The 2021 New Year's Eve Scientific Speech of "Understand Physics in the New Year"—"What Is the Theory of Relativity" was held in the M234 Lecture Hall of the Institute of Physics (IOP) of the Chinese Academy of Sciences (CAS) on the evening of December 30. Prof. Cao Zexian from IOP gave a lecture on "What is the Theory of Relativity," bringing the audience a hardcore New Year's Eve science feast.

This event was co-organized by the Bureau of Science Communication of CAS, IOP and the Yangtze River Delta Physics Research Center (Liyang, China), and was supported by the China Science Daily and the University of Chinese Academy of Sciences. Attendees included heads from the Bureau of Science Communication of CAS, the Department of Overseas Intellectual Resources Cooperation of the Ministry of Science and Technology, P.R.C., the Yangtze River Delta Physics Research Center, the Zhongguancun No. 1 Primary School, the Kindergarten of CAS, and peers from all walks of life who are committed to science popularization. The event was hosted by Chun Ni, a famous TV hostess from BTV.

At the beginning of his speech, Cao Zexian aroused the audience's interest with two questions: "What is the Theory of Relativity" and "Why do we have to learn it." According to the Wei of Shangshu · Kao Ling Yao (a Chinese ancient book that interprets Confucian classics The Book of History via theology), "the earth keeps turning but people cannot perceive it, just like people sitting in a ship with windows closed without knowing that the ship is moving," which demonstrates a simple understanding of relativity of the ancients. In modern times, scientists like Galileo and Newton put forward concepts related to inertia and acceleration. On the basis of this knowledge, Cao Zexian cited various authorities and depicted a broad picture from special relativity to general relativity. He insisted that the theory of relativity is widely applied in our lives, such as clock calibration, time service, distance measurement, and satellite navigation. In his two-hour-plus speech, Cao captivated the audience with humorous expressions and brilliant explanations.

After the speech, Gao Qingyi, a popular science blogger on Sina Weibo, Wen Zhifan, the person in charge of the account I'm EyeOpener on bilibili, and MommyTalk, a creator on the short video platform ixigua, as representatives of the audience, discussed with Cao Zexian on issues of public interest. Additionally, the student representatives from the University of Chinese Academy of Sciences also raised several professional questions via video link, and Cao Zexian answered them in detail. Audiences, both online and offline, were enlightened by the fascinating speech and the entertaining Q&A session.

At the end of the event, IOP surprised the audience by the debut of the trailer of hilarious physics sitcom "Cheering Up, Mr. Fei". In 2020, due to the COVID-19 pandemic, many students studied at home through online courses. Based on this background, the sitcom shows the real-life scenes of a frank father who is a physics teacher, and a young rebellious and curious daughter who is studying online at home. The creators of the sitcom collect scientific materials with the most dedicated spirit, produce the hilarious contents with the most earnest attitude, present the most interesting "contrasts" with the most rigorous style, and disseminate the most attention-grabbing scientific knowledge of physics in an unprecedented way. At the event site, the hostess announced that the sitcom will be officially launched in 2021.

In view of the pandemic, the organizers has been sticking to epidemic prevention and control requirements throughout the event, including strictly controlling the number of on-site audiences, and adopting the form of live streaming. This event was live broadcast on xuexi.cn, the apps of People's Daily, Xinhuanet, and China Youth Daily, Guangming Online, CCTV.com, Yangshipin, Broadcast Media Center of Hunan Broadcasting System, Jiangsu Broadcasting Corporation Convergence Media News Center "Li Live", YNET, ScienceNet.cn, bilibili, Headline Science, Ixigua, Douyin, haokan, WeChat Video Account, Tencent News, Tencent Kandian, Zhihu Science, Weibo Open Class, tech.sina.com, Kuaishou, koushare.com, Fanpu, keyanyun.com, University of Chinese Academy of Sciences, Center for S&T Innovation and Development of CAS, kepu.net.cn, and Academic Service Department of IOP, attracting an audience of millions. Netizens said that against the backdrop of the global fight against the pandemic, people have increasingly come to realize the importance of science for the development of human society. On the occasion of "Farewell to 2020 and Greeting to 2021", IOP, as a fresh flow of the scientific community, successfully held the second session of New Year's Eve Scientific Speech, concluding the year 2020 in an intriguing and impressive way.

As a national research institute, IOP, while striving to promote cutting-edge scientific and technological innovation, actively assumes the responsibility of scientific popularization by disseminating scientific knowledge to the public through a variety of activities and contents, thus improving public scientific literacy. Through launching the New Year's Eve Scientific Speech of "Understand Physics in the New Year" and rolling out more innovative popular science works, IOP aims to arouse more people's, especially teenagers' interest in and passion for scientific knowledge, and create a better scientific culture.

Live video link: https://www.bilibili.com/video/BV18V411b7YD