At 15:45 yesterday, the fourth lesson of "Tiangong Classroom" began on the Chinese space station. The "doctoral crew" composed of Shenzhou 16 astronauts Jing Haipeng, Zhu Yangzhu and Gui Haichao introduced the work and life scenes of the new "classroom", the Mengtian experimental module of the Chinese space station, and demonstrated a series of wonderful scientific experiments in the microgravity environment of space.
The teaching mode of Tiandi Interactive continues. A total of 5 ground classrooms were set up in Beijing, Alxa League of Inner Mongolia Autonomous Region, Yan'an City, Shaanxi Province, Tongcheng City of Anhui Province and Ningbo City of Zhejiang Province, with about 2,800 student representatives attending the lectures. Beihang University is where the Beijing ground classroom is located, and it is also the school where Gui Haichao works. After nearly 4 months of space "business trips", his students saw the teacher on the "podium" again.
On September 21, in the Ejina Banner of the Alxa League in Inner Mongolia, students were doing interesting experiments. Xinhua News Agency
On September 21, at Beihang University, students watched the fourth lesson of "Tiangong Classroom". Photo by Xinhua News Agency reporter Ju Huanzong
Teachers and students of the Affiliated Experimental School of the Chinese Academy of Sciences conducted the "Heaven and Earth Comparison" experiment. Photo by our reporter and Guanxin
Scientific experimental equipment "lies" overhead
The Mengtian Experiment Module concentrates the most scientific experiment equipment on the space station, and can provide 13 scientific experiment cabinets with installation space. As soon as the class started, Jing Haipeng served as a cameraman, introducing the "classroom" through the lens.
Different from the Wentian experimental cabin, there is no sleeping area, health area, etc. in the Mengtian experimental cabin. Its airlock cabin is not used for astronaut out-of-cabin activities, and its load transfer mechanism is like a shuttle car, which can cooperate with the extravehicular robotic arm to realize the automatic entry and exit of goods. Under the guidance of Zhu Yangzhu and Gui Haichao, the lens focused on the core area, and many space science experiment cabinets such as two-phase system experiment cabinet, fluid physics experiment cabinet, and online maintenance and assembly experiment cabinet appeared one by one.
Unlike the ground, the scientific installations in the "classroom" are not standing on the ground, but are placed 360 degrees. This is because in the space microgravity environment, there is no up, down, left and right and other directions, so in the lens, the high-temperature material experiment cabinet is steadily "lying" on the top of the astronaut's head. Zhu Yangzhu wittily compared it to a "space alchemy furnace" - the furnace temperature can reach 1600 degrees Celsius, and it can carry out research and preparation of various new materials.
Zhu Yangzhu revealed that the first batch of materials that were tested by high temperatures in the "alchemy furnace" had returned to the ground with Shenzhou 15. Among them, indium selenide semiconductor materials have very good flexible properties, can be bent and folded arbitrarily, very suitable for making new transistor electronic devices, and are promising to promote the progress and upgrading of semiconductor technology.
Near the "alchemy furnace", there is also an ultra-cold atomic physics experiment cabinet. It can create ultra-low temperatures close to absolute zero, can visualize macroscopic quantum phenomena visible to the naked eye, and help researchers explore the bizarre world of quantum mechanics.
The equipment under the astronauts' feet is called the aerospace basic experiment cabinet, and five experiments are being carried out, including the cultivation and maturation of microalgae and the thermal management of liquid metal space. He introduced the microalgae experiment in particular, mainly exploring the long-term cultivation of microalgae in weightless environment, and carrying out research on the in-situ processing of microalgae food, "This is a very beneficial attempt and exploration for our future interstellar voyage." ”
Light "fire" and play "water" balls in the space station
In February this year, the Mengtian experimental cabin combustion science experiment cabinet completed the first ignition experiment. From the backhaul images, it can be seen that in microgravity, the methane flame becomes short and rounded.
This time, the "doctoral crew" lit candles in the space station and invited students to observe the characteristics of the flames. Zhu Yangzhu first took out a candle, and Gui Haichao lit a match to try to light it. "There are actually some risks associated with candles at space sites, and we are well prepared for this." Gui Haichao said.
In the ground classroom, the teacher also lit a candle. Between heaven and earth, one of the flames of the two candles is "blue, the shape is almost spherical", and the other is "bright orange, cone-shaped". Zhu Yangzhu gently turned the candle, and the shape of the flame hardly changed. The candle flame on the ground swings with the flow of air.
"The ground has a gravity effect, the hot gas rises, the cold gas falls, forming buoyant convection, so the flame takes on a cone-shaped. But the station's microgravity environment virtually eliminates this convection, and the burning gas tends to move in all directions in the same direction, so the flame is approximately spherical regardless of which direction the candle is facing. Gui Haichao said that it is precisely because the convection is weak, the oxygen replenishment is not as timely as the ground, the candles in the space station are not burning as fully as the ground, and the temperature of the flame is lower, which is blue.
