Life could exist in many different forms, each with its own requirements for the environment. What was hell to one species might be paradise to another. For example, before leaving Earth, how could Xiao Yu have imagined that on Titan, there would actually be creatures like the Black Bugs?
Even now, Xiao Yu’s ship still preserved some specimens of the Black Bugs. Analyzing them with his current understanding, Xiao Yu believed these Black Bugs should be classified among Alien Beasts rather than ordinary organisms.
This reality brought a certain difficulty to Xiao Yu’s efforts to search for intelligent life. The reason was simple, he had no unified standard for deciding which star systems were worth approaching to conduct closer investigations. And obviously, surveying every single star was unrealistic.
Here, the stellar density was slightly higher than the density near the Solar System’s position. Within a range of twenty light-years, there were over a thousand stars. Xiao Yu did not believe his luck would be so exceptional that he could find intelligent beings within just these twenty light-years.
Xiao Yu’s psychological bottom line was within a three-thousand-light-year radius. He intended to spend no more than two thousand years to complete this mission. The number of stars within three thousand light-years was truly astronomical. If he needed to conduct close-range surveys of each one, even extending the two-thousand-year period tenfold would not be enough.
To deal with this situation, Xiao Yu convened all the scientists under his command for many rounds of discussion.
“First of all, I believe a planet capable of supporting life must possess liquid substances on its surface. Whether it’s liquid water, liquid methane, or ethane doesn’t matter, there simply must be some liquid present. This is because the internal energy exchange of an organism must rely on liquid as the medium.”
A scientist presented this viewpoint.
“No, I disagree with that,” another scientist objected. “Although all of our more than one hundred species use liquid as the medium for internal energy exchange, why can’t there be organisms in this universe that use gaseous substances for that? After all, in theory, gases can fully achieve the same function.”
This statement triggered a wave of debate.“This point remains in question for now, we can neither prove nor disprove it, so let’s move to the next topic. Also related to material exchange, I believe a suitable life-bearing planet must have a liquid core. Only with a liquid core will there be geological activity, mountain building, and so on. Moreover, it must have a sufficiently large moon to generate tidal forces and winds to create a planet-wide system of material exchange.”
“I don’t agree with this either. I think we should broaden the criteria a bit further. As long as a planet has an atmosphere, it already holds sufficient value. Under the irradiation of a star, the uneven heating of the atmosphere will cause air circulation, and that circulation alone provides enough material exchange.”
Another scientist shared this opinion.
“No, it doesn’t necessarily have to be that way. Why must there be atmospheric circulation and material exchange? Can’t life evolve on a planet without an atmosphere? I disagree with that restriction. I think we should drop this criterion.”
—
This discussion continued for a full two months. Xiao Yu repeatedly relaxed the restrictions, combining the needs of over one hundred kinds of lifeforms and the conditions of their respective home systems. In the end, he arrived at the following conclusions.
Xiao Yu believed that these conclusions should, at the very least, possess universality within the Milky Way Galaxy. In other words, as long as a planet harboring intelligent life existed, it would generally fulfill the following conditions. Exceptions certainly existed, but their number would be so small as to be negligible. In the future, as he continued his search, he would conduct his operations guided by these points.
First, any stellar system capable of sustaining life must have a primary star that was stable, able to output energy steadily and consistently over long periods. This criterion alone eliminated all stars in their late stages or early stages of life. Young stars exhibited excessively violent activity, and their systems were far too chaotic. A single impact from an asteroid over ten kilometers in diameter could easily wipe out the spark of life. In newly formed star systems, collisions of this magnitude were commonplace. As for aged stars, once they became red giants, stellar activity would intensify even further.
Second, the star’s lifespan had to be sufficiently long. Only if the primary star had a long enough lifespan could it provide adequate time for the slow process of biological evolution. This requirement ruled out all giant stars.
Because the mass of a star and its lifespan were inversely proportional: the greater the mass, the shorter the lifespan. A star dozens of times the Sun’s mass might have a lifespan of only a few million years or less. On the scale of the universe, such a brief existence was nothing but a fleeting moment. That duration was clearly insufficient for the development of intelligent organisms.
