“But we’ve seen a lot of it,” Morrie pointed out.
“I get you,” Cargraves agreed. “Between librations and such—the eccentricity of the moon’s orbit and its tilt, we get to peek a little way around the edges from time to time and see about 6o per cent of its surface—if the surface is globular. But I’m talking about that missing 40 per cent that we’ve never seen.”
“Oh,” said Ross, “you mean the side we can’t see might just be sliced off, like an apple with a piece out of it. Well, you may be right, but I’ll bet you six chocolate malts, payable when we get back, that you’re all wet.”
“Nope,” Cargraves answered, “this is a scientific discussion and betting is inappropriate. Besides, I might lose. But I did not mean anything of the slice-out-of-an-apple sort. I meant just what I said: no back side at all. The possibility that when we swing around the moon to look at the other side, we won’t find anything at all, nothing, just empty space—that when we try to look at the moon from behind it, there won’t be any moon to be seen—not from that position. I’m not asserting that that is what we will find; I’m asking you to prove that we will find anything.”
“Wait a minute,” Morrie put in, as Art glanced wildly at the moon as if to assure himself that it was still there—it was! “You mentioned something of that sort on earth—a thing with no back. What was it? I’m from Missouri.”
“A rainbow. You can see it from just one side, the side that faces the sun. The other side does not exist.”
“But you can’t get behind it.”
“Then try it with a garden spray some sunny day. Walk around it. When you get behind it, it ain’t there.”
“Yes, but Doc,” Ross objected, “you’re just quibbling. The cases aren’t parallel. A rainbow is just light waves; the moon is something substantial.”
“That’s what I’m trying to get you to prove, and you haven’t proved it yet. How do you know the moon is substantial? All you have ever seen of it is just light waves, as with the rainbow.”
Ross thought about this. “Okay, I guess I see what you’re getting at. But we do know that the moon is substantial; they bounced radar off it, as far back as ’46.”
“Just light waves again, Ross. Infra-red light, or ultra-shortwave radio, but the same spectrum. Come again.”
“Yes, but they bounced.”
“You are drawing an analogy from earth conditions again. I repeat, we know nothing of moon conditions except through the insubstantial waves of the electromagnetic spectrum.”
“How about tides?”
“Tides exist, certainly. We have seen them, wet our feet in them. But that proves nothing about the moon. The theory that the moon causes the tides is a sheer convenience, pure theory. We change theories as often as we change our underwear. Next year it may be simpler to assume that the tides cause the moon. Got any other ideas?”
Ross took a deep breath. “You’re trying to beat me down with words. All right, so I haven’t seen the other side of the moon. So I’ve never felt the moon, or taken a bite out of it. By the way, you can hang on to the theory that the moon is made of green cheese with that line of argument.”
“Not quite,” said Cargraves. “There is some data on that, for what it’s worth. An astronomer fellow made a spectrograph of green cheese and compared it with a spectrograph of the moon. No resemblance.”
Art chortled. “He didn’t, really?”
“Fact. You can look it up.”
Ross shrugged. “That’s no better than the radar data,” he said correctly. “But to get on with my proof. Granted that there is a front side to the moon, whatever it’s nature, just as long as it isn’t so insubstantial that it won’t even reflect radar, then there has to be some sort of a back, flat, round, square, or wiggly. That’s a matter of certain mathematical deduction.”
Morrie snorted.
Cargraves limited himself to a slight smile. “Now, Ross. Think it over. What is the content of mathematics?”
“The content of mathe—” He collapsed suddenly. “Oh…I guess I finally get it. Mathematics doesn’t have any content. If we found there wasn’t any other side, then we would just have to invent a new mathematics.”
“That’s the idea. Fact of the matter is, we won’t know that there is another side to the moon until we get there. I was just trying to show you,” he went on, “just how insubstantial a ‘common sense’ idea can be when you pin it down. Neither ‘common sense’ nor ‘logic’ can prove anything. Proof comes from experiment, or to put it another way, from experience, and from nothing else. Short lecture on the scientific method—you can count it as thirty minutes on today’s study time. Anybody else want breakfast but me? Or has the low weight made you queasy?” He started to climb out of his chair.
