The Moon is indeed very small, and at first glance, the horizon is close at hand (about 2.5 km), and the surface of the Moon intersects with space, showing a distinct arc.

Shortly after the sun rose from the east side of the horizon, the scorching light shone on the moon's surface, casting a large area of light and shadow, and the surrounding sky was empty and lonely, and the sky was full of stars, giving people an unusually vast and magnificent feeling. (Stars can be seen on the moon day and night, but due to the camera's light sensitivity, we will find that whether it is a Chinese or American lunar landing spacecraft, the sky photographed from the surface of the moon is always pitch black.) ）

The gravity on the moon is very small, Chen Xin tried to jump lightly on the surface of the moon twice, and he could easily jump out of a height of two or three meters, as if he could break away from the gravitational pull of the moon and fly into the universe with a little more force.

The steel hammer also jumped off the lunar rover, learned to jump and roll on the ground, and laughed excitedly: "Haha, it's so cool, Lao Dou, I haven't smelled such a pure universe for a long time." ”

Although the earth's environment is very comfortable for humans, the steel hammer is not very adaptable, whether it is viscous air or moist moisture, it feels awkward, and it likes this pure vacuum very much.

Chen Xin looked at the steel hammer that was spreading joy on the side, shook his head and smiled dumbly.

The two of them circled around the spaceship, quickly trampling the thick layer of lunar soil around them beyond recognition.

The lunar soil rose in large quantities, staining the silvery-white spacesuit with a layer of earth ash.

Since the moon has no atmosphere, there is a huge temperature difference between the sunlit area of the lunar surface and the shady area, and this drastic temperature change leads to thermal expansion and contraction, which will cause the rock to crack.

The fractured rock is exposed to the sun's ultraviolet rays, X-rays and gamma rays for a long time, and the crystalline structure of the conductive rock is destroyed. Prompting further fragmentation of the rock.

Coupled with the meteorite impact, various factors have accumulated over the years, and the rocks have gradually turned into dust-like tiny particles, and the original landform of the lunar surface has also changed.

Until now, the surface of the Moon has long been covered by a layer of lunar soil composed of small, sticky particles less than 1 mm in diameter. These lunar soils vary in thickness throughout the moon, from a few centimeters in thin places and five or six meters in thick places.

Don't underestimate lunar soil, if you take it to the earth, every gram of lunar soil is worth a thousand gold.

In addition to being used for scientific research, lunar soil is also rich in helium-3 resources. It is estimated. The total amount of helium-3 in lunar soil can reach 1 million to 5 million tons. If helium-3 is used for nuclear fusion reaction to generate electricity, 100 tons of helium-3 can meet the world's power generation needs for a year, and the total amount of helium-3 on the moon can be used by humans for tens of thousands of years.

In addition, the moon is also extremely rich in titanium, iron, cerium and other metal resources, if human beings build factories and bases on the moon in the future. They will provide sufficient material support for human lunar cities.

It is no wonder that the steel hammer often says that the solar system in which humans live is too wonderful for low-level civilizations, and that the eight planets can provide sufficient mineral energy support for human beings to develop the solar system, and the moon is the creator's divine stroke.

In a way, the Moon is as important to life on Earth as the Sun.

Without the Moon, the Earth's axis of rotation would oscillate much more than it does now, and the four seasons that are now very regular will be extremely unstable, causing global climate disorder. Very detrimental to the evolution of life.

The gravitational pull of the moon causes the oceans to create tides, prompting the Earth to flood the warm waters of the equator across the globe, and we know that life was born in the oceans in the first place. Therefore, tides are essential for the evolution of life from marine to terrestrial organisms. At the same time, warm sea water can accelerate evaporation after walking around the world, prompting the earth's continents to obtain more abundant rainfall, and also making the global temperature more balanced, providing a decisive guarantee for the survival of terrestrial life in the future.

What's more, the existence of the Moon has shielded the Earth from a large number of exoromantic meteorites, including asteroids that have destroyed life on Earth.

Such a unique condition. It has created a rich and colorful life environment on the earth today.

"Old Bean, look over there!"

The steel hammer jumped back to Chen Xin's shoulder. Pointing to the towering circular mountain path thousands of meters away.

