loading . . . Many have wondered why the Chinese-American physicist Chien-Shiung Wu never won a share of the 1957 Nobel Prize for Physics for her experimental verification of parity violation.**Mats Larsson** and **Ramon Wyss** reveal the true story after becoming the first people to open that year’s Nobel archives
**Experienced experimentalist** Chien-Shiung Wu in 1958, the year after she first missed out on the Nobel Prize for Physics. (Courtesy: Smithsonian Institution Archives)
The facts seem simple enough. In 1957 Chen Ning Yang and Tsung-Dao Lee won the Nobel Prize for Physics “for their penetrating investigation of the so-called parity laws which has led to important discoveries regarding the elementary particles”. The idea that parity is violated shocked physicists, who had previously assumed that every process in nature remains the same if you reverse all three spatial co-ordinates.
Thanks to the work of Lee and Yang, who were Chinese-American theoretical physicists, it now appeared that this fundamental physics concept wasn’t true (see box below). As Yang once told _Physics World_ columnist and historian of science Robert Crease, the discovery of parity violation was like having the lights switched off and being so confused that you weren’t sure you’d be in the same room when they came back on.
But one controversy has always surrounded the prize.
Lee and Yang published their findings in a paper in October 1956 (_Phys_._Rev_. **1** 254), meaning that their Nobel prize was one of the rare occasions that satisfied Alfred Nobel’s will, which says the award should go to work done “during the preceding year”. However, the first verification of parity violation was published in February 1957 (_Phys. Rev._ **105** 1413) by a team of experimental physicists led by Chien-Shiung Wu at Columbia University, where Lee was also based. (Yang was at the Institute for Advanced Study in Princeton at the time.)
Surely Wu, an eminent experimentalist (see box below “Chien-Shiung Wu: a brief history”), deserved a share of the prize for contributing to such an fundamental discovery? In her paper, entitled “Experimental Test of Parity Conservation in Beta Decay”, Wu says she had “inspiring discussions” with Lee and Yang. Was gender bias at play, did her paper miss the deadline, or was she simply never nominated?
## The Wu experiment
(Courtesy: IOP Publishing)
Parity is a property of elementary particles that says how they behave when reflected in a mirror. If the parity of a particle does not change during reflection, parity is said to be conserved. In 1956 Tsung-Dao Lee and Chen Ning Yang realized that while parity conservation had been confirmed in electromagnetic and strong interactions, there was no compelling evidence that it should also hold in weak interactions, such as radioactive decay. In fact, Lee and Yang thought parity violation could explain the peculiar decay patterns of K mesons, which are governed by the weak interaction.
In 1957 Chien-Shiung Wu suggested an experiment to check this based on unstable cobalt-60 nuclei radioactively decaying into nickel-60 while emitting beta rays (electrons). Working at very low temperatures to ensure almost no random thermal motion – and thereby enabling a strong magnetic field to align the cobalt nuclei with their spins parallel – Wu found that far more electrons were emitted in a downward direction than upward.
In the figure, (_a_) shows how a mirror image of this experiment should also produce more electrons going down than up. But when the experiment was repeated, with the direction of the magnetic field reversed to change the direction of the spin as it would be in the mirror image, Wu and colleagues found that more electrons were produced going upwards (_b_). The fact that the real-life experiment with reversed spin direction behaved differently from the mirror image proved that parity is violated in the weak interaction of beta decay.
Back then, the Nobel statutes stipulated that all details about who had been nominated for a Nobel prize – and why the winners were chosen by the Nobel committee – were to be kept secret forever. Later, in 1974, the rules were changed, allowing the archives to be opened 50 years after an award had been made. So why did the mystery not become clear in 2007, half a century after the 1957 prize?
The reason is that there is a secondary criterion for prizes awarded by the Royal Swedish Academy of Sciences – in physics and chemistry – which is that the archive must stay shut for as long as a laureate is still alive. Lee and Yang were in their early 30s when they were awarded the prize and both went on to live very long lives. Lee died on 24 August 2024 aged 97 and it was not until the death of Yang on 18 October 2025 at 103 that the chance to solve the mystery finally arose.
## Chien-Shiung Wu: a brief history
**Overlooked for a Nobel** Chien-Shiung Wu in 1963 at Columbia University by which time she had already received the first three of her 23 known nominations for a Nobel prize. (Courtesy: Smithsonian Institution)
Born on 31 May 1912 in Jiangsu province in eastern China, Chien-Shiung Wu graduated with a degree in physics from National Central University in Nanjing. After a few years of research in China, she moved to the US, gaining a PhD at the University of California at Berkeley in 1940. Three years later Wu took up a teaching job at Princeton University in New Jersey – a remarkable feat given that women were not then even allowed to study at Princeton.
