Earth.

After a few months, Starship traveled from galaxy to galaxy, finally destroying all known supernova cannons and removing the imminent threat.

However, although the speed of the Star Ark is fast, the return to Earth is not so positive.

The base appeared near the earth, and on a whim, Ray planned to take a closer look at the beautiful earth, but when he looked up, he saw a group of warships parked near the moon.

"What is this for? Who are you going to war with?" Ray craned his neck, looking like a curious baby.

Gong Yiding's thought moved, and he had already retrieved the cause and effect from the internal network: "This is mainly to use old things and sell the obsolete old ships to other civilizations."

Originally, it was just a very ordinary response, but unexpectedly, Lei suddenly widened his eyes and asked in an extremely stunned tone, "Can the old ones be sold?"

Gong Yiding was taken aback by his violent reaction: "Yes, what's wrong?"

Lei glanced at Gong Yiding and then looked outside the ship, his eyes full of incredulity: "Is this business?"

This time it's Gong Yiding's turn, obviously a pair of mechanical prosthetic eyes, but revealing an abnormal gaze: Big man, do you always have any misunderstandings about business?

It took him a while before he reluctantly replied, "It's just one type of business."

"Can you tell me more about it?" Ray asked with interest.

"That's a long story." Gong Yiding immediately organized his language, "Do you know about general equivalents?"

"What equivalent?"

"It's money, it's gold, or something like that!" Gong Yiding tried his best to explain.

Let a scientific researcher of his level teach these basic knowledge, which is a bit like a cannon fighting mosquitoes.

Lei suddenly realized, and when he figured out the meaning of money, Gong Yiding popularized to him what is a business behavior, to put it simply, as long as there are benefits between buying and selling, even if it is a negative benefit, it can be classified as a commercial behavior.

Selling warships is bound to make a lot of money, but all the profits are invested in the manufacture of new ships, which can be seen but not touched.

In order to enhance his persuasiveness, Gong Yiding bought and sold now, and told Lei about some business war cases from the Internet, which made the latter praise again and again, and the praise was amazing.

However, Ray's expression changed suddenly, and he restrained all his smiles: "But I think your warships must be sold too cheaply, you know, within a radius of a few hundred light years, here is the richest in heavy elements......

Rebala is a good idea of the scarcity of heavy elements, especially how rare a planet like Earth is with all the natural heavy elements, and finally concluded how unreliable it is for humans to sell warships cheaply.

In the end, Lei also put forward an opinion, thinking that human beings can make a fortune by selling heavy elements with relatively large reserves.

It wasn't over yet, and his chest rose and fell rapidly for a while before he slowly regained his composure.

Gong Yiding was stunned for a moment, and a thought suddenly popped up in his mind: With such a long speech, how much resentment does the prophet have against the heavy elements?

He couldn't help but ask, and Lei's originally very tangled expression suddenly turned into loneliness, and he instantly fell into a long memory: "Heavy element, that is a hurdle that all civilizations must face, and the vast majority of civilizations have disappeared for various reasons before they even have a chance to cross...... Do you know how we felt when we first found Earth?" ….

Gong Yiding quickly grasped the point: "You mean, the earth is not chosen at random? Didn't you flee to Earth in the first place to escape the Black Universe people?"

"Yes and no." Ray continued, "It's true to hide from the Black Universe, but Earth is not chosen randomly. Without heavy elements, even if the seeds of civilization are sown here, there is no chance of developing a true interstellar civilization."

Speaking of this, he obviously hesitated: "Have you ever thought about why there are so many civilizations here, don't you think there are too many civilizations in the universe?"

Gong Yiding's cheeks twitched, and his tone trembled: "Are they all the seeds you left back then?"

"Yes!" Ray smiled happily, "We'd love to know,

How will intelligent life develop in an environment lacking heavy elements, and what kind of structure will it be if it has the opportunity to become an interstellar civilization."

Gong Yiding instantly became extremely curious: "Have you gotten the answer?"

"Didn't get it all." Ray said.

If you change to another person, you may not be able to understand the meaning of the words, but Gong Yiding understands it in an instant.

It should be like this: the prophet was focused on cultivating the civilization of the earth, but he was also observing the situation of the Getha civilization.

The seeds sown by those prophets took root and some flourished, but many more died silently in the long course of history.

Those who have died, Ray has seen the results, and those who have thrived, naturally they have not seen it.

Speaking of this, Gong Yiding suddenly had a question: "If it is all based on natural evolution and there is no intervention from external factors, how many civilizations should there be in this star field?"

Ray thought for a moment and said, "Half a Orion arm, definitely no more than ten...... I'm talking about interstellar civilizations!"

Only ten?

Gong Yiding immediately fainted.

Don't be a lot of ten, the Orion arm is more than 10,000 light-years long, more than 3,000 light-years wide, and more than 2,000 light-years thick.

Not to mention just ten civilizations, even if a thousand interstellar civilizations are thrown into it, it won't make much waves.

This is still taking into account the influence of heavy elements on the original civilization.

Gong Yiding immediately came up with another question: "What about non-interstellar civilizations? How many are there?"

"Thirty or fifty times." Ray said.

"500?"

"Not much." Ray said again.

Gong Yiding sighed faintly: "So, life...... No, civilization is still a very small minority in this universe, right?"

"Of course." Ray nodded in agreement, "Planets with primary ecology are very common, but habitable planets with complex ecology are very rare, and civilization will only appear on a very small number of habitable planets. But among many civilizations, less than one percent has a chance of stepping out of their home planet."

Gong Yiding suddenly interrupted Lei's eloquent talk: "What about a civilization like ours?"

Thunder's voice stopped abruptly, as if something had choked his neck.

"Is it much?" Gong Yiding asked again.

This time, Ray was silent for a long time before replying softly, "I can only say, more than I imagined, at least more than the original interstellar civilization."

"May I ask why?"

"Because native civilizations are all terrestrial species, they are naturally only suitable for staying on the surface of planets, while artificial species are longer-lived and more adaptable, and are more suitable for long-term survival outside the stars.

Gong Yiding sighed quietly: We have always thought that we have enough knowledge of this universe, but in fact it is just a peek at the leopard, and the real galaxy is far more complicated than what we have seen!.

Cracks in the metal