Ross was very thoughtful while they made preparations for breakfast. This was to be a proper meal, prepared from their limited supply of non-canned foods. The Galileo had been fitted with a galley of sorts, principally a hot plate and a small refrigerator. Dishes and knives, forks, and spoons could be washed, sparingly, with the water which accumulated in the dump of the air-conditioner, and then sterilized on the hot plate. The ship had everything necessary to life, even a cramped but indispensable washroom. But every auxiliary article, such as dishes, was made of zinc—reserve mass for the hungry jet.
They sat, or rather squatted, down to a meal of real milk, cereal, boiled eggs, rolls, jam, and coffee. Cargraves sighed contentedly when it had been tucked away. “We won’t get many like that,” he commented, as he filled his pipe. “Space travel isn’t all it’s cracked up to be, not yet.”
“Mind the pipe, Skipper!” Morrie warned.
Cargraves looked startled. “I forgot,” he admitted guiltily. He stared longingly at the pipe. “Say, Ross,” he inquired, “do you think the air-conditioner would clean it out fast enough?”
“Go ahead. Try it,” Ross urged him. “One pipeful won’t kill us. But say, Doc—”
“Yes?”
“Well, uh, look—don’t you really believe there is another side to the moon?”
“Huh? Still on that, eh? Of course I do.”
“But—”
“But it’s just my opinion. I believe it because all my assumptions, beliefs, prejudices, theories, superstitions, and so forth, tend that way. It’s part of the pattern of fictions I live by, but that doesn’t prove it’s right. So if it turns out to be wrong I hope I am sufficiently emotionally braced not to blow my top.”
“Which brings us right back to study time,” he went on. “You’ve all got thirty minutes credit, which gives you an hour and a half to go. Better get busy.”
Art looked dumfounded. “I thought you were kidding Uncle. You don’t mean to run such a schedule on the moon, do you?”
“Unless circumstances prevent. Now is a good time to work up a little reserve, for that matter, while there is nothing to see and no work to do.”
Art continued to look astonished, then his race cleared. “I’m afraid we can’t, Uncle. The books are all packed down so far that we can’t get at them till we land.”
“So? Well, we won’t let that stop us. A school,” he quoted, “is a log with a pupil on one end and a teacher on the other. We’ll have lectures and quizzes—starting with a review quiz. Gather round, victims.”
They did so, sitting cross-legged in a circle on the hold bulkhead. Cargraves produced a pencil and a reasonably clean piece of paper from his always bulging pockets. “You first, Art. Sketch and describe a cyclotron. Basic review—let’s see how much you’ve forgotten.”
Art commenced outlining painfully the essential parts of a cyclotron. He sketched two hollow half-cylinders, with their open sides facing each other, close together. “These are made of copper,” he stated, “and each one is an electrode for a very high frequency, high voltage power source. It’s actually a sort of short-wave radio transmitter—I’ll leave it out of the sketch. Then you have an enormously powerful electromagnet with its field running thro
ugh the opening between the dees, the half-cylinders, and vertical to them. The whole thing is inside a big vacuum chamber. You get a source of ions—”
“What sort of ions?”
“Well, maybe you put a little hydrogen in the vacuum chamber and kick it up with a hot filament at the center point of the two dees. Then you get hydrogen nuclei—protons.”
“Go ahead.”
“The protons have a positive charge, of course. The alternating current would keep them kicking back and forth between the two electrodes—the dees. But the magnetic field, since the protons are charged particles, tends to make them whirl around in circles. Between the two of them, the protons go whirling around in a spiral, gaining speed each revolution until they finally fly out a little thin, metal window in the vacuum chamber, going to beat the band.”
“But why bother?”
