The Dark Forest

by Liu Cixin

  “What’s the magnification?” Ding Yi asked.

  “A hundred times.” Xizi pointed to a number in the corner of the screen, then adjusted the magnification to one thousand.

  The enlarged surface remained a smooth mirror.

  “Your device is broken,” the lieutenant colonel said.

  Xizi removed the microscope from the droplet and placed it against her space suit visor. The other three drew closer to look at the screen, where the visor—a surface which, to the naked eye, looked as smooth as the droplet—was a rough and rocky beach on the screen under one-thousand-times magnification. Xizi returned the microscope to the surface of the droplet, and the screen once again displayed a smooth mirror, no different from the surrounding, unmagnified surface.

  “Increase it by another factor of ten,” Ding Yi said.

  This was beyond the capabilities of optical magnification, so Xizi carried out a series of operations to switch the microscope from optical to electron tunneling mode. Now the magnification power stood at ten thousand.

  The magnified surface remained a smooth mirror. The smoothest surface that human technology could produce revealed itself as rough at just one thousand times magnification, like Gulliver’s impression of the face of the beautiful giantess.

  “Adjust to a hundred thousand times,” the lieutenant colonel said.

  Still they saw a smooth mirror.

  “A million times.”

  A smooth mirror.

  “Ten million times.”

  Macromolecules would be visible at this magnification, but what they saw on the screen remained a smooth mirror without the slightest sign of roughness, no difference in smoothness from the surrounding unmagnified surface.

  “Push it up again!”

  Xizi shook her head. This was the electron microscope’s highest level of magnification.

  More than two centuries before, in his novel 2001: A Space Odyssey, Arthur C. Clarke had described a black monolith left on the moon by an advanced alien civilization. Surveyors had measured its dimensions with ordinary rulers and had found a ratio of one to four to nine. When these were rechecked using the most high-precision measurement technology on Earth, the ratio remained an exact one to four to nine, with no error at all. Clarke described it as a “passive yet almost arrogant display of geometrical perfection.”

  Now, humanity was facing a far more arrogant display of power.

  “Can an absolutely smooth surface really exist?” Xizi gasped.

  “Yes,” Ding Yi said. “The surface of a neutron star is nearly absolutely smooth.”

  “But this has a normal mass!”

  Ding Yi considered this, then looked about him. “Hook up to the spaceship computer and find the spot that the robot arm gripped during capture.”

  This was accomplished remotely by a fleet surveillance officer. The Mantis computer projected thin red laser beams to mark the position on the droplet surface that had been gripped by the steel claw. Xizi examined one of the spots with the microscope, and at a magnification of ten million times, she still saw a smooth, flawless mirror.

  “How high was the pressure at the point of contact?” the lieutenant colonel asked, and soon received a reply from the fleet: approximately two hundred kilograms per square centimeter.

  Smooth surfaces are easily scratched, but the strong metal clamp did not leave any scratches on the droplet’s surface.

  Ding Yi floated away in search of something within the cabin. He returned with a rock pick, perhaps dropped in the cabin by someone during collection of rock samples. Before anyone could stop him, he slammed it forcefully into the mirror surface. There was a clang, crisp and melodious, like the pick had smashed into jade-paved ground. The sound traveled through his body, but the other three didn’t hear it because of the vacuum. With the handle of the pick, he pointed out the spot he had struck, and Xizi examined it with the microscope.

  At ten million times magnification, it was still a smooth mirror.

  Ding Yi tossed the pick aside dejectedly and looked away from the droplet, deep in thought. The eyes of the three officers, and the eyes of the million people in the fleet, were all focused on him.

  “All we can do is guess,” he said, looking up. “The molecules in this thing are neatly arranged, like an honor guard, and they’re mutually solidifying. Do you know how solid it is? It’s as if the molecules are nailed into place. Even their own vibrations are gone.”

  “That’s why it’s at absolute zero!” Xizi said. She and the other two officers understood what Ding Yi was getting at: At normal densities of matter, the separation between atomic nuclei is quite large. It would be no easier to fix them all in place than it would be to join the sun to the eight planets with rods to form a stationary truss.

