According to the latest news, the list of Shenzhou 18 astronauts has been determined, and the flight mission will be carried out at 8:59 on April 25 to replace the three crew members of Shenzhou 17.
Judging from the information released so far, Shenzhou 18 will perform two out-of-cabin missions during the mission, that is, two spacewalks. From the audience's point of view, a spacewalk is a very romantic event, but from the perspective of an astronaut, this is not the case.
Zhai Zhigang, the first person to walk in space, once gave an interview after returning from space, in which he mentioned the real feeling of spacewalking, which is completely different from the feeling of ordinary people.
According to Zhai Zhigang, the moment he opened the hatch, he saw a piece of azure blue, but when he looked down, outer space was black, the kind of black that he couldn't see anything, like nothingness.
The spaceship is suspended in the dark space, and even the Earth is suspended in space. There is nothing to support, and all of them are not relied on. At that moment, he had a feeling that the earth was not safe, and he was afraid that the earth would drift away from space.
We can close our eyes and imagine this picture, in the darkness and vastness of space, the earth is suspended in the air alone, without any fulcrum, without any support. It has been suspended for 4.5 billion years, and it will be suspended for billions of years in the future.
This kind of experience is on the earth, completely incapable of feeling the shock, so the question is, why does the earth float in space, neither falling nor floating away, just suspended there?
Why can the Earth's 60 trillion tons be suspended in space?
According to scientists' estimates, the weight of the earth is 5.965*10^21 tons, because there are too many zeros behind, there is no specific concept, so when converted into an easy-to-understand weight, it is 60 trillion tons.
In our daily lives, it is often talked about how much it weighs. What we call weight is just a physical property of an object that is affected by the gravitational pull of the earth, and this weight is affected by the gravitational pull of celestial bodies.
For example, if an object of 6 kg on Earth is on the Moon, it will weigh only 1 kg, because the gravitational pull of the Moon is only about 1/6 of that of the Earth.
However, mass is different, mass is only one of the basic properties of matter, and does not change with the change of the external environment. Therefore, when describing the size of a celestial body, it is generally the mass used.
Due to the existence of weight, that is, the existence of gravity, when people act on the earth, they will have a sense of down-to-earth, with fulcrums and supports.
People are already familiar with this feeling, but why does this feeling of being grounded? More than 200 years ago, someone gave the answer, and that is gravity.
In fact, everything has a gravitational force, from everyone to a celestial body, to its own gravitational field. It's just that the gravitational pull of the human being itself is very weak and negligible. And because of the huge mass of celestial bodies, such as the mass of the earth reaches 60 trillion tons, its gravitational pull is very obvious.
Newton actually only discovered the phenomenon of gravity, but did not understand why objects produce gravity, until Einstein gave the answer, that is, the more massive the object, will cause space distortion, just like an iron ball falling on a spring mattress, it will form a bowl-shaped gravitational field, the closer the object, the faster it will fall down.
In fact, Einstein only explained the reason for this phenomenon, and so far, the nature of gravity has not been clarified, but this is not the focus of this article.
Therefore, the reason why the earth is able to float in space is actually affected by the gravitational pull of the sun. Logically speaking, just like an apple falls to the ground, the earth will also fall into the sun, so why not fall, but instead suspended in space?
Why didn't the Earth fall into the sun
If this is the case, the Earth should have fallen into the Sun under the Sun's enormous gravitational pull, so why didn't it fall, but was suspended in space?
There are two main reasons for this: distance and speed.
1. Distance
Gravitational force is a long-range force, and the theoretical range of gravity is infinite, which is why the distance of gravitational waves can reach 1 billion light-years for the first time.
Therefore, the major planets in the solar system are releasing their own gravitational pull, and the entire solar system is full of various gravitational forces. However, gravity is directly proportional to mass, and the greater the mass of a celestial body, the greater the gravitational pull it releases. The Sun is the most massive object in the solar system, accounting for about 99.8% of the mass of the solar system. As a result, the entire solar system is affected by the sun's gravitational pull.
Although gravity is proportional to the mass of the celestial body, gravity is inversely proportional to distance, which means that the farther away you are, the more the effect of gravity is attenuated. The Earth's distance from the Sun is very far, reaching 150 million kilometers.
Since this distance is far enough, the gravitational attenuation is more powerful. The reason for distance is one of the reasons why the earth is suspended in space, and another reason is speed.
2, Speed
A very important reason why probes and satellites in space can float in space is speed. To make an analogy, a child with a rope tied to a ball, under rapid motion, will get rid of gravity and float, and gravity is like the middle rope, as long as the speed reaches a certain level, the ball can levitate.
The reason is that in this process, the kinetic energy is greater than the potential energy generated by gravity, so that the earth can get rid of part of the gravitational pull and not fall into the sun, forming a kind of equilibrium.
As long as the velocity of an object on the earth reaches the first cosmic velocity, which is 7.9 km/s, it can move in a circle around the earth, so as to levitate above the earth, as long as the speed decreases, it will be pulled by the gravitational pull of the earth and fall down.
Although Zhai Zhigang saw that the earth was suspended in the air, as if it was not moving, in fact, the earth was moving at a high speed all the time, and its speed reached 29.79 km/s, which has exceeded the speed of most human detectors.
Therefore, the earth can be understood as a huge spaceship in the solar system, taking humans to fly quickly in the solar system, as long as the speed reaches a certain level, you can get rid of the gravitational pull of the sun and take humans to other galaxies, and the wandering earth can really have.
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