CHIEN-SHIUNG WU was born on 31 May 1912 in Jiangsu province, China, at a time when her homeland forbade girls from going to school. Extremely curious as a child, she was blessed with having a father who was supportive of her creative and intellectual pursuits […] and so he took it upon himself to start a girls’ school – the fi rst in the area – to help his daughter and others like her receive a formal education. […]. After primary school she was forced to travel 14 miles to a boarding school that would accept girls. [But] her father told her: “Ignore the obstacles; just put your head down and keep walking forward”. This is something that she recalled a number of times throughout her life.

With such encouragement, Wu dedicated herself to studying maths and science to university level. She […] was really interested in atomic physics, which was very much a burgeoning science at the time. In the 1930s, she completed high school and enrolled at the National Central University in Nanjing. She started as a maths major but eventually moved into physics. She graduated from college four years later and was the school’s undisputed top student. Unfortunately, China didn’t have a graduate programme in atomic physics. At the advice of her mentor, she decided to apply to the University of Michigan and was accepted. […]

COMING TO AMERICA

Following her arrival in San Francisco in the late summer of 1936, Wu had the opportunity to spend time in California before heading to Michigan. There she met Luke Chia-Liu Yuan, a graduate student in physics at the University of California Berkley (UC Berkley) and he helped introduce her to the person who would become her graduate advisor at UC Berkley – Ernest Lawrence. […]

Around a year after she arrived in America, word got out that Japan had invaded her part of China. This was a drastic event in her life because, for eight years, she had no idea if her family was safe or not. There were 42,000 civilians in her home province that were either raped or murdered before the end of that year. This was devastating news for her but she remembered what her father told her about keeping her head down and moving forward; on his advice she pursued her thesis. She fi nished her PhD by 1940 and was considered an expert in the new science of nuclear fi ssion.

SUSTAINING A REACTION

Wu stayed on at UC Berkley for two years as a research assistant. […] During this time, scientists were trying to create sustained nuclear reactions and they were having problems keeping them going – you can’t have nuclear energy or a nuclear bomb without a sustained reaction. Legend has it that someone had suggested that scientists investigating this problem,

Professor Chien-Shiung WuProfessor Chien-Shiung Wu was an eminent Chinese nuclear physicist. Having moved to the US to undertake doctoral studies, she subsequently became a leader in her fi eld and is celebrated as one of the most important physicists of the 20th Century

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A representation of conservation of parity – a problem for which Wu made critical insights.

pioneers of science:

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led by Enrico Fermi, go and ask Wu what to do. She figured out the problem immediately and, just like that, had solved one of the biggest issues in nuclear physics at the time.

Wu and Yuan got married, and in 1942 moved to the East Coast […] where Wu started working at Smith College as a teacher. […] Fortunately, she had the opportunity to start working on the Manhattan Project at Columbia University, which was the US secret programme to develop a nuclear weapon. […] When the War was over, her work there finished but she stayed on at Columbia.

FAMILY MATTERS

After not being able to speak with her family for eight years, Wu had some good news – they were all alive and well in China. Her father had been regarded as a war hero for engineering a crucial transportation route that was used by the Allies to send supplies to Chinese troops. She also gave birth to her only son, Vincent, who is now also a nuclear physicist in Los Alamos, New Mexico. […]

After the War, Wu needed something to focus on and found beta decay – a type of radioactivity where a large atomic nucleus emits energy and turns into another element. At the time no one really understand why this happened. Enrico Fermi […] had devised a theory for how beta decay worked but, even though a number of scientists had tried to figure out what was going on with this theory, no one was getting anywhere. Wu realised that there was a problem with one of the assumptions underlying the machinery; to do with the difference in thickness of material used. By controlling for thickness the error went away and, once again, she was a miracle worker and was able to show that Enrico Fermi’s beta decay model was actually true. […]

CONSERVATION OF PARITY

Next came what she is best known for – conservation of parity. Wu overturned what had been considered a law of nature, a feat that requires extraordinary evidence to achieve. Law of parity states that nature does not favour left or right. This had not been proven experimentally, only mathematically. In a

conference in 1956, physicist Richard Feynman floated the idea that maybe the law was wrong and thus needed investigating. As a consequence, two theoreticians – Tsung-Dao Lee from Columbia and Chen-Ning Yang from the Advanced Institute of Study in Princeton – started wrestling with this problem. They came to think that parity might not be conserved in certain situations, particularly those involving beta decay. They didn’t know how this could be tested so sought out Wu for help, as Lee worked in the same department and knew she was an expert in this area. She suggested a specific approach using an isotope of cobalt to try to figure out if the conservation of parity law would hold true in all cases. […] It was the experiment of a lifetime for her. It took six months to set up using specialist equipment at the National Bureau of Standards in Washington, DC. Two days after Christmas in 1956, the team was ready and she knew that, either way, she would be testing the law in a way that hadn’t been done before. […] The results showed that parity was not conserved!

OVERLOOKED

After the paper was published, the results were heralded on the front page of the New York Times. […]. The parity results were spectacular and the Nobel Prize committee decided to confer an award on Yang and Lee but not on Wu. She was hugely disappointed with this, and many people consider this one of the most serious examples of a woman being looked over for a Nobel Prize. […] Despite this setback, over the next 20 years she racked up an enviable list of honours, awards and firsts. She carried out a number of additional groundbreaking investigations, not only on beta decay but also in the field of short-lived exotic atoms, and even in the biophysics of sickle-cell anaemia.

Chien-Shiung Wu died on 16 February 1997 of a stroke at the age of 84. In addition to her husband and her son she left behind a granddaughter and an enormous legacy.

This is an extract from a talk given by Maia Weinstock from the Massachusetts Institute of Technology, USA, at the Revealing Lives: Women in Science 1830-2000 conference at the Royal Society, London, UK, on 22 May 2014. The talk was based on a book chapter published in A Passion for Science: Stories of Discovery and Invention; a collection of essays celebrating women in STEM. The full chapter can be read here: http://bit.ly/Wh0hB5

“Science is not static but is dynamic and ever improving; it is the courage to doubt what has long been believed and it is the incessant search for verification of proof that pushes the wheels of science forward” – Chien-Shiung Wu

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