Chien-Shiung Wu
1912 – 1997
Chien-Shiung Wu
Physicist
Parity Nonconservation
Beta Decay
Portrait of Dr. Chien-Shiung Wu.
Dr. Chien-Shiung Wu, an esteemed Chinese experimental physicist, played a pivotal role in revolutionizing the understanding of nuclear physics and beta decay. Regarded as one of the foremost physicists of the 20th century, her pioneering and definitive work on parity nonconservation marked a critical juncture in modern physics. Her work not only provided robust and unequivocal experimental tests but also challenged and reshaped foundational paradigms and models in subatomic physics. Often regarded as the “First Lady of Physics,” Wu’s remarkable journey from a small town near Shanghai to the front lines of the Manhattan Project stands as a testament to her ground-breaking contributions to the field of nuclear physics.
First StepsWu was born on May 31, 1912 and raised in a modest fishing town just north of Shanghai, China. Her family, notably progressive for the time, placed a high value on education, a rarity for girls in the early 1900s (particularly regarding education at higher levels). Wu's mother, a committed teacher, and her father, an accomplished engineer, nurtured Wu’s interest in science and mathematics from a young age. Her father's belief in the importance of education for girls led him to establish the Mingde Women's Vocational Continuing School (now Mingde High School), where Wu began her educational journey. This early support played a crucial role in laying the foundation for Wu to progress and develop into a renowned scientist.
Later in 1930, Wu embarked on her academic journey at National Central University (now Nanjing University) in Nanjing, one of China's oldest and most revered higher educational institutions. Originally enrolling in mathematics, Wu soon shifted her focus to physics, profoundly influenced by the pioneering works of Dr. Marie Curie and Dr. Jing-Wei Gu. During her graduate studies, Wu was mentored and supervised by Gu. She played an instrumental role in shaping Wu's academic trajectory. Under Gu's guidance, Wu was inspired to pursue a doctoral degree in the United States (U.S.), keen to emulate the path of her supervisor.
The First Lady of Physics and the Father of the Atomic BombAt just 24 years old, Dr. Chien-Shiung Wu left her home country in pursuit of knowledge at the University of California, Berkeley where she delved further into her studies, concentrating on a highly sought-after topic of that era, uranium fission products. She studied under the mentorship of the distinguished physicist Dr. Ernest Lawrence, who received the Nobel Prize in 1939 for his invention of the cyclotron, a revolutionary particle accelerator. Wu immersed herself in research at Lawrence’s radiation laboratory, deepening her expertise in the field.
During this period, Wu collaborated with some of the United States' leading experimental physicists. This period was not just an extension of her academic endeavours, but also a significant opportunity for professional development and networking within the scientific community. Among the notable figures, she worked with was Dr. Julius Robert Oppenheimer, who would later become renowned as Director of the Manhattan Project and often hailed as the father of the atomic bomb. Working under his guidance, Wu was able to delve deeper into the complex nuances of nuclear physics. Her interactions with these prominent scientists and the environment at Berkeley, known for its cutting-edge research and intellectual rigour, provided Wu with a fertile ground for academic growth. This phase of her career not only enhanced Wu’s knowledge base but also solidified Wu’s reputation as a formidable physicist in her own right. Wu’s time at Berkeley was much more than just an academic pursuit; it was a period of profound immersion in the forefront of nuclear physics research.
Regrettably, despite her exceptional contributions and capabilities, Wu was not offered an opportunity to continue her work at the University of California, Berkeley. She encountered significant obstacles in obtaining faculty positions at leading universities, a reflection of widespread gender and racial discrimination. Societal biases against women and individuals of East-Asian descent were prevalent at the time. Anti-Asian sentiments were growing and were further fueled by geopolitical events, particularly Japan's attack on Pearl Harbor and the United States’ involvement in World War II. An atmosphere of mistrust and prejudice intensified against Asians in the United States, adversely affecting their professional and personal lives.
