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  • November 10, 2005

    Episode 9: Hans Bethe

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    Everyone asks whether the Sun is shining. Hans Bethe asked why it was shining. Bethe, who died in March 2005 at age 98, was the first to explain how the Sun generates energy to shine. In the 1920s, when Bethe was first studying physics, scientists knew that the Sun could release energy by contracting gravitationally. But such shrinking does not produce enough energy to account for the Sun's output. In the late 1930s, Bethe and fellow scientist Charles Critchfield demonstrated how a sequence of nuclear reactions could make the Sun shine. He won the Nobel Prize in 1967 for solving this puzzle and others involving energy production in stars. Bethe was borne on July 2, 1906, in Strasbourg, Germany. He exhibited an early interest in numbers and could do square roots at age 4, and fractions and most other math functions by the age of 5. He fled Europe for America in 1935 under the shadow of Nazism, and joined Cornell University. He worked on the atomic bomb, but became a champion of arms control after World War II. He continued to study stars and the Sun, focusing on supernovae and the high energy physics. Near the end of his long life, at age 95, he saw his theories about solar particles called neutrinos confirmed by difficult, precise measurements made possible with new technology.