1912-

German physicist who, independent of Hans Bethe, proposed a series of nuclear-fusion reactions as the mechanism whereby stars produce energy (1938). Weizsäcker also modified Pierre Simon Laplace's nebular hypothesis. According to Laplace, the planets formed from a gaseous nebula rotating uniformly—like a solid disk—around the Sun. Weizsäcker noted there would be differential rotation resulting in vortices from which the planets coalesced. Though failing to consider the solar system's angular momentum, Weizsäcker's improvements advanced our understanding of planetary formation.