Jianxiong Wu

Chien-Shiung Wu
Chien-Shiung Wu when young
Born 1912
Taicang, Jiangsu, China
Died February 16, 1997(1997-02-16) (aged 84)
New York City, United States
Nationality China
United States
Fields Physics
Institutions Institute of Physics, Academia Sinica
University of California at Berkeley
Smith College
Princeton University
Columbia University
Alma mater National Central University, China
Zhejiang University
University of California at Berkeley
Doctoral advisor Ernest Lawrence
Known for parity violation experiments
Beta decay research
The Manhattan Project
Notable awards Wolf Prize (1978)
National Medal of Science (1975)
Bonner Prize (1975)
Comstock Prize in Physics (1964)

Chien-Shiung Wu (simplified Chinese: 吴健雄; traditional Chinese: 吳健雄; pinyin: Wú Jiànxíong, May 31, 1912 – February 16, 1997) was a Chinese American physicist with expertise in the techniques of experimental physics and radioactivity. She worked on the Manhattan Project, helping to develop the process for separating uranium metal into the U-235 and U-238 isotopes by gaseous diffusion. Wu later performed the Wu Experiment, which contradicted the "Law of Conservation of Parity" and which confirmed the theories of her colleagues. Her honorary nicknames include the "First Lady of Physics", the "Chinese Marie Curie", and "Madame Wu".

Early Life and Education

Wu was born in Taicang in Jiangsu Province in 1912. She was raised in Liuhe, a small town in Taicang about 40 miles from Shanghai.[1]:1 Her father, Wu Zhongyi (吳仲裔), was a proponent of gender equality, and he founded the Mingde Women's Vocational Continuing School.[2] Wu left her hometown at the age of 11 to go to the Suzhou Women's Normal School No. 2.

In 1929 Wu was admitted to the National Central University which later became the Nanjing University in mainland China and was reinstated in Taiwan. According to the governmental regulations of the time, "normal school" (teacher-training college) students wanting to move on to the universities needed to serve as schoolteachers for one year. Hence, in 1929 Wu went to teach in the Public School of China (中國公學), which had been founded by Hu Shi in Shanghai.

From 1930 to 1934, Wu studied at the National Central University, first in mathematics, but later transferring to physics.[2] For two years after graduation, she did graduate-level study in physics and also worked as an assistant at the Zhejiang University. After this, Wu became a researcher at the Institute of Physics of the Academia Sinica.

Wu decided that she wanted and needed to continue her studies in physics at a higher level than was possible in China.[1]:18[2] Therefore, she started filling out applications to study at universities overseas, especially in California. Upon receiving a favorable response from the University of Michigan, Wu and her female friend, Dong Ruofen (董若芬), a chemist from Taicang, China, embarked on the long steamship voyage from China to the West Coast of the United States.

The two women arrived in San Francisco in 1936.[3]:259 Wu's plans for graduate study changed completely after visiting the University of California located in Berkeley, California.[2] First, she met physicist Luke Chia-Liu Yuan (袁家骝). Luke Chia-Liu Yuan's grandfather was Yuan Shikai, the first President of the Republic of China and, notoriously, a short-lived, self-proclaimed Emperor of China.[3]:259 But also, Wu's achievements earned her an offer to study under Ernest O. Lawrence, who would soon win the Nobel Prize for Physics in 1939 for his invention of the cyclotron particle accelerator and the development of its applications in physics.[3]:260 Wu abandoned her plans to study at Michigan and enrolled instead at Berkeley.[1]:20 She made rapid progress in her education and her research, completing her Ph.D. in physics in 1940. Wu and Yuan were married two years later, in 1942.[4]:39


Early Work

Wu and Yuan moved to the East Coast of the U.S., where Wu became a faculty member at, first, Smith College, then Princeton University in New Jersey for 1942-44, where she became the first female instructor in the Physics Department. Finally, she found herself at Columbia University in New York City, beginning in 1944 and continuing for many years after the war, all the way through 1980.

