What would happen if the “Tiangong Classroom” was moved to Earth? The result of our work is…

The "penguin suit" that embodies the ingenuity of aerospace technology experts, the cells that flicker and jump under the fluorescent light, the five "twisted" ways of turning around in space, the beautiful water film experiment... I believe that many people experienced a magical science fiction journey in the "Tiangong Classroom" on December 9.

However, a 60-minute science class does not quench one's thirst.

The three astronauts of the "Feel Good Crew" not only brought us these "exclamation points", but also aroused the curiosity of many people: What would be the effect if these space experiments were repeated on Earth? What other similar interesting experiments are there?

On December 12, Science and Technology Daily invited Li Yili, the first deputy chief designer of the Shenzhou spacecraft, and Dr. Chen Zheng, a member of the space science teaching expert group, to open the "Tiangong Classroom" and "Advanced Class" at the Beijing Bayi School to tell the story of astronauts' dream-chasing journey, comprehensively review scientific experiments, and answer the questions that the audience had in their minds.

Students who missed the advanced class live broadcast should not panic. The series of videos will be released on December 16 in Tencent's youth mode "Master Lectures for Children". This is a science class that makes children applaud. Heavyweight scientific masters use humorous language to explain scientific knowledge in a simple and easy-to-understand way. While sharing their rich life experiences, they inspire children's curiosity and imagination to explore the world of science. With the wisdom of masters, they open the eyes of teenagers to the future.

If there was a weightlifting competition in space

Lifting the earth is not a dream!

"Imagine, if we hold a sports meeting in space, which event can break the record?" Chen Zheng asked first.

"High jump or long jump!" "Javelin!" "Shooting!" The students rushed to answer.

"What I want most is to break the record in weightlifting, and even want to lift the earth!" Chen Zheng told everyone that weightlifting is relatively easy to achieve in space.

Chen Zheng also said that although the space station is in a microgravity environment and everyone is as light as a swallow, at the same time, the forward momentum provided by the friction of the ground is lost, so it is difficult for people to walk in space. This surprised many students who thought they could run faster in space because their bodies became lighter.

After some interaction, Chen Zheng picked up the gimbal gyroscope to explain to everyone. "When rotating at high speed, the gyroscope has a fixed axis. No matter how the gimbal is rotated, the gyroscope always maintains one direction." Chen Zheng further explained that if a direction is specified for the gyroscope, at any time, we only need to compare the angle with the gyroscope axis direction to determine the current direction. This is the core principle of gyroscope navigation.

In addition to the GPS navigation that is familiar to the public, based on the inertial navigation system, the gyroscope can work all the time regardless of signal changes and play a navigation role. In other words, whether it is on the ground, at sea, in the air, or even in the deep sea or underground, it can help you know where you are at any time and anywhere.

Learn about conservation of angular momentum from cats

After the "Tiangong Classroom" ended, even Teacher Ye Guangfu himself probably did not expect that he had become famous for his "left-right twist" and became China's tallest "space turning model".

Chen Zheng said that the key word of the space turning experiment is angular momentum, which is a physical quantity that describes the rotation of an object.

In this "advanced class", Chen Zheng served as a "ground model", standing on a freely rotating turntable. In the absence of external torque, when the upper body moves to the left, the lower body will move to the right involuntarily. This is a simple and intuitive manifestation of the conservation of angular momentum in life.

Chen Zheng also specifically mentioned the process of a cat landing. When a cat is in the air, it can circle its body and then twist and stretch it out. During the process, the body will not be fixed in a straight line. It completes the turn while maintaining the conservation of angular momentum, so the cat always lands on its feet first.

So, how can we turn around gracefully like the "cats" while ensuring the conservation of angular momentum? Chen Zheng personally took the stage and demonstrated an interesting "freestyle"-style pose on the turntable, and it really turned around! "Although I am fat and my pose is not good-looking, this move is very effective." Chen Zheng said with a smile.

