Noise

by Hal Clement

  “Are you sure, ’Ao?” he asked. “I’ve only seen Muamoku, I know, and I suppose cities differ from each other, but still—” He doubted this on-the-spot conclusion even as it left his lips. Cities on Kainui all had the same environment and faced the same engineering design constraints. They should be pretty similar. He did not end his sentence, and closed with “Are you sure?” again.

  “What else could it be?” the child responded indignantly. “There’s nothing else in the world anywhere near that big.”

  “You mean that high out of water,” Keo corrected.

  “Of course I do. Metal-fish are bigger,” granted the child. Even Mike could feel her effort to make the lack of precision seem unimportant. “But I couldn’t have seen a metal-fish or anything except a city that far anyway.”

  “Of course you couldn’t,” the captain interjected soothingly, “but how about Mike’s question? Are you really sure that’s a city? We’re heading within a few degrees of it; keep your eyes bright and let us know when you spot anything strange.”

  Everyone noticed the “when,” but only Mike wondered whether the captain, too, thought there was something odd in the sighting or whether mere wish might be involved. He felt pretty sure by now that Wanaka was in no real hurry to reach a city. She was not actually an indecisive person—no one in her position could be—but, at the moment, would have been very pleased with any source of data that might make decisions less nebulous.

  “Don’t spend all your time looking at that hump. Check for ships in the neighborhood,” she added to ’Ao after a few minutes. Hoani conceded her a point; there had always been scores of full-sized ships and smaller vessels busy, and visible if close enough, within a few kilometers of Muamoku. He had seldom known just what they were about, but they had been there. Of course, Mata was too far yet to let ’Ao spot such an entourage, but he, too, followed Wanaka’s order as well as he could from deck level.

  The captain’s next command, only a few minutes later, fully restored Mike’s normal tendency to keep his question count low. It was called to the masthead, but not to ’Ao.

  “’Oloa! Look as closely as the haze will let you for the next few minutes, and see whether you can figure how much of that thing’s motion is due to wind alone. A city’s floats wouldn’t reach very deep. You know what the shallow currents are from this metal-maker’s drift. Is there any sign that the big thing is being influenced by deep currents as well as wind?”

  The doll’s tiny voice was inaudible over the background noise, of course, but ’Ao reported that it had acknowledged the command and was presumably obeying.

  The object was farther away, and much larger in size, than anyone had guessed at first. One side of its water line was now almost on Mata’s course as she was borne along by the metal source; the other, Keo and Wanaka judged as their viewing angle changed and gave them a better idea of its size, must extend at least two kilometers to the left of it. It was certainly not following surface currents, though the wind should be having some influence on anything that size; its peak seemed three hundred meters or more above the sea, though estimation was difficult. As it neared, the general gray tone showing through the haze became patchier. The spots reflecting the sparkles of sunlight remained too small to show any details, but did grow brighter.

  “Hadn’t we better get out of this mess so we can maneuver, before it’s too close?” suggested Keo. Wanaka shook her head slowly.

  “Anyone spotted any boats?” she asked, loudly enough to be heard aloft. No one had. ’Ao, however, saw something.

  “There are floating things. Not boats. Some of them are almost black. Some of them might be ice floes—but remember I’ve never actually seen one of those. Just pictures. These are sort of humped up out of the water, and I thought ice floes were pretty flat. If they’re mostly ice, they must go too deep to get over this creature we’re on; but if they’re shallow-draft enough to float over it, maybe we’d better get clear. We’re not actually aground on it, but it sometimes humps up enough to push on the keels, and it’ll drag on them if we’re sailing. I can feel that from up here.”

  Wanaka took the advice, to the child’s delight. “Right, ’Ao. Quarter sail, Keo; if we do hit anything, we don’t want to hit it hard. Head us to starboard of the big lump. ’Ao, keep us clear of any small ones. There shouldn’t be much ice until we’re farther south, of course, but you’re right. Some of those bits could be floes, and we certainly don’t want to hit the higher stuff.”

