Monday, 18 August 2014

The Hot and the Dead – Chien-Shiung Wu

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By the time you’ve finished reading this (and please do – there might be teddy bears in it), you will be thoroughly convinced that I know precious little about physics. So it’s just as well women like Chien Shiung Wu knew a lot about physics, or we might never have learned about subatomic particles and the amazing things they’re capable of when we’re not paying attention.

Chien Shiung Wu was a great example of what happens when a top-notch brain is given the opportunity to learn and grow and go wherever it wants to, without paying too much attention to popular ideas about keeping quiet and doing the washing up. Born in May 1912 in the town of Liuhe near Shanghai, Wu was always encouraged to read and think and discover.

Wu’s brain (accompanied by her charming dimples) led her through teacher’s college and then to the National Central University in Nanjing, where she studied mathematics. Unlike the kind of people who grow up to write medium-length quasi-historical articles for a living, Wu found mathematics intriguing, but not quite complicated enough. So she transferred to physics, and something clicked.

1930s China had a lot going for it – a growing population, expanding opportunities for women and some exceptional cups of tea. But for a beautiful and well-educated twenty-four-year-old with an appetite for science, the United States beckoned. In 1936, Chien Shiung Wu jumped on a steamship and headed for Michigan State University, via California.

Shortly after arriving stateside, Wu met fellow physicist Luke Chia-Liu Yuan. Then, much like some people who grow up to write medium-length quasi-historical articles for a living even though they originally wanted to be a sound engineer, she changed her plans. She enrolled at the University of California, Berkeley, completed her PhD in physics in 1940, married Yuan in 1942 and bore a son, Vincent, in 1947.

Meanwhile, Wu’s brain was in demand. She taught at Smith College, Massachusetts and Princeton University before settling in for a long stint at Columbia University from 1944 until her retirement as in 1981 as a Professor of Physics. She continued to teach others after her retirement, speaking to audiences about science and the many achievements of women in it.

So what of her achievements, then? Wu contributed to the Manhattan Project* in 1944, by helping to separate uranium into particular isotopes to make it more blow-uppable. She helped to improve the way Geiger counters worked, so that people unlucky enough to have the job of measuring nuclear radiation levels could do so with relative ease. But Wu’s biggest contribution to science, for which she was awarded the Wolf Prize in Physics in 1978, was when she contradicted the Law of Conservation of Parity.

If you already know about the Law of Conservation of Parity, you can stop here and skip to the end, where I usually make a tepid joke in an attempt to mitigate the anguish of death. If you don’t already know about the Law of Conservation of Parity and you’d like to learn about it in a slightly-inaccurate-but-surprisingly-fluffy way, stay with me.

Ok. In physics, every object or process has, theoretically, a corresponding mirror image. This can apply to elementary particles and their interactions, but let’s assume it also applies to teddy bears. When you hold up a teddy bear to a mirror and you wiggle its arm around, the corresponding mirror-arm also wiggles, right? The Law of Conservation of Parity says that every time you wiggle the teddy bear’s left arm, the mirror image will also wiggle its corresponding arm in the same-but-opposite way.

Additionally in physics, there are four fundamental interactions of nature. There’s the strong interaction (responsible for holding some parts of an atom together), electromagnetism (responsible for electricity and holding electricity bills on the fridge), gravitation (responsible for holding you on your chair) and the weak interaction (responsible for radioactivity).

Now imagine that the teddy bear is an elementary particle (a quark or electron or whatevs) and that you wiggling its arm around is one of the four fundamental interactions of nature. In Wu’s era, physicists had pretty much proven that in strong interactions and electromagnetism, the teddy bear’s mirror-arm always wiggled in the expected way. But the Law hadn’t been tested for weak interactions. And that’s where Wu came in.

Under the direction of theoretical physicists Tsung-Dao Lee and Chen Ning Yang, Wu designed, set up and performed an experiment that tested the Law of Conservation of Parity using the weak interaction. And there were surprising results. Wu proved that the Law did not apply in this case. In effect, one teddy bear was wiggling its arm around and the mirror-teddy was wearing a different coloured waistcoat and doing jazz hands.

This was a big thing. Wu’s experiment played a major role in the way particle physics was understood from that point forward. Thanks to her, humankind is closer to unravelling the mysteries of the physical universe. By my reckoning, there are probably only two or three more things we need to find out.

Chien Shiung Wu died from a stroke on February 16, 1997 at the age of 84. Even magnificent brains have their physical limits.

 

*Sure, the Manhattan Project was responsible for turning Hiroshima and Nagasaki into the charred remains of humanity, but keep in mind that the vast majority of people who worked on the project had no idea of its ultimate aims.

 wu chien shiung

 

Shelley Stocken

Shelley Stocken is a freelance writer when she’s not feeding, clothing and wiping family members.

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