Mission of Gravity (16 page)
The situation reached a climax at about two hundred gravities, with more than a third of the sea journey behind them. The minutes of daylight were longer now as spring progressed and the Bree moved ever farther from her sun, and the sailors were relaxing accordingly. The individual who had the bailing job was not, therefore, very attentive as he pulled the canoe up the stern rafts and climbed over its gunwale. He was aroused immediately thereafter. The canoe, of course, settled a trifle as he entered; and as it did so, the springy wood of the sides gave a little. As the sides collapsed, it sank a little farther — and the sides yielded more — and it sank yet farther-Like any feedback reaction, this one went to completion in a remarkably short time. The sailor barely had time to feel the side of the canoe pressing inward when the whole vessel went under and the outside pressure was relieved. Enough of the cargo was denser than methane to keep the canoe sinking, and the sailor found himself swimming where he had expected to be riding. The canoe itself settled to the end of its towrope, slowing the Bree with a jerk that brought the entire crew to full alertness.
The sailor climbed back into the Bree, explaining what had happened as he did so. All the crew whose duties did not keep them elsewhere rushed to the stern, and presently the rope was hauled in with the swamped canoe at the end of it. With some effort, the canoe and such of its load as had been adequately lashed down were hauled aboard, and one of the sets turned to view it. The object was not very informative; the tremendous resilience of the wood had resulted in its recovering completely even from this flattening, and the canoe had resumed its original shape, still without leaks. This last fact was established after it had once more been unloaded.
Lackland, looking it over, shook his head and offered no explanation. „Tell me just what happened — what everyone who saw anything at all did see.”
The Mesklinites complied, Barlennan translating the stories of the crewman who had been involved and the few others who had seen the event in any detail. It was the first, of course, that provided the important bit of information.
„Good Earth!” Lacklaiid muttered, half aloud. „What’s the use of a high school education if you can’t recall it when needed later on? Pressure in a liquid corresponds to the weight of liquid above the point in question — and even methane under a couple of hundred gravities weighs a good deal per vertical inch. That wood’s not much thicker than paper, either; a wonder it held so long.” Barlennan interrupted this rather uninformative monologue with a request — for information.
„I gather you now know what happened,” he said. „Could you please make it clear to us?”
Lackland made an honest effort, but was only partly successful. The concept of pressure, in a quantitative sense, defeats a certain number of students in every high school class.
Barlennan did get the idea that the deeper one went into the sea the greater was the crushing force, and that the rate of increase with depth went up along with gravity; but he did not connect this force with others such as wind, or even the distress he himself had experienced when he submerged too rapidly in swimming.
The main point, of course, was that any floating object had to have some part of itself under the surface, and that sooner or later that part was going to be crushed if it was hollow. He avoided Dondragmer’s eye as this conclusion was reached in his conversation with Lackland, and was not comforted when the mate pointed out that this was undoubtedly where he had betrayed his falsehood when talking to Reejaaren. Hollow ships used by his own people, indeed! The islanders must have learned the futility of that in the far south long since.
The gear that had been in the canoe was stowed on deck, and the voyage continued. Barlennan could not bring himself to part with the now useless little vessel, though it took up a good deal of space. He disguised its uselessness thinly by packing it with food supplies which could not have been heaped so high without the sides of the canoe to retain them. Dondragmer pointed out that it was reducing the ship’s flexibility by extending the length of two rafts, but the captain did not let this fact worry him.
Time passed, as it had before, first hundreds and then thousands of days. To the Mesklinites, long-lived by nature, its passage meant little; to the Earthmen the voyage gradually became a thing of boredom, part of the regular routine of life. They watched and talked to the captain as the line on the globe slowly lengthened; measured and computed to determine his position and best course when he asked them to; taught English to or tried to learn a Mesklinite language from sailors who sometimes also grew bored; in short, waited, worked where possible, and killed time as four Earthly months — nine thousand four hundred and some odd Mesklinite days — passed. Gravity increased from the hundred and ninety or so at the latitude where the canoe had sunk to four hundred, and then to six, and then further, as indicated by the wooden spring balance that was the Bree’s latitude gauge. The days grew longer and the nights shorter until at last the sun rode completely around the sky without touching the horizon, though it dipped toward it in the south. The sun itself seemed shrunken to the men who had grown used to it during the brief time of Mesklin’s perihelion passage. The horizon, seen from the Bree’s deck through the vision sets, was above the ship all around, as Barlennan had so patiently explained to Lackland months before; and he listened tolerantly when the men assured him it was an optical illusion. The land that finally appeared ahead was obviously above them too; how could an illusion turn out to be correct? The land was really there. This was proved when they reached it; for reach it they did, at the mouth of a vast bay that stretched on to the south for some two thousand miles, half the remaining distance to the grounded rocket. Up the bay they sailed, more slowly as it finally narrowed to the dimensions of a regular estuary and they had to tack instead of seeking favorable winds with the Flyer’s help, and finally to the river at its head. Up this they went too, no longer sailing except at rare, favorable intervals; for the current against the blunt faces of the rafts was more than the sails could usually overcome, broad as the river still was. They towed instead, a watch at a time going ashore with ropes and pulling; for in this gravity even a single Mesklinite had a respectable amount of traction. More weeks, while the. Earthmen lost their boredom and tension mounted in the Toorey station. The goal was almost in sight, and hopes ran high.
