Like we all who built it first and all, but how did the humans know that such a weapon could be possible to build with so much capability? Was there research from older scientists and physicists that led to the idea that such a thing was possible and only needed to be built?
In: 985
Lise Meitner. She is how.
Lise Meitner (7 November 1878 – 27 October 1968) is the physicist that the element meitnerium (109) is named after. She came up with the theoretical basis for nuclear fission upon receiving the results of an experiment by a colleague of hers, chemist Otto Hahn.
A Jewish woman, she was born in Austria but lived her later life in Sweden, to which she had fled after her citizenship was revoked during the *Anschluss*. Her work discovering fission was done in Sweden, in the forests around Kungälv near Gothenburg, after receiving a correspondence from Hahn containing his results.
[An article by Jeremy Bernstein](https://inference-review.com/article/the-discovery-of-nuclear-fission) describes the historical moment when she discovered that an atomic bomb was possible, as related primarily by her nephew, Otto Frisch:
>>When I came out of my hotel room after my first night in Kungälv I found Lise Meitner studying a letter from Hahn and obviously worried by it. … Its content was indeed so startling that I was at first inclined to be skeptical. Hahn and Strassmann had found that those three substances [formed by bombarding uranium with neutrons] were not radium, chemically speaking; indeed they had found it impossible to separate them from the barium which, routinely, they had added in order to facilitate the chemical separations. They had come to the conclusion, reluctantly and with hesitation, that they were isotopes of barium.
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>Frisch asked whether Hahn and Strassmann might have made a mistake, but his aunt was adamant:
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>>No, said Lise Meitner; Hahn was too good a chemist for that. But how could barium be formed from uranium? No larger particles than protons or helium nuclei (alpha particles) had ever been chipped away from nuclei…
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>>At that point we both sat down on a tree trunk … and started to calculate on scraps of paper. The charge of a uranium nucleus, we found, was indeed large enough to overcome the effect of the surface tension almost completely; so the uranium nucleus might indeed resemble a very wobbly, unstable drop, ready to divide itself at the slightest provocation, such as the impact of a single neutron.
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>The pair then proceeded to work out for the very first time the physical characteristics of nuclear fission:
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>>But there was another problem. After separation, the two drops would be driven apart by their mutual electric repulsion and would acquire high speed and a very large energy, about 200 MeV in all; where could that energy come from? Fortunately Lise Meitner remembered the empirical formula for computing the masses of nuclei and worked out that the two nuclei formed by the division of a uranium nucleus would be lighter than the original uranium nucleus by about one-fifth the mass of a proton. Now whenever mass disappears energy is created, according to Einstein’s formula E = mc2, and one-fifth of a proton mass was just equivalent to 200 MeV. So here was the source for that energy; it all fitted!
Word spread. Danish physicist Niels Bohr took word of the discovery to a lecture he was giving at Princeton. Two Princeton scientists attending the lecture took word back to Columbia University, where Enrico Fermi, an Italian physicist, had recently been offered a job after fleeing Fascist Italy with his Jewish wife. He relates:
>…I remember one afternoon Willis Lamb came back very excited and said that Bohr had leaked out great news. The great news that had leaked out was the discovery of fission and at least the outline of its interpretation. Then, somewhat later that same month, there was a meeting in Washington where the possible importance of the newly discovered phenomenon of fission was first discussed in semi-jocular earnest as a possible source of nuclear power.
Notice how, even on the verge of war, as scientists were fleeing countries left and right to avoid the racial oppression that would become known as the Holocaust, still the memory is not of the bombs that could be made, but of a bright nuclear-powered future.
* On March 18, 1939, Fermi gave a lecture to military leaders at the Navy Department warning them of the potential impact of nuclear power.
* On August 2, 1939, four scientists, including Einstein, sent a letter to President Roosevelt asserting that Nazi Germany would probably try to build an atomic bomb. Roosevelt took notice.
* The Manhattan Project developed a bomb, and the rest is history.
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