At the invitation of China Science and Technology Museum (CSTM), Mr. Li Tianchu, academician of the Chinese Academy of Engineering and president of the China Instrument and Control Society (CIS), came to the museum recently and delivered a popular science lecture entitled "Laser-Driven Quantization of the International Basic Units of Measurement and the Researches Conducted by China National Institute of Metrology to Cope with the Situation". The lecture was attended by over 150 persons, including members of CSTM‘s leadership and the museum‘s staff.

In his lecture, Li Tianchu introduced the relationship between optics and metrology; he also narrated the scientific knowledge of time measuring, including the evolution process of the definition of "second" (a time measurement unit) from astronomical second to atomic second, how the unified time of the world came into being, the existing phenomenon of leap second, how benchmark atomic clocks realize the benchmark of a second‘s length, the important applications of accurate time frequency in industry, scientific research, military and national defense etc., the strategic significance of China‘s launch of its Beidou (Big Dipper) Navigation Satellite System, how the length measurement unit "meter" is precisely defined, the relationship between meter in terms of length and the science of optics, and so on. At the conclusion of the lecture, the audience and Li Tianchu had an in-depth Q & A session focusing on certain issues touched upon in the lecture.

As part of the "Academics and Experts Talking about Popular Science" serial activities organized by the Chinese Optical Society in commemoration of the "International Year of Light in China", the lecture was jointly sponsored by China Science and Technology Museum and the Chinese Optical Society with a view to popularizing optical science in China, enabling more people to learn about knowledge of optics and scientific results in relation to optics, as well as to promoting the general public‘s scientific and cultural literacy of optics.