"Why are you a little weird today?"

"Am I weird?"

Huo Gu's eating action obviously paused, and then resumed, responding in a salty and non-light, in order to hide his gaffe, and how could this kind of behavior escape Karena's eyes.

Karena sighed with a 'don't hide it, I've seen it through'.

"You eat quickly every time, and you are always in a hurry to go back to the library to read, but today you are not like this, for a strange man who is eager to learn, doesn't that explain the problem?"

Huo Gutou turned to the side, his eyes scanning back and forth over the pedestrians outside through the window of the restaurant, his eyes as sharp as falcon eagles.

Kalena didn't think much about it when she saw Huo Gu tilting her head, she just lost her temper because she was poked by someone.

"I want to slow down the pace of life, but you, don't you want to explain it to me?"

"Uh, what does that mean?"

Being asked by Huo Gu so suddenly, Kalena was slightly stunned, pondered carefully, hammered her palm, seemed to understand something, and looked at Huo Gu with a sudden understanding.

"Oh, you're expecting me to answer that question you had last time, right? That's a scary question to ponder. ”

"You understand?"

Hogu's movements were paused again, but this time it was different from before, it was surprised that Karena could actually understand it, according to the impression that Kalena had been given by this incident, it was not very studious, not very talented, not too self-motivated, and at most average in the whole group.

Such a person claims to have understood the question from two prompts, and it is very skeptical.

"Of course."

I saw that Karena was straight, with her waist crossed strongly, and she looked like she was full of ambition and victory.

She cleared her throat and began to explain the inferences she had drawn from the two prompts that Hogu had given that day.

"Today's empire has been able to make a detector of a certain mass reach sub-light speed, and the diameter of the river system we are in is about 10,000 light-years, and the maximum value can be taken to get the answer that it takes 200,000 years for a sub-light speed detector to cross the entire river system."

"In other words, assuming that there are other civilizations in the river system, it only needs to reach the current level of the empire 200,000 years before the empire and launch a probe, and the empire should have made contact with them by now."

"This is only 200,000 years earlier than the empire, if it is an alien civilization 10 million years earlier, 100 million years earlier, I am afraid that the Serens should have known about their existence or established communication when they first came into contact with the universe in the era of great powers, because these civilizations have already occupied the entire river system."

"However, the reality is the opposite, except for the amoeba, an alien civilization in this star system, we have never been in contact with any aliens at all, and the whole universe is very quiet."

That's right, this is the famous 'Fermi paradox' on Earth, one day in 1951, Fermi proposed - 'Where are they?' This question leads to a series of scientific derivations.

Now, in this corner of the universe where I don't know what time and location, on the home planet of an alien civilization far away from the earth, Huo Gu asked that question again.

"yes, so why is that?"

This scientific question, the Serens did not discover, although they were aware of the concept of 'aliens', but they were not aware of the Fermi paradox, so when Hogu gave another hint, Kalena did not immediately give Hogu an answer.

Everything she knew now was based on the two hints that Hogu had given.

When discussing academic issues, Kalena gradually put away her usual playfulness and looked more like a scholar.

"From the question you asked, three explanations can be derived, the first is that we Serenes and Amoebas were the first civilizations in the early days of this river system, so there has not yet been a flood of regular signals across the river system."

"Second, regular signals exist, but because our technology gap is too large, even readable regular signals are mistaken as natural phenomena as they should be, and they are ignored."

"Third, those civilizations have perished, without exception, and they have not yet reached the current height of the empire, otherwise, according to the desire for the continuation of civilization itself, even if it encounters an unavoidable danger of extinction, at least the evidence of the existence of its own civilization must be left."

Later, Kalena explained why the probe was used as a tombstone.

"The detector is an excellent tombstone choice, because it will diffuse information, and it is easy for other civilizations to learn the information of the destroyed civilization, and accelerate to sub-light speed, the shrinkage effect will extend the life of the detector in disguise, tens of thousands of times or even hundreds of millions of times, across the entire river system, the normal time is more than 100,000 years, but for the detector may only be a few years past."

“…… Gu, did you mean this when you meant imminent? ”

After explaining her understanding, Kalena looked at Hogu with complicated eyes, because this bad guy's unusual thinking made her realize a terrible thing.

At the same time, unparalleled admiration secretly rose in her heart, but soon, Karena's feelings of admiration disappeared because of Hogu's next words......

"It's a little surprising that you think of you, after all, I've always thought you're a dumb guy who doesn't study much."

Ignoring Karena, who looked a little stiff, Huo Gu continued to talk to himself, explaining why he was leaning towards the third option.

"The first one is too proud, the age of the river system is as old as the universe, and the history of tens of billions of years, whether it is the Serens or the amoeba, is just a drop in the ocean in the vast years, and it is simply a big laugh to say that it is the first batch."

"The second can only explain those advanced civilizations that have existed for a long time, but the civilizations like the one in your example that are 200,000 or 300,000 years earlier are not among them, so these civilizations can only be explained by the third way."

Hogu paused and put down the cutlery in his hand as it finished eating.

"There is an unknown terror that erases these civilizations, and you are wrong about one thing."

"What is wrong?"

Kalena looked thoughtful, she shouldn't have missed anything, what went wrong?

And then, Hogu told her what was wrong and why.

"Why should you subjectively assume that there will not be a civilization that will reach the height of an empire? Isn't it true that amoeba can also achieve sub-light speed? If the two known civilizations have reached this level, can it be assumed that it is common for the universe Chinese to reach sub-light speeds? ”