Do astronauts sleep while floating? Can the space environment cause genetic mutations? Let's find out what the truth is!

April 24, 2023 is the eighth " China Space Day ". This year's theme is "Studying Things to Gain Knowledge and Questioning the Sky".

Facing the mysterious and vast universe, astronauts are the people at the forefront. They are the ones who travel between the stars and are the focus of public attention. Therefore, many questions arise about them, such as, do astronauts in the space station sleep while floating? Will living in space change human genes? Will astronauts get fat in space? Is this really the case?

Today, Science Rumors Refutation and China Aerospace Culture and Creativity have teamed up to reveal the truth.

Image source: Copyright Library

01

Rumor: On Earth, we go to bed every night and wake up in the morning. Even if an accident happens occasionally, we just fall to the ground. But in space, because the spacecraft flies around the earth at high speed, a weightless environment is formed, causing the astronauts in the space station to sleep while floating.

Analysis: This is not true. Floating in a small cabin can easily cause collisions with various instruments and equipment, which can be dangerous. Therefore, astronauts must specifically secure themselves when sleeping.

In the early stages of the Shenzhou spacecraft mission, astronauts fixed their sleeping bags in the cabin and then crawled into them to sleep.

Now that China's manned space program has officially entered the space station era, today's astronauts are extremely happy because they have spacious and comfortable independent sleeping areas. The Tianhe core module and the Wentian laboratory module of China's space station each have three independent sleeping areas.

The sleeping area of ​​the Tianhe core module is set up horizontally, and the astronauts sleep "lying down". The sleeping area of ​​the Wentian laboratory module is set up vertically, and the astronauts sleep "standing up". However, in a weightless environment, there is no difference in the feeling when sleeping.

In the sleeping area, astronauts can flexibly choose the way to fix the sleeping bag according to their preferences. Some astronauts prefer the more stable fully fixed method, while some astronauts prefer a freer floating feeling and adopt a semi-fixed method to allow the sleeping bag a certain amount of space to move.

The designers also thoughtfully set up a porthole for each sleeping area, so that if you like, you can enjoy the beautiful space view at any time.

02

Rumor: There are many kinds of radiation in the universe where the earth is located, and astronauts will live in space for a long time when performing their missions. They are out of the atmosphere, and these cosmic radiations will seriously change their genes.

Analysis: This statement is very one-sided and has no strong scientific basis. There are indeed many types of radiation in the universe, and radiation is also one of the important reasons for inducing gene mutations. However, the space that can be reached by manned spaceflight in various countries is still in "near-Earth space" and is protected by the Earth's magnetic field. In addition, the spacecraft cabin and the space suit outside the cabin will block most of the cosmic rays for them. Scientific researchers will also conduct radiation dose checks on astronauts to ensure their health.

Genes, also known as hereditary factors, support the basic structure and performance of life. All life phenomena such as the birth, growth, aging, disease and death of organisms are related to genes. Genes are generally very stable and can accurately replicate themselves in every replication. However, the stability of genes is relative, and sometimes genes will mutate.

Gene mutations give species a precious opportunity to adapt to environmental changes, and are the key to the survival of existing species on Earth, including humans. However, gene mutations are likely to have negative effects on individual life. Modern medical research has found that radiation is one of the important causes of gene mutations, and in the universe where the Earth is located, there is an ionizing radiation environment formed by galactic cosmic radiation, geomagnetic capture radiation, and solar proton events, as well as non-ionizing radiation such as ultraviolet radiation and radio frequency radiation.

The scientific community generally believes that without the protection of the atmosphere and the Earth's magnetic field, life on Earth would not be able to survive in such a strong radiation environment. However, as the pioneers of human exploration of the universe, astronauts must work in outer space without the protection of the atmosphere. When astronauts enter space, they are protected by the spacecraft cabin and space suits outside the cabin. These high-tech equipment will block most of the cosmic rays for them, but even so, the radiation dose they receive in space is much greater than that of people on Earth.

The issue of genetic changes in astronauts in the space environment has always been an important issue of concern to major space powers, and the radiation doses received by astronauts are also being monitored in the space station.

One of the most representative studies on human genetic changes in space is NASA's comparative study of a pair of identical twin astronauts, Scott Kelly and Mark Kelly.

In 2015, Scott carried out an unusual space mission, staying in the International Space Station for 340 consecutive days, while his twin brother Mark worked on the ground. This mission provided an extremely rare research opportunity. In the 2019 issue of Science magazine, researchers published a research report that found that after entering space, Scott's DNA methylation rate was lower than Mark's, but the maximum difference was no more than 5%; at the same time, some of Scott's genes, especially those related to the immune system, also showed abnormal expression, but six months after returning to the ground, more than 90% of the abnormally expressed genes returned to normal.

According to the results of this study, after nearly a year of continuous space life, Scott did not show any long-term, major epigenetic changes, which is an exciting result. Although the results of this study cannot draw a universal conclusion because the subjects of this experiment were only two people, it is still of great significance for people to understand the impact of the space environment on human health, especially genes.

At present, my country's Tiangong Space Station and the International Space Station have maintained the practice of each flight crew to perform a six-month mission in orbit, and will conduct radiation dose checks on each astronaut who has performed a flight mission to ensure their health. As more people around the world have the opportunity to enter space, research on the impact of the space environment on human genes will continue to deepen, and fully prepare and respond to human beings' future journey to the stars and the sea.

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03

Rumor: In the "Tiangong TV" program we can see the real condition of the astronauts in space. At the same time, many careful netizens discovered through this program that the astronauts' faces in space are obviously bigger than when they are on the ground. So there are rumors that the food in the space station is too good and the astronauts have gained weight.

Analysis: Netizens are actually half right. The food in the space station is indeed good, but the reason why the face looks fat is that in a weightless environment, more body fluids are distributed in the head, so the face looks as if it has gained weight.

Because astronauts are prone to water loss and muscle atrophy in a weightless environment, their weight will generally decrease by 2 to 3 kilograms.

The real reason why the face looks fat is that in a weightless environment, the distribution patterns of various body fluids, including blood, in the body have undergone corresponding changes. Compared with the ground environment, the most obvious thing is that more body fluids are distributed in the head, so the face looks like it has gained weight.

In addition, there are also symptoms such as nasal and oral mucosal congestion, eye socket swelling, and head and neck vein dilation. When more body fluids are distributed to the head, they will inevitably be distributed less in the lower limbs, so when the astronauts' faces become fatter, there is another phenomenon that is not easy to observe: their legs become thinner.

These phenomena are most obvious in the first few days after entering space. As the human body adapts to the weightless environment, they will gradually ease to a certain extent, and the astronauts will fully recover after returning to the ground for a period of time.

in conclusion

Astronauts in the space station will specially secure themselves when they sleep; radiation in the universe can induce gene mutations, but currently human activities in space are still within the protection of the Earth's magnetic field. At the same time, the spacecraft cabin and the spacesuit outside the cabin will block most of the cosmic rays. Scientific researchers will also conduct radiation dose checks on the astronauts to ensure their health; affected by the weightless environment in space, blood and other body fluids will be more distributed in the astronauts' heads than on the ground, so the astronauts' faces will look fatter.

Author: Wang Junyi, member of the Space Culture Communication Youth Working Committee of the China Society of Science and Technology Journalism

Tan Xinpeng, Deputy Director of Aerospace Cultural and Creative Center, Aerospace Planning and Design Group Co., Ltd.

Review｜He Chen, Engineer of Beijing Mechanical and Electrical Engineering General Design Department

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