South-to-North Water Diversion Immigrants to Liu Yang

Editor's note: I didn't expect that one day, it will be as difficult to prove that I live on the earth as it is to prove that I am not a brain flower in a jar.

The sunshine here is strong, the water waves are gentle and the east wind is constant. Darkness and light alternate every 24 hours, and the parameters such as surface area, gravity and magnetic field are almost the same as those of the earth ... Teacher Liu Yang built such a tube in space, but because it was made so much like the earth, even he began to suspect that we still lived in the same place, or we were meeting the drum-shaped space station where Rama and Blissful Space were slowly rotating.

Quick, call a taxi, tell the master to "go to the end of the world" and see if he will hit an obstacle. Write in big letters: Please don't open the lid while dehydration is in progress.

The world in the barrel

Author | Liu Yang

Sooner or later, the sun will come to the end of the star's life. After a short explosion, it will become a red giant. The process of explosion will flood the whole earth orbit and completely destroy the ecological environment on this planet that allows human survival. But that was a long time ago. Before that, maybe man himself will make a mess of the whole earth, so that he has to leave the earth and find another way out. In The Wandering Earth, Liu imagines the whole earth as a huge spaceship, and pushes it out of the solar system. But perhaps there is another more pleasing way: we can build an ecosystem the size of the earth and greatly reduce the energy needed to propel this ecosystem for space travel.

That is to build a huge roller-shaped space station, similar to Clark's Rama series spacecraft, but our space station is much bigger than Rama. The cylinder radius of this space station is equal to that of radius of the earth, and the length is consistent with the diameter of the earth. The inner surface area of the cylindrical space station (except the two circular tops) constructed in this way is equal to the surface area of the earth, which ensures that the whole ecosystem is complex enough and will not fall into a state of collapse in a short time.

The space station rotates around the axis of the cylinder, thus building an artificial gravity equal to that of the earth on the inner wall of the cylinder. The linear rotation speed of the cylinder wall is 7.9km/s and the rotation period is about 84 minutes. As long as the rotating speed is kept, all the objects rotating with it on the cylinder wall will be subjected to a centripetal acceleration equal to the acceleration of the earth's gravity, and feel that they are still in the earth's gravity circle. Many tangential propulsion systems are evenly distributed on the outer wall of the space station. When the rotation speed of the space station deviates from the above value, the correction signal from the sensor will activate it, so as to adjust the rotation speed of the space station in time.

Another difference with the Rama spacecraft is that our space station is actually composed of two layers of cylinders. Humans live on the inner wall of the outer cylinder. If they look up, they will not see the "ground" on the other side of the cylinder, but the "sky"-a cylinder with a radius smaller than that of the outer cylinder. A lighting system simulating sunlight is distributed on one half surface of the inner cylinder, while the darkness simulating the environmental state at night is distributed on the other half surface. The inner cylinder and the outer cylinder rotate in the same direction, but the rotation speed is slightly slower than that of the outer cylinder-specifically, its rotation speed makes the outer cylinder make just one more revolution than the inner cylinder in 24 hours. In this way, the human on the inner wall of the outer tube will experience a day and night within 24 hours to conform to the biological clock originally formed on the earth.

Therefore, on the space station, the outer cylinder layer is usually called the "crust", and its inner surface is the land where human beings live, while the inner cylinder layer is called the "celestial shell", which constitutes the sky that people can see. The distance between the two shells is about 20km, and it is filled with air, and the total amount of gas is roughly equivalent to the earth's atmosphere.

In this space station, besides gravity and day and night, we can also simulate most of the geographical features existing on the earth. For example, in this new world, there is also a "geomagnetic field". That's because under the influence of cosmic radiation and other factors, the outer shell of the space station will inevitably be charged with static electricity, and the inner and outer shell layers will rotate at different speeds, thus forming a magnetic field with uniform intensity parallel to the axial direction of the cylinder in the area between the outer shells. If we imitate the name on the earth, according to the direction of the magnetic field, we can call one end of the cylinder the south pole and the other end the north pole-but there is no pole, because the magnetic field lines will not converge at a certain point at the end of the cylinder.

If we adjust the intensity of artificial sunlight so that the light intensity at the north and south poles is weaker than that in the middle of the cylinder, then we can simulate various climatic zones such as cold zone, temperate zone and tropical zone: the two sides of the cylinder are cold zone, temperate zone and tropical zone are arranged in turn, and the center line of the cylinder is equator. In this way, people can choose their own climate zone according to their original residence on the earth.