And they were dashed, as they had been for a moment months before when Lackland’s tank reached the end of its journey. The reason was much the same; but this time the Bree and its crew were at the bottom of a cliff, not the top. The cliff itself was three hundred feet high, not sixty; and in nearly seven hundred gravities climbing, jumping and other rapid means of travel which had been so freely indulged at the distant Rim were utter impossibilities for the powerful little monsters who manned the ship.
The rocket was fifty miles away in horizontal distance; in vertical, it was the equivalent, fot a human being, of a climb of nearly thirty-five — up a sheer rock wall.
The change of mind that had so affected the Bree’s crew was not temporary; the unreasoning, conditioned fear of height that had grown with them from birth was gone. They Still, however, had normal reasoning power; and in this part of their planet a fall of as much as half a body’s length was nearly certain to be fatal even to their tough organisms. Changed as they were, most of them felt uneasy as they moored the Bree to the riverbank only a few rods from the towering cliff that barred them from the grounded rocket.
The Earthmen, watching in silence, tried futilely to think of a way up the barrier. No rocket that the expedition possessed could have lifted itself against even a fraction of Mesklin’s polar gravity; the only one that had ever been built able to do so was already aground on the planet. Even had the craft been capable, no human or qualified non-human pilot could have lived in the neighborhood; the only beings able to do that could no more be taught to fly a rocket than a Bushman snatched straight from the jungle.
„The journey simply isn’t as nearly over as we thought.” Rosten, called to the screen room, analyzed the situation rapidly. „There should be some way to the plateau or farther slope whichever is present — of that cliff. I’ll admit there seems to be no way Barlennan and his people can get up; but there seems to be nothing preventing their going around.” Lackland relayed this suggestion to the captain.
„That is true,” the Mesklinite replied. „There are, however, a number of difficulties. It is already getting harder to procure food from the river; we are very far from the sea. Also, we have no longer any idea of how far we may have to travel, and that makes planning for food and all other considerations nearly impossible. Have you prepared, or can you prepare, maps with sufficient detail to let us plan our course intelligently?”
„Good point. I’ll see what can be done.” Lackland turned from the microphone to encounter several worried frowns. „What’s the matter? Can’t we make a photographic map as we did of the equatorial regions?”
„Certainly,” Rosten replied. „A map can be made, possibly with a lot of detail; — but it’s going to be difficult. At the equator a rocket could hold above a given point, at circular velocity, only six hundred miles from the surface — right at the inner edge of the ring. Here circular velocity won’t be enough, even if we could use it conveniently. We’d have to use a hyperbolic orbit of some sort to get short-range pictures without impossible fuel consumption; and that would mean speeds relative to the surface of several hundred miles a second. You can see what sort of pictures that would mean. It looks as though the shots will have to be taken with long-focus lenses, at extremely long range; and we can only hope that the detail will suffice for Barlennan’s needs.”
„I hadn’t thought of that,” admitted Lackland. „We can do it, though; and I don’t see any ‘alternative in any case. I suppose Barlennan could explore blind, but it would be asking a lot of him.”
„Right. Well launch one of the rockets and get to work.” Lackland gave the substance of this conversation to Barlennan, who replied that he would stay where he was until the information he needed was obtained.
„I could either go on upstream, following the cliff around to the right, or leave the ship and the river and follow to the left. Since I don’t know which is best from the point of view of distance, well wait. I’d rather go upstream, of course; carrying food and radios will be no joke otherwise.”
