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

One thing to say, "wandering Earth 2" is really good, in the face of epic narrative and Chinese-style positive energy, Marvel snapping fingers is suddenly too pediatric and boring.

"wandering Earth 2" movie posters, however, like it, since you have all the good things to say, as a nuclear engineer, there is no point in putting on the icing on the cake, so we have no choice but to pick on the magnifying glass and find fault with it.

As a reminder, the following content involves a slight spoiler. Friends who have not yet seen the movie can share this article to the moments and come back to read it after watching the movie.

Did you find that Da Liu likes nuclear fusion in wandering Earth 2? The main settings of wandering Earth 2 are almost all related to nuclear fusion:

Solar helium flash is a kind of nuclear fusion.

The planetary engine used to push the earth away, which also relies on heavy nuclear fusion, can generate 150 trillion tons of thrust, so large that only Eurasia and America can bear it.

Many of the 3614 nuclear bombs detonated on the moon were hydrogen bombs based on the principle of nuclear fusion.

Crucially, these nuclear bombs also triggered fusion at the core of the moon, shattering the moon and saving mankind!

Nuclear fusion is the process of combining several lighter nuclei into a heavier nucleus.

Nuclear fusion on the sun, for example, can be generally thought of as the aggregation of four hydrogen nuclei into a helium 4 nucleus (made up of two protons and two neutrons).

Because the nucleus of helium 4 is lighter than the four hydrogen nuclei combined, the depleted mass is converted into energy, so the nuclear fusion inside the sun can release huge amounts of energy, allowing the sun to emit light and heat continuously.

As for the subsequent helium flash, three helium 4 are polymerized into a carbon 12 nucleus.

The sun's energy comes from nuclear fusion in the sun's core. "wandering Earth 2" trailer screenshot the hydrogen bomb in the nuclear bomb and the controlled nuclear fusion device is deuterium-tritium fusion. Deuterium and tritium are also hydrogen elements, but the deuteron is a proton plus a neutron, and the tritium nucleus is a proton plus two neutrons.

Deuterium-tritium fusion forms a helium 4 and a neutron, which can also release a lot of energy, so the hydrogen bomb is far more powerful than the atomic bomb.

The process of deuterium-tritium fusion produces a helium 4 and a neutron, and releases energy. in the big wave of "wandering Earth 2" nuclear fusion, the most reliable thing is the more than 3000 nuclear bombs made by humans, which can really explode, and the goods are genuine, both young and old.

The heavy nuclear fusion of the planetary engine and the more amazing nuclear fusion of the moon are described in one sentence: it is difficult to bring God here!

Well, I'm sure a lot of people will think that my brain is locked by Tomoko (now the "three-body" TV series is also very popular), but in the current laws of physics, I can only come to this conclusion.

Planetary engine

The Planetary engine in wandering Earth 2. Screenshots of the movie trailer first talk about the 12000 magnificent planetary engines. Without it, the earth would not be able to set out to wander.

The planetary engine is probably the most powerful engine ever described in science fiction. Big Liu can imagine this thing, the movie can make it convincing, the author is really very impressed!

In terms of scientific principles, planetary engines basically make sense. Planetary engine fuel is made of stone, and the bulk of the stone is silicon, which can be fused to form iron nuclei and release energy at the same time.

The watchman asked, why not use deuterium, tritium or hydrogen as fuel? These can be extracted from sea water. The reason is that the consumption of planetary engines is so large that the sea water on the earth is not enough to burn. Therefore, it is better to have stones everywhere. They are inexhaustible.

The structure of the planetary engine is not described in detail in the original novel, only that it has a height of 11 kilometers and a diameter of 50 kilometers at the bottom. Trucks pour stones through the feed ports, and the nozzles at the top of the engine spew huge plasma jets upward.

The movies "wandering Earth" and "wandering Earth 2" reproduce these huge engines on the screen, and they are full of details. The author speculates that the planetary engine should come from the current magnetically confined controllable nuclear fusion device, namely tokamak.

Planetary engine under construction in wandering Earth 2 Movie poster even the lower threshold of deuterium-tritium fusion requires stringent conditions. This is because nuclei are positively charged, and to trigger fusion, you need to keep them close to 10-15 meters, which is less than 1/100000000000 of a hair. As the so-called homosexual repulsion, the charge carried by the nucleus will produce a huge repulsive force at such a short distance.

