Shulou(Shulou.com)11/24 Report--

This article comes from the official account of Wechat: SF Chinese (ID:kexuejiaodian), author: SF

In sci-fi movies like Alien, we often see a segment like this: the spaceship is ready to begin a long voyage, during which the spacecraft will be on autopilot or controlled by a robot. the crew of the ship will enter a capsule-shaped device to start a long sleep for a long interstellar journey. Perhaps some partners may ask, this is a good plan for space travel, in reality, can astronauts spend a long time in space travel through sleep?

(by Mei Lin / tr. by Robert Taylor)

In the real world, the fastest spacecraft launched by humans is NASA's Parker solar probe, which was launched in 2018 to the sun and can fly at speeds of up to 200km per second. As we all know, long-distance space travel is measured in light years-the nearest star system to our solar system is also more than four light-years away. It still takes 1500 years to sail at the speed of the Parker solar probe, so it can be said that long-range space travel is not feasible for human beings at this stage.

Going back to the original question, can humans spend long-distance space travel through sleep? The answer is no, because although human body functions such as neural response, metabolism and breathing decrease during sleep, maintaining such a long sleep still requires continuous supply of oxygen, water and various nutrients for the human body. Moreover, the human body is also constantly aging, which still does not solve the problem that long-distance space travel takes far longer than human lifespan, which is only based on the assumption that human beings can sleep that long.

Can people spend long space travel through hibernation? To this end, some scientists have turned their attention to hibernation. On cold winter days, the overall physical functions of some animals decline sharply-weak breathing, slower heartbeats and less sensitivity to external stimuli. These animals put themselves into a lethargic state in this way, ensuring that they survive the cold winter with very low body consumption. This is hibernation.

What attracts scientists' attention is that hibernating animals can not eat or drink during hibernation, which is too important for human beings to achieve long-distance space travel. If humans can enter hibernation, and do not need to replenish water and nutrients, only need to provide oxygen, then the hope of a long space travel will be greatly increased. However, there is another question: human beings do not have the habit of hibernating. Can non-hibernating animals like humans go into hibernation and wake up safely and healthily?

Hibernation and awakening of animals have their inherent mechanisms, which scientists do not fully understand at present. However, there is one kind of animal that has attracted the attention of scientists, that is, bears. Bear hibernation behavior is very characteristic: for a long time, sleep for half a year, do not eat or drink, and the bear hibernation is more "flexible", you can wake up at any time, but also go back to hibernation and sleep. This kind of hibernation is perfect for human long-distance space travel-in such a state of hibernation, the body's metabolism slows down, body temperature drops, humans travel longer, travel longer distances, and save limited supplies.

In 2022, a team of biologists, veterinarians and forest rangers came to the ice and snow of northern Canada to explore the secrets of brown bear hibernation. Through the signal collar, the researchers found where the brown bear hibernates. After that, they collected fat and muscle samples from brown bears and brought them back to the laboratory for research, hoping to discover the mechanism of brown bears hibernating. In a laboratory in France, biologists have found that some physiological reactions in muscle cells may also occur in humans during brown bear hibernation, which may lead to hibernation.

Now that we can assume that humans can also go into hibernation, it is possible to use such a method to achieve long-distance space travel. The question now is how to make people go into hibernation and wake up healthily and safely.

Does ultrasound stimulate the human brain to cause hibernation? In previous studies, scientists have found that specific groups of neurons in the preoptic area of the hypothalamus (POA) are key brain regions that manipulate hibernation in animals. Some scientists have genetically engineered these neurons to allow some non-hibernating animals to enter hibernation through human intervention, but such techniques are difficult to apply to humans and are not safe or ethically feasible.

To this end, a team led by Chen Hong, a bioengineer at Washington University in St. Louis, used ultrasound instead of genetic engineering to manipulate some ion channels on neurons, thus manipulating POA neurons.

In the experiment, Chen Hong's team carried out experiments on mice. They used miniature loudspeakers to concentrate the ultrasound on the POA area of the mice. It was found that the core body temperature of the mice decreased by about 3 ℃. This is a typical sign of mouse hibernation. In order to make the conclusion more reliable, Chen Hong's team also conducted a comparative experiment: if the ultrasound pen is stopped for POA, the body temperature of the mice will rise and wake up from dormancy without any adverse reaction; if the mice continue to use ultrasound to treat POA during the period of rising body temperature, the mice will enter a continuous dormancy. Therefore, it can be said that the dormancy of mice (hibernation is a kind of hibernation) is controlled by the POA region of the brain.

So, we can boldly imagine: if ultrasound is used to act on the POA of the human brain, perhaps human beings can also enter a "hibernating" state, and continuous ultrasonic stimulation may lead to a long-term "hibernation", so that human beings are more likely to carry out long-distance space travel.

However, some scientists have also poured cold water on the research results. Shaun Morrison, a neurosurgery expert at Oregon Health and Science University, believes that ultrasound can heat up the brain and animals keep their body temperature constant by lowering their body temperature, which does not prove that ultrasound stimulation can cause hibernation. Moreover, the human brain is larger and deeper than the mouse brain, ultrasound can play a role in the mouse brain may not necessarily work in the human brain.

References:

Https://doi.org/10.1038/s42255-023-00804-z

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