During the Second World War, Wu joined the Manhattan atomic-bomb project, working on radiation detectors at Columbia University in New York. After the conflict was over, she started studying beta decay – one of the weak interactions associated with radioactive decay. Wu famously led a crucial experiment studying the beta decay of cobalt-60 nuclei, which confirmed a prediction made in October 1956 by her Columbia colleague Tsung-Dao Lee and Chen Ning Yang in Princeton that parity can be violated in the weak interaction.
Lee and Yang went on to win the 1957 Nobel Prize for Physics but the Nobel Committee was not aware that Lee had in fact consulted Wu in spring 1956 – several months before their paper came out – about potential experiments to prove their prediction. As she was to recall in 1973, studying the decay of cobalt-60 was “a golden opportunity” to test their ideas that she “could not let pass”.
The first woman in the Columbia physics department to get a tenured position and a professorship, Wu remained at Columbia for the rest of her career. Taking an active interest in physics well into retirement, she died on 16 February 1997 at the age of 84. Only now, with the publication of this _Physics World_ article, has it become clear that despite receiving 23 nominations from 18 different physicists in 16 years between 1958 and 1974, she never won a Nobel prize.
## Entering the archives
As two physicists based in Stockholm with a keen interest in the history of science, we had already examined the case of Lise Meitner, another female physicist who never won a Nobel prize – in her case for fission. We’d published our findings about Meitner in the December 2023 issue of _Fysikaktuellt_ – the journal of the Swedish Physical Society. So after Yang died, we asked the Center for History of Science at the Royal Swedish Academy of Sciences if we could look at the 1957 archives.
A previous article in _Physics World_ from 2012 by Magdolna Hargittai, who had spoken to Anders Bárány, former secretary of the Nobel Committee for Physics, seemed to suggest that Wu wasn’t awarded the 1957 prize because her _Physical Review_ paper had been published in February of that year. This was after the January cut-off and therefore too late to be considered on that occasion (although the trio could have been awarded a joint prize in a subsequent year).
**History in the making** Left image: Mats Larsson (centre) and Ramon Wyss (left) at the Center for History of Science at the Royal Swedish Academy of Sciences in Stockholm, Sweden, on 13 November 2025, where they become the first people to view the archive containing information about the nominations for the 1957 Nobel Prize for Physics. They are shown here in the company of centre director Karl Grandin (right). Right image: Larsson and Wyss with their hands on the archives, on which this _Physics World_ article is based. (Courtesy: Anne Miche de Malleray)
After receiving permission to access the archives, we went to the centre on Thursday 13 November 2025, where – with great excitement – we finally got our hands on the thick, black, hard-bound book containing information about the 1957 Nobel prizes in physics and chemistry. About 500 pages long, the book revealed that there were a total of 58 nominations for the 1957 Nobel Prize for Physics – but none at all for Wu that year. As we shall go on to explain, she did, however, receive a total of 23 nominations over the next 16 years.
Lee and Yang, we discovered, received just a single nomination for the 1957 prize, submitted by John Simpson, an experimental physicist at the University of Chicago in the US. His nomination reached the Nobel Committee on 29 January 1957, just before the deadline of 31 January. Simpson clearly had a lot of clout with the committee, which commissioned two reports from its members – both Swedish physicists – based on his recommendation. One was by Oskar Klein on the theoretical aspects of the prize and the other by Erik Hulthén on the experimental side of things.
## Report revelations
Klein devotes about half of his four-page report to the Hungarian-born theorist Eugene Wigner, who – we discovered – received seven separate nominations for the 1957 prize. In his opening remarks, Klein notes that Wigner’s work on symmetry principles in physics, first published in 1927, had gained renewed relevance in light of recent experiments by Wu, Leon Lederman and others. According to Klein, these experiments cast a new light on the fundamental symmetry principles of physics.
Klein then discusses three important papers by Wigner and concludes that he, more than any other physicist, established the conceptual background on symmetry principles that enabled Lee and Yang to clarify the possibilities of experimentally testing parity non-conservation. Klein also analyses Lee and Yang’s award-winning _Physical Review_ paper in some detail and briefly mentions subsequent articles of theirs as well as papers by two future Nobel laureates – Lev Landau and Abdus Salam.
Klein does not end his report with an explicit recommendation, but identifies Lee, Yang and Wigner as having made the most important contributions. It is noteworthy that every physicist mentioned in Klein’s report – apart from Wu – eventually went on to receive a Nobel Prize for Physics. Wigner did not have to wait long, winning the 1963 prize together with Maria Goeppert Mayer and Hans Jensen, who had also been nominated in 1957.
