In the circular control room of the String Light Research Institute's deep space detection center, the air seemed to solidify into a transparent crystal, with only flickering points of light on the holographic star chart silently narrating the implementation progress of a grand plan. Mozi stood before a spherical star map over ten meters in diameter, his profound gaze penetrating those virtual stars, directly fixed on the vast, dark expanse beyond Neptune's orbit—the Kuiper Belt. At this distance exceeding fifty astronomical units from the Sun, hundreds of millions of icy celestial bodies drifted like cosmic ghosts, orbiting in eternal silence, their surface temperatures plummeting to minus 230 degrees Celsius, making it one of the coldest and most stable environments in the solar system. The control room was filled with a solemn, almost religious atmosphere; every engineer and scientist held their breath, as if participating in a sacred ceremony that would determine the fate of human civilization. This was the moment when the "Civilization Tombstone" plan entered its final launch preparation phase. Twelve self-replicating von Neumann probes had completed all system self-checks on the launch pad, their silver casings gleaming with a calm light under the spotlights, like twelve steel emissaries about to embark on an expedition.
These probes were far from ordinary space exploration equipment; they were the "ultimate insurance" meticulously designed by Mozi for the entire human civilization, bearing the heavy mission of preserving the flame of civilization in the event of potential global catastrophes. Each probe's design embodied the highest wisdom of human engineering, with a core consisting of a perfect sphere three meters in diameter. The outer shell used multi-layer graphene and carbon nanotube composite materials, with a strength 250 times that of steel yet only one-sixth its density, capable of maintaining structural integrity for hundreds of thousands of years in the extreme environment of the Kuiper Belt. Mozi slowly walked toward the main control console, his slender fingers gently sliding across the virtual interface, calling up the probe's detailed structural diagram. The sphere's interior was precisely divided into five functional areas: the civilization archive repository, the self-replication factory, the fusion energy module, the quantum propulsion system, and the distributed intelligent control core. Each functional area employed modular design, ensuring ultimate reliability through redundant backups and cross-connections.
"The core of the graphene-based life support system lies in its dynamic balance mechanism," Mozi's voice rang out steadily in the silent control room as he conducted final parameter confirmations with the team. "We have embedded hundreds of millions of nanoscale sensors and actuators into the graphene skeleton. These devices can monitor the material's structural integrity in real time and activate self-repair programs upon detecting minute damage." The life support system's design drew inspiration from Xiuxiu's team's breakthrough achievements in self-healing materials but elevated it to brand new heights. The system's interior maintained a miniature closed ecological loop containing specially gene-edited extreme-environment microorganisms, algae, and plant seeds. These organisms could remain in metabolic stasis for tens of thousands of years at temperatures of minus 196 degrees Celsius, rapidly resuscitating upon receiving specific environmental signals. The system's temperature control employed active phase-change material technology, maintaining a constant low-temperature environment through precise regulation of paraffin-like materials' solid-liquid phase transitions, ensuring biological samples and electronic devices could be preserved intact across geological timescales.
The energy supply came from a revolutionary compact deuterium-tritium fusion reactor, whose design integrated the breakthrough results of Xiuxiu's team in tokamak devices and Yue'er's theoretical innovations in quantum field theory. The entire reactor's volume was compressed to only zero point eight cubic meters, yet it could continuously output fifteen kilowatts of power for up to five thousand years. The reactor's core was a miniaturized magnetic confinement system generating magnetic fields up to twenty tesla through superconducting coils, confining plasma within an extremely limited space to complete fusion reactions. The fuel supply system employed automatic replenishment design, capable of extracting deuterium and lithium-6 (which produces tritium through neutron irradiation) from Kuiper Belt objects, achieving energy self-sustainment. "The special feature of the fusion reactor is its adaptive regulation capability," the energy system head added. "It can automatically adjust output power based on the probe's energy demands, minimizing power during dormancy periods and peaking during self-replication stages."
The self-replication capability was the soul of the entire von Neumann probe design and the domain where technical challenges were most concentrated. Mozi called up the self-replication logic's detailed flow chart, explaining its exquisite working mechanism to the team: "When the probe arrives at the Kuiper Belt, it will autonomously search for celestial bodies composed of water ice, ammonia ice, and methane ice as raw material sources. First, the probe will release tens of thousands of nanoscale mining robots. These robots possess molecular-level recognition and manipulation capabilities, able to decompose ice layers into basic elements such as hydrogen, oxygen, carbon, and nitrogen. Then, through quantum-level precision three-dimensional printing technology, these elemental raw materials are used to manufacture new detector components." This process's design drew inspiration from biological cells' self-replication mechanism but was entirely established upon engineering principles. The probe's intelligent control core contained a complete digital industrial system, capable of guiding nanorobots through the entire process from raw material collection, refining and purification, to part manufacturing, assembly, and testing. Each newly manufactured probe would completely inherit the mother probe's knowledge base and technical capabilities, then autonomously choose new targets for continued diffusion, forming an exponential network distribution.