„All right. How is your food situation? You said something about its being hard to get that far from the ocean.”
„It’s scarcer, but the place is no desert. We’ll get along for a time at least. If we ever have to go overland we may miss you and your gun, though. This crossbow has been nothing but a museum piece for nine tenths of the trip.” „Why do you keep the bow?”
„For just that reason — it’s a good museum piece, and museums pay good prices. No one at home has ever seen, or as far as I know even dreamed of, a weapon that works by throwing things. You couldn’t spare one of your guns, could you? It needn’t work, for’that purpose.”
Lackland laughed. „I’m afraid* not; we have only one. We don’t expect to need it, but I don’t see how we could explain giving it away.” Barlennjui gave the equivalent of an understanding nod, and turned back to his own duties. He had much to bring up to date on the bowl that was his equivalent of a globe; the Earthmen, throughout the trip, had been giving him bearing and distance to land in all directions, so he was able to get most of the shores of the two seas he had crossed onto the concave map.
It was also necessary to see to the food question; it was not, as he had told Lackland, really pressing, but more work with the nets was going to be necessary from now on. The river itself, now about two hundred yards wide, appeared to contain fish enough for their present needs, but the land was much less promising. Stony and bare, it ran a few yards from one bank of the stream to end abruptly against the foot of (he cliff; from the other, a series of low hills succeeded each other for mile after mile, presumably far beyond the distant horizon. The rock of the escarpment’s face was polished glass-smooth, as sometimes happens even on Earth to the rocks at the sliding edges of a fault. Climbing it, even on Earth, would have required the equipment and body weight of a fly (on Mesklin, the fly would have weighed too much). Vegetation was present, but not in any great amount, and in the first fifty days of their stay no member of the Bree’s crew saw any trace of land animal lif e. Occasionally someone thought he saw motion, but each time it turned out to be shadows cast by the whirling sun, now hidden from them only by its periodic trips beyond the cuff. They were so near the south pole that there was no visible change in the sun’s altitude during the day.
For the Earthmen, the time was a little more active. Four of the expedition, including Lackland, manned the rocket and dropped planetward from the rapidly moving moon. From their takeoff point the world looked rather like a pie plate with a slight bulge in the center; the ring was simply a line of light, but it stood out against the background of star-studded blackness and exaggerated the flattening of the giant world.
As power was applied both to kill the moon’s orbital velocity and bring them out of Mesklin’s equatorial plane the picture changed. The ring showed for what it was, but even the fact that it also had two divisions did not make the system resemble that of Saturn. Mesklin’s flattening was far too great for it to resemble anything but itself — a polar diameter of less than twenty thousand miles compared to an equatorial one of some forty-eight thousand has to be seen to be appreciated. All the expedition members had seen it often enough now, but they still found it fascinating.
The fall from the satellite’s orbit gave the rocket a very high velocity, but, as Rosten had said, it was not high enough. Power had to be used in addition; and although the actual pass across the pole was made some thousands of miles above the surface, it was still necessary for the photographer to work rapidly. Three runs were actually made, each taking between two and three minutes for the photography and many more for the whipping journey around the planet. They made reasonably sure that the world was presenting a different face to the sun each time, so that the height of the cliff could be checked by shadow measurements on all sides; then, with the photographs already fixed and on one of the chart tables, the rocket spent more fuel swinging its hyperbola into a wide arc that intercepted Toorey, and killing speed so that too much acceleration would not be needed when they got there. They could afford the extra time consumed by such a maneuver; the mapping could proceed during the journey.
Results, as usual with things Mesklinite, were interesting if somewhat surprising. In diis case, the surprising fact was the size of the fragment of planetary crust that seemed to have been thrust upward en bloc. It was shaped rather like Greenland, some thirty-five hundred miles in length, with the point aimed almost at the sea from which the Bree had come. The river leading to it, however, looped widely around and actually contacted its edge at almost the opposite end, in the middle of the broad end of the wedge. Its height at the edges was incredibly uniform; shadow measurements suggested that it might be a trifle higher at the point end than at the Bree’s present position, but only slightly.
Except at one point. One picture, and one only, showed a blurring of the shadow that might be a gentler slope. It was also in the broad end of the wedge, perhaps eight hundred miles from where the ship now was. Still better, it was upstream — and the river continued to hug the base of the cliff. It looped outward at the point where the shadow break existed as tiiough detouring around the rubble pile of a collapsed slope, which was very promising indeed. It meant diat Barlennan had sixteen or seventeen hundred miles to go instead of fifty, with half of it overland; but even the over-
land part should not be overwhelmingly difficult. Lackland said so, and was answered with the suggestion that he make a more careful analysis of the surface over which his small friend would have to travel. This, however, he put off until after the landing, since there were better facilities at the base.