Third, life should emerge and evolve on planets. Although Xiao Yu could not completely rule out the possibility that life might exist on stars themselves, that likelihood was too infinitesimal to consider. This criterion therefore eliminated all star systems lacking planets.
The remaining requirements, for example, that a life-bearing planet must have a sufficiently large moon to slow its rotation and generate tidal forces to enable material exchange; or that it must have large gaseous planets in the outer system for protection; or that its distance from the star must be appropriate and it must contain liquid water, could not be demonstrated to have universal applicability, so Xiao Yu discarded them.
In other words, Xiao Yu decided that as long as a stellar system met these three criteria, it was worth approaching and investigating.
A star’s current status, age, mass, and lifespan could be analyzed using reconstructed light methods, while the existence of planets could be confirmed through the wobble method or the transit method. Detection via light had no distance limitation, or rather, it massively increased the detection range, allowing Xiao Yu to survey any stellar system within twenty light-years at any time.
If a system satisfied these three criteria, Xiao Yu would alter course to approach the star and conduct close-range tachyon scanning. If the scan revealed evidence of intelligent civilization, the fleet would exit faster-than-light flight and establish a presence there. If there were no signs of intelligent life, he would move on to the next star.
With such relaxed conditions, the number of suitable star systems increased dramatically. Roughly one in every hundred stars met the criteria. After all, massive stars, and stars either too old or too young, were a minority. And planetary presence was not as sparse as Xiao Yu had initially imagined. It was important to note that he had not required planets to be rocky, he believed that intelligent life might even arise on gaseous planets.
This endeavor was not one Xiao Yu expected to yield results in the short term. It was a new round of searching for a needle in a cosmic haystack, demanding enormous effort and patience before it might bear fruit.
“This star is good, moderate size, moderate age, and the planet is a rocky planet with 1.6 times Earth’s mass… Yes, worth a look.” In the midst of the long voyage, a message from the probes caught Xiao Yu’s attention.
Before this, Xiao Yu had already investigated at least five hundred stellar systems, and every time, the outcome had been disappointment. The terrains, geologies, and conditions of these planets were all unimaginably diverse. Not only had he found no intelligent civilizations, but not a single primitive lifeform.
Some planets were extremely close to their primary star, constantly scorched by stellar fire. Due to their own rotation, they resembled roast ducks in an oven, as if afraid of being undercooked. Others were tidally locked by the star’s gravity, with rotation and revolution in perfect sync, so that one side always faced the star, like Mercury in the Solar System, one hemisphere a blazing inferno, the other an icy wasteland.
Some planets were simply too chaotic, lacking large gaseous planets for protection and any atmospheric buffer, constantly bombarded by uninterrupted barrages of interstellar debris, pockmarked with craters like the Moon. Still others were so far from their star that the entire planet was a gigantic freezer…
These myriad worlds, while broadening Xiao Yu’s horizons, also left him with a profound sense of disappointment.
“So this is the truth, in this universe, death and desolation are the norm, and life is the exception. Based on the ratio of one suitable star for every hundred, I have already surveyed over five hundred stars. That means fifty thousand stars have been ruled out. Fifty thousand stars, and not a single life-bearing planet…”
“Life… what an extraordinary phenomenon it truly is.” Xiao Yu sighed deeply in his heart.
Through this search, Xiao Yu once again felt the presence of that faint, hidden hand of conspiracy behind everything. The reason was simple, since life was so rare, and intelligent life rarer still, then how could it be that ever since he had left Earth, he had continuously encountered so many civilizations? What was going on? Why was he so… unlucky, or perhaps, so fortunate?
Xiao Yu did not know what it meant.
“Like I always say, just focus on doing my own part well, and only then consider everything else.” Xiao Yu sighed inwardly. “I hope this time, the target won’t disappoint me.”
Once again, Xiao Yu altered the course of his fleet, heading toward that stellar system.
Far behind him, hundreds of billions of kilometers away, that Level 4 Alien Beast still trailed him like a piece of sticky gum, lurking in and out of sight.