  “What force would allow that?”

  “There’s only one option: strong interaction.”23 Through his visor, it was obvious that Ding Yi’s forehead was covered in sweat.

  “But … that’s like shooting the moon with a bow and arrow!”

  “Indeed, they’ve shot the moon with a bow and arrow.… The tear of the blessed mother?” He gave a chilly laugh, a mournful sound that made them shiver, and the three officers knew what it meant: The droplet wasn’t fragile like a tear. Entirely the opposite: Its strength was a hundred times greater than the sturdiest material in the Solar System. All known substances were as fragile as paper by comparison. It could pass through the Earth like a bullet through cheese, without even the slightest harm to its surface.

  “Then … what’s it here for?” the lieutenant colonel blurted out.

  “Who knows? Maybe it really is just a messenger. But it’s here to give humanity a different message,” Ding Yi said, turning his gaze away from the droplet.

  “What?”

  “If I destroy you, what business is it of yours?”

  The words were followed by a momentary silence as the three other members of the expeditionary team and the million members of the combined fleet ruminated over their meaning. Then, all of a sudden, Ding Yi said, “Run.” The word was uttered softly, but then he raised his hands and shouted hoarsely, “Stupid children. Run!”

  “Run where?” Xizi asked in fright.

  Just seconds after Ding Yi, the lieutenant colonel realized the truth. Like Ding Yi, he shouted desperately: “The fleet! Evacuate the fleet!”

  But it was too late. Powerful interference had already wiped out their communication channels. The image being transmitted from Mantis vanished, and the fleet was unable to hear the lieutenant colonel’s final call.

  A blue halo emerged from the tip of the droplet’s tail. It was small at first, but very bright, and cast a blue shroud over its surroundings. Then it dramatically expanded, turning from blue to yellow and finally to red. It almost seemed as if the droplet wasn’t producing the halo, but had just drilled out from within it. The halo weakened in luminosity as it expanded, and when it had reached a diameter twice that of the largest part of the droplet, it vanished. The instant it vanished, a second small blue halo emerged from the tip. Like the first one, it expanded, changed color, weakened, and quickly disappeared. The halos continued to emerge from the droplet’s tail at a rate of two or three a second, and under their propulsion, the droplet began to move forward, and then rapidly accelerated.

  But the four members of the expedition team never saw the second halo emerge, because the first one was accompanied by ultra-high temperatures approaching that of the sun’s core, which vaporized them instantly.

  The hull of Mantis glowed red, resembling from the outside a paper lantern whose candle had just been lit. Its metal body melted like wax, but no sooner had the ship begun to melt than it exploded, dispersing into space as an incandescent liquid with hardly any solid fragments left behind.

  From a thousand kilometers away, the fleet had a clear view of Mantis’s explosion, but the initial analysis was that the droplet had self-destructed. Everyone felt sorrow for the sacrifice of the four expedition t
eam members, followed by disappointment that the droplet was not a messenger of peace. But the human race did not have even the slightest bit of psychological preparation for what was about to happen.

  The first anomaly was identified by the fleet’s space surveillance computer, which discovered during the course of processing images of Mantis’s explosion that one of the fragments was abnormal. Most of the pieces were molten metal that flew uniformly through space following the explosion, but this one was accelerating. Of course, only a computer was able to find a tiny object among the massive quantity of flying fragments. From an immediate search of its database and knowledge bank, which included an enormous amount of information on Mantis, it arrived at several dozen possible explanations for the peculiar debris, but none was correct.

  Neither computer nor human realized that the explosion had destroyed only Mantis and the four-member expedition team, but not the droplet.