Once there, microscopes and densitometers in the hands of professional cartographers were a little less encouraging, for the plateau itself seemed rather rough. There was no evidence of rivers or any other specific cause for the break in the wall that Lackland had detected; but the break itself was amply confirmed. The densitometer indicated that the center of the region was lower than the rim, so that it was actually a gigantic shallow bowl; but its depth could not be determined accurately, since there were no distinct shadows across the inner portion. The analysts were quite sure, however, that its deepest part was still well above the terrain beyond the cliffs.
Rosten looked over the final results of the work, and sniffed.
„I’m afraid that’s the best we can do for him,” he said at last. „Personally, I wouldn’t have that country on a bet even if I could live in it. Charlie, you may have to figure out some way to give moral support; I don’t see how anyone can give physical.”
„I’ve been doing my best all along. It’s a nuisance having this crop up when we were so close to home plate. I just hope he doesn’t give us up as a bad job this close to the end; he still doesn’t believe everything we say, you know. I wish someone could explain that high-horizon illusion to his — and my — satisfaction; that might shake him out of the notion that his world is a bowl, and our claim to come from another is at least fifty per cent superstition on our part.”
„You mean you don’t understand why it looks higher?” one of the meteorologists exclaimed in a shocked tone.
„Not in detail, though I realize the air density has something to do with it.”
„But it’s simple enough — ”
„Not for me.”
It’s simple for anyone. You know how the layer of hot air just above a road on a sunny day bends sky light back upward at a slight angle, since the hot air is less dense and the light travels faster in it; you see the sky reflection and tend to interpret it as water. You get more extensive mirages sometimes even on Earth, but they’re all based on the same thing — a ‘lens’ or ‘prism’ of colder or hotter air refracts the light. It’s the same here, except the gravity is responsible; even hydrogen decreases rapidly in density as you go up from Mesklin’s surface. The low temperature helps, of course.”
„All right if you say so; I’m not a — ” Lackland got no chance to finish his remark; Rosten cut in abruptly a and grimly.
„Just how fast does this density drop off with altitude?”
The meteorologist drew a slide rule from his pocket and manipulated it silently for a moment.
„Very roughly, assuming a mean temperature of minus one-sixty, it would drop to about one per cent of its surface density at around fifteen or sixteen hundred feet.” A general stunned silence followed his words.
„And — how far would it have dropped at — say — three hundred feet?” Rosten finally managed to get the question out.
The answer came after a moment of silent lip movement. „Again very roughly, seventy or eighty per cent — probably rather more.”
Rosten drummed his fingers on the table for a minute or two, his eyes following their motions; then he looked around at the other faces. All were looking back at him silently. „I suppose no one can suggest a bright way out of this one; or does someone really hope that Barlennan’s people can live and work under an air pressure that compares to their normal one about as that at forty or fifty thousand feet does to ours?”
„I’m not sure.” Lackland frowned in concentration, and
Rosten brightened a trifle. „There was some reference a long time ago to his staying under water — excuse me, under methane — for quite a while, and swimming considerable distances. You remember those river-dwellers must have moved the Bree by doing just that. If it’s the equivalent of holding breath or a storage system such as our whales use, it won’t do us any good; but if he can actually get a fair part of the hydrogen he needs from what’s in solution in Mesklin’s rivers and seas, there might be some hope.” Rosten thought for a moment longer.
„All right. Get your little friend on the radio and find out all he knows himself about this ability of his. Rick, look up or find out somehow the solubility of hydrogen in methane at eight atmospheres pressure and temperatures between minus one forty-five and one eighty-five Centigrade. Dave, put that slide rule back in your pocket and get to a calculator; get as precise a value of the hydrogen density on that clifftop as physics, chemistry, math, and the gods of good weather men will let you. Incidentally, didn’t you say there was a drop of as much as three atmospheres in the center of some of those tropical hurricanes? Charlie, find out from Barlennan whether and how much he and his men felt that. Let’s go.” The conference broke up, its members scattering to their various tasks. Rosten remained in the screen room with Lackland, listening to his conversation with the Mesklinite far below.