George Gamow, a Soviet physicist trained in Leningrad and then visiting Max Born's institute in Göttingen, solves in summer 1928 the Schrödinger equation for an alpha particle confined in a nuclear potential well, with mathematical help from Nikolai Kochin. He shows that, despite not having sufficient energy according to classical physics, the alpha particle has a finite probability of crossing the potential barrier (tunneling) and escaping the nucleus. The result quantitatively explains the empirical Geiger-Nuttall law, which relates the energy of the emitted alpha particle to the nucleus's half-life. It is the first application of quantum mechanics to a nuclear physics problem. The same result was obtained independently and almost simultaneously by Ronald Gurney and Edward Condon at Princeton, whose paper in Nature was published approximately a month before Gamow's in Zeitschrift für Physik, though without the same level of quantitative detail.