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Weizsäcker, Carl Friedrich, Freiherr

energy proposed reaction solar

(Baron) von [ viyt seker] (1912– ) German physicist: proposed theories for stellar energy generation, and for the origin of the solar system.

Weizsäcker studied and later taught physics at both Berlin and Leipzig; from 1957 he was professor of philosophy at Hamburg. Independently of he suggested in 1938 that the energy of stars is generated by a catalytic cycle of nuclear fusion reactions, whereby hydrogen atoms are converted into helium with much evolution of energy. More specifically, this reaction (the proton fusion reaction) has as its net result the conversion of four hydrogen nuclei (ie protons) into a helium nucleus. The reaction requires a high temperature (˜ 10 9 K) and yields also a massive amount of thermal energy, along with gamma radiation. The energy is sufficient to maintain a star’s energy output (such as the Sun’s) for billions of years. It is widely accepted as the key process in stellar energy generation.

Weizsäcker proposed a scheme in 1944 for the origin of the solar system; this scheme developed the older ideas of that the Sun had been surrounded by a disc of gas, which rotated, became turbulent and aggregated to form the planets. Weizsäcker’s theory (like Laplace’s) failed to account for the angular momentum of the solar system, but it was developed by and then by , who proposed that the Sun’s magnetic field could generate the required momentum.

During the Second World War Weizsäcker worked with to develop nuclear energy from uranium for power or weaponry, but with trivial success in comparison with the Allies.

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