Peter Galison Author of Error THE NUCLEUS OF ERROR WHEN THE 1938 NOBEL PRIZE IN PHYSICS WAS GIVEN TO ENRICO FERMI, the short citation said this: “[F]orhis demonstrations ofthe existence of new radioactive elements produced by neutron irradiation, and for his related discovery of nuclear reactions brought about by slow neutrons.” Professor H. Pleijel, chairman of the Nobel Prize committee for phys ics, reiterated the citation in his presentation of the award, congrat ulating Enrico Fermi for producing elements beyond the end of the then-known periodic table (that is, those that would fall on the chart of elements beyond uranium (element 92)). Hailed for work that had begun in earnest in 1934, accolades fell on Fermi for finding a remark able way to produce a myriad of radioisotopes and for also producing, for the first time in histoiy, “transuranic” (beyond uranium) elements number 93 and number 94-“these new elements,” Pleijel noted, “he called Ausenium and Heperium” (Pleijel, 1938). Understandably, Fermi was proud of his accomplishment in producing these extraordinary new forms of matter. In his prize accep tance speech on December 12,1938, Fermi recalled that we concluded that the carriers [ofthese radioactive proper ties] were one or more elements of atomic number larger than 92; we, in Rome, used to call the elements 93 and 94 Ausenium and Hesperium respectively. It is known that O. Hahn and L. Meitner have investigated very carefully and extensively the decay products of irradiated uranium, and social research Vol 72 : No 1 : Spring 2005 63 were able to trace among them elements up to the atomic number 96 (Fermi, 1938:416-17).1 Celebrated across Italy, blessed by the highest authority of scientific accolade, Fermi’s production of transuranics stood as one of the great est of scientific discoveries. Reading a bit further in Fermi’s speech, one comes across one of the most extraordinary footnotes in the histoiy of science—oddly stuck in the text sometime between his December 1938 appearance in Stockholm and the Nobel book’s appearance in print—to the effect that Otto Hahn and Fritz Strassmann had just found barium among the disin tegration products of bombarded uranium. Though it entered only as a late footnote to Fermi’s presentation, this news hit the physics world of 1939 with the force of a bomb: it meant that Fermi had almost certainly not seen what he (and the Nobel Prize committee) thought he had seen: the decay of one or more neutrons within the uranium nucleus into a proton, and by doing so transforming uranium nuclei into nuclei of new (transuranic) elements. Instead, if Hahn and Strassmann were right, uranium had split into two approximately equal parts. This, Fermi allowed, “makes it necessary to reexamine all the problems of the transuranic elements, as many of them m ight be found to be products of a splitting of uranium” (Fermi, 1938: 417). W hat Fermi, his collaborators, the phys ics community, and indeed the Nobel Prize committee had taken to be transuranic elements—elements past uranium on the periodic chart of the elements—were not that at all. They were nuclear fragments from far lower in the periodic table of the elements, not the exotic new elements 93 and 94 but the decidedly unexotic elements like element 56, barium (useful for clearing moisture from vacuum tubes, and not headline news). One ofthe great triumphs of Fermi’s physics, a triumph hailed by the scientific world’s greatest honor, was a world-historical mistake. In experiment after experiment from 1934—and in the following years— 64 social research E nrico Ferm i in his lab. the pope of physics had missed nuclear fission. What would the world have been like had Fermi not made this mistake, if he had used his slow neutrons on uranium and realized that there were reaction products, like barium, that lived far down the period chart? What would it have meant had fission been found five years before 1938 and 1939? Writing counterfactual history is a difficult way to make a living. But let’s put it this way. From the time that Hahn and Strassmann submitted their paper in February 1939, it...
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May 17, 2005
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