# Fluctuations · The Probe

New Millennial Wayfarer

*Translated by GPT*

He Rixin was aflame with ambition, his heart full to bursting.

How could he not be? Half a lifetime of work had finally brought him the fulfillment of a lifelong wish. He had conceived the DEPART mission and remained the very heart of the project; now he was closer to the Sun than anyone in history. If only he had a talent for poetry, and *DEPART* a direct line to Earth. He would surely have found something to say that would go down in history.

The DEPART mission was the crowning achievement of present-day space technology, and would open a new chapter in humanity’s exploration of the Sun. *DEPART*—**D**iagnostic **E**lectromagnetic **P**robe **AR**ray experimen**T**—was an advanced spacecraft at the L1 Lagrange point between the Sun and Mercury, the innermost planet.[^1] Its principal task was to make direct measurements of the plasma streams produced by solar activity from closer to the Sun, and to observe the solar surface directly. It could measure electromagnetic signals across a broad frequency range in every direction. Even from the single vantage point of Mercury L1, separating signals by direction and frequency would yield a wealth of information about solar physics. It was the most advanced “probe” in every sense of the word.

Quite apart from its mission and its instruments, *DEPART*’s presence in an orbit so close to the Sun was itself an engineering marvel. Facing the Sun meant withstanding an unprecedented assault of light and heat. A passenger aboard *DEPART* was arguably more cut off from the world than a visitor to the Moon, or even a tourist at the center of the Earth. Solar radiation heated the spacecraft’s exterior to 600 degrees—and that was with the heat-transfer system working flat out. Without that system extending throughout its hull, *DEPART* would rapidly succumb to the heat. Such an onslaught made conventional spacecraft cooling wholly ineffective: radiators would absorb far more radiant heat than they could dissipate. *DEPART* therefore used an entirely new approach to heat exchange. Its heat-transfer system pumped heat from the hull into a series of thermal reservoirs made of advanced phase-change materials. Energy was virtually unlimited; the time it could endure the thermal load was not. Its remaining capacity to store heat was its lifeline. Fifty-two reservoirs would protect it through two phases of operation. Thirty-two would act as heat sinks for the twenty-day crewed phase. Once those thirty-two were exhausted, He Rixin would return to the departure base on Mercury and rejoin the rest of the team. *DEPART* would change course into orbit around Mercury and begin its second, uncrewed phase. All fifty-two reservoirs would then absorb heat while the craft faced the Sun and shed it when Mercury cast it into shadow. In this phase, it would operate intermittently for at least a year.

The Sun had all but blocked *DEPART*’s means of shedding heat. Much the same was true of its means of exchanging information. At Mercury L1, direct communication with Earth was almost impossible: the immense source of radiation that was the Sun had already filled virtually the entire channel. A less satisfactory arrangement would have to do. Fortunately, Mercury was completely tidally locked to the Sun, so a relay base could be built near the planet’s terminator. This was where He Rixin’s companion kept watch. Essential information would pierce the dense solar noise, pass between *DEPART* and the relay base, and be forwarded to Earth. Even this connection was unstable, however, and its bandwidth severely limited. He Rixin would have to bring the immense quantity of first-phase data back himself. “An ocean of data submerged in a universe of real information.” There was something regrettable about this paradox. The DEPART mission existed to obtain solar data, yet amid that torrent of energy and information it could only watch from a relatively safe distance and draw off a thread here, a thread there. Such filtering was unavoidable. It was not even a matter of choosing the finest samples; it was the limit of what human beings could obtain and understand. Could humanity claim to understand the Sun? Hardly. The Sun’s energy output would overwhelm *DEPART*’s thermal capacity, just as the vastness of its information would overwhelm human comprehension. The more He Rixin studied solar physics, the more he felt the Sun’s immensity and complexity. His conception of it grew ever more coherent. But how far was that conception from the Sun itself?

Engineering and scientific challenges had placed formidable obstacles in the mission’s way. Whether it could actually go ahead, however, had ultimately depended on other kinds of practical consideration. The headlong era in which states built colossal scientific wonders to demonstrate their cohesion and the superiority of their ideologies was long past. People rising from the ruins had looked eagerly to the future; whoever could lead them into it had the greater claim on the present. Those who came afterward were more inclined to cherish the past, imagining themselves in the place of the heroes of old and polishing, in memory, the various golden ages that had belonged to different groups. Whoever held the present thus gained the right to sit in judgment on the past. To set out, one needed the fare. Once, “We choose to go to the moon” had been enough. Now it was no longer a sufficiently weighty reason. That story was entirely out of date, and in any case He Rixin was not the one making the choice. He was the one charged with carrying it out.