  A thought struck Hoani, and after a moment he decided it offered an excuse for a question. “You said something, a long time ago, about people who assembled bergs—big ice masses—and rode them into city latitudes to sell for water.”

  “So I did. But this is a hundred times as big as anything of that sort I ever heard of. Besides, all that was long ago, early in history. Of course, someone may be playing with some improved technique. That may be why it doesn’t all look like ice.”

  “And why I thought it was a city.”

  “A bigger berg would lose a lot smaller percentage to melting in a given time,” Mike remarked.

  “So it would. On the other hand, a piece of ice that size would lose most of itself to melting before any city could use much of it up. I don’t see why anyone would make one that big. ’Ao, take a look at that thing and see if you can spot any people on it.”

  “Can’t, tautai. There’s too much of this smaller stuff floating around us, and I have to watch that. We’re starting to move, so I won’t be able to look out for anything else. Mike has good eyes, though.”

  For the first time since reaching adulthood, Mata was moving under her own sail, drifting slowly over the jelly, dragging on it sometimes, but finally reaching not very open sea. Nothing, as far as anyone could tell, was under her keels but water for nearly three thousand vertical kilometers.

  The huge drifter was less than a kilometer away by now.

  “’Oloa, do you think it’s mostly wind or mostly current?” Wanaka called to the masthead. The doll’s owner answered.

  “She’s not sure, since she doesn’t know how deep it goes, but there must be a good deal of deep current. She says to tell you, ‘Three unknowns at least, only one equation.’ I don’t know what she means, but those were the words.”

  “I do. Thanks,” shouted Wanaka.

  Mike knew, too, and assumed that Keokolo did.

  Keo, at the tiller, guided them close enough to one of the small floating objects to give everyone a good look. For a minute or two they examined it silently.

  It was about three meters across and extended something over half that distance above the surface. If it had much vertical symmetry, which seemed doubtful, it must be nearly spherical. There was indeed ice covering much of the thing, but under, or inside, that ice was some much darker material. Keo hove to, a few meters from whatever it was, without waiting for orders. Its motion was almost entirely current controlled, apparently, like their own at this point.

  “Shall I take a real look, Captain?” asked the mate.

  Wanaka shook her head negatively. “Mike,” she said slowly, “take a safety line and see what you can make of it.”

  The order made sense. The thing was unfamiliar to the natives; Hoani was as likely as they to make some sense out of it—perhaps more likely. If he got into trouble, Wanaka and Keokolo were much better qualified to help him than he would be to help them. He flipped his helmet forward, latched it, and went overboard. Two or three strokes, even with his limited—by Kainui standards—swimming skills, brought him against the object. He could not, of course, remove his helmet, but the others were close enough to read his fingers. He reported after only a minute or two of examination.

  “The light stuff is ice, all right. It should be melting; I suppose it is. It feels a lot colder than the water. What there is above the water line is mostly dark stuff glued together by ice, but just below the surface and as far down as I can see there’s more ice and less of the dark stuff. It’s mos
tly orange and red in color. Just a minute. It’s either bobbing up and down a lot, or staying put as the waves pass; there’s no telling which.” The others had seen this already, and given up much hope of Mike’s being able to make a detailed examination, but Wanaka made a brief, encouraging gesture.

  Mike turned back to the floe for a moment, then faced Mata again with a golf ball-sized fragment that showed no ice coating at all resting on his palm, and held it up for the others to see. “Shall I bring this aboard, or could it be something that shouldn’t touch the hull?”

  “Bring it. Just don’t pound on anything with it,” replied the captain. Keo gently pulled Mike back by his safety line, allowing him to give full attention to keeping the specimen from striking the hull. Hoani reached up, handed it to Wanaka, and climbed aboard. Examination was interrupted briefly by a call from the masthead.