The temperature difference between climatic zones also brings atmospheric circulation: at high altitude near the "celestial crust", the atmosphere moves from the equator to the poles, while on the ground, the atmosphere moves from the high pressure area of the poles to the low pressure area of the equator. Of course, in addition to the characteristics of air flow in the north-south direction, there is also a phenomenon that air moves in the east-west direction relative to the "crust" (that is, the direction perpendicular to the axis of the cylinder). Because the rotational speeds of the "celestial crust" and the "earth crust" are different, according to Newton's law of viscosity, the air between the two shells can be regarded as many parallel air layers, and the speed of each layer is different. The closer to the earth's crust, the faster the air speed. From the perspective of human beings living on the earth's crust, air flows from east to west, which means that there is a never-ending easterly wind blowing all year round. Therefore, in general, in the northern part of the New World (north of the equator), the main wind direction is southeast wind; In the south of the New World, the main wind direction is the northeast wind.

It can be seen that in the whole new world, the environment people feel is almost exactly the same as the earth. Therefore, it can be considered that life style and social organization form will not change much after people migrate from the earth. There are still continents and oceans close to the outline of the earth on the "crust", and the distribution of countries and cities is roughly the same. High-speed rail is the main means of transportation between cities. Of course, if you want to travel a long distance, such as from China to the United States, or move from one side of the earth's crust to the other, you need to rely on a new type of transportation, not an airplane-a "ladder".

Seen from the earth's crust, the ladder is a towering tower. They are actually some super-long elevators that run through the whole space station, and their maximum length is the diameter of the cylinder (12800 km). People ride a ladder, from the earth's crust up, through the atmosphere, and then through the earth's crust, into the vacuum zone in the middle of the inner shell, and then through the earth's crust again on the other side, back to the living area. The whole process takes about two hours. In the first half of the journey, as the elevator rises, the gravity that people feel will gradually decrease, and they will experience a state of complete weightlessness on the axis of the cylinder. Therefore, during the whole process-especially in the middle-passengers must fasten their seat belts in order to fix their bodies on the seats. In the second half, on the contrary, the "gravity" will get bigger and bigger, and the direction will be opposite to that before. So in the second half, the elevator will turn up and down, otherwise the passengers will arrive at the station head down.

At this point in the discussion, we found that life on the space station is nothing new and strange except that the ladder is slightly beyond the experience of modern people. So, if we smuggle a person from the earth to the space station, can he soon find that he is no longer on the earth? I'm afraid it's difficult.

On the earth, observing the sailboats at the end of the sea level always shows the top of the mast first, which is the early evidence that the earth has a radian. However, if you look at the sea level on the space station, its end will extend in the direction of the sky and eventually connect with the sky. If a sailboat comes from far away, we will first find its submerged hull at the junction of the sea and the sky, and then gradually go up and see its deck and mast on the deck. However, this method requires us to be able to see a very far area, which is probably difficult to do if you are in an ordinary living area.

In addition, in theory, in such a cylindrical space station, when you move at the same speed along or against its rotation direction, you feel different gravity. When you move in the direction of rotation, "gravity" will increase, on the contrary, "gravity" will decrease. This is because our movement changes our linear velocity relative to the central axis of the cylinder, thus affecting the size of the centripetal acceleration. However, because the linear speed of the "crust" rotation is too large, the general speed can't change the "gravity" at all. So it is not feasible to judge where you are by this.

So, is there really no simple way to tell where we are? In Inception, people can tell whether they are dreaming by spinning the top. In the space station, there is actually a very simple way to judge whether the gravity we feel is real or artificial. The method is as follows:

To prepare a server, first of all, carefully adjust its ball outlet pipe to keep it vertical. In this way, the ball emitted from it will be thrown vertically. In order to avoid the influence of wind, we must choose a windless time to do this experiment and choose a heavier ball. Start the server and observe where the ball landed. If it is on the earth, because the service tube is vertical, the ball will fall back to its original position, and it is likely to hit the service tube, or it will be randomly distributed very close to the service tube (considering the irregular vibration of the service tube).

However, if you are on a space station that generates artificial gravity by rotation, the experimental results will be very different: you will see that all the balls have a displacement in the horizontal direction and fall on a point just east of the throwing point. And this horizontal displacement distance will increase rapidly with the increase of throwing speed. For example, when the throwing speed is 20m/s, the horizontal displacement distance is about 14cm, while when the throwing speed is increased to 30m/s, the horizontal displacement distance has increased to about 47cm.

Readers, if you happen to have a server or similar equipment around you now, you might as well try it right away. Maybe you will be surprised to find that you are no longer on the earth. ...

Note: This article first appeared in the "Non-existent Everyday" column of the science fiction world in August 20 16.

Keywords: # Liu Yang # # Space Station # # Earth # # arthur clarke #

Editor: Gao Xiaoshan, captain