An extremely high temperature is needed to overcome this repulsion. Deuterium-tritium fusion on Earth requires a high temperature of about 100 million ℃, even higher than the center of the sun.

The central temperature of the sun is only about 15 million ℃. It can achieve fusion because of the high pressure and mass of the core. Even if the temperature is low, the probability of fusion is low, but its huge mass makes the total power of fusion still very large.

At a high temperature of 100 million ℃, no substance can remain solid and become plasma, and no container made of any material can hold these plasmas, so it needs to be restrained by a magnetic field to prevent the plasma from touching the container wall directly.

The tokamak device constrains the plasma in an annular vacuum chamber for fusion. At present, the international thermonuclear test reactor ITER under construction is a tokamak, which can generate 10 times the input energy of fusion, but there is no controllable fusion device to achieve continuous output of fusion energy.

International thermonuclear reactor under construction ITER if the planetary engine achieves continuous and controllable silicon nuclear fusion, it also needs to overcome a big problem, that is, how to convert energy into the momentum of plasma jets.

At present, the fuel density in the vacuum chamber of the tokamak is very low, even if the temperature reaches hundreds of millions of degrees, the pressure is not high, and the highest is only 2.05 atmospheric pressure. With this pressure, it is impossible to produce a high-speed jet like a planetary engine.

Wandering Earth 2 movie poster so the planetary engine must achieve nuclear fusion at extremely high density and high pressure, and to control such a high-density plasma requires an unimaginably strong magnetic field. Do not let the feed and jet destroy the stability of the plasma. This difficulty is unimaginable with existing scientific and technological capabilities, and perhaps future human beings will be able to do it.

But can this kind of silicon nuclear fusion really be realized on Earth?

Heavy nuclear fusion takes into account that the planetary engine burns stone, that is, the fusion of silicon nuclei, which is more demanding than deuterium-tritium fusion, because the larger the atomic number, the greater the electric charge. the stronger the repulsive force.

Hydrogen nuclear fusion can take place in the interior of the sun at 15 million ℃, or even lower, but helium flashover, that is, from three helium 4 to a carbon 12, requires 100 to 200 million ℃, and a large amount of helium 4 has to be accumulated as stars do in their later years.

For the real sun, this condition will take at least billions of years to achieve, so there is no need to worry about the solar helium flash crisis within 100 years, as the "wandering Earth" setting.

For fusion of two silicon nuclei (14 protons + 14 neutrons), the repulsive force between charges is much greater than helium fusion, you can imagine how difficult it will be.

Direct fusion of two oxygen nuclei (8 protons + 8 neutrons), which is much smaller than the atomic number of silicon, requires a high temperature of 1.5 billion ℃ and a high density of 10 million tons per cubic meter.

There are few literatures about how high conditions are needed to realize the fusion of two silicon nuclei. Some articles say that 3 billion ℃ is needed, which is a reasonable guess.

So even in the interior of a star, fusion from silicon nuclei to heavier nuclei does not simply add up to two silicon nuclei, but constantly absorbs helium 4 nuclei, adding two atomic numbers each time, a total of seven additions, to fuse to nickel 56 nuclei. This nucleus is so unstable that it quickly decays into cobalt 56 and then into stable iron 56 (26 protons + 30 neutrons).

The process of fusion within a massive star to form iron 56, but this process cannot be achieved by our sun, requiring stars with more than 8 times the mass of the sun to eventually produce iron 56.

In other words, the planetary engine in the wandering earth needs to simulate the internal environment of a massive star several times larger than the sun before it is possible to burn "stone" and realize silicon fusion. But the problem is that there is not so much helium on earth. Helium resources have always been scarce and are not as easy to find as stones.

Therefore, the planetary engine must achieve high temperatures of 1.5 billion-3 billion ℃ and unimaginably high density, so that the silicon nucleus and oxygen, magnesium, or its own defusion.

Do you think this condition can be realized on earth?

Even if it can be realized, there will be a basin of cold water next, that is, from silicon polymerization to iron, it will not release a lot of energy!

This is because the specific binding energy of the nucleus is different.

The specific binding energy is the total disassembly of a nucleus into nucleons, averaging the energy required for each nucleus. The higher the specific binding energy, the more stable the nucleus.

The specific binding energy of different nuclei changes from hydrogen or deuterium-tritium to helium 4, which increases very fast, so a lot of energy is released, but from helium 4 all the way up to iron 56, the specific binding energy increases slowly, and the energy released is very limited.

