International Symposium on Frontiers in Science
in honor of the 80th birthday of Prof CN Yang

After-Banquet Speech

Kenneth Young
The Chinese University of Hong Kong

Prof Yang, President Wang Dazhong, Ladies and Gentlemen

I am honored to have been asked to say a few words on this occasion, when we gather to celebrate Prof CN Yang's 80th birthday.

Much that we all want to say to express our respect and affection has already been said with such feeling and eloquence this morning by Prof Zhou Guangzhao, and also just now by Prof Paul Chu - but Paul almost stole my story.

So I shall only add a few remarks of an informal nature, which I hope may be of interest.

Namely, I hope to be able to resolve for you a central mystery, central to this occasion, when we celebrate Prof Yang's birthday - what is Prof Yang's birthday? Therein lies a tale, and therein lies my minor contribution to the history of science.

Yang Chen Ning was born in 1922, on the 11th day of the 8th month according to the Chinese lunar calendar. Now you have to realize that in those days, people would reckon only by the lunar calendar, and that would have been how the birthday was remembered within the family and among friends.

After the war, CN Yang won a Boxer scholarship to go to the US to study. For that, he needed a passport, and for the passport he needed a birthday according to the standard Gregorian calendar. In the aftermath of war, the almanac for doing the conversion was not easily available. But a physicist, even a young one, could solve this problem on the back of an envelope.

The zero-order approximation for the 11th day of the 8th month would be 11th of August obviously. Since Chinese New Year is about a month later than New Year in the international calendar, the one-loop correction would give the middle of September. But actually Chinese New Year tends to be around the middle of February, so the two-loop correction gave 22nd September, which is the date that was adopted, and which even now appears on Prof Yang's passport.

But of course, knowing CN Yang, we cannot tolerate anything less than an exact solution to this problem, correct to all orders in perturbation theory. So, many years later, by consulting the almanac, it was determined that the birthday is actually 1st October 1922. The first of October is by coincidence an important and auspicious date for China; it is our national day, the day when the Peoples' Republic was established.

But there is more. Prof Yang is first and foremost a man of science. Of his many important works, there is little doubt that parity and gauge fields are the two that stand out. I don't have to tell you that Yang wrote a paper with Robert Mills on "Conservation of Isotopic Spin and Isotopic Gauge Invariance"; but I do have to tell you that this paper was published in Physical Review on 1st October 1954. I don't have to tell you that Yang wrote a paper with TD Lee on the "Question of Parity Conservation in Weak Interactions"; but again I do have to tell you that this paper was published in Physical Review on 1st October 1956.

I leave it as an exercise to the reader to compute the odds of this coincidence. To me, this remarkable convergence of dates symbolizes how the monumental contributions to science are both a personal triumph for Yang Chen Ning and a matter of national pride for the Chinese people. I refer to national pride not in the abstract, for it is without a doubt that this shining personal example has been a factor that has encouraged many Chinese of our generation into careers in science, especially physics, including many here tonight.

It goes beyond physics or even science. In the copy of Xin Tsinghua, the campus newspaper that was part of the Symposium package, there was, on the back page, a quotation from Prof Yang that is familiar to many of us. It is in Chinese, so allow me to give a rough translation. Prof Yang said: "If you were to ask me what my greatest contribution is, I would say it is that I have helped to change the feeling among the Chinese people that they may be inferior to others."

Is it therefore not apt that he published his greatest works on his birthday, which is also our national day?

Prof Yang's shining example as a scientist, as a gentleman and a scholar, in the classical, almost Confucian sense of that word, is an inspiration to us all. This example is not as well known to the younger generation as it ought to be, and needs to be told.

We at The Chinese University of Hong Kong feel a particular responsibility, because Prof Yang has most generously given all his medals and his manuscripts to The Chinese University of Hong Kong, to establish an archive, for the public, and for historians of science. I take this opportunity to appeal to you all, friends of Prof Yang, for copies of correspondence and any memorabilia that might enhance the archive, that might shed light on how scientific ideas have developed.

I should now come back to the birthday we are here to celebrate. In one region of spacetime we would use a basis according to which Yang Chen Ning was born on the 11th day of the 8th month of the lunar calendar. In another region of spacetime we would use another basis according to which Frank Yang was born on 1st October of the Gregorian calendar. Obviously a gauge transformation. Out of this one can construct a global gauge invariant, namely that CN Yang is a towering physicist, whose contribution belongs to all of humanity.

And on this occasion let us to Prof Yang say "happy birthday", and look forward to more important contributions on forthcoming October firsts.

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