A glass of water for the space station?

Recently, some foreign netizens found that the water did not float out of the cup during the space class at the Chinese space station, suspecting that it was not filmed in the space station environment. In response to questions from foreign netizens, Pang Zhihao, the chief scientific communication expert of national space exploration technology, said in an interview with a reporter from China News Agency that this is actually a natural science phenomenon in the space environment in which the surface tension of water is at work in the weightless environment of space. .

Some foreign netizens believe that objects should be weightless in space, but when the Chinese space station is teaching in space, the water is still the same as on the ground. A “conspiracy theory” was unfolded, doubting whether China did not launch a space station at all, and that the “Tiangong” was nothing more than a “prop” filmed on the ground.

In this regard, Pang Zhihao believes that individual foreign netizens only know the weightlessness of water and do not know the tension of water, which is a typical example of “only knowing one and not the other”. Water cannot float out of the water cup. This phenomenon is due to the surface tension of water. Even if the cup is turned upside down, the water will not flow down. This is the characteristic of water in the weightless environment of space. In fact, on the ground, the liquid also has surface tension, but it is also affected by factors such as gravity and is not easily observed.

As we all know, on the ground, when the cup is full, the water will flow down along the wall of the cup, but careful observation can find that when the cup is about to be full, the water level will gradually rise, and when it is higher than the rim of the cup, the water will not fall. The surface of the water is like an inflated balloon. With the increase of water, it gradually becomes richer, until it is higher than the rim of the cup to a certain extent, the water will flow down the wall of the cup. When the water is about to fall, the water surface is tightly covered with a water film, preventing the water from flowing down, which is the surface tension of the liquid.

In the weightless environment of space, since water does not flow to low places, how do astronauts “pour” water into the cup? Pang Zhihao said that there are many ways to put water into the cup, such as first sealing the cup with a film, then injecting water with a needle, and removing the film after the water adheres to the cup.

Regarding why astronauts don’t drink water directly from cups during their “business trips” in space, Pang Zhihao said that if the astronauts drink water from cups in space, the water will fly out immediately when the astronauts suck with their mouths, so they need to use drinking bags or straws to drink water.

There are also foreign netizens who asked why the water cup can be placed on the table as smoothly as it is on the ground when teaching in space? Pang Zhihao pointed out that this is very easy to achieve, as long as the bottom of the cup and the table top are glued with pull-tabs.

Pang Zhihao said that space teaching at the Chinese space station is a brand-new way to open up science education. Some foreign netizens have observed these details, which shows the importance of global space science. In space teaching, almost every detail reflects the difference between heaven and earth, breaking people’s daily life experience and original cognition. It can make the public, especially children, rethink the common phenomena in life, and invisibly convey the attitude and spirit of respecting science.