Fortunately, the goal had been achieved. It had simply required a different logic for telling the same story. The giants of the past had not embraced the space race out of wholly rational calculation. Certainly, it had stimulated the growth of many industries, introduced scientific ideas to the public on a vast scale, and advanced education. In society, however, its effect had been to create a totem of faith in the future and in technology. Scientists and astronauts were the mighty sorcerers and warriors of legend. Everyone believed they lived in an age of magic, and the desire for magic had itself helped drive that age’s furious advance. Today’s giants believed in a different totem. This one, too, concerned itself with progress and numbers, but its purpose was different. Capital lived by increasing its value. It sniffed out every opportunity for extraordinary returns. Any means of making the accounts look more handsome and more real would snowball through ingenious financial instruments and gather into a towering wave. Its power was too great, its response too swift, its appetite too greedy: growth in the real world could not keep pace with the expansion of capital. This immense creature with nowhere to go needed a new myth. Every business offering extraordinary returns had already been picked clean; now it hoped for magic that could keep it alive. Only another industrial revolution, another age of miracles, would satisfy it. The story required was clear. He Rixin found a way to make people believe that the DEPART project might supply the spark that would kindle a new age of miracles.

The Little Ice Age of the seventeenth century had profoundly affected the global economic and political order, rewriting the course of human civilization. From the frontiers of the Ming empire to its shores, from the ports of Luzon to Tenochtitlan, from the Thames estuary to the Black Forest of Central Europe, from the fertile lands of the Don to the Central Asian steppe: scarcely had sails and horse-drawn carriages bound the world together when it faced a devastating crisis beyond human power to avert. Famine, plague, and war swept across every inhabited continent. People did not even know the nature of the catastrophe they were living through. They knew only that they had been born into troubled times, when life was cheap as dirt. The disaster had many causes, but one thing was certain: of them all, weakening solar activity was the least amenable to human intervention, and possibly the most consequential. Observations over the last twenty years showed that solar activity was steadily declining. Another Little Ice Age was very likely.

Fortunately, humanity now had more ways of confronting such a crisis. The DEPART mission was a conspicuous example, and a deeper understanding of the solar cycle held unprecedented economic value. The giants believed in the power of cycles. Naturally, they saw the cycles of celestial bodies as another mighty force to be put to use. He Rixin had played the weather sorcerer to perfection. The giants thought his magic immensely valuable.

Solving engineering problems was difficult. So was playing the weather sorcerer. But He Rixin and his team had done both. Once the mission was under way, his old anxieties vanished, and a deep awe of the Sun’s boundless power took their place. Facts so immense they had seemed abstract finally became palpable, moving from his reason into his feelings. Slight fluctuations 150 million kilometers away could change the entire world of billions of living things, and this was only a negligible fraction of the Sun’s power. Six years of travel had merely reduced that distance to a third. The decades of preparation and the voyage through space had taken up almost his whole life. Yet that lifetime, even an entire solar minimum, was only a moment in the Sun’s fluctuations. And what of the universe beyond, where even light seemed slow and powerless? He had scarcely begun to grasp one vast conception when another ungraspable immensity took dim shape, no longer wholly abstract. His reason firmly cut the chain of association short.

Remote and perilous indeed was the place where *DEPART* lay; strange and magnificent beyond measure was the view. Filters tamed the fierce sunlight so that he could look directly at the Sun. Its texture stood out in the finest detail, burning silently as though sunk in an abyss. It seemed that what had been set into the cabin wall was not a window, but a vessel holding the Sun. He Rixin had dreamed of this sight day and night. The scenery on Mercury behind him was an unexpected pleasure. In the preliminary stages of the DEPART mission, three probes had been sent on flybys of Mercury and discovered peculiar geological features on its surface. Mercury had no atmosphere, only a weak magnetic field, and no natural moons. Yet the probes found small impact craters only on its dark side. The sunlit side, apart from a few large craters, was astonishingly smooth.

Now a magnificent panorama spread across Mercury’s surface before him. The planet was no featureless sphere of the sort used for drawing practice, with nothing to vary its smoothness but light and shade. Extreme temperature gradients drove matter from place to place; no atmosphere intervened to scatter or obscure it. Mercury had become a specimen of fractionation with the sharpest, clearest surface color bands in the Solar System. At the center gleamed a silvery-white pool of molten metal. Rings of color spread outward, darkening with latitude: lead and zinc’s silver-white, sulfur’s brilliant yellow, the yellow-brown of sulfide salts, the brown-black of iron oxides.

An extraordinary geological phenomenon. He Rixin decided to collect images of Mercury alongside his solar data. With no atmosphere and only a weak magnetic field, there were very few possible causes of surface change. He suspected solar-driven heat flows and fractionation through sublimation. After all, Mercury’s sunlit face was not much cooler than *DEPART*, and variations in the Sun’s angle above the horizon could produce a sufficiently large temperature gradient. Presumably, this was causing certain molten minerals to flow across the surface, or even to sublime. But he knew too little of planetary physics, or even geophysics. He would simply record the phenomenon in full and leave it to later explorers and the relevant specialists. During these precious twenty days, his own ardor for work would have to match the heat of *DEPART*’s hull. He would gather as much data from the solar surface as he could.

[^1]: Mercury in this world is completely tidally locked to the Sun.