"Old man, do you think it was inevitable that Earth would be hit by an asteroid?"

"What's so strange about that? Take the Moon, the closest planet to Earth, which is much smaller than Earth, for example. Doesn't it have plenty of craters?" the old man continued. "And take Mars, the closest planet to Earth, where we are now. Doesn't it have plenty of craters?"

"Why do you all think that Earth shouldn't be hit by asteroids?"

"This..." Zhang Fan didn't know how to answer for a moment.

"We should have been prepared long ago. It was inevitable that Earth would be hit by an asteroid; the only difference was the time. It would be surprising if it weren't hit."

"So, this is the origin of the 'Human Backup Project' and the 'Mars Colonization Project'?" Zhang Fan asked.

“Part of it, but not all of it,” the old man replied. “To explain, we have to start with the manned Mars mission 100 years ago.”

“I’ve heard about that Mars mission; it made headlines all over the world,” Zhang Fan continued. “The mission ultimately failed, and the gorilla ‘Caesar’ remained in Mars orbit forever.”

"That's exactly how we released the information to the public," the old man said with a smile and a shake of his head. "But you've misunderstood. The mission was a success, and the experimental module carrying 'Kaiser' has successfully returned to Earth."

"It succeeded?" Zhang Fan was stunned; this was different from what people generally believed.

“Yes,” the old man nodded, “and the test chamber brought back some extra stuff.”

"It was from this point that we realized there were other civilizations in the universe. Although we were unable to make any real contact with them, the things we brought back from the test chambers allowed us to glimpse their existence."

"What kind of being is it?"

“A highly advanced civilization with extremely advanced technology, and unfriendly to us,” the old man replied. “Moreover, this unfriendliness is innate and will not change because we take the initiative to show goodwill or back down.”

"Congenital?" Zhang Fan asked, somewhat puzzled.

“Yes, civilizations in the universe can be roughly divided into two camps: silicon-based civilizations and carbon-based civilizations. We humans belong to the carbon-based civilization camp,” the old man continued to explain. “The development of one civilization inevitably encroaches on the living space of the other. It’s like two sides of a coin; it’s either heads or tails, and you can’t put both sides of the coin facing up at the same time.”

“Since ancient times, in places unseen by humans, the war between carbon-based civilizations and silicon-based civilizations has continued for millions of years.”

"The reason why Earth has not been affected is simply because our solar system is too remote, with 100 light-years of surrounding space being a cosmic wasteland, and our civilization level is too low, so neither our enemies nor our friends have been able to detect our existence."

Zhang Fan listened quietly. The amount of information was too much, and the content was too grand, making it feel like his thoughts were jumping around and lacking a sense of reality.

"These are all things from a very distant past, and my knowledge of them is incomplete. You young people can explore them at your own pace. Let's talk about what's relevant to us first." The old man withdrew his gaze and looked at Zhang Fan, saying, "Young man, do you know where humanity originated?"

"Uh..." Zhang Fan didn't know how to answer for a moment.

This is such a huge question that even now, humanity doesn't have a definitive and convincing answer; all we have are various speculations and assumptions.

"It originated here," the old man said, stamping his foot. "Human beings originated on Mars."

"Underground."

"Why?" Zhang Fan wasn't too surprised by this.

There are many theories about the origin of humankind, some even suggesting that humans were raised by aliens. However, the idea that humans originated on Mars is more readily accepted.

“In its early days, Mars was not as barren as it appears today. It was actually a hollow sphere with a space 6,000 kilometers in diameter inside, where life was born.”

"The process of life evolution is similar to what happened on Earth; you can imagine it based on that."

"But," Zhang Fan still couldn't imagine, "even if there was such a vast space beneath Mars, without sunlight, how could life have evolved like it did on Earth?"

"It's sunny."

"Sunlight?" Zhang Fan was stunned. "Where does the sunlight underground come from?"

“The star core,” the old man replied. “I cannot yet describe to you the specific operating principle of the ‘star core,’ but you can think of it as a sphere that hangs in the very center of Mars, shining like the sun.”

"Due to centrifugal force, everything inside the sphere adheres to the sphere's wall, pointing towards the star's core. The star's core provides the energy needed for the planet's evolution; it contains mountains, rivers, lakes, seas, forests, and grasslands, where life was born."

"This internal space is exactly the opposite of our world, so we call it the 'Inverted World,' where the ancestors of ancient humans were born."

"In the understanding of ancient humans, the universe was a space with a diameter of 6,000 kilometers, and the core of a star was the center of the universe. They were developing their own technology and even launched manned spacecraft to approach the core of a star."

"Oh? They've reached the star core?" Zhang Fan's interest also grew.

“I need to correct a misconception of yours first. Things with enormous energy in the universe can be very small in size,” the old man said earnestly. “The diameter of a star’s core is only 22 cm, about the size of a football.”

"So small?"

"Different planets may have different core sizes, but the core of Mars is only this size."

"Wouldn't that be easy to steal?" Zhang Fan joked.

“Yes.” The old man nodded seriously. “Therefore, the ancient humans designated the area within 100 kilometers of the star’s core as a restricted zone and equipped it with anti-aircraft weapons. Any unauthorized approach would be shot down.”

"Because the sky was limited, ancient humans turned their exploration focus to the underground. They believed that the universe consisted of two parts: one was a spherical space with a radius of 6,000 kilometers in which they lived, and the other was a rock layer surrounding this space, which extended infinitely in all directions."

"Therefore, it is possible that there are similar spherical spaces in the infinite rock layers, either near or far from them, and human curiosity becomes the endless driving force for their exploration."

"They cracked the molten engine technology and gained the ability to navigate freely through the rock layers. Finally, one day, the ancient humans broke through the limitations of the rock layers and came to the surface."

"The real ground."

"What would the first person to reach the ground feel like?" Zhang Fan's thoughts drifted far away, imagining what it would be like for the first human to see the infinitely vast starry sky.

...

The first ancient human to break through the rock layer was lifted upwards by an invisible force. The immense inertia propelled his cockpit more than ten meters into the air before crashing onto the vast, shimmering surface, gently bobbing with the waves.

Later humans named this plane "the sea".

He carefully opened the cabin door, slowly leaned out, and immediately felt the sea breeze blowing.

He raised his head, and at that moment, the exploration of ancient human civilization over 100,000 years had been rewarded.

Humanity has witnessed the magnificent starry sky.

From then on.

The stars and the sea are etched into the very bones of every human being.

"And then?" Zhang Fan asked, somewhat bewildered. "What happened to humanity after that?"

"And then?" The old man sighed. "And then, it became a history of suffering for ancient humans."

"Our star core has been taken away."