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Ele Willoughby, PhD

Happy birthday to Lise Meitner (1878-1968) who explained . She worked with chemists Hahn & Straßmann in 30s Berlin, investigating whether there were any stable elements beyond uranium. They discovered bombarding nucleus of U-235 with neutrons actually triggered it to fission, or break, into 2 nuclei of roughly half the size & some free neutrons! Hahn’s chemistry lead to startling discovery of barium,🧵

but no explanation of the mechanism involved; Meitner’s physics provided the explaination of how fission could be possible & its implications. Hahn won the 1945 Nobel prize for chemistry. Though Meitner won many accolades, the Nobel committee neglected her contribution, in one of the most blatant & egregious instances of their overlooking women’s scientific achievements.⁠ ⁠

The research was disrupted by WWII. Meitner was of Jewish heritage & made a daring escape via Holland to a new home 🧵2/n

in Sweden, in 38. Despite their separation, they continued to work together, planning experiments which lead to the discovery of fission at a meeting in Copenhagen. Hahn & Straßmann performed the experiments & Hahn realized that the presence of Ba could only make sense if the nuclei had split, but he needed Meitner’s help to understand how this could be. Meitner was able to apply the latest physics, the liquid-drop model of the nucleus, to explain how the absorption of an extra neutron 🧵3/n

could produce an unstable nucleus which split into 2 large daughter nuclei, & more free neutrons. Most importantly she saw that the combined mass of the neutron & U-235 was larger than the products & the ‘missing mass’ would all be transformed into vast amounts energy according to Einstein’s famous equation E = mc². She also saw how the newly produced high-energy neutrons would in turn strike other U nuclei, leading to a chain reaction. 🧵4/5

She worked with her nephew Frisch to develop this theory. In Germany, Hahn could not publish jointly with Meitner. Hahn & Straßmann submitted the team’s results for publication in 38. Meitner & Frisch interpreted these results as nuclear fission in 39.⁠

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