On the afternoon of March 23, at an altitude of 400 kilometers, the second lesson of "Tiangong classroom" was successfully opened, and a series of interesting experiments such as space "ice and snow" experiment, liquid bridge demonstration experiment, water oil separation experiment and space parabolic experiment were staged in turn. What kind of experiment can be selected into the schedule of "Tiangong classroom"? What other experiments can be demonstrated in future space teaching? Chen Zheng, a member of the teaching expert group of "Tiangong classroom" and an associate professor of Beijing Jiaotong University, interpreted it. In the second lesson of "Tiangong classroom", the crystal clear water set up a "liquid bridge" between two pieces of plastic, which impressed the audience. Chen Zheng introduced the liquid bridge demonstration experiment as an example. This experiment is carried out on the space station and can be analyzed from multiple angles. "From the perspective of a physics teacher, although many of us are familiar with the phenomenon of surface tension, we don't have much contact with fluid from small to large." Chen Zheng said that the liquid bridge demonstration experiment gives you more opportunities to pay attention to, explore and understand the fluid. He added that from the perspective of science communication, this is another very cool experimental phenomenon: the most common and common water around us will have unimaginable phenomena in the microgravity environment. In Chen Zheng's view, it is not only a wonder, but also a good means to stimulate people's curiosity. In addition to stimulating interest and curiosity, teaching in space on the space station puts forward more requirements for experiments. "The first is safety, which can not endanger the operation of our space station and there can be no potential safety hazards; the second is that the experimental phenomenon should be significantly different from that on the ground; the third is to facilitate the operation of astronauts and will not cause too much additional burden to astronauts." Chen Zheng said. According to Chen Zheng's analysis, the liquid bridge demonstration experiment meets the above conditions in all aspects: doing the liquid bridge experiment on the ground requires high pressure and other harsh conditions, while only ordinary water and containers are required in the space station. The experimental phenomenon is obviously different from the ground, the equipment requirements are simple, and the operation is very convenient and safe. In the microgravity environment of the space station, what fun, good-looking, simple and safe experiments may be done in the future? "Microgravity environment is a basic condition. In that environment, some (phenomena) we can think of and some (phenomena) we can't think of." Chen Zheng said. Chen Zheng imagined that in the weightless environment of space, will the growth direction of plants, such as phototropism and hydrotropism, be affected by gravity? He believes that not only physical phenomena, gravity is related to many phenomena around us, which can be tried on the space station. (Xinhua News Agency)