  As for the accelerating fragment, the fleet’s space surveillance system issued only a level-three attack alarm, because the approaching object was not a warship and was headed toward one corner of the rectangular formation. On its current heading, it would pass outside the formation and would not strike any warship. Due to the large number of level-one alarms issued following the Mantis explosion, this level-three alarm was completely ignored. The computer had, however, also noted the fragment’s high rate of acceleration. By three hundred kilometers it had already passed the third cosmic velocity and was continuing to gain speed. The alert was upgraded to level two, but was still ignored.

  By the time the fragment had flown roughly 1,500 kilometers from the explosion site toward the corner of the formation, only fifty-one seconds had elapsed. By the time it reached the corner, it was traveling at a speed of 31.7 kilometers per second. Now it was on the periphery of the formation, 160 kilometers away from Infinite Frontier, the first warship in this corner of the array. The fragment did not pass by the formation, but executed a thirty-degree turn, and, without slowing down, sped straight toward Infinite Frontier. In the roughly two seconds it took to cover that distance, the computer actually dropped its alert from level two back to level three, concluding that the fragment wasn’t actually a physical object due to the fact that its motion was impossible under aerospace mechanics. At twice the third cosmic velocity, executing a sharp turn without a drop in speed was like slamming into an iron wall. If it was a vessel containing a metal block, the change in direction would have exerted such force as to flatten that metal block into a thin film. So the fragment had to be an illusion.

  In that manner, the droplet struck Infinite Frontier at twice the third cosmic velocity, at a heading straight along the first row of the fleet rectangle.

  The droplet struck Infinite Frontier in its rear third and passed through with no resistance, as if penetrating a shadow. The extreme speed of the impact meant that two highly regular entry and exit holes roughly the diameter of the droplet’s thickest part appeared in its hull. But no sooner had they appeared than the holes deformed and vanished as the surrounding hull melted under the heat produced by the high-speed impact and the ultrahigh temperature of the droplet’s trailing halo. The part of the ship that had been hit turned red-hot, and the redness spread from the point of impact until it covered half the ship, like a chunk of iron that had just been taken out of the forge.

  After passing through Infinite Frontier, the droplet continued onward at a speed of thirty kilometers per second. In the space of three seconds it had crossed ninety kilometers, passing first through Yuanfang, Infinite Frontier’s neighbor in the first row, and then through Foghorn, Antarctica, and Ultimate, leaving their hulls red-hot, as if the warships were giant lamps lined up.

  Then Infinite Frontier exploded. It and the four warships after it were hit in the fusion fuel tanks. But unlike Mantis’s conventional, high-temperature explosion, this explosion was a fusion reaction triggered in Infinite Frontier’s fuel. No one ever figured out whether the fusion reaction had been sparked by the droplet’s ultra-high-temperature propulsive halo or some other factor. The fireball of the thermonuclear explosion appeared at the point of impact with the fuel tank and swiftly expanded until it illuminated the entire fleet against the velvety background of space, outshining the Milky Way.

  Nuclear fireballs then took shape on Yuanfang, Foghorn, Antarctica, and Ultimate in succession.

  In the next eight seconds, the droplet passed through ten more stellar-class warships.

  By this point, the expanding nuclear fireball had engulfed the entirety of Infinite Frontier and had begun to shrink, while more fireballs were lighting up and expanding on other ships that had been struck.

  The droplet continued to traverse the length of the array, penetrating one stellar-class warship after another at intervals of less than a second.

  The fusion fireball on Infinite Frontier had gone out, leaving the ship’s hull totally melted. Now it exploded, spewing a million tons of glowing, dark-red metallic liquid like a bud bursting into bloom, the molten metal scattering unimpeded in an omnidirectional storm of burning metallic magma.

  The droplet continued its advance, following a straight line through more warships and leaving a line of ten nuclear fireballs behind it. The entire fleet shone in the flames of these burning small suns as if it had been set ablaze and turned into a sea of light. Behind the line of fireballs, the melted warships continued to fling waves of hot molten metal into space, as if massive rocks were being pitched into a magma sea.

  In one minute and eighteen seconds, the droplet had completed a two-thousand-kilometer course, passing through each of the hundred ships in the first row of the combined fleet’s rectangular formation.

