He seems to be an old man lived in his past glory. It seems that he no longer function as an out-standing physicist to deal with new problems any more. Yang is over 85! People should not expect that he is as energetic as many years ago.

While biology is really a good field to explore, physics is far from "is done" as has been said from time to time. This probably reflects the fact that they are done with physics. Biology is a relatively younger field and thus would be easier to make a mark on it. In fact, I have told youngsters that please do not expect to have a easy life in theoretical physics.