"The propulsion system uses propellant-less fusion propulsion technology, with a specific impulse reaching one hundred twenty thousand seconds, more than a hundred times that of traditional chemical propulsion," the propulsion system chief engineer reported key parameters. These probes needed to fly completely autonomously to the Kuiper Belt, with no possibility of human intervention during the journey. The navigation system employed multiple redundancy design, combining pulsar navigation, stellar recognition, and quantum inertial navigation, capable of maintaining navigation accuracy within hundred-meter level over flights lasting several years. The communication system was based on quantum entanglement principles; even when separated by tens of astronomical units, it could achieve virtually zero-delay data transmission, ensuring the Earth control center could monitor the probes' status in real time.
The countdown entered the final thirty minutes, and the atmosphere in the control room grew even more somber. Mozi walked to the specially designed observation window, gazing at those exquisitely crafted probes on the distant launch pad. In the dim light of dawn, their silver casings reflected a soft luster, like twelve meticulously carved diamonds about to be sown into the depths of the cosmos. Behind this plan lay Mozi's profound reflection on the fate of human civilization—in the face of existential risks such as nuclear war, asteroid impacts, supervolcano eruptions, global pandemics, and artificial intelligence失控, human civilization appeared so fragile. And the "Civilization Tombstone" plan was the ultimate solution to counter this fragility, the cross-spacetime insurance that humanity purchased for its own civilization.
"All systems passed final inspection," the controller's voice sounded exceptionally clear in the silence. Launch commands began to be issued in an orderly manner. On the distant launch pad, the twelve probes sequentially activated their propulsion systems. Due to the use of propellant-less propulsion technology, the launch process was exceptionally quiet, with only the propulsion nozzles flickering with faint blue Cherenkov radiation. The probes slowly ascended, their posture as elegant as ballet dancers. Then, after reaching safe altitude, they began to accelerate, soon becoming twelve gradually receding points of light in the dawn sky, flying resolutely toward the edge of the solar system.
The entire launch process lasted a full eight hours. When the last probe confirmed entry into the predetermined orbit and began autonomous navigation, the control room erupted into sustained applause. But Mozi remained quietly standing at the observation window, gazing in the direction where those probes had already disappeared from view, whispering in a nearly inaudible voice: "May these gifts never be unwrapped." This statement contained profound philosophical contemplation—these probes would only be activated if human civilization faced extinction-level disaster. He sincerely hoped this day would never come. These "time capsules" carrying the essence of human civilization had best remain forever dormant in the cold abyss of the Kuiper Belt, becoming a symbol of civilization's continuity rather than a practical lifeline desperately needed.
In the months that followed, the probe team continuously monitored the flight status of these "civilization seeds." They successively flew past Mars orbit, the asteroid belt, and the Jupiter system. Each time they passed an important milestone, they would send back detailed detection data through the quantum communication system. Surprisingly, these probes also undertook additional deep space scientific investigation missions during their flight. The precious data they transmitted back about the outer solar system greatly updated human understanding of multiple frontier fields such as Kuiper Belt object composition, heliopause structure, and interstellar medium characteristics. One probe, while flying past Jupiter, even accidentally discovered a previously unknown small moon of Jupiter. This small celestial body with a diameter of only two kilometers was named "Civilization Tombstone No. 1."
When the first detector successfully arrived at the Kuiper Belt and began the self-replication process, the control room boiled over again. High-definition video transmitted back through quantum communication showed the probe precisely selecting a large Kuiper Belt object composed of water ice and rock mixtures, establishing the first self-replication base on its surface. The nanoscale mining robots, like a highly organized colony of worker ants, methodically mined ice layer raw materials, while molecular 3D printers manufactured new probe components with atomic-level precision. The entire process was filled with a sense of futurism, like watching some kind of precision mechanical life reproduce in the silence of the cold cosmos. Particularly astonishing was that the self-replication process completely followed preset physical laws and engineering specifications, without any unpredictable abnormal behavior occurring, proving the maturity of the entire system design.