Just after finishing a fire-related experiment, Zhu Yangzhu did another "water" experiment. He squeezed out a water ball with a water bag, and Gui Haichao picked up an ordinary ping-pong racket and hit it, and the water ball was not ejected, but stuck to the surface of the racket.
Zhu Yangzhu took out the "secret weapon" - a dry towel to wipe sweat while moving in orbit. Wrap the towel around the surface of the racket, and with another swing, the water balloon becomes a "ping-pong ball".
"Ready to catch the ball!"
"Teacher Zhu played a good ball!"
This space "table tennis game" demonstrated the surface tension of water and the properties of hydrophobic materials. Chen Zheng, associate professor at the School of Physical Science and Engineering at Beijing Jiaotong University, said that towels have a certain hydrophobicity, so that water will not be quickly sucked into the fiber, but stay on the surface of the fiber or be squeezed between the fibers, so astronauts can play "water balloons". In daily life, similar processes are used in the fabrics of storm jackets and quick-drying clothing, and when the gap between the fibers is greater than the size of the water molecules, it can be both breathable and quick-drying.
"Space Turn" recreates the space station
With the advancement of the course, the experiment has gradually deepened from the level of phenomenon observation to quantitative exploration. The "Dr. Crew" pasted a standard mesh cloth on the hatch of the Dream Weather Lock, one square meter in size. Gui Haichao aimed at a stationary steel ball and threw the steel ball in his hand. Against the background of the mesh cloth, the trajectory after the collision of the two balls is clear at a glance.
This simple collision experiment is to verify the conservation of momentum in space. Chen Zheng explained that collision phenomena are common in life. But everyone may not realize that the most basic concepts of momentum and kinetic energy in modern physics are established by scientists on the basis of research on collision problems.
In class, there are also classic reproductions. Previously, the Shenzhou 13 crew astronaut Ye Guangfu raised his arm and rotated, driving the entire body to rotate in the air. Reproducing the "space turn", Gui Haichao is assisted by a gyroscope. It can be rotated longitudinally with grips on both sides.
Gui Haichao, who was floating in the air, first held the stationary top, raised and lowered his left and right hands alternately, and his body posture did not change. When Zhu Yangzhu let the top turn quickly, and then made the same action, Gui Haichao's body obviously rotated. This reflects the principle of conservation of angular momentum.
"Students can imagine my body as a space station, hands and a gyroscope in my hands, a special device called a control torque gyroscope." Gui Haichao said that this device can achieve four or two thousand pounds. With only a few hundred kilograms of gyroscopes, the space station weighing nearly 100 tons can easily turn around in space.
"It should be noted that the angular momentum is large and small, whether it is to let Mr. Gui turn or let the space station turn, the weight, size, rotation speed, etc. of the gyro have been quantitatively designed and calculated. Otherwise, the effect will not be so good. Zhu Yangzhu extended the topic to the scientific research process, and scientific research must not stop at qualitative observation, but should look at the essence through phenomena. Physics is a highly quantitative discipline, and only by excavating the quantitative characteristics behind phenomena can we better grasp and apply the laws.
The reporter compared the timetable of the previous "Tiangong Classroom" and found that the teaching content of the "Space Teacher" is gradually shifting from arousing students' interest in science to scientific inquiry. During this lecture, the astronauts specially provided basic information such as the quality of the experimental ball and the size of the mesh cloth. "The background of the crash experiment with mesh cloth is my suggestion, and I am honored to be adopted." Chen Zheng said that with a reference background, younger students can observe the collision phenomenon more clearly, and older students can obtain position information from it, which is from qualitative to quantitative. "For physics teachers, this video can also be used as fodder for future classroom teaching."
Space Q&A
No space junk was seen on the space station
Inner Mongolia ground classroom students: Can you see space junk? Has the space station taken corresponding protective measures?
Jing Haipeng: Space junk is generally called space debris or space debris, which does exist, and the potential harm to the space station is not small. We often look through the portholes of the space station, and even use telescopes to find them. So far, however, no traces of space junk have been found. Aerospace scientists and technicians will always keep an eye on space junk, and once they find a threat to the space station, they will actively avoid it through orbital maneuvering and other measures. The space station is also equipped with some protective equipment, as if wearing armor, even if it touches some space debris.
Wear "sunglasses" when you encounter sunlight when you go out of the cabin
Zhejiang Ground Classroom Students: Compared with the sun seen on the ground and the earth seen on the plane, what is the difference between looking at the earth and the sun on the space station? Zhu Yangzhu: Looking at the earth from the space station is more vast and spectacular.
Looking at the sun from the space station requires special attention. Because without the atmosphere, sunlight becomes particularly intense and dazzling. When going out of the capsule, astronauts must use special protective windows, similar to special "sunglasses", in the sunny area to prevent eyes from being burned. On the space station, astronauts can see sunrises and sunsets 16 times a day.
