Chien Shiung Wu: Spotlight on Asymmetry

We have written a few articles already about the personal beliefs and political convictions of scientists—how these elements shaped not only their worldviews but also their contributions within and beyond their disciplines. Yet, for those of us within the scientific community, it is evident that much of the work, particularly in the physical sciences, is rarely undertaken with the explicit aim of societal benefit. Rather, it is often driven by something more elusive: the raw human desire to understand the world.  

I am not trying to claim objectivity or detachment of science from the world’s politics, but to recognize that more often than not, the primary aspiration of science is knowledge for its own sake, and not for immediate technological gain or social application. And yet, this pursuit—so seemingly removed from politics and policy—can ripple outward, shaping our understanding of the universe and, at times, changing the course of history. Chien-Shiung Wu’s career stands as a testament to where such curiosity can lead: her meticulous work on beta decay transformed modern physics, and her contributions to the Manhattan Project show how pure scientific inquiry can intersect with powerful, real-world consequences. 

Chien-Shiung Wu, often remembered by titles like “Madame Wu,” “the First Lady of Physics,” and even “the Chinese Marie Curie,” carved a singular path through the world of 20th-century science.  Her reputation rests not only on her crucial role in the clandestine Manhattan Project during World War II, but also on her revolutionary experiment with cobalt-60, which upended the long-standing assumption that the universe is symmetric in mirror-image physical interactions—a principle known as the conservation of parity. “These are moments of exaltation and ecstasy,” Wu later said. “A glimpse of this wonder can be the reward of a lifetime.”

Chien Shiung Wu in her lab in Columbia University copyrights @ Scientific American

Chien-Shiung Wu was born on May 31, 1912, in Liuhe near Shanghai—the same year the Republic of China was founded. Raised in a progressive household that championed education, Wu was the middle child of a teacher mother and an engineer father who established a school for girls. Encouraged by her father to pursue academics, she left home at age 10 for boarding school in Suzhou, graduating top of her class in 1929 with a growing interest in science. 

She pursued physics at National Central University in Nanking, completing her degree in 1934. Wu found inspiration in the pioneering work of Marie Curie and was mentored by Dr. Jing-Wei Gu, a physicist under whom she worked as a research assistant. It was Dr. Gu who recognized Wu’s potential and encouraged her to pursue graduate studies abroad. In 1936, with the support of her mentors and an uncle, Wu made the decision to leave for the United States.

It was a time of upheaval, both in the field of nuclear science and in her home country. Political instability and rising tensions with Japan had begun to unsettle life in China. Against this backdrop, Wu’s departure was not merely academic—it was an act of complete replanting. She would not return to China for 36 years, nor see her parents again. As a woman in science today, I find myself struck by the weight of that choice. To leave behind family, language, and familiar landscapes—not for certainty, but for the belief that your mind could belong in the unfolding future of physics. That your curiosity was enough. It’s a kind of quiet, courageous leap that still echoes through generations of women who move continents in pursuit of knowledge. 

Initially, Chien-Shiung Wu had intended to pursue graduate studies at the University of Michigan. However, a visit to the University of California, Berkeley—combined with the unsettling revelation that women at Michigan were barred from entering the student center through the front door—prompted her to reconsider. That early brush with sexism was only the beginning. Physics at the time was overwhelmingly male-dominated, with women frequently excluded or relegated to peripheral roles. Wu, already a standout by virtue of both her brilliance and her background, would soon discover how persistent these barriers could be.

At Berkeley, Wu stood out not just for her intellect but also for her identity—as a Chinese woman in a space built almost entirely for white men. Her presence did not go unnoticed. While some colleagues recognized her remarkable talent, others focused on her appearance. Her advisor, Nobel laureate Emilio Segrè, later recalled that Wu was often followed around campus by admirers “like a queen.” 

Wu, however, focused on securing a place at the prestigious Radiation Laboratory, where she immersed herself in the cutting-edge field of nuclear physics, learning from pioneers like Ernest Lawrence and J. Robert Oppenheimer, and working alongside peers who would go on to shape modern experimental science. Wu completed her Ph.D. in 1940, conducting research in the newly discovered domain of nuclear fission. She had already gained a reputation for her technical precision and hands-on brilliance in the lab. But despite her achievements and the strength of her thesis, Berkeley did not offer her a permanent position—almost certainly due to her race and gender.

In 1942, Wu married fellow physicist and UC Berkeley classmate Luke Chia-Liu Yuan. Together, they left California in search of new opportunities, as anti-Asian sentiment intensified following Japan’s attack on Pearl Harbor. Wu accepted a position at Smith College, a women’s institution on the East Coast. It marked the beginning of a phase in her career where the wartime demand for scientific talent would open doors previously closed to women and minorities.

In 1943, Wu broke new ground by becoming the first woman to teach in Princeton University’s Physics Department—a quiet yet meaningful achievement in a field dominated by men. Her appointment reflected the gradual shifts brought on by wartime necessity, as institutions began turning to women to fill scientific roles traditionally reserved for men.

