Latest news with #Meitner
Yahoo
22-03-2025
- Science
- Yahoo
Lise Meitner – the forgotten woman of nuclear physics who deserved a Nobel Prize
Nuclear fission – the physical process by which very large atoms like uranium split into pairs of smaller atoms – is what makes nuclear bombs and nuclear power plants possible. But for many years, physicists believed it energetically impossible for atoms as large as uranium (atomic mass = 235 or 238) to be split into two. That all changed on Feb. 11, 1939, with a letter to the editor of Nature – a premier international scientific journal – that described exactly how such a thing could occur and even named it fission. In that letter, physicist Lise Meitner, with the assistance of her young nephew Otto Frisch, provided a physical explanation of how nuclear fission could happen. It was a massive leap forward in nuclear physics, but today Lise Meitner remains obscure and largely forgotten. She was excluded from the victory celebration because she was a Jewish woman. Her story is a sad one. Meitner based her fission argument on the 'liquid droplet model' of nuclear structure – a model that likened the forces that hold the atomic nucleus together to the surface tension that gives a water droplet its structure. She noted that the surface tension of an atomic nucleus weakens as the charge of the nucleus increases, and could even approach zero tension if the nuclear charge was very high, as is the case for uranium (charge = 92+). The lack of sufficient nuclear surface tension would then allow the nucleus to split into two fragments when struck by a neutron – a chargeless subatomic particle – with each fragment carrying away very high levels of kinetic energy. Meisner remarked: 'The whole 'fission' process can thus be described in an essentially classical [physics] way.' Just that simple, right? Meitner went further to explain how her scientific colleagues had gotten it wrong. When scientists bombarded uranium with neutrons, they believed the uranium nucleus, rather than splitting, captured some neutrons. These captured neutrons were then converted into positively charged protons and thus transformed the uranium into the incrementally larger elements on the periodic table of elements – the so-called 'transuranium,' or beyond uranium, elements. Some people were skeptical that neutron bombardment could produce transuranium elements, including Irene Joliot-Curie – Marie Curie's daughter – and Meitner. Joliot-Curie had found that one of these new alleged transuranium elements actually behaved chemically just like radium, the element her mother had discovered. Joliot-Curie suggested that it might be just radium (atomic mass = 226) – an element somewhat smaller than uranium – that was coming from the neutron-bombarded uranium. Meitner had an alternative explanation. She thought that, rather than radium, the element in question might actually be barium – an element with a chemistry very similar to radium. The issue of radium versus barium was very important to Meitner because barium (atomic mass = 139) was a possible fission product according to her split uranium theory, but radium was not – it was too big (atomic mass = 226). Meitner urged her chemist colleague Otto Hahn to try to further purify the uranium bombardment samples and assess whether they were, in fact, made up of radium or its chemical cousin barium. Hahn complied, and he found that Meitner was correct: the element in the sample was indeed barium, not radium. Hahn's finding suggested that the uranium nucleus had split into pieces – becoming two different elements with smaller nuclei – just as Meitner had suspected. Meitner should have been the hero of the day, and the physicists and chemists should have jointly published their findings and waited to receive the world's accolades for their discovery of nuclear fission. But unfortunately, that's not what happened. Meitner had two difficulties: She was a Jew living as an exile in Sweden because of the Jewish persecution going on in Nazi Germany, and she was a woman. She might have overcome either one of these obstacles to scientific success, but both proved insurmountable. Meitner had been working as Hahn's academic equal when they were on the faculty of the Kaiser Wilhelm Institute in Berlin together. By all accounts they were close colleagues and friends for many years. When the Nazis took over, however, Meitner was forced to leave Germany. She took a position in Stockholm, and continued to work on nuclear issues with Hahn and his junior colleague Fritz Strassmann through regular correspondence. This working relationship, though not ideal, was still highly productive. The barium discovery was the latest fruit of that collaboration. Yet when it came time to publish, Hahn knew that including a Jewish woman on the paper would cost him his career in Germany. So he published without her, falsely claiming that the discovery was based solely on insights gleaned from his own chemical purification work, and that any physical insight contributed by Meitner played an insignificant role. All this despite the fact he wouldn't have even thought to isolate barium from his samples had Meitner not directed him to do so. Hahn had trouble explaining his own findings, though. In his paper, he put forth no plausible mechanism as to how uranium atoms had split into barium atoms. But Meitner had the explanation. So a few weeks later, Meitner wrote her famous fission letter to the editor, ironically explaining the mechanism of 'Hahn's discovery.' Even that didn't help her situation. The Nobel Committee awarded the 1944 Nobel Prize in Chemistry 'for the discovery of the fission of heavy nuclei' to Hahn alone. Paradoxically, the word 'fission' never appeared in Hahn's original publication, as Meitner had been the first to coin the term in the letter published afterward. A controversy has raged about the discovery of nuclear fission ever since, with critics claiming it represents one of the worst examples of blatant racism and sexism by the Nobel committee. Unlike another prominent female nuclear physicist whose career preceded her – Marie Curie – Meitner's contributions to nuclear physics were never recognized by the Nobel committee. She has been totally left out in the cold, and remains unknown to most of the public. After the war, Meitner remained in Stockholm and became a Swedish citizen. Later in life, she decided to let bygones be bygones. She reconnected with Hahn, and the two octogenarians resumed their friendship. Although the Nobel committee never acknowledged its mistake, the slight to Meitner was partly mitigated in 1966 when the U.S. Department of Energy jointly awarded her, Hahn and Strassmann its prestigious Enrico Fermi Award 'for pioneering research in the naturally occurring radioactivities and extensive experimental studies leading to the discovery of fission.' The two-decade late recognition came just in time for Meitner. She and Hahn died within months of each other in 1968; they were both 89 years old. This article is republished from The Conversation, a nonprofit, independent news organization bringing you facts and trustworthy analysis to help you make sense of our complex world. It was written by: Timothy J. Jorgensen, Georgetown University Read more: Atomic age began 75 years ago with the first controlled nuclear chain reaction How nuclear power-generating reactors have evolved since their birth in the 1950s Why more women don't win science Nobels Timothy J. Jorgensen does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.
Yahoo
08-03-2025
- Science
- Yahoo
EDITORIAL: A month for honoring women
Mar. 7—Nuclear fission Kevlar Scotchgard DNA structure All of these and many, many more examples have two things in common — they changed the world in which we live and women played primarily roles in conceiving and developing these ideas. Meitner, along with Otto Hahn and Otto Robert Frisch, led a group that discovered nuclear fission. Kevlar was developed by Kwolek, Scotchgard by Sherman and the DNA structure by Franklin. And of course you can add to this list the likes of Maya Angelou, Rosa Parks, Sally Ride, Amelia Earhart, Gloria Steinem and Kamala Harris — all of whom have contributed to the world in powerful and meaningful ways. March 8 is International Women's Day, and this month is International Women's Month, worthy reminders to ruminate on the contributions of women to both our daily lives and personal lives. Whether we are honoring the women mentioned above, those others unnamed or simply taking the time to recognize the work our mothers, grandmothers, aunts and sisters put in each day — it's with great admiration that we bring women to the forefront to recognize their contributions. At the same time, International Women's Day is an opportunity to recognize the progress in women's rights as well as understanding there is still so much to accomplish in the ever-evolving quest for true equality. Women around the world play an integral role in our society, whether that's on a personal level, a business level, national level or international level. In a lot of ways, we don't come as far as we have without their contributions.