  “Keo! Maneuver! There’s another one closing in.” The mate sprang to the tiller, and started to work Mata over to a less crowded area. The motions of the floes had a random component; they were high enough to be affected by wind, but no two were more than vaguely alike in shape. The captain stopped him almost at once. “Heave to again. There’s no dodging everything. Look.” She gestured around.

  Every two or three meters there floated a dark, apparently ice-free fragment of the red-brown material. The hulls had already struck a number of the pieces, apparently with no damage; the impacts had not been hard enough to attract attention, though Hoani suspected there’d better be another close paint check before long. He lay down on the deck, reached overside, and picked up a much larger ice-free piece. This one crumbled into almost invisibly small particles in his grip.

  The fragments that fell back into the water sank at once, to his surprise. He thought about this for a moment while getting back on his feet. The others had not, apparently, seen; the adults were still examining the first specimen, and ’Ao on her masthead wasn’t close enough.

  The captain looked up, first at the mate and then at Hoani.

  “’Amu,” she said firmly, “but I’ve never seen any just like this. Have you, Keo?”

  To Mike, the word was a general Samoan one for coral, but must, he was sure, carry a different meaning here; this ocean was far too acidic for anything made of calcium carbonate, and silica wasn’t an option.

  “The big pieces float higher than ice,” he pointed out vocally. The others looked at him quizzically. He lay down once more, reached overboard, and repeated his previous attempt to pick up one of the dark floating fragments. The result was the same, including the behavior of the crumbled bits. Wanaka nodded thoughtfully.

  “Full of air cells whose walls break very easily. I wonder why they last as long as they do? That whole piece pulverized under finger pressure, but some of them have hit the hulls time after time without collapsing; and that big chunk you took this one from…I don’t understand. Does this remind you of anything you’ve seen on Earth—or anywhere else?”

  Mike had to admit it didn’t.

  “Air cells would account for the low overall density,” he admitted slowly, “and the actual cell walls must be a lot denser; but why are they so fragile under one treatment but hold together, as they’d pretty well have to, under storms, waves, hail, and other ways this world of yours can beat things up?”

  Since he had merely restated Wanaka’s implicit question, he got no answer.

  ’Ao called their attention to another bit of data.

  “Look! The big piece is turning over!”

  It was, though not very rapidly. The side toward Mata was rising, revealing a new ice-coral mixture. Mike wondered briefly whether his removal of a few grams from the near side had upset some remarkably delicate equilibrium, but decided as the turning went on that this couldn’t be the answer. The lump did not stop rolling until it had made something like a third of an overturn. Not an exact half, they all could see, though it was now evident that its overall shape was very nearly a sphere.

  The masthead made another report. “There’s a little more ice showing in what’s just come up.” There was a brief pause, then, “’Oloa says we all should see that the ice is denser than the other stuff, and says I should be able to tell her why the big lump turned over. I can’t, right now. How long do I have before I lose points?”

  “At least an hour after one of us figures it out,” Wanaka answered promptly. Then she added, “And if that takes more than ten minutes, you don’t lose any.” The doll’s voice could just be made out in a momentary pause in the thunder, but its words were indistinguishable to Mike. If they carried any meaning to the captain, she did not relay it.

  It was evident that there was no use trying to dodge all the flotsam. If it were going to do any damage, it had probably already done it. Keo, at the captain’s orders, got under way again, though very slowly indeed—they were still avoiding the larger collections of ice and coral. The city, which it probably wasn’t, still floated with its near side about half a kilometer away, and a trader would no more forgo a closer look than would a scientist.

  The fine bits of coral were everywhere; there was no avoiding them. The larger chunks of ice-coral mixture, many up to ten meters across, were no problem. Twice, as they passed close to one of these, it turned itself leisurely over; the roughly spherical shape was starting to seem reasonable to the adults, but well over ’Ao’s allotted hour had passed before any of them actually worked out the cause. As usual, it was embarrassingly simple. Keo, for good reason, saw the answer first.

