"Easily. There's a two-thirds margin of safety."

"And you haven't considered that it may get harder to push? You know the increase of ma.s.s with velocity. You can't take one-half of the relativity theory without the other. And they've actually measured the increase of weight in an electron."

"The electron never knew it; it's all a matter of reference points. I can't follow the math, but I know that from the electron's standards it stayed exactly the same weight. Anything else is nonsense."

"Well, there may be a flaw in the reasoning, but as they've worked it out, nothing can go faster than light. As you approach that velocity, the ma.s.s keeps increasing, and with it the amount of energy required for a new increase in speed. At the speed of light, the ma.s.s would be infinite, and hence no finite energy could get you any further."

"Maybe so. It won't take long to find out."

A few of the brightest stars had begun to appear. We could just see the parallelogram of Orion, with red Betelguese at one corner, and across from it Rigel, scintillant like a blue diamond.

"See," Garth said, pointing at it. "Three months from now, that's where I'll be. The first man who dared to sail among the stars."

"Only because you don't let anyone else share the glory and the danger."

"Why should I? But you wouldn't go, anyway."

"Will you let me?"

I had him there.

"On your head be it. The Comet could hold three or four in a pinch, and I have plenty of provisions. If you really want to take the chance--"

"It won't be the first we've taken together."

"All right. We'll start in ten minutes." He went inside the s.h.i.+p.

"Don't go," Kelvar whispered, coming into the Comet's shadow. "Tell him anything, but don't go."

"I've got to. I can't go back on my word. He'd think I was afraid."

"Haven't you a right to be?"

"Garth is my friend and I'm going with him."

"All right. But I wish you wouldn't."

From inside came the throb of engines.

"Kelvar," I said, "you didn't worry when only Garth was going."

"No."

"And there's less danger with two to keep watch."

"I know, but still...."

"You are afraid for me?"

"I am afraid for you."

My arm slipped around her, there in the shadow.

"And when I come back, Kelvar, we'll be married?"

In answer, she kissed me. Then Garth was standing in the doorway of the Comet.

"Dunal, where are you?"

We separated and came out of the shadow. I went up the plank to the door, kicking it out behind me. Kelvar waved, and I called something or other to her. Then the door clanged shut. Seated before the control board at the front of the room, Garth held the switch for the two projectors.

"Both turned up," he yelled over the roar of the generators. His hands swung over and the noise died down, but nothing else seemed to have happened. I turned back again to look out the little window fixed in the door.

Down far below, I could see for a moment the city of Nardos with its great white bridge, and a spot that might be Kelvar. Then there was only the ocean, sparkling in the Earth-light, growing smaller, smaller. And then we had shot out of the atmosphere into the glare of the sun and a thousand stars.

On and up we went, until the moon was a crescent with stars around it. Then Garth threw the power forward.

"Might as well turn in," he told me. "There'll be nothing interesting until we get out of the solar system and I can put on real speed. I'll take the first trick."

"How long watches shall we stand?"

"Eighteen hours ought to match the way we have been living. If you have another preference--"

"No, that will be all right. And I suppose I might as well get in some sleep now."

I was not really sleepy, but only dazed a little by the adventure. I fixed some things on the floor by one of the windows and lay down, switching out the light. Through a top window the sunlight slanted down to fall around Garth, at his instrument board, in a bright glory. From my window I could see the Earth and the gleaming stars.

The Earth was smaller than I had ever seen it before. It seemed to be moving backward a little[TN-2], and even more, to be changing phase. I closed my eyes, and when I opened them again, sleepily, the bright area was perceptibly smaller. If I could stay awake long enough, there would be only a crescent again. If I could stay awake--But I could not....

Only the rattling of dishes as Garth prepared breakfast brought me back to consciousness. I got to my feet sheepishly.

"How long have I slept?"

"Twenty hours straight. You looked as if you might have gone on forever. It's the lack of disturbance to indicate time. I got in a little myself, once we were out of the solar system."

A sandwich in one hand, I wandered over the vessel. It was rea.s.suringly solid and concrete. And yet there was something lacking.

"Garth," I asked, "what's become of the sun?"

"I thought you'd want to know that." He led me to the rear telescope.

"But I don't see anything."

"You haven't caught on yet. See that bright yellowish star on the edge of the constellation Scorpio. That's it."

Involuntarily, I gasped. "Then--how far away are we?"

"I put on full acceleration fifteen hours ago, when we pa.s.sed Neptune, and we have covered thirty billion miles--three hundred times as far as from the moon to the sun, but only one half of one per cent of a light-year."