“Well, if you aim this stream of high-speed protons at some material, say a piece of metal, things begin to happen. It can knock electrons off the atoms, or it can even get inside and stir up the nuclei and cause transmutations or make the target radioactive—things like that.”
“Good enough,” Cargraves agreed, and went on to ask him several more questions to bring out details. “Just one thing,” he said afterwards. “You know the answers, but just between ourselves, that sketch smells a bit. It’s sloppy.”
“I never did have any artistic talent,” Art said defensively. “I’d rather take a photograph any day.”
“You’ve taken too many photographs, maybe. As for artistic talent, I haven’t any either, but I learned to sketch. Look, Art—the rest of you guys get this, too—if you can’t sketch, you can’t see. If you really see what you’re looking at, you can put it down on paper, accurately. If you really remember what you have looked at, you can sketch it accurately from memory.”
“But the lines don’t go where I intend them to.”
“A pencil will go where you push it. It hasn’t any life of its own. The answer is practice and more practice and thinking about what you are looking at. All of you lugs want to be scientists. Well, the ability to sketch accurately is as necessary to a scientist as his slipstick. More necessary, you can get along without a slide rule. Okay, Art. You’re next, Ross. Gimme a quick tell on the protoactinium radioactive series.”
Ross took a deep breath. “There are three families of radioactive isotopes: the uranium family, the thorium family, and the protoactinium family. The last one starts with isotope U-235 and—” They kept at it for considerably longer than an hour and a half, for Cargraves had the intention of letting them be as free as possible later, while still keeping to the letter and spirit of his contract with Ross’s father.
At last he said, “I think we had better eat again. The drive will cut out before long. It’s been cutting down all the time—notice how light you feel?”
“How about a K-ration?” inquired Morrie, in his second capacity as commissary steward.
“No, I don’t think so,” Cargraves answered slowly. “I think maybe we had better limit this meal to some amino acids and some gelatine.” He raised his eyebrows.
“Umm—I see,” Morrie agreed, glancing at the other two. “Maybe you are right.” Morrie and Cargraves, being pilots, had experienced free fall in school. The stomachs of Ross and Art were still to be tried.
“What’s the idea?” Art demanded.
Ross looked disgusted. “Oh, he thinks we’ll toss our cookies. Why, we hardly weigh anything now. What do you take us for, Doc? Babies?”
“No,” said Cargraves, “but I still think you might get drop-sick. I did. I think predigested foods are a good idea.”
“Oh, shucks. My stomach is strong. I’ve never been air sick.”
“Ever been seasick?”
“I’ve never been to sea.”
“Well, suit yourself,” Cargraves told him. “But one thing I insist on. Wear a sack over your face. I don’t want what you lose in the air-conditioner.” He turned away and started preparing some gelatine for himself by simply pouring the powder into water, stirring, and drinking.
Ross made a face but he did not dig out a K-ration. Instead he switched on the hot plate, preparatory to heating milk for amino-acid concentrates.
A little later Joe the Robot awoke from his nap and switched off the jet completely.
They did not bounce up to the ceiling. The rocket did not spin wildly. None of the comic-strip things happened to them. They simply gradually ceased to weigh anything as the thrust died away. Almost as much they noticed the deafening new silence. Cargraves had previously made a personal inspection of the entire ship to be sure that everything was tied, clamped, or stored firmly so that the ship would not become cluttered up with loosely floating bric-a-brac.
Cargraves lifted himself away from his seat with one hand, turned in the air like a swimmer, and floated gently down, rather across—up and down had ceased to exist—to where Ross and Art floated, loosely attached to their hammocks by a single belt as an added precaution. Cargraves checked his progress with one hand and steadied himself by grasping Art’s hammock. “How’s everybody?”
“All right, I guess,” Art answered, gulping. “It feels like a falling elevator.” He was slightly green.
“You, Ross?”
“I’ll get by,” Ross declared, and suddenly gagged. His color was gray rather than green.