As for Hulthén’s experimental report, it acknowledges that Wu’s experiment started after early discussions with Lee and Yang. In fact, Lee had consulted Wu at Columbia on the subject of parity conservation in beta-decay before Lee and Yang’s famous paper was published. According to Wu, she mentioned to Lee that the best way would be to use a polarized cobalt-60 source for testing the assumption of parity violation in beta-decay.
Many physicists were aware of Lee and Yang’s paper, which was certainly seen as highly speculative, whereas Wu realized the opportunity to test the far-reaching consequences of parity violation. Since she was not a specialist of low-temperature nuclear alignment, she contacted Ernest Ambler at the National Bureau of Standards in Washington DC, who was a co-author on her _Physics Review_ paper of 15 February 1957.
Hulthén describes in detail the severe technical challenges that Wu’s team had to overcome to carry out the experiment. These included achieving an exceptionally low temperature of 0.001 K, placing the detector inside the cryostat, and mitigating perturbations from the crystalline field that weakened the magnetic field’s effectiveness.
Despite these difficulties, the experimentalists managed to obtain a first indication of parity violations, which they presented on 4 January 1957 at a regular lunch that took place at Columbia every Friday. The news of these preliminary results spread like wildfire throughout the physics community, prompting other groups to immediately follow suit.
Hulthén mentions, for example, a measurement of the magnetic moment of the mu (μ) meson (now known as the muon) that Richard Garvin, Leon Lederman and Marcel Weinrich performed at Columbia’s cyclotron almost as soon as Lederman had obtained information of Wu’s work. He also cites work at the University of Leiden in the Netherlands led by C J Gorter that apparently had started to look into parity violation independently of Wu’s experiment (_Physica_ **23** 259).
## Wu’s nominations
It is clear from Hulthén’s report that the Nobel Physics Committee was well informed about the experimental work carried out in the wake of Lee and Yang’s paper of October 1956, in particular the groundbreaking results of Wu. However, it is not clear from a subsequent report dated 20 September 1957 (see box below) from the Nobel Committee why Wigner was not awarded a share of the 1957 prize, despite his seven nominations. Nor is there any suggestion of postponing the prize a year in order to include Wu. The report was discussed on 23 October 1957 by members of the “Physics Class” – a group of physicists in the academy who always consider the committee’s recommendations – who unanimously endorsed it.
## The Nobel Committee report of 1957
(Courtesy: The Nobel Archive, The Royal Swedish Academy of Sciences, Stockholm)
This image is the final page of a report written on 20 September 1957 by the Nobel Committee for Physics about who should win the 1957 Nobel Prize for Physics. Dated 20 September 1957 and published here for the first time since it was written, the English translation is as follows. “Although much experimental and theoretical work remains to be done to fully clarify the necessary revision of the parity principle, it can already be said that a discovery with extremely significant consequences has emerged as a result of the above-mentioned study by Lee and Yang. In light of the above, the committee proposes that the 1957 Nobel Prize in Physics be awarded jointly to: Dr T D Lee, New York, and Dr C N Yang, Princeton, for their profound investigation of the so-called parity laws, which has led to the discovery of new properties of elementary particles.” The report was signed by Manne Siegbahn (chair), Gudmund Borelius, Erik Hulthén, Oskar Klein, Erik Rudberg and Ivar Waller.
Most noteworthy with regard to this meeting of the Physics Class was that Meitner – who had also been overlooked for the Nobel prize – took part in the discussions. Meitner, who was Austrian by birth, had been elected a foreign member of the Royal Swedish Academy of Sciences in 1945, becoming a “Swedish member” after taking Swedish citizenship in 1951. In the wake of these discussions, the academy decided on 31 October 1957 to award the 1957 Nobel Prize for Physics to Lee and Yang. We do not know, though, if Meitner argued for Wu to be awarded a share of that year’s prize.
> A total of 23 nominations to give a Nobel prize to Wu reached the Nobel Committee on 10 separate years and she was nominated by 18 leading physicists, including various Nobel-prize winners and Tsung-Dao Lee himself
Although Wu did not receive any nominations in 1957, she was nominated the following year by the 1955 Nobel laureates in physics, Willis Lamb and Polykarp Kusch. In fact, after Lee and Yang won the prize, nominations to give a Nobel prize to Wu reached the committee on 10 separate years out of the next 16 (see graphic below). She was nominated by a total of 18 leading physicists, including various Nobel-prize winners and Lee himself. In fact, Lee nominated Wu for a Nobel prize on three separate occasions – in 1964, 1971 and 1972.