Despite these challenges, Wu eventually secured a teaching position in the Physics Department at Smith College. Within just a year, she made another significant stride by becoming the first woman to serve as an instructor in the Physics Department at Princeton University. Building upon her doctoral thesis and connections with physicists such as Oppenheimer and Dr. Emilio Segrè, Wu was invited to contribute to the Manhattan Project at Columbia University. The Manhattan Project was a top-secret United States government initiative during World War II, intending to develop the first atomic weapons and represented a monumental collaboration among America's foremost nuclear scientists.
Wu's contributions to the Manhattan Project were pivotal, particularly in her collaboration with Dr. Enrico Fermi, the celebrated creator of the world's first nuclear reactor and a key figure in the development of the atomic bomb. Wu played a crucial role in helping Fermi solve a critical challenge: a self-sustaining chain reaction in the nuclear reactor would consistently falter after a few hours. Wu's investigations identified xenon, a by-product of the nuclear reaction, as the culprit. Due to its high neutron absorption capacity, xenon was inhibiting the reactor's ability to maintain a self-sustaining reaction. Additionally, Wu's work was instrumental in the construction and operation of the B reactor, the first large-scale nuclear reactor. The B reactor was designed to transform natural uranium into plutonium-239, a critical component of weapons-grade material. Her expertise also significantly contributed to refining the process of separating uranium into U-235 and U-238 isotopes via gaseous diffusion, a key step in producing large quantities of uranium for the first atomic bomb.
Similar to many of the Manhattan Project physicists, Wu distanced herself from the project following the detonation of the atomic bombs over Hiroshima and Nagasaki, Japan. Though Wu seldom discussed her personal views or her role in the project publicly, in a 1962 meeting with Taiwan's President Chiang Kai-shek, Wu advised against pursuing a nuclear weapons program in Taiwan.
Parity NonconservationAt its core, physics is centred around the study of symmetries, which are essential in identifying consistent patterns in natural processes. This understanding enables the development of precise mathematical laws that describe the foundational principles of the physical universe. One key symmetry in physics is parity symmetry, which posits that the behaviour of particles in processes like collisions and decays should be identical even when their positions and orientations are mirrored. In the 1950s, Wu made a ground-breaking discovery about the violation of parity symmetry under certain conditions, a finding that significantly challenged established norms in particle physics. However, Wu did not receive full recognition for her seminal work.
Law of parity, demonstrating Wu’s experiment.
Following her departure from the Manhattan Project in 1945, Wu focused her career on experimental beta decay and weak nuclear force physics at Columbia University's Department of Physics, emerging as a leader in experimental beta decay and weak interaction physics. In 1956, Wu’s expertise caught the attention of her two male colleagues in the field, Dr. Tsung-Dao Lee and Dr. Chen Ning Yang, who sought her consultation regarding beta decay. The pair hypothesized that parity conservation, a law asserting nature’s indifference to left and right orientations, might not apply to weak nuclear reactions.
Illustration of radioactive beta decay, showcasing the emission of a beta particle (either an electron or proton) from an atomic nucleus, accompanied by an antineutrino or neutrino. The depiction on the right illustrates the beta decay of an isolated neutron.
To test this bold proposition, Wu conducted a challenging experiment, demonstrating that there was no evidence supporting the law of conservation of parity during beta decay. Her experiments with radioactive cobalt at temperatures near absolute zero showed that identical nuclear particles do not always behave the same way during beta decay. Wu successfully validated Lee and Yang's theory. Her monumental experiment disproved a firmly entrenched law in physics, an event that is extremely rare and significant.
Reflecting on the discovery, Wu commented on the controversy,
Reflecting on how it felt, she also shared,
Despite the critical importance of this experiment, widely known as the "Wu Experiment," Wu was overlooked for the Nobel Prize in 1957, which was awarded exclusively to Yang and Lee. This exclusion strongly reflects the gender biases that often overshadowed the contributions of female scientists at the time.