Space sickness is not a joke, as every cadet rocket pilot knows. It is something like seasickness, like the terrible, wild retching that results from heavy pitching of a ship at sea—except that the sensation of everything dropping out from under one does not stop!
But the longest free-flight portions of a commercial rocket flight from point to point on earth last only a few minutes, with the balance of the trip on thrust or in glide, whereas the course Cargraves had decided on called for many hours of free fall. He could have chosen, with the power at his disposal, to make the whole trip on the jet, but that would have prevented them from turning ship, which he proposed to do now, until the time came to invert and drive the jet toward the moon to break their fall.
Only by turning the ship would they be able to see the earth from space; Cargraves wanted to do so before the earth was too far away.
“Just stay where you are for a while,” he cautioned them…“I’m about to turn ship.”
“I want to see it,” Ross said stoutly. “I’ve been looking forward to it.” He unbuckled his safety belt, then suddenly he was retching again. Saliva overflowed and drooled out curiously, not down his chin but in large droplets that seemed undecided where to go.
“Use your handkerchief,” Cargraves advised him, feeling none too well himself. “Then come along if you feel like it.” He turned to Art.
Art was already using his handkerchief.
Cargraves turned away and floated back to the pilot’s chair. He was aware that there was nothing that he could do for them, and his own stomach was doing flip-flops and slow, banked turns. He wanted to strap his safety belt across it. Back in his seat, he noticed that Morrie was doubled up and holding his stomach, but he said nothing and gave his attention to turning the ship. Morrie would be all right.
Swinging the ship around was a very simple matter. Located at the center of gravity of the ship was a small, heavy, metal wheel. He had controls on the panel in front of him whereby he could turn this wheel to any axis, as it was mounted freely on gymbals, and then lock the gymbals. An electric motor enabled him to spin it rapidly in either direction and to stop it afterwards.
This wheel by itself could turn the ship when it was in free fall and then hold it in the new position. (It must be clearly understood that this turning had no effect at all on the course or speed of the Galileo, but simply on its attitude, the direction it faced, just as a fancy diver may turn and twist in falling from a great height, without thereby disturbing his fall.)
The little wheel was able to turn the huge vessel by a very simple law of physics, but in an application not often seen on th
e earth. The principle was the conservation of momentum, in this case angular momentum or spin. Ice skaters understand the application of this law; some of their fanciest tricks depend on it.
As the little wheel spun rapidly in one direction the big ship spun slowly in the other direction. When the wheel stopped, the ship stopped and just as abruptly.
“Dark glasses, boys!” Cargraves called out belatedly as the ship started to nose over and the stars wheeled past the port. In spite of their wretched nausea they managed to find their goggles, carried on their persons for this event, and get them on.
They needed them very soon. The moon slid away out of sight. The sun and the earth came in to view. The earth was a great shining crescent like a moon two days past new. At this distance—one-fourth the way to the moon—it appeared sixteen times as wide as the moon does from the earth and many times more magnificent. The horns of the crescent were blue-white from the polar ice caps. Along its length showed the greenish blue of sea and the deep greens and sandy browns of ocean and forest and field…for the line of light and dark ran through the heart of Asia and down into the Indian Ocean. This they could plainly see, as easily as if it had been a globe standing across a school room from them. The Indian Ocean was partly obscured by a great cloud bank, stormy to those underneath it perhaps, but blazing white as the polar caps to those who watched from space.
In the arms of the crescent was the nightside of earth, lighted dimly but plainly by the almost full moon behind them. But—and this is never seen on the moon when the new moon holds the old moon in her arms—the faintly lighted dark face was picked out here and there with little jewels of light, the cities of earth, warm and friendly and beckoning!
Halfway from equator to northern horn were three bright ones, not far apart—London, and Paris, and reborn Berlin. Across the dark Atlantic, at the very edge of the disk, was one especially bright and rosy light, the lights of Broadway and all of Greater New York.