  By the time the last ship in the row, Adam, was swallowed up in a nuclear fireball, the bursts of metallic magma at the opposite end had scattered, cooled, and spread out, leaving the heart of the explosion—the spot where Infinite Frontier had been a minute before—empty of practically everything. Yuanfang, Foghorn, Antarctica, Ultimate … all of them vanished one after another into metallic magma. When the last nuclear fireball in the line went out and darkness fell upon space once more, the gradually cooling magma that had barely been visible reappeared as dark red lights in the blackness of space, like a two-thousand-kilometer-long river of blood.

  After punching through Adam, the droplet flew a short distance of about eighty kilometers through empty space, then executed another sharp turn unexplainable by humanity’s aerospace mechanics. This time the angle it described was even smaller: just fifteen degrees off a total reversal, executed nearly instantaneously even as it maintained a constant speed. Then, after a small heading adjustment that brought it in line with the second row of warships in the fleet’s array—or what was now the first row, in light of the recent destruction—it sped toward the first ship in that row, Ganges, at thirty kilometers per second.

  Until this point, Fleet Command had not made any response.

  The fleet’s battle information system had faithfully carried out its mission and captured through its massive monitoring network a complete record of all battle information over the course of that one minute and eighteen seconds. The sheer amount of information was for the time being only analyzable by the computerized battlefield decision-making system, which had arrived at the following conclusion: A powerful enemy space force had appeared in the vicinity and had launched an attack on the fleet. However, the computer did not provide any information about that enemy force. Only two things were certain: 1. The enemy space force was located at the position occupied by the droplet, and 2. The force was invisible to every means of detection they possessed.

  By this time, fleet commanders were in a state of numb shock. For nearly two centuries, research into space strategy and tactics had dreamed up every possible kind of extreme battle condition, but witnessing a hundred warships blowing up like a string of firecrackers in under a minute was beyond what their minds could comprehend. The tide of information surging out of the bat
tle information system meant that they were forced to rely on the analyses and judgments of the computer battlefield decision-making system and focus their attention on detecting an invisible enemy fleet that didn’t even exist. All battle monitoring capacity was directed into the distant regions of space, ignoring the danger right in front of them. A fair number of people even believed that the powerful invisible enemy might be a third-party alien force distinct from humanity and Trisolaris, because in their subconscious minds, Trisolaris remained the weaker, losing side.

  The fleet’s battle monitoring system did not detect the droplet’s presence any earlier primarily because it was invisible to radar at all wavelengths and could only be located through analysis of visible spectrum images, but visible images were treated with far less importance than radar data. Most of the fragments scattered through space in storms of exploded debris were liquid metal melted by the high-temperature nuclear blasts, upward of a million tons melted in the destruction of each ship. A fair proportion of this massive amount of molten debris was roughly the same size and shape as the droplet, which presented the computer image analysis system with the difficult task of distinguishing the droplet from the debris. Besides, practically all of the commanders believed that the droplet had self-destructed inside Mantis, so no one issued specific instructions to perform such an analysis.

  Meanwhile, other circumstances were exacerbating the confusion of battle. Debris ejected from the explosions of the first row of warships soon reached the second row, prompting their battle defense systems to respond with high-energy lasers and railguns to intercept the debris. These flying fragments, consisting largely of metal melted by the nuclear fireballs, were irregular in size, and although they had been partially cooled in flight by the low temperatures of space, only their outer shells had solidified. Their insides were still in a fiery liquid state, and when struck, they scattered in a brilliant explosion of fireworks. It was not long before the second row turned into a flaming barrier parallel to the dull “river of blood” left behind by the exploded warships in the first, roiling with explosions as if washed in a tide of fire surging from the direction of that invisible enemy. Debris flew thick as hail, more than defensive systems could block, and when fragments slipped through and struck the warships, the impact of these jets of solid-liquid metal possessed considerable destructive power. A number of the ships in the fleet’s second row suffered major hull damage, and some were even punctured. Shrill decompression alarms blared.…