Aware of the gender disparities in her field, Wu expressed her perspective during an MIT symposium in October 1964, questioning,
Later Life and LegacyDespite the lack of recognition of her ground-breaking work, Chien-Shiung Wu carried on, continuing to forge a distinguished career and achieving significant milestones. In 1958, she was promoted to Full Professor, becoming the first woman to hold a tenured faculty position in Columbia University's Physics Department. Even though Science, Technology, Engineering, and Mathematics (STEM) fields were all heavily male-dominated disciplines, Wu remained steadfast and not only maintained her leadership in physics, but even ventured into interdisciplinary fields like biology and medicine. Among her diverse research endeavours, Wu’s investigation into the molecular changes in red blood cells stands out, as it provided valuable insights into conditions such as sickle-cell disease and anemia. Wu's passion for her work is encapsulated in her own words when she famously remarked,
Dr. Chien-Shiung Wu at her Columbia University lab.
Though overlooked for the Nobel Prize, Wu received numerous accolades throughout her career. These honours include her election as the seventh woman to the National Academy of Sciences in 1958, the Comstock Prize in Physics from the National Academy of Sciences, and serving as the first woman president of the American Physical Society in 1975. She was also the inaugural recipient of the Wolf Prize in Physics in 1978 and received the Michael Pupin Medal in 1991. Moreover, Wu was the first woman to be awarded an honorary doctorate from Princeton University. In 1990, her legacy was further commemorated with the naming of asteroid 2752 Wu Chien-Shiung.
Upon retiring from Columbia University in 1981, Wu shifted her focus to educational initiatives in the People's Republic of China, Taiwan, and the United States. A fervent advocate for encouraging girls' interest in STEM fields, Wu delivered numerous lectures and became a role model for aspiring young female scientists globally. Wu's influence persisted even after her retirement, with her book "Beta Decay" (1965), which remains a foundational reference for nuclear physicists today. Reflecting on her career, Wu noted in a paper presented at the International Conference on History of Original Ideas and Basic Discoveries in Particle Physics,
“Greatest Female Chinese Scientist of the Twentieth Century”Inspired by women like Dr. Marie Curie and Dr. Lise Meitner, Dr. Chien-Shiung Wu was a trailblazer for physicists and women across the globe. Wu unquestionably earned her seat next to her role models and is immortalized today as the "greatest female Chinese scientist of the twentieth century." Wu's extraordinary accomplishments and her unwavering determination in the field of physics will forever be revered.
Wu was not only remarkable for her scientific achievements but also for her deep respect and connection to her cultural roots. Known for her composed and elegant demeanour, Wu’s friends and family seldom saw her in a disordered state as she would always dress elegantly, wearing traditional Chinese qipao dresses for most of her life. Remarkably, during the years when China was isolated from the outside world and her access to these dresses was limited, Wu would sew her own qipao dresses.
Silhouette of Dr. Chien-Shiung Wu next to a qipao dress pattern.
Over the past 120 years, only a handful of women have been honoured with the Nobel Prize in Physics — Wu, unfortunately, is not among these select few. Her story underscores the challenges that many women encounter in securing recognition for their scientific contributions and highlights the persistent gender biases within the STEM and scientific community. Recognizing this, Wu dedicated her post-retirement life to empowering young girls to pursue careers in science. By openly discussing her challenges, Wu aimed to inspire young women to overcome obstacles and persist in their scientific endeavours.
Dr. Chien-Shiung Wu passed away due to stroke complications on February 16, 1997, in New York City at the age of 84. Wu's ashes were laid to rest in China, at Mingde Women's Vocational Continuing School, a location deeply intertwined with her personal history. This was the same institution where Wu began her educational journey as a young girl and the very school her father had established decades earlier. The decision to inter her ashes at the school symbolizes a full-circle moment in Wu's life, connecting her final resting place with the origins of her academic and personal growth.