However, it appears she was never nominated by Yang (at the time of writing, we only have archive information up to 1974). One reason for Lee’s support and Yang’s silence could be attributed to the early discussions that Lee had with Wu, influencing the famous Lee and Yang paper, which Yang may not have been aware of. It is also not clear why Lee and Yang never acknowledged their discussion with Wu about the cobalt-60 experiment that was proposed in their paper; further research may shed more light on this topic.
Following Wu’s nomination in 1958, the Nobel Committee simply re-examined the investigations already carried out by Klein and Hulthén. The same procedure was repeated in subsequent years, but no new investigations into Wu’s work were carried out until 1971 when she received six nominations – the highest number she got in any one year.
## Nominations for Wu from 1958 to 1974
(Courtesy: IOP Publishing)
Our examination of the newly released Nobel archive from 1957 indicates that although Chien-Shiung Wu was not nominated for that year’s prize, which was won by Chen Ning Yang and Tsung-Dao Lee, she did receive a total of 23 nominations over the next 16 years (1974 being the last open archive at the time of writing). Those 23 nominations were made by 18 different physicists, with Lee nominating Wu three times and Herwig Schopper, Emilio Segrè and Ryoya Utiyama each doing so twice. The peak year for nominations for her was 1971 when she received six nominations. The archives also show that in October 1957 Werner Heisenberg submitted a nomination for Lee (but not Yang); it was registered as a nomination for 1958. The nomination is very short and it is not clear why Heisenberg did not nominate Yang.
That year the committee decided to ask Bengt Nagel, a theorist at KTH Royal Institute of Technology, to investigate the theoretical importance of Wu’s experiments. The nominations she received for the Nobel prize concerned three experiments. In addition to her 1957 paper on parity violation there was a 1949 article she’d written with her Columbia colleague R D Albert verifying Enrico Fermi’s theory of beta decay (_Phys. Rev_. **75** 315) and another she wrote in 1963 with Y K Lee and L W Mo on the conserved vector current, which is a fundamental hypothesis of the Standard Model of particle physics (_Phys. Rev. Lett_. **10** 253).
After pointing out that four of the 1971 nominations came from Wu’s colleagues at Columbia, which to us may have hinted at a kind of lobbying campaign for her, Nagel stated that the three experiments had “without doubt been of great importance for our understanding of the weak interaction”. However, he added, “the experiments, at least the last two, have been conducted to certain aspects as commissioned or direct suggestions of theoreticians”.
In Nagel’s view, Wu’s work therefore differed significantly from, for example, James Cronin and Val Fritsch’s famous discovery in 1964 of charge-parity (CP) violation in the decay of Ko mesons. They had made their discovery under their own steam, whereas (Nagel suggested) Wu’s work had been carried out only after being suggested by theorists. “I feel somewhat hesitant whether their theoretical importance is a sufficient motivation to render Wu the Nobel prize,” Nagel concluded.
## Missed opportunity
The Nobel archives are currently not open beyond 1974 so we don’t know if Wu received any further nominations over the next 23 years until her her death in 1997. Of course, had Wu not carried out her experimental test of parity violation, it is perfectly possible that another physicist or group of physicists would have something similar in due course.
Nevertheless, to us it was a missed opportunity not to include Wu as the third prize winner alongside Lee and Yang. Sure, she could not have won the prize in 1957 as she was not nominated for it and her key publication did not appear before the January deadline. But it would simply have been a case of waiting a year and giving Wu and her theoretical colleagues the prize jointly in 1958.
Read more
####
Credit where credit’s due?
Another possible course of action would have been to single out the theoretical aspects of symmetry violation and award the prize to Lee, Wigner and Yang, as Klein had suggested in his report. Unfortunately, full details of the physics committee’s discussions are not contained in the archives, which means we don’t know if this was a genuine possibility being considered at the time.
But what is clear is that the Nobel committee knew full well the huge importance of Wu’s experimental confirmation of parity violation following the bold theoretical insights of Lee and Yang. Together, their work opened a new chapter in the world of physics. Without Wu’s interest in parity violation and her ingenious experimental knowledge, Lee and Yang would never have won the Nobel prize.
### Want to read more?
Registration is free, quick and easy
**Note:** The verification e-mail to complete your account registration should arrive immediately. However, in some cases it takes longer. Don't forget to check your spam folder.
If you haven't received the e-mail in 24 hours, please contact [email protected].
* E-mail Address
Register https://physicsworld.com/a/twenty-three-nominations-yet-no-nobel-prize-how-chien-shiung-wu-missed-out/