This crater is unusually large, with a height of at least three thousand meters. When you look down from the air, the diameter is more than 60 kilometers, and I don't know what kind of majestic power it is to create such a miracle.

However, Chen Xin and Gangyi did not pay attention to the crater itself, their attention was firmly attracted by the giant spaceship that was clearly a creation of an alien civilization on the outer side of the crater.

Chen Xin swallowed his saliva and his eyes widened.

The spacecraft is only half a section, but its length reaches seven or eight kilometers, and its diameter is more than two kilometers.

Its surface is metallic and as smooth as new, and thousands of years have left no trace on it.

"Steel hammer, I'm afraid that such a spaceship is enough to hold seven billion people on the earth!" Chen Xin muttered.

Quack laughed: "Old Bean, it's just a satellite-level spaceship, it's not a big deal, when I reach the third-level civilization, I can also build it." This kind of spaceship is nothing to a fifth-level civilization. ”

"Satellite-class spaceship?"

Chen Xin thought for a moment and asked, "Gangyi, I remember that you also said before that stellar-class spaceships, river-level spaceships, I don't know what these spaceships mean?"

Quack laughed: "Old Bean, this is actually very simple, different levels of spaceships represent the size of the spaceships that can be made by different levels of civilization. From the lowest-level Meteorite-class ships to the highest-level River-class ships, there are no exceptions. ”

After a pause, Gangyi said again: "Generally speaking, there are seven levels of spacecraft from low to high, which are meteorite, small planetary, satellite (dwarf), planetary, dwarf, stellar, and river...... Among them, the size of the meteorite-star spacecraft is between 100 meters and hundreds of meters, and the second-level civilization can be manufactured, such as the International Space Station in the earth's low-earth orbit, which can be regarded as a meteorite-star spacecraft, and our dream is also a meteorite-star spacecraft. Of course, the combat power of meteorite-star spaceships manufactured by different levels of civilization is completely incomparable. The size of a small planetary-level spaceship is generally between one kilometer and two kilometers, and such a spaceship can only be built by a third-level civilization. The satellite-class spaceship is about ten kilometers away, and this kind of spaceship can be regarded as the top combat power of the third-level civilization. As for the planetary-level spaceships, they are big guys with a size of hundreds of kilometers, and they belong to the battle fortresses of the fourth-level civilization. Dwarf stellar warships have reached the level of 1,000 kilometers, and this kind of spaceship, one can easily destroy the solar system. However, in the "Universal Civilization Convention", the major intelligent civilizations are strictly forbidden to attack the stars, so you don't have to worry about it. ”

Chen Xin was a little frightened and asked, "What about the sixth-level civilization stellar-level spaceship and the seventh-level civilization river-level spaceship?"

Gang's tone gradually became stricter: "The materials it needs for these two levels of spaceships are extremely expensive, so the sixth- and seventh-level civilizations can generally only pick up ready-made ones for transformation. ”

"Ready-made?"

Chen Xin didn't understand.

Gangyi smiled: "Old Bean, what do you think is the strongest material in the universe?"

Chen Xin hesitated for a moment and asked tentatively, "Could it be a neutron material?"

"Not bad!"

Gangyi nodded and said: "So the River-class battleship of the seventh-level civilization is actually a neutron star, and the spaceship of this level can be said to be the overlord of the entire Virgo Super Galaxy, and it is also extremely difficult for the seventh-level civilization to manufacture, and it generally takes hundreds of thousands of years and countless resources to successfully modify one." As for the sixth-level civilization, they couldn't even hurt a single hair of the neutron star, so they could only retreat to the next best thing and modify the white dwarf. ”

Chen Xin's heart was fascinated, and he suddenly thought of a question, and said suspiciously: "Gangyi, I remember you said before, your Vajra clan's home planet, Cybertron, is a neutron star, are you only a seventh-level civilization?"

Gangyi shook his head and said, "I don't know about this, after all, I have only reached the seventh level at the highest, but one thing is for sure, the Vajra Clan is definitely not only the seventh level." ”

"Why?"

"Because even a seventh-level civilization can't change the appearance and shape of a neutron star. And Cybertron, it's square. (To be continued) R655