I was speechless, and Garth led me back to the control board. He pointed out the acceleration control, now turned up to its last notch forward; he also showed me the dials which were used to change our direction.

"Just keep that star on the cross hairs. It's Pi Orionis, a little out of our course, but a good target since it is only twenty-five light-years away. Half the light is deflected on this screen, with a delicate photo-electric cell at its center. The instant the light of the star slips off it, a relay is started which lights a red lamp here, and in a minute sounds a warning bell. That indicator over there shows our approach to any body. It works by the interaction of the object's gravitational field with that of my projector, and we can spot anything sizable an hour away. Sure you've got everything?"

It all seemed clear. Then I noticed at the top three clock-like dials; one to read days, another to record the speeds of light, and the third to mark light-years traveled.

"These can't really work?" I said. "We have no way to check our speed with outer s.p.a.ce."

"Not directly. This is geared with clockwork to represent an estimate based on the acceleration. If your theory is right, then the dials are all wrong."

"And how long do you expect to go ahead without knowing the truth?"

"Until we ought to be at Pi Orionis. At two weeks and twenty-five light-years by the dials, if we aren't there we'll start back. By your figuring, we shouldn't be yet one light-year on the way. Anything more?"

"No, I think I can manage it."

"Wake me if anything's wrong. And look out for dark stars." Then he had left me there at the controls. In five minutes he was asleep and the whole s.h.i.+p was in my hands.

For hours nothing happened. Without any control of mine, the s.h.i.+p went straight ahead. I could get up and walk about, with a weather eye on the board, and never was there the flash of a danger light. But I was unable to feel confident, and went back to look out through the gla.s.s.

The stars were incredibly bright and clear. Right ahead were Betelguese and Rigel, and the great nebula of Orion still beyond. There was no twinkling, but each star a bright, steady point of light. And if Garth's indicators were correct, we were moving toward them at a speed now seventy-five times that of light itself. If they were correct.... How could one know, before the long two weeks were over?

But before I could begin to think of any plan, my eye was caught by the red lamp flas.h.i.+ng on the panel. I pressed the attention b.u.t.ton before the alarm could ring, then started looking for the body we were in danger of striking. The position indicators pointed straight ahead, but I could see nothing. For ten minutes I peered through the telescope, and still no sign. The dials put the thing off a degree or so to the right now, but that was too close. In five more minutes I would swing straight up and give whatever it was a wide berth.

I looked out again. In the angle between the cross hairs, wasn't there a slight haze? In a moment it was clear. A comet, apparently, the two of us racing toward each other. Bigger it grew and bigger, hurtling forward. Would we hit?

The dials put it up a little and far off to the right, but it was still frightening. The other light had come on, too, and I saw that we had been pulled off our course by the comet's attraction. I threw the nose over, past on the other side for leeway, then straightened up as the side-distance dial gave a big jump away. Though the gaseous globe, tailless of course away from the sun, showed as big as the full Earth, the danger was past.

As I watched, the comet vanished from the field of the telescope. Five minutes, perhaps, with the red danger light flickering all the time. Then, with a ghastly flare through the right hand windows, it had pa.s.sed us.

Garth sat straight up. "What happened?" he yelled.

"Just a comet. I got by all right."

He settled back, having been scarcely awake, and I turned to the board again. The danger light had gone out, but the direction indicator was burning. The near approach of the comet had thrown us off our course by several degrees. I straightened the s.h.i.+p up easily, and had only a little more difficulty in stopping a rocking motion. Then again the empty hours of watching, gazing into the stars.

Precisely at the end of eighteen hours, Garth awakened, as if the consummation of a certain number of internal processes had set off a little alarm clock in his brain. We were forty-one hours out, with a speed, according to the indicator, of one hundred and twenty-eight times that of light, and a total distance covered of slightly over one quarter of a light-year. A rather small stretch, compared to the 466 light-years we had to go. But when I went back for a look out of the rear telescope, the familiar stars seemed to have moved the least bit closer together, and the sun was no brighter than a great number of them.

I slept like a log, but awakened a little before my trick was due.

Exactly on schedule, fourteen days and some hours after we had started off, we pa.s.sed Pi Orionis. For long there had been no doubt in my mind that, whatever the explanation, our acceleration was holding steady. In the last few hours the star swept up to the brilliance of the sun, then faded again until it was no brighter than Venus. Venus! Our sun itself had been a mere dot in the rear telescope until the change in our course threw it out of the field of vision.