At Columbia University, Wu also did research and development for the Manhattan Project. She helped to develop the process for separating uranium metal into the U-235 and U-238 isotopes by gaseous diffusion. This was the process that was implemented on a gigantic scale at the K-25 Plant near Oak Ridge, Tennessee, whose construction began in 1944.

In her research at Columbia, Wu also worked to develop improved Geiger counters for measuring nuclear radiation levels.

In 1947, Wu and her husband became the parents of one son, Vincent Yuan (袁緯承), who also became a physicist.

Beta Decay and the Conservation of Parity

At Columbia Wu knew the Chinese-born theoretical physicist Tsung-Dao Lee personally. In the mid-1950s, Lee and another Chinese theoretical physicist, Chen Ning Yang, grew to question a hypothetical law in elementary particle physics, the "Law of Conservation of Parity". Their library research into experimental results convinced them that this "Law" was valid for electromagnetic interactions and for the strong nuclear force. However, this "Law" had not been tested for the weak nuclear force, and Lee and Yang's theoretical studies showed that it would probably not hold true for this kind of interaction. Lee and Yang worked out the pencil and paper design of several experiments for testing the "Conservation of Parity" in the laboratory. Lee then turned to Wu for her expertise in choosing and then working out the hardware manufacture, set-up, and laboratory procedures for carrying out the experiment.

Wu chose to do this for an experiment that involved taking a sample of radioactive cobalt 60 and cooling to cryogenic temperatures with liquid gasses. Cobalt 60 is an isotope that decays by beta particle emission, and Wu was also an expert on beta decay. The extremely low temperatures were needed to reduce the amount of thermal vibration of the cobalt atoms to practically nil. Also, Wu needed to apply a constant and uniform magnetic field across the sample of cobalt 60 in order to cause the spin axes of the atomic nuclei to all line up in the same direction.

For this cryogenic work, Wu needed the expertise and the facilities of the National Bureau of Standards in liquid gases to aid her. She thus traveled to NBS headquarters in Maryland with her equipment to carry out the experiments.

Lee and Yang's theoretical calculations predicted that the beta particles from the cobalt 60 atoms would be emitted asymmetrically if the hypothetical "Law of Conservation of Parity" proved invalid. Wu's experiments at the NBS showed that this is indeed the case: parity is not conserved under the weak nuclear interactions. This was also very soon confirmed by her colleagues at Columbia University in different experiments, and as soon as all of these results were published—in two different research papers in the same issue of the same physics journal—the results were also confirmed at many other laboratories and in many different experiments.

The discovery of parity violation was a major contribution to high energy physics and the development of the Standard model. In recognition for their theoretical work, Lee and Yang were awarded the Nobel Prize for Physics in 1957. Wu received the first Wolf Prize in Physics in 1978 for her experimental work.

Wu's book titled Beta Decay (published 1965) is still a standard reference for nuclear physicists.

Other Work and Accomplishments

An additional important experiment carried out by Wu[5] was the confirmation of the Pryce and Ward calculations[6] on the correlation of the quantum polarizations of two photons propagating in opposite directions. This was the first experimental confirmation of quantum results relevant to a pair of entangled photons as applicable to the Einstein-Podolsky-Rosen (EPR) paradox, or situation.[7][8]

Wu later conducted research into the molecular changes in the deformation of hemoglobins that cause sickle-cell disease.

Later Life and Death

Wu died on February 16, 1997 after suffering a stroke.[9] At the time of her death, Wu was Pupin Professor Emerita of Physics at Columbia.

Honors, Awards and Distinctions


Further reading

External links

  • Chien-Shiung Wu in CWP at UCLA
  • Wu Chien Shiung Education Foundation (Chinese-English bilingual)
  • Eulogy-biography (Columbia)
  • A large black/white photo and a mini-bio

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