Mozi gathered all project team members at this historic moment, conducting an in-depth philosophical discussion. "What we do today," he said standing before the holographic star chart, "is not merely to preserve civilization's knowledge and technology, but more importantly, to preserve the spiritual core and value system of humanity. In each probe's civilization archive repository, we have not only stored scientific knowledge, technical blueprints, and historical records but also carefully selected humanity's most outstanding artistic works, most profound philosophical thoughts, and most universal moral standards. Because true civilization is not merely a collection of technical capabilities, but the inheritance and sublimation of spiritual values." He particularly emphasized that the archive repository contained classic literature from various cultural backgrounds, from the Epic of Gilgamesh to the Tao Te Ching, from Plato's dialogues to Shakespeare's plays, from Bach's fugues to Beethoven's symphonies, ensuring civilization's diversity and richness were completely preserved.
As time passed, the number of probes in the Kuiper Belt began to show exponential growth. From the initial twelve, they developed to one hundred, then ten thousand. They were like dandelion seeds in the cosmos, continuously diffusing at the edge of the solar system. Each newly manufactured probe would autonomously choose new target celestial bodies—some delving deep into the Kuiper Belt interior to establish new bases, some heading toward the more distant Oort Cloud, and others already targeting the neighboring Proxima Centauri system. This distributed, networked diffusion strategy ensured that even if probes in a certain region were destroyed—whether due to celestial collisions, stellar activities, or other unknown factors—probes in other regions could still continue the mission, maximizing the reliability of civilization's insurance.
On the first anniversary of the plan's implementation, Mozi received stunning news: one probe, during observations in the outer Kuiper Belt, discovered a celestial body with an anomalous orbit. This celestial body temporarily designated KBO-2029-01 displayed unusual characteristics—its orbital eccentricity was extremely high, its orbital inclination also showed significant deviation from the ecliptic plane. More importantly, spectral analysis revealed its surface contained an unusually rich abundance of heavy metal elements. The probe automatically initiated deep detection procedures, and the data transmitted back astonished all astronomers. Although further observations eventually confirmed these anomalies could be explained by natural processes, this incident made Mozi even more firmly convinced of the value of the "Civilization Tombstone" plan: these probes scattered across the edge of the solar system were not only civilization's insurance but also humanity's extended sensory organs toward the cosmic depths. The observational network they constituted could provide unique perspectives unobtainable from Earth-based facilities.
Late at night, Mozi was alone in his office reviewing the year's achievements. On his office desk sat a precision scale model of a probe. This small device carried such a heavy mission, making him ponder the essence and meaning of civilization. The "Civilization Tombstone" plan also triggered widespread controversy and discussion during its implementation. Some considered it a waste of resources for scientific fantasy; others worried these self-replicating probes might bring unknown risks—such as potentially triggering a so-called "gray goo scenario." There were also philosophers who questioned the morality of this "backup civilization" approach, arguing it might weaken humanity's sense of responsibility when facing crises. But Mozi always firmly believed that in facing cosmic-scale time and space, in confronting those existential risks with extremely low probability but extremely severe consequences, humanity must prepare for the worst-case scenarios. This preparation was not born from fear but from responsibility—responsibility for civilization's inheritance, responsibility for the value of life, responsibility for the unique spark of thought that may be unique in the cosmos.
At the end of the annual summary report, Mozi wrote: "'The Civilization Tombstone' plan is not merely a technical engineering project; it is a product of humanity's profound reflection on its own fate, an important marker of our species' maturation. Through these probes scattered across the edge of the solar system, we have not only purchased cross-spacetime insurance for civilization but, more importantly, declared to the cosmos the resilience and foresight of the human species. Even if civilization on Earth disappears due to some reason, these probes will continue to propagate human knowledge, art, and thought in the cosmos, proving we once existed, thought, created, loved. This may be the most magnificent epitaph humanity can write for itself, and the most affectionate confession we leave for the cosmos."
When the report was finished, the east already showed the first light of dawn. Mozi walked to the window, gazing at the gradually brightening sky. A new day had begun, while in the Kuiper Belt billions of kilometers away, those probes were still silently working, replicating, spreading. They were the guardians of civilization, the messengers of thought, the eternal imprint of life left in the cosmos. In the cold cosmic depths, they waited quietly, both anticipating the activation signal that would never come and praying this signal would never sound. This contradictory expectation precisely embodied humanity's deepest love and responsibility for its own civilization.