In recognition of her monumental contributions, Wu was posthumously inducted into the American National Women's Hall of Fame in 1998, a year after her passing. In a lasting homage to her legacy, a bronze statue was erected on June 1, 2002, in the courtyard of Mingde Women's Vocational Continuing School. This statue not only commemorates Wu's remarkable life and achievements but also serves as a continuous source of inspiration for young girls, ensuring that Wu's influence continues to echo for future generations.
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Website Name: The Matilda Project
Title of Entry: Chien-Shiung Wu
Author: Shehroze Saharan
Illustrator: Juno Shemano
Editors: Sandy Marshall
Original Publication Date: February 16, 2024
Last Updated: March 31, 2024
Copyright: CC BY-NC-ND
Webpage Specific Tags: Chien-Shiung Wu; - Experimental physicist; Beta decay; Weak force parity violation; Manhattan Project; Chinese-American scientist; "First Lady of Physics"; National Medal of Science; Wolf Prize in Physics; Nuclear physics; Columbia University; Women in STEM; Madame Curie of China; Precision experimental methods; Conservation of parity; Physical Review; Law of conservation violation; Role model for women in physics; Pioneering female physicist; Nobel Prize controversy; Physics education advocate; Wu experiment; Elementary particle physics; Advocacy for women in science; East-West scientific collaboration.
Website Tags: The Matilda Project, The Matilda Effect; Margaret W. Rossiter; Matilda Joslyn Gage; Implicit bias; Unconscious bias; Gender attribution bias; Scientific recognition bias; Gender discrimination in academia; Stereotype threat; Pay gap in STEM; Glass ceiling in science; Sexism in scientific research; Gender stereotypes in education; Gender bias in peer review; Bias in STEM hiring practices; Impact of gender bias on scientific innovation; Underrecognition of female scientists; History of women in science; Women scientists in history; Notable women in science; Pioneering women scientists; Women Nobel laureates; Female role models in science; Gender disparities in scientific research; Women's suffrage movement; Historical women's rights leaders; Historian of science; STEM gender gap; Women in STEM; STEM education; Challenges faced by women in STEM; Representation of women in tech; Initiatives to support women in STEM; Gender equity in STEM education; Encouraging girls in STEM; STEM outreach programs; Diversity in STEM curriculum; Equity, Diversity, Inclusion; Equity in education and workplace; Diversity training; Inclusion strategies; Inclusive leadership; Gender equality; Racial equity; Pay equity and transparency; Representation in media.
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APA Citation:
Saharan, S. (2024, March 31). Chien-Shiung Wu. The Matilda Project. https://www.thematildaproject.com/scientists/chien-shiung-wu
Author
Shehroze Saharan
Educational Technology Developer - Office of Teaching and Learning at the University of Guelph
Shehroze Saharan, as the Educational Technology Developer at the Office of Teaching & Learning, supports the University of Guelph's educational objectives. His critical expertise helps faculty, instructors, and learners to navigate the complexities of the educational landscape. Informed by best practices in design and communication, Saharan focuses on advancing Critical Digital Pedagogy. As a leader in the field, he leads initiatives that embrace evolving digital pedagogies, including artificial intelligence. Saharan integrates cutting-edge tools, methods, and best practices to enhance student engagement. His proficiency extends to various tools, such as online learning platforms, microcredentials, and online modules using Articulate. Shehroze adopts an approach encompassing gamification, multimedia content, H5P content, Open Educational Resources (OER), and Data Analytics, showcasing a comprehensive integration of technology to enhance the educational experience. He holds a Master of Information from the University of Toronto and a Bachelor's in Biomedical Science with a Minor in Media Studies and Cinema from the University of Guelph. In 2024, Saharan is set to commence his Ph.D. in Curriculum and Pedagogy at the Ontario Institute for Studies in Education (OISE), University of Toronto.
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