Physical activity is done every day
Shaanxi ground classroom students: long-term "business trips" in space, how to overcome the adverse effects of weightless environment on the human body?
Zhu Yangzhu: The impact of weightless environment on astronauts includes redistribution of body fluids, muscle atrophy, bone loss, etc. But don't worry, researchers have carefully designed protective equipment such as penguin suits for astronauts. Astronauts have to do physical exercise every day, from space treadmills, space bicycles, resistance exercise facilities, to grip devices, pullers, etc., which can help fight muscle atrophy and bone loss. At present, these protective measures are very effective.
Beidou positioning equipment is installed on the space station
Beijing ground classroom students: The space station is flying in space, there is no obvious reference around it, how to judge the attitude and orbit changes of the space station?
Gui Haichao: The space station is equipped with special sensors, including earth sensors, sun sensors, star sensors, etc., to help the space station determine the attitude. At the same time, the mainland's Beidou satellite positioning system can also "guide the way" for the space station.
The flight of the space station in space has specific laws, and the method of orbital mechanics can be used to calculate "where it will go". Astronauts only need to turn on the instrument, and the "geographic information" of the space station will be clear at a glance.
The error of 100 million years is no more than 1 second
Anhui ground classroom students: How accurate is the high-precision time-frequency experiment cabinet? What are the uses?
Gui Haichao: At present, the atomic clock on the ground can achieve an error of no more than 1 second for tens of millions of years. The cold atomic microwave clock in the space station can achieve an error of no more than 1 second for 100 million years. This ultra-high-precision time reference can be used not only for fundamental physics research, such as high-precision testing of related theories such as supporting relativity, but also for improving positioning accuracy and other performance for satellites flying in space.
Live repercussions
"Maybe in the future, there will be a chance for Teacher Gui to take the spaceship we designed and go into space again!"
Reporter Liu Suya
Su Wenjie, a direct doctoral student at the School of Astronautics and Astronautics of Beihang University, is a student of Gui Haichao, and met her tutor in class through video, she said excitedly that the space station is a great scientific research platform, many experiments that cannot be carried out on the ground can be carried out here, "I hope to see more experiments in space in the future, I also look forward to devoting myself to the aerospace industry, maybe in the future there will be the opportunity to let Mr. Gui take the spacecraft we designed and go to space again!" ”
As a teacher in the Beijing ground classroom, Zhang Xiaotian, associate professor of the School of Astronautics and Astronautics of Beihang University, and Gui Haichao made a "heaven-earth partnership". "Seeing Gui Haichao on the space station, just like I usually see his state in the office or laboratory, I am also very happy as his colleague." "Teacher Gui's space journey, for Beihang students, is the process of turning dreams into reality." Liu Rui, secretary of the Party Committee of the School of Astronautics and Astronautics of Beihang University, said that this teaching form of heaven and earth dialogue can give students greater inspiration. "I look forward to Mr. Gui returning to Earth and school, and then telling the students about his work status and research direction on the space station, exploring the development of new scientific payloads and carrying out new work together."
The "Heaven and Earth" experiment lights up students' scientific dreams
Reporter Niu Weikun
"Students, clear your desktop." At about 16:40 yesterday, just after the fourth space lecture on the Chinese space station, Wang Zhu, a chemistry teacher at the Affiliated Experimental School of the Chinese Academy of Sciences, walked onto the stage, took out the prepared candles, and continued to speak.
Wang Zhu carefully lit the candle in her hand. "Students, look carefully, what shape is the flame of the candle in the teacher's hand?" "Cone!"
"It's not the same shape as the flame you just saw." She continued, "The teacher on the space station just explained to us that the difference behind it is related to gravity. ”
On the basis of space teaching, Wang Pearl added new knowledge points, not all matter burning will have a flame, combustible liquid or solid must first become a gas before it can burn to generate a flame.
After Wang Zhu's simple lecture, physics teacher Li Jing said with a smile: "Let me perform a little magic trick for everyone." She spread a towel on one hand, picked up a straw dipped in bubble liquid with the other, blew gently, and the small bubbles gently fell off, disappearing before touching the towel. The students made a lamenting sound. Li Jing said: "This also tells us that experiments are not successful at one time, and that doing scientific research requires perseverance." ”
After many attempts, the small bubble finally completed multiple bounces on the towel. Seeing the success of the "magic", the students were amazed. Li Jing continues to inspire students, hoping that students can also think outside the norm and think boldly, maybe one day there will be new discoveries.
"The teacher's supplementary experiments gave me a more detailed understanding of the content of the space lecture and a stronger interest in science." Ninth grade student Tu Yuping said. Student Shuang Sicheng was fascinated by the burning experiment: "Science is so interesting! In the future, I will also contribute to the progress of science and technology. ”
Source: Beijing Daily
Reporter Liu Suya