Nobel Prize-winning theoretical physicist Chen-ning Yang, died in Beijing on Saturday at the age of 103. He was often ranked alongside Albert Einstein as one of the 20th century’s greatest physicists. In 1954, he co-authored a set of equations with the American physicist Robert Mills that turned out to be as important to physics as Einstein’s theory of relativity. The resulting Yang–Mills theory described how three of nature’s four fundamental forces — the electromagnetic, weak and strong...