Wu’s growing reputation soon drew the attention of leaders at the forefront of wartime research. At the recommendation of physicist Enrico Fermi, who had taken note of her dissertation work on nuclear fission, Wu was invited to join the Manhattan Project at Columbia University.  There, she developed highly sensitive radiation detectors and played a key role in perfecting the technique of gaseous diffusion to separate uranium isotopes—an essential step in producing enriched uranium for atomic weapons. “Gaseous diffusion was absolutely essential for the bomb on Hiroshima,” notes nuclear historian Alex Wellerstein. The method became the United States’ primary enrichment technology during the Cold War, and its importance was such that key details remain classified even today. Though Wu was almost certainly aware of the destructive goal of her work, she remained reticent in later years to speak about the atomic bomb or its consequences.  

Due to the turmoil of World War II and the Chinese Civil War, Wu was unable to return home. So, in 1954, she officially became a U.S. citizen and continued her research at Columbia University, focusing on beta decay. It was during this period that physicists Tsung-Dao Lee and Chen-Ning Yang approached her with a bold theory: that the long-standing law of conservation of parity might (the assumption that physical processes behave the same if left and right are flipped) not hold true during beta decay. If proven, their theory would overturn a pillar of physics, challenging the idea that the laws of nature are mirror-symmetric. Wu agreed to put their theory to the test. 

In 1956, working at the National Bureau of Standards in Washington, D.C., she designed a challenging experiment using radioactive cobalt cooled to near absolute zero, aligning the atoms in a magnetic field to observe their behavior during decay. With just a 15-minute experimental window, Wu demonstrated that beta decay was not symmetrical, proving that identical nuclear particles do not always act the same—thus overturning the conservation of parity.

Though Lee and Yang were awarded the Nobel Prize in Physics that same year for their theory, Wu’s experimental confirmation—now famously called the 'Wu Experiment'—went unrecognized by the Nobel Committee. This was not an anomaly; many women scientists, such as Rosalind Franklin and Lise Meitner, had made groundbreaking contributions only to be overlooked by the Nobel Prize in their time. Despite this, Wu’s achievement fundamentally reshaped modern particle physics and solidified her place as one of the most formidable experimental physicists of her time. The story goes that in 1957, Wu stood before a packed hall at Princeton University, where some of the greatest minds in physics gathered to hear her speak. As she unveiled the results of her groundbreaking experiment, the audience sat in stunned, breathless silence. Then, as the weight of her achievement sank in, the room erupted into thunderous applause and a standing ovation, honoring the woman who had upended one of physics’ most sacred laws. 

Wu accepted a permanent teaching position at Columbia University in 1958, solidifying her place as one of the world’s leading experimental physicists. She remained at Columbia until her retirement in 1981, contributing not just to fundamental physics but also branching into medical research, particularly in understanding sickle-cell disease. Her influence extended beyond the laboratory: Wu was a fierce advocate for gender equality, speaking out against discrimination in science and encouraging young women to pursue careers in the field.

In 1964, Wu was awarded the Comstock Prize in Physics, and in 1965, she published her landmark textbook Beta Decay, which remains a foundational reference for nuclear physicists today. Her accolades continued to mount: she received the National Medal of Science in 1975, became the first woman to serve as president of the American Physical Society, and was honored with the inaugural Wolf Prize in Physics in 1978. In her role as APS president, Wu successfully petitioned President Gerald Ford to establish a scientific advisory body, leading to the creation of the Office of Science and Technology Policy.

After retiring, Wu dedicated herself to educational programs, passionately encouraging young girls to embrace scientific careers. She also continued her advocacy for human rights, notably speaking out against China’s violent crackdown after the Tiananmen Square massacre. Chien-Shiung Wu never shied away from the struggles she faced in a male-dominated world, turning obstacles into opportunities time and again. As she once remarked, “There is only one thing worse than coming home from the lab to a sink full of dirty dishes, and that is not going to the lab at all.”

In 1990, the Chinese Academy of Sciences named an asteroid after her—an extraordinary honor for a living scientist. Wu passed away on February 16, 1997, at her home in New York. Her ashes were returned to China and laid to rest in the courtyard of Mingde School, the very school her father had founded and where her own love of learning first took root.

We may never fully know whether Wu truly wanted to contribute to the creation of the atomic bomb or whether her heart was more drawn to solving the mysteries of sickle-cell anemia. History moves with a momentum no one mind can fully steer. What endures is that Wu chose science itself as her compass, even when the consequences lay far beyond her control. Her story reminds us that science, at its heart, is an act of courage—a willingness to venture into the unknown without certainty of reward or absolution. Wu’s legacy stretches from the cold chambers of cobalt experiments to the naming of an asteroid in the stars: a fitting tribute to a woman who proved that the most powerful force in the universe might just be a mind that refuses to stop asking questions.

Written by Janaky S. and edited by Parvathy Ramachandran @ThinkHer

References:

1.https://www.womenshistory.org/education-resources/biographies/chien-shiung-wu

2.https://www.nationalgeographic.com/premium/article/chien-shiung-wu-chinese-american-woman-physics-manhattan-project

3.https://www.biography.com/scientist/chien-shiung-wu

4.https://www.nobelprize.org/uploads/2018/06/yang-lecture.pdf