Ringuet’s first main involvement in the field of cosmic rays, in which he eventually acquired a worldwide reputation.
After several experiments with Auger on mountain peaks and with balloon flights, Leprince-Ringuet developed his own laboratory for cosmic-ray research in 1936, when he became a professor, with a chair of physics, at Ecole Polytechnique. He attracted to his laboratory a host of young and brilliant researchers, among them Bernard Gregory, who became the director general of CERN in the late 1960s, and André Lagarrigue, famous for the discovery of the neutral current interaction in the early 1970s. Leprince-Ringuet played an important role in the revival of physics research in France after World War II.
Even though his mountain work with cosmic rays was slowed down by the war, Leprince-Ringuet continued his research, which bloomed and had culminated by the time of the Bagnères-de-Bigorre conference in 1953. At that watershed conference, he presented the summary of a talk covering the important results obtained with the many surprising particles discovered. He is credited for finding evidence for a heavy particle and also for coining the term hyperon.
Leprince-Ringuet was also saying farewell to cosmic-ray research at that conference. Realizing the impending and overwhelming competing power of accelerators in the GeV range, he decided to reorient his laboratory toward accelerator physics. He effectively argued for the construction of bubble chambers at Saclay, which resulted in a plan for two French bubble chambers, one filled with hydrogen and the other with heavy liquid, to be installed at CERN as the proton synchrotron was commissioned in 1959. Commonly heard at the time was this: “There are 13 CERN members, those with a flag at the entry and Ecole Polytechnique!” This effort eventually led to the development of the giant Gargamelle chamber in the late 1960s and the discovery there of the neutral-current weak interactions in 1973.
In 1959, Leprince-Ringuet succeeded Frédéric Joliot-Curie at the Collège de France as professor and became head of two large laboratories, there and one at Ecole Polytechnique. He retired as the Collège de France’s chair of physics and as head of the lab at Ecole Polytechnique in 1972.
In 1991, still remembered as a physicist on mountaintops, Leprince-Ringuet was one of the two guests of honor at the dedication of the newly established “Refuge des Cosmiques” (Cosmic Refuge) near Mont Blanc in the Alps in remembrance of the cosmic-ray work done during the 1940s in the old refuge, which the new one replaced. He shared the honor of dedicating the refuge with author Roger Frison-Roche.
Leprince-Ringuet was a man of many interests. As a member of the French Academy of Sciences and of the French Atomic Energy Commission’s governing board, he had the means to exert his influence. He advocated strongly for the creation of CERN and remained its indefatigable supporter. He was vice chair (1956–69) and chair (1964–66) of CERN’s scientific policy committee. He was elected to the French Academy in 1966. He also was a champion of outreach, engaging in activities involving ecology and sustainable sources of energy.
When a special symposium was held at Ecole Polytechnique to celebrate Leprince-Ringuet’s 96th birthday, it took not less than six contributors to do justice to his achievements in many fields, ranging from science, to art, to tennis. Many physicists are much indebted to him for his guidance, for developing very good research conditions, and for making fundamental research a popular enterprise and for helping to popularize physics and science through the media.
Leprince-Ringuet was a devoted Christian, and a painter who presented several exhibitions. On one such occasion, he had to compare the creative work of the artist to that of the scientist. It seems proper to conclude with his view of science, his first and main love all along, which he repeated at the celebration of his 96th birthday:
Our work is part of a never-ending study of natural phenomena, of their understanding, and of finding their relationship through a formalism that we have to invent for that purpose. Even if our work relies on imagination, critical thinking, tenacity, and creative spirit, it reveals little and very seldom the deepest and most private reality of our own self. In that sense we are not poets but we sing in wide choirs the greatness of nature and the power of humankind.
