Arthur Clarke - A Fall of Moondust

To be the skipper of the only boat on the Moon was a distinction that Pat Harris enjoyed. As the passengers filed aboard Selene, jockeying for window seats, he wondered what sort of trip it would be this time. In the rear-view mirror he could see Miss Wilkins, very smart in her blue Lunar Tourist Commission uniform, putting on her usual welcome act. He always tried to think of her as “Miss Wilkins”, not Sue, when they were on duty together; it helped to keep his mind on business. But what she thought of him, he had never really discovered.

There were no familiar faces; this was a new bunch, eager for their first cruise. Most of the passengers were typical tourists — elderly people, visiting a world that had been the very symbol of inaccessibility when they were young. There were only four or five passengers on the low side of thirty, and they were probably technical personnel on vacation from one of the lunar bases. It was a fairly good working rule, Pat had discovered, that all the old people came from Earth, while the youngsters were residents of the Moon.

But to all of them, the Sea of Thirst was a novelty. Beyond Selene's observation windows, its gray, dusty surface marched onward unbroken until it reached the stars. Above it hung the waning crescent Earth, poised forever in the sky from which it had not moved in a billion years. The brilliant, blue-green light of the mother world flooded this strange land with a cold radiance — and cold it was indeed, perhaps three hundred below zero on the exposed surface.

No one could have told, merely by looking at it, whether the Sea was liquid or solid. It was completely flat and featureless, quite free from the myriad cracks and fissures that scarred all the rest of this barren world. Not a single hillock, boulder, or pebble broke its monotonous uniformity. No sea on Earth — no millpond, even — was ever as calm as this.

It was a sea of dust, not of water, and therefore it was alien to all the experience of men; therefore, also, it fascinated and attracted them. Fine as talcum powder, drier in this vacuum than the parched sands of the Sahara, it flowed as easily and effortlessly as any liquid. A heavy object dropped into it would disappear instantly, without a splash, leaving no scar to mark its passage. Nothing could move upon its treacherous surface except the small, two-man dust-skis — and Selene herself, an improbable combination of sledge and bus, not unlike the Sno-cats that had opened up the Antarctic a lifetime ago.

Selene's official designation was Dust-Cruiser, Mark I, though to the best of Pat's knowledge, a Mark II did not exist even on the drawing board. She was called “ship”, “boat”, or “moon bus”, according to taste; Pat preferred “boat”, for it prevented confusion. When he used that word, no one would mistake him for the skipper of a spaceship — and spaceship captains were, of course, two a penny.

“Welcome aboard Selene”, said Miss Wilkins, when everyone had settled down. “Captain Hams and I are pleased to have you with us. Our trip will last four hours, and our first objective will be Crater Lake, a hundred kilometers east of here, in the Mountains of Inaccessibility

Pat scarcely heard the familiar introduction; he was busy with his count-down. Selene was virtually a grounded spaceship; she had to be, since she was traveling in a vacuum, and must protect her frail cargo from the hostile world beyond her walls. Though she never left the surface of the Moon, and was propelled by electric motors instead of rockets, she carried all the basic equipment of a full-fledged ship of space-and all of it had to be checked before departure.

Oxygen — O. K. Power — O. K. Radio — O. K. (“Hello, Rainbow Base, Selene testing. Are you receiving my beacon?”) Inertial navigator — zeroed. Air-lock safety — On. Cabin-leak detector — O. K. Internal lights — O. K. Gangway — disconnected. And so on for more than fifty items, every one of which would automatically call attention to itself in case of trouble. But Pat Harris, like all spacemen hankering after old age, never relied on autowarnings if he could carry out the check himself.

At last he was ready. The almost silent motors started to spin, but the blades were still feathered, and Selene barely quivered at her moorings. Then he eased the port fan into fine pitch, and she began to curve slowly to the right. When she was clear of the embarkation building, he straightened her out and pushed the throttle forward.

She handled very well, when one considered the complete novelty of her design. There had been no millennia of trial and error here, stretching back to the first neolithic man who ever launched a log out into a stream. Selene was the very first of her line, created in the brains of a few engineers who had sat down at a table and asked themselves: “How do we build a vehicle that will skim over a sea of dust?”

Some of them, harking back to Ole Man River, had wanted to make her a stern-wheeler, but the more efficient submerged fans had carried the day. As they drilled through the dust, driving her before them, they produced a wake like that of a high-speed mole, but it vanished within seconds, leaving the Sea unmarked by any sign of the boat's passage.

Now the squat pressure-domes of Port Roris were dropping swiftly below the sky line. In less than ten minutes, they had vanished from sight: Selene was utterly alone. She was at the center of something for which the languages of mankind have no name.

As Pat switched off the motors and the boat coasted to rest, he waited for the silence to grow around him. It was always the same; it took a little while for the passengers to realize the strangeness of what lay outside. They had crossed space and seen stars all about them; they had looked up — or down — at the dazzling face of Earth, but this was different. It was neither land nor sea, neither air nor space, but a little of each.

Before the silence grew oppressive — if he left it too long, someone would get scared — Pat rose to his feet and faced his passengers.

“Good evening, ladies and gentlemen”, he began. “I hope Miss Wilkins has been making you comfortable. We've stopped here because this is a good place to introduce you to the Sea — to give you the feel of it, as it were.”

He pointed to the windows, and the ghostly grayness that lay beyond.

“Just how far away”, he asked quietly, “do you imagine our horizon is? Or, to put it in another way, how big would a man appear to you if he was standing out there where the stars seem to meet the ground?”

It was a question that no one could possibly answer, from the evidence of sight alone. Logic said, “The Moon's a small world — the horizon must be very close.” But the senses gave a wholly different verdict. “This land”, they reported, “is absolutely flat, and stretches to infinity. It divides the Universe in twain; for ever and ever, it rolls onward beneath the stars…”

The illusion remained, even when one knew its cause. The eye has no way of judging distances when there is nothing for it to focus upon. Vision slipped and skidded helplessly on this featureless ocean of dust. There was not even — as there must always be on Earth — the softening haze of the atmosphere to give some hint of nearness or remoteness. The stars were unwinking needle points of light, clear down to that indeterminate horizon.

“Believe it or not”, continued Pat, “you can see just three kilometers — or almost two miles, for those of you who haven't been able to go metric yet. I know it looks a couple of light years out to the horizon, but you could walk there in twenty minutes, if you could walk on this stuff at all.”