At sixty-five light-years, twenty-three days out, Beta Eridani was almost directly in our path for Rigel. Slightly less than a third of the distance to the midpoint, in over half the time. But our speed was still increasing 200 miles a second every second, almost four times the speed of light in an hour. Our watches went on with a not altogether disagreeable monotony.

There was no star to mark the middle of our journey. Only, toward the close of one of my watches, a blue light which I had never noticed came on beside the indicator dials, and I saw that we had covered 233 light-years, half the estimated distance to Rigel. The speed marker indicated 3975 times the speed of light. I wakened Garth.

"You could have done it yourself," he complained, sleepily, "but I suppose it's just as well."

He went over to the board and started warming up the rear gravity projector.

"We'll turn one off as the other goes on. Each take one control, and go a notch at a time." He began counting, "One, two, three ..."

On the twentieth count, my dial was down to zero, his up to maximum deceleration, and I pulled out my switch. Garth snapped sideways a lever on the indicators. Though nothing seemed to happen, I knew that the speed dial would creep backward, and the distance dial progress at a slower and slower rate. While I was trying to see the motion, Garth had gone back to bed. I turned again to the gla.s.s and looked out at Rigel, on the cross hairs, and Kappa Orionis, over to the left, and the great nebula reaching over a quarter of the view with its faint gaseous streamers.

And so we swept on through s.p.a.ce, with Rigel a great blue glory ahead, and new stars, invisible at greater distances, flaring up in front of us and then fading into the background as we pa.s.sed. For a long time we had been able to see that Rigel, as inferred from spectroscopic evidence, was a double star--a fainter, greener blue companion revolving with it around their common center of gravity. Beyond Kappa Orionis, three hundred light-years from the sun, the s.p.a.ce between the two was quite evident. Beyond four hundred light-years, the brilliance of the vast star was so great that it dimmed all the other stars by comparison, and made the nebula seem a mere faint gauze. And yet even with this gradual change, our arrival was a surprise.

When he relieved me at my watch, Garth seemed dissatisfied with our progress. "It must be farther than they've figured. I'll stick at twenty-five times light speed, and slow down after we get there by taking an orbit."

"I'd have said it was nearer than the estimate," I tried to argue, but was too sleepy to remember my reasons. Propped up on one elbow, I looked around and out at the stars. There was a bright splash of light, I noticed, where the telescope concentrated the radiation of Rigel at one spot on the screen. I slept, and then Garth was shouting in my ear: "We're there!"

I opened my eyes, blinked, and shut them again in the glare.

"I've gone around three or four times trying to slow down. We're there, and there's a planet to land on."

At last I could see. Out the window opposite me, Rigel was a blue-white disk half the size of the sun, but brighter, with the companion star a sort of faint reflection five or ten degrees to the side. And still beyond, as I shaded my eyes, I could see swimming in the black a speck with the unmistakable glow of reflected light.

With both gravity projectors in readiness, we pulled out of our orbit and straight across toward the planet, letting the attraction of Rigel fight against our still tremendous speed. For a while, the pull of the big star was almost overpowering. Then we got past, and into the gravitational field of the planet. We spiralled down around it, looking for a landing place and trying to match our speed with its rotational velocity.

From rather unreliable observations, the planet seemed a good deal smaller than the moon, and yet so dense as to have a greater gravitational attraction. The atmosphere was cloudless, and the surface a forbidding expanse of sand. The globe whirled at a rate that must give it a day of approximately five hours. We angled down, picking a spot just within the lighted area.

A landing was quite feasible. As we broke through the atmosphere, we could see that the sand, although blotched with dark patches here and there, was comparatively smooth. At one place there was a level outcropping of rock, and over this we hung. It was hard work, watching through the single small port in the floor as we settled down. Finally the view was too small to be of any use. I ran to the side window, only to find my eyes blinded by Rigel's blaze. Then we had landed, and almost at the same moment Rigel set. Half overlapped by the greater star, the faint companion had been hidden in its glare. Now, in the dusk, a corner of it hung ghostlike on the horizon, and then too had disappeared.

I flashed on our lights, while Garth cut out the projector and the floor gravity machine. The increase in weight was apparent, but not particularly unpleasant. After a few minutes of walking up and down I got used to it.

Through a stop-c.o.c.k in the wall, Garth had drawn in a tube of gas from the atmosphere outside, and was a.n.a.lyzing it with a spectroscope.

"We can go out," he said. "It's unbreathable, but we'll be able to use the s.p.a.ce suits. Mostly fluorine. It would eat your lungs out like that!"

"And the suits?"