In the Dark

I’ve just heard the sad news of the death at the age of 97 of TD Lee (shown left) who, together with CN Yang, won the Nobel Prize for Physics in 1957 for his work on parity violation in particle physics. I always find it difficult on occasions like this to find ways of describing the work of people of such eminence in fields other than my own, but in this case it turns out I have a personal connection of a sort. Way back in 2006 when I was at Nottingham, the University decided to award Prof. Lee an honorary degree and I was chosen to deliver the oration at the graduation ceremony before spending some time chatting to him with some students. I remember that it was a very hot day and I was wilting under the graduation robes, but he took it all in his stride despite being 80 years old. Anyway, here is the text that I prepared for that occasion, which I hope will serve as a fitting obituary.

PROFESSOR TSUNG-DAO LEE

ORATION DELIVERED BY PROFESSOR PETER COLES

ON MONDAY 17 JULY 2006

Chancellor, Vice-Chancellor, Ladies and Gentlemen, it is both a pleasure and a privilege to present Professor Tsung-Dao Lee for the award of an honorary degree.  Professor Lee is a distinguished theoretical physicist whose work over many years has been characterized, in the words of Dr J Robert Oppenheimer, by “a remarkable freshness, versatility and style.”

Tsung-Dao Lee was born in Shanghai and educated at Suzhou University Middle School in Shanghai.  Fleeing the Japanese invasion, he left Shanghai in 1941.  His education was interrupted by war.  In 1945 he entered the National Southwest University in Kunming as a sophomore.  He was soon recognized as an outstanding young scientist and in 1946 was awarded a Chinese Government Scholarship enabling him to start a PhD in Physics under Professor Enrico Fermi at the University of Chicago.  He gained his doctorate in physics in 1950 with a thesis on the Hydrogen Content of White Dwarf Stars, and subsequently served as a research associate at the Yerkes Astronomical Observatory of the University of Chicago in Williams Bay, Wisconsin.

Astronomy is a science that concerns the very large, but it was in the physics of the very small that Professor Lee was to do his most famous work.  After one year as a research associate and lecturer at the University of California in Berkeley, he became a fellow of the Institute of Advanced Study in Princeton and, in 1953, he accepted an assistant professorship position at Columbia University in New York.  Two and a half years later, he became the youngest full professor in the history of Columbia University.  During this time he often collaborated with Chen Ning Yang whom he had known as a fellow student in Chicago.  In 1956 they co-authored a paper whose impact was both immediate and profound.  Only a year later, Lee and Yang were jointly awarded the Nobel Prize in Physics.  Professor Lee was thirty-one at the time and was the second youngest scientist ever to receive this distinction.  (The youngest was Sir Lawrence Bragg who shared the Physics Prize with his father in 1915, at the age of twenty-five; Werner Heisenberg was 31 when his Nobel Prize was announced, in 1932, but he did not receive the prize until the following year.)

It is usually difficult to explain the ideas of theoretical physics to non-experts.  The mathematical language is inaccessible to those without specialist training.  But some of the greatest achievements in this field are so bold and so original that they appear, at least with hindsight, to be astonishingly simple.  The work of Lee and Yang on parity violation in elementary particle interactions is an outstanding example.

Subatomic particles interact with each other in very complicated ways.  In high energy collisions, particles can be scattered, destroyed or transformed into other particles.  But governing these changes are universal rules involving things that never change.  The existence of these conservation laws is a manifestation of the symmetries possessed by the mathematical theory of particle interactions.

Lee and Yang focussed on a particular attribute called parity, which relates to the “handedness” of a particle and symmetry with respect to mirror reflections.  Physicists had previously assumed that the laws of nature do not distinguish between left- and right-handed states: a left-handed object when seen in a mirror should be indistinguishable from a right-handed one.  This symmetry suggests that parity should be conserved in particle interactions, as it is in many other physical processes.  Unfortunately this chain of thought led to a puzzling deadlock in our understanding of the so-called weak nuclear interaction.  Lee and Yang made the revolutionary suggestion that parity is not conserved in weak interactions and consequently that the laws of nature must have a built-in handedness.  A year later their theory was tested experimentally and found to be correct.  Their penetrating insight led to a radical overhaul of the theory of weak interactions and to many further discoveries.  Physicists around the world said “Of course!  Why didn’t I think of that?”

This classic “Eureka moment” happened half a century ago, but Professor Lee has since made a host of equally distinguished contributions to fields as diverse as astrophysics, statistical mechanics, field theory and turbulence.  He was made Enrico Fermi Professor at Columbia in 1964 and University Professor there in 1984.  With typical energy and enthusiasm he took up the post of director of the RIKEN Research Center at Brookhaven National Laboratories in 1998.  He has played a prominent role in the advancement of science in China, including roles as director of physics institutes in Beijing and Zhejiang.

Professor Lee has received numerous awards and honours from around the world, including the Albert Einstein Award in Science, the Bude Medal, the Galileo Galilei Medal, the Order of Merit, Grande Ufficiale of Italy, the Science for Peace Prize, the China National-International Cooperation Award, the New York City Science Award, the Pope Joannes Paulis Medal, Il Ministero dell’Interno Medal of the Government of Italy and the New York Academy of Sciences Award.  His recognition even extends beyond this world, for in 1997 Small Planet 3443 was named in his honour.

Chancellor, Vice-Chancellor, to you and to the whole congregation I present Professor Tsung-Dao Lee as eminently worthy to receive the degree of Doctor of Science, honoris causa.