  He was still at the helm, and had been watching a particularly large chunk for many minutes, since their course lay quite close to it. It slowly dawned on him, as they neared, that it was not now turning over but was, very slowly indeed, rising. There was more of it out of the water than had been the case five or six minutes before. Then as Mata reached the nearest point to it on her course, the turnover started with unusual speed. This time, again, the near side was rising, and without waiting for orders the mate steered even closer. Wanaka seemed about to say something, but apparently decided to trust the helmsman.

  He used voice, and his tone held satisfaction.

  “I get it. I see what ’Oloa meant. The ice is denser, and of course the part under water melts faster. The body rises, and its center of gravity rises faster because it’s the part under water that’s losing weight. When the center of gravity gets higher than the center of buoyancy, it has to turn over. Anyone who’s ever planned a boat knows that. Since the things aren’t perfectly round, and probably don’t have the same density all through, they don’t always tip in the same direction or by the same amount.”

  The others nodded slowly, and Wanaka called the information up to the masthead. ’Ao, while long since relieved from the worry about losing points, was audibly annoyed at not having worked the answer out for herself. She had, after all, been taught the relevant physics, like anyone who would be expected to spend her entire adult life between floating cities and boats.

  They had reduced their distance from the “city” to a few hundred meters when the child restored her own self-respect.

  She called a question down from her perch. It was carefully not worded as a warning or even a question, of course, but it deflected the thoughts of all three adults onto an interesting line.

  “I wonder how often this big thing turns over…and which way is next.” Wanaka and Keo reacted, but not verbally.

  The basic wind was still fairly strong at this latitude, but its direction was inconvenient. Keokolo had to tack several times. He also made skillful use of the more or less random gusts around two local storms, in a maneuver that Mike thought of as slingshotting; but it was over an hour before they were out of the thickest part of the flotsam. Even then, three of the crew felt a little uneasy whenever they looked back at the huge drifter; their line of sight was still uncomfortably upward. That was unusual on Kainui.

  Wanaka looked straight back, without any upward component to her line of sight, and a frustrated expression sh
owed around her mask.

  “Well, it can’t be a city, but there’s a lot more there than ice. I wonder what it would be worth?”

  “We could wait until it does roll. Then there’d be plenty of time before it happened again,” suggested ’Ao.

  VII

  Glissando

  Wanaka did not respond to this suggestion, leaving both Mike and the child wondering whether or not it had been silly enough to cost points.

  She also said no more about the forty-five-degree latitude limit. She had managed to scoop up several bits of the floating coral without destroying them, and spent hours during the next days as Mata was borne southward in examining them as closely and thoughtfully as possible. Sometimes she did this alone, sometimes she consulted with Keo or even Mike. ’Ao stayed at the masthead most of her waking time, since in a sense they were under way.

  The ship’s equipment did include a small magnifying lens. This had failed to reveal individual grains of the still unknown metal powder, but did make barely visible the separate cells in the coral that apparently held air for flotation but which shattered completely all the way through a particular specimen if given even a slight excuse. The gas might not, actually, have been air, they all realized; destroying one under fresh water—the captain decided the knowledge might be worth the use of that commodity—produced sinking dust motes and rising bubbles, but there was no way to tell what either might consist of. If the solid was at all like any coral she or Keo had seen, it was probably some form of the carbohydrate-protein copolymer that even Mike understood composed lobster shells at home. All the adults could think of ways to measure the density of the dust and become more certain about this, but sadly all the ways needed delicate weighing equipment that was not to be had. Mata, like her parent, was a cargo craft rather than a research vessel. The seed from which she had grown had plans for a basic ship only, with only basic equipment. The seed had not reproduced itself; it had been provided by the original ship-growers as part of the original sale, quite expensively as Wanaka had plainly remarked once or twice. Mike, after hearing the captain describe the deal, had come to regard the seed as a sort of limited warranty, which had now expired. Without actually worrying, he now did feel a little more conscious of the personal risks he had casually accepted.