Prof. Chen Nanxian from Tsinghua University, also a member of the Chinese Academy of Science,  delivered his speech on The Inverse Problems in Scientific Research in the 168th Luo Jia Lecture. Prof. Xu Hongxing, dean of the School of Physics and Technology, awarded Prof. Chen, the Luojia lecturer, with a commemorative certificate.

The lecture began with a simple question---what is the inverse problem? Prof. Chen answered that “if the precondition of problem A is partial or the whole solution of problem B, then these two problems are inverse problems. In other words, forward problems and inverse problems are symbiotic with each other.”

Prof. Chen delivering his speech

Prof. Chen illustrated the existence of inverse problems by historical facts in scientific research. He indicated that “nearly all the innovation in scientific research, technological breakthroughs and engineering designs is inverse problem solving, and these problems are always ill-posed. In other words, they are not always formal logical.” “The inverse problems are always a stepping stone to new fields, and the research on inverse problems depends on multidisciplinary cooperation,” Prof. Chen said, “The ill-posed problems are even more interesting and useful.”  Meanwhile Prof. Chen also reminded the audience that innovation is not the purpose but the result, or else it would become innovation vulgarization. “Some basic data requires decades to gather, while in China we are often too eager for success to do this fundamental work; conclusions drawn from forward problems need testing and additional experimentation under many circumstances in order to be verified, but we also see a lack of willingness to do this.” Prof. Chen concluded that this situation caused the lack of inverse problem research foundations.

Prof. Chen criticized the current fickleness phenomenon in our society. He said that “the so-called impetuous trend is essentially a packing and covering problem, which is packing old problems into a new one, or it’s not actually a question, but a pseudo-problem.” Prof. Chen worried that “we pay high attention to innovation, but ignore the accumulation process, which is the foundation of creation.” He thought that the inverse problems are “based on forward problems we solved very well.” Prof. Chen added that “we already accumulated plenty of successful and unsuccessful experiences, only in such way can we solve inverse problems smoothly.”

Chen Nanxian, vice chairman of the CPPCC Beijing Municipal Committee, was born in 1937, and he is also a member of the 10th NPC Standing Committee as well as vice chairman of the 11th Central Committee of the China Association for Promoting Democracy. Prof. Chen majored in physics at Peking University and then taught at the Beijing Institute of Iron and Steel Engineering. He got a doctorate in electric engineering at the University of Pennsylvania, and following post-doctoral studies, was an academician of the New York Academy of Sciences from 1980 to 1986. Returning to China in 1987, he was a professor and director of the Institute of Applied Physics and director of the physics department's academic committee at the Peking University of Science and Technology. He did research on the physics of condensed matter and cooperated in finding an exact solution to the problem of lattice specific heat. Additionally, Prof. Chen is also the translator of "Vibration and Wave Physics".

Prof. Chen ended his speech with a ragged verse

Photo by Liu Tianxiang

Edited by Sun Jingyi, Edmund Wai Man Lai