Szilard, Leo. Highly important typed letter signed, 2 pages (11 x 8 ½ in.; 279 x 216 mm.), “New York,” 25 January 1939 to Lewis L. Strauss, a partner in the international banking firm Kuhn, Loeb and Company who played a pivotal role in shaping nuclear policy in the United States; date of letter boldly circled in red pencil with arrow, received stamp dated 26 January 1939 at top right corner of first page; slight marginal browning.
Szilard reports on a very sensational new development—nuclear fission—the key discovery in opening the door to the creation of the atomic bomb.
In 1935, Lisa Meitner, Otto Hahn and Fritz Strassman began work to sort out all of the substances into which the heaviest of natural elements transmuted under neutron bombardment. By early 1938, they had identified no fewer than ten different half-life activities. At the same time, Irene Curie began looking into uranium and came up with results which contradicted those of Hahn and Meitner. The debate raged on.
Not long after, Hahn and Strassman succeeded in identifying no fewer than 16 different radioactive substances with varying half-lives. Three of these substances were previously unknown isotopes, and were felt to be isotopes of radium. After several more weeks of tedious work, it seemed that these “radium” isotopes must be barium, element 56, slightly more than half as heavy as uranium. At first they could not believe the results they were seeing and cabled Lisa Meitner in Stockholm for some sort of confirmation. Her reply seemed to suggest that although it appeared to be impossible, they should keep an open mind. Hahn and Strassman continued with further refinements and again cabled Meitner: “Our radium proofs convince us that as chemists we must come to the conclusion that the three carefully-studied isotopes are not radium, but, in fact, barium.”
On January 3rd of 1939, Otto Frisch returned to Copenhagen from visiting his aunt, Lisa Meitner, and informed Niels Bohr of Hahn’s “barium” hypothesis. Niels Bohr was immediately gleeful as if he had been expecting such results. That same day, Lisa Meitner cabled Hahn again: “I am fairly certain now that you really have a splitting towards barium and I consider it a wonderful result for which I congratulate you and Strassman very warmly . . . you now have a wide, and beautiful field of work ahead of you.” What they had succeeded in doing, for the first time, was “splitting” an atom.
As a final step, these results need further interpretation. Lisa Meitner in Stockholm and her nephew in Copenhagen did so by long-distance telephone. Frisch carried out some further confirming experiments in his own lab using a simple ionization chamber. Over the following weekend, aunt and nephew conferred by phone to prepare two papers for Nature: a joint explanation of the reaction and Frisch’s report of the confirming evidence of his experiment. Both reports - “Disintegration of uranium by neutrons: a new type of nuclear reaction” and “Physical evidence for the division of heavy nucleii under neutron bombardment”- used the new term “fission” for the first time. The discovery spread like wildfire. After reading the Hahn-Strassman paper, Leo Szilard, wrote the present letter to Lewis Strauss.
Szilard writes in full: I feel that I ought to let you know of a very sensational new development in nuclear physics. In a paper in the “Naturwissenschaften” Hahn reports that he finds when bombarding uranium with neutrons the uranium breaking up into two halves giving elements of about half the atomic weight of uranium. This is entirely unexpected and exciting news for the average physicist. The Department of Physics at Princeton, where I have spent the last few days, was like a stirred-up ant heap.
Apart from the purely scientific interest there may be another aspect of this discovery, which so far does not seem to have caught the attention of those to whom I spoke. First of all it is obvious that the energy released in this new reaction must be very much higher than all previously known cases. It may be 200 million volt instead of the usual 3-10 million volt. This in itself might make it possible to produce power by means of nuclear energy, but I do not think that this possibility is very exciting, for if the energy output is only two or three times the energy input, the cost of investment would probably be too high to make the process worthwhile. Unfortunately, most of the energy is released in the form of heat and not in the form of radioactivity.
I see, however, in connection with this new discovery potential possibilities in another direction. These might lead to large-scale production of energy and radioactive elements, unfortunately also perhaps to atomic bombs. This new discovery revives all the hopes and fears in this respect which I had in 1934 and 1935, and which I have as good as abandoned in the course of the past two years. At present I am running a high temperature and I am therefore confined to my four walls, but perhaps I can tell you more about these developments some other time. Meanwhile you may look out for a paper in “Nature” by Frisch and Meitner which will soon appear and which might give you some information about this new discovery.
Leo Szilard is best known for his pioneering work in nuclear physics, his participation in the Manhattan Project during World War II, and his fervent opposition to the nuclear arms race in the postwar era. His letter to Lewis Strauss is an extraordinary record of arguably the most important discovery in modern science.
The draft letter Szilard wrote for Albert Einstein to be sent to Franklin Delano Roosevelt regarding the use of the bomb ushering in the atomic age from Szilard’s personal papers sold for $1,900,000 at Christie’s New York, 27 March 2002, lot 161. The letter offered here is of enormous scientific importance in the development of nuclear warfare.