Then, in order to present an easier way to turn around, Chen Zheng picked up a rotating wheel, held it tightly with both hands, stretched out his arms, and was able to turn around easily.

Magical and exciting "water" experiment

Pay attention! Students who listened carefully must remember that when Wang Yaping placed a ping-pong ball in a cup of water, the ping-pong ball could not float. This is because under the microgravity conditions of space, the internal pressure of the liquid is equal everywhere, and there is no buoyancy caused by the pressure difference between the upper and lower surfaces. In other words, if you place an iron ball on the water in space, it will not sink.

This time, Chen Zheng did the same experiment and the ping-pong ball floated up easily. This verifies the coexistence of gravity and buoyancy. "In the microgravity environment of the space station, because each part of the water does not need to carry the water around it, it all floats in the air. Therefore, the pressure of the water in the cup in space is the same. When the ping-pong ball is put in, the forces cancel each other out and the buoyancy disappears," said Chen Zheng.

Next, Chen Zheng "conjured up" a sink and made a rectangular "bubble". He told everyone that we are used to adding hand sanitizer, dishwashing liquid, soap liquid, etc. into water to make a water film. Since these surfactants can reduce the surface tension of water, in space, water droplets are not disturbed by gravity. With the help of solid water rings, water can easily form a film. This is the knowledge point of "liquid surface tension". Attracted by internal molecules, the molecules on the surface of the liquid tend to be pulled into the interior, causing the surface to be like a taut rubber film. This taut force that causes the liquid surface to shrink is the surface tension.

In order to review the "water ball optics" experiment, Chen Zheng drew a left-pointing arrow on a piece of paper with a pen and placed a beaker of water in front of the paper. When the water overflowed the arrow, a magical thing happened: the arrow in the beaker turned around! Chen Zheng explained: "This experiment is similar to the 'double portrait' in space. The convex lens can present an inverted real image beyond 2 times the focal length."

In order to reproduce the magic of the "double image" on the ground, Chen Zheng took an empty test tube, created an air column, and inserted it into the beaker filled with water. The direction of the arrow observed through the empty test tube was exactly opposite to the direction of the arrow observed at other positions in the beaker, and the students were very excited!

The vast universe is far more interesting than this. In answering the students' questions, Chen Zheng said that every night when you look up at the starry sky, nature has proved to you that the speed of light is limited; when the weather is good, people can see very distant stars, perhaps from 5 years ago, 50 years ago, or even millions of years ago... What we see is like a star-version "epic".

Further reading

No great scientific achievement is achieved overnight. In the "Advanced Class", Li Yili, the first deputy chief designer of the Shenzhou spacecraft, who has been engaged in the research and design of rocket and spacecraft systems for nearly 60 years, introduced the history of my country's manned space program to the students.

Li Yili introduced that on April 24, 1970, shortly after my country launched its first artificial satellite, Chairman Mao Zedong signed a report on the development of manned spacecraft in my country. The spacecraft, named "Shuguang-1" at the time, was scheduled to be launched at the end of 1973. Since then, my country has begun to train reserve astronauts, and related research and development work has also been carried out one after another. In April 1971, more than 80 units and more than 400 experts and scientific and technological personnel across the country carried out the demonstration and development of "Shuguang-1" in an all-round way. Due to certain historical reasons, many manned spacecraft work could not be carried out, and the development plan of long-range rockets was also forced to be postponed. Although it failed to be successfully launched, the research results of "Shuguang-1" laid a certain foundation for the conceptual research and development of the Shenzhou manned spacecraft project. It was not until 1992, after the "921 Project" was established, that China's manned space program gained new life.

Today, the Chinese finally have their own space station. Although Li Yili, who worked hard on Zhichun Road in Haidian District, Beijing, has white hair now, his eyes still twinkle with stars when he recalls the journey home accompanied by the moonlight...

Source: Popular Science Times

Author: Epic

Editor: Wu Tong

Review: Wang Fei

Final judge: Chen Lei