Noting that “the element uranium may be turned into a new and important source of energy in the immediate future,” Einstein adds, “it is conceivable . . . that extremely powerful bombs of a new type may thus be constructed.” The letter spurred government action that ultimately led to the Manhattan Project and the dawn of the nuclear age. When Einstein wrote that message, uranium was the heaviest known element and sat immediately below tungsten in the periodic table. It didn’t hold either position for long. In early 1940, researchers at the University of California, Berkeley, used their new cyclotron particle accelerator to slam neutrons into a uranium-238 target, creating a heavier element they named neptunium.
by Mark Peplow, special to C&EN |
March 04, 2019