For the sake of this limited energy to achieve the extreme conditions at the core of a massive star, even if it can be done, the loss may outweigh the gain.

After the nuclear explosion of the moon, let's talk about the "burning stone" planetary engine, and then talk about the bombing of the moon in wandering Earth 2.

This is such a big brain that people have to admire the imagination of the screenwriter. after all, the original novel only pushes away the moon without blowing it up.

But 3614 nuclear bombs are obviously not enough to blow up the moon. It is also mentioned in the film that the energy generated by these nuclear bomb explosions is only 10 / 1/100000000 of the energy needed to destroy the moon. Because although the moon is much smaller than the earth, it is still very large, with a diameter of 3476 kilometers. Even if there were tens of thousands of nuclear bombs, it would only tickle the moon and stir up a cloud of dust.

So the movie is set to put these bombs in a huge crater to form an array, by precisely detonating the nuclear bomb array, causing the fusion of the core of the moon, and then blowing up the moon.

Detonate the moon | "wandering Earth 2" trailer screenshot these nuclear bombs only act as a "trigger" or "fuse", a bit like the principle of a hydrogen bomb: an atomic bomb is used as a fuse, triggering fusion of deuterium and tritium.

However, in the detonation process of the hydrogen bomb, the atomic bomb does not directly rely on high temperature to cause fusion, but uses the X-rays produced during the explosion to compress and heat the fusion fuel, so as to achieve the condition of nuclear fusion.

The lunar crust is mainly composed of rocks, which is not conducive to the propagation of X-rays, so the author speculates that the shock wave produced by a nuclear explosion may be used to achieve instantaneous compression of the lunar central point to trigger lunar nuclear fusion.

At this point, everything makes sense, but then it goes too far. Because the moon, like the earth, has an iron core, that is, the main component of the lunar core is iron 56.

As mentioned earlier, the volume of the moon is not small, larger than Pluto, so there will be element differentiation within it. In the early days of the birth of the moon, the internal matter was in a state of melting, so heavy matter continued to sink and light matter continued to float. Because metals such as iron are relatively heavy, they gradually "sink" to the center to form a metal core, mainly iron, with small amounts of sulfur and nickel.

Iron 56, the internal structure of the moon, is very famous in the universe, its specific binding energy is the highest, and its structure is more stable than any other nucleus (except hydrogen). Fusion from iron 56 upward no longer releases energy, but requires energy absorption and unimaginable extreme conditions-for example, when the shell of a massive star collapses inward into the core at the moment of a supernova explosion, or when two neutron stars merge.

Most of the earth's elements with higher atomic numbers than iron, such as gold, silver and uranium, are formed under these extreme conditions.

Instantaneous schematic diagram of the merging of neutron stars | can such a condition be formed with only more than 3000 nuclear bombs in University of Warwick / Mark Garlick? Obviously not!

Even if it is really wrong, with a very small probability, a lost iron 56 at a certain point will be fused, because this fusion is an energy absorption reaction, it will not produce a violent explosion, and the energy of the nuclear explosion shock wave will be absorbed directly.

Some people say that lunar nuclear fusion can also be seen as a supernova explosion, because there is also an iron core before a supernova explosion. This idea is grossly wrong.

A supernova is a big explosion of a massive star at the end of its life. the cause of the explosion is not because of iron core fusion, but because the massive star burns up everything that can be fused, and the rest of the iron core does not converge, losing the power to resist gravitational collapse. under the action of huge gravity, the star's shell crashed into the inner iron core, which triggered the Big Bang.

Diagram of a supernova explosion so the energy source of a supernova explosion is the gravitational potential energy of the star itself, not the fusion of the iron core. For a planet as small as the moon, there is no need to rely on fusion to resist gravitational contraction, so it is impossible to have a supernova explosion.

So, you want to blow up the moon? Even if he handed over more than 3000 nuclear bombs to God, he could only spread out his hands: it was impossible!

Then again, wandering Earth 2, as a science fiction movie, requires a huge imagination, and it is inevitable that there are some unreasonable places in science. As long as it can meet the needs of the plot and promote the development of the plot, it makes sense logically!

Just like the author, although I have found so many faults, I am still interested in watching movies in the cinema, which is definitely the pinnacle of sci-fi movies.

Say no more, this is the second brush!

This article comes from the official account of Wechat: fruit Shell (ID:Guokr42), author: Sagittarius A

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