"At last, though, after long ages, there drew down toward them the doom which they had averted for so long. Alto was still shrinking, cooling, and now they were settled upon its warmest, inmost planet, and had no warmer world to which to flee. But a short time longer, as they measured time, and their planet would become a frozen, lifeless world, for their sun would inevitably cool still further until it was one of the countless dark stars, dead and burned-out suns, which throng the heavens. It seemed, indeed, that this time there was to be no escape.
"But now there came forward a party among them which advanced a proposal of colossal proportions. They pointed out that Alto was moving steadily toward another sun, one much the same size as their own but flaming with heat and life, which it would pass closely within a short time. But if, instead of passing each other, the two suns should meet, should crash into each other, what then would be the result? It would be, of course, that the collision would form one new sun instead of the former two-one titanic, flaming sun whose heat would be sufficient to support life on any planet for countless ages. The inmost planets of Alto's system, and virtually all the planets of the other sun's system, would be annihilated by the collision, of course, would perish in that flaming shock of suns. But the outermost planets of Alto, which lay in orbits billions of miles from it, would be safe enough and would take up their orbits around this great new sun in place of Alto. And on these planets the globe-people could exist for eons, supported by the heat of the great new sun. It was a perfect plan, and required only that their own sun, Alto, be swerved from its path just enough to make it crash into the other sun instead of passing it.
"To accomplish this, to swerve their star from its course, the globemen made use of a simple physical principle. You know that a round, spinning body, moving across or through any medium, changes its direction if the rate of its spinning is changed. A ball that rolls across a smooth table without spinning at all will move in a straight line. But if the ball spins as it rolls it will move in a curved line, the amount and direction of curve depending upon the amount and direction of spin. Now their sun, which had rotated at the same rate for ages, had rolled through the ether for ages on the same great course, never swerving. And so, they reasoned, if their sun's rate of spin or rotation could be increased a little it would curve aside a little from its accustomed course.
"The problem, then, was to increase their sun's rate of spin, and to accomplish this they gathered all their science. A mighty tower was erected over their city, on whose great top-platform were placed machines which could generate an etheric ray or vibration of inconceivable power, a ray which could be directed at will through the great telescopelike projector which they had provided for it.
"This done, they waited until the moment calculated by their astronomers, then aimed the great projector-tube at the edge of their sun that was rotating away from them, and turned on the ray. This was the crucial point of their scheme, for now they were risking their very universe. It was necessary for them to increase their sun's rate of spin just enough to make it swerve aside, but if the rate of spin were increased just a little too much it would mean disaster, since when a sun spins too fast it breaks up like a great flywheel, splits into a double star. It is that process, the process of fission, which has formed the countless double stars and bursted suns in the heavens around us, since each was only a single star or sun which broke up because of its too-great speed of rotation, or spin. And the globe-men knew that it would require but very little increase in their own sun's rate of spin to make it, too, split asunder. So they watched with infinite care while their brilliant ray stabbed up toward the sun's edge, and when, under the terrific power of that pushing ray, the star began to spin faster, they at once turned off the ray, which was used for a short time only. But it had been effective; for now, as their sun spun faster, it began to swerve a little from its usual course, and they knew that now it would crash into the other approaching sun instead of passing it. So their end was achieved, and so they began their preparations for their great migration out to Alto's outermost planets, a migration which would take place just before the collision. And then-we came.
"We came, and now we have discovered that for which we came, the reason for Alto's change in course. For it was the science and will of the globe-men that turned their sun aside, that threatens now the annihilation of the Eight Worlds. Doom presses upon them, and to escape that doom they are destroying our sun, our planets, our very universe!"
IV
I do not remember that any of us spoke, when Sarto Sen's voice had ceased. And yet, stunned as we were by the thing he had told us, our knowledge was in some ways a relief. We had discovered, at least, what had swerved Alto from its course, and if science and intelligence alone could cause the sun to veer from its path, science and intelligence might steer it back into that path.
When I said as much to Sarto Sen his face lit up. "You are right, Jan Tor!" he exclaimed. "There's a chance! And even as Mur Dak predicted, that chance depends on us. For if we can escape from here and get back to the Eight Worlds, we can come back with a greater force and crush these globe-men, and use their own force-projector to swerve their sun out of its present path."
"But why go back to the Eight Worlds?" objected Hal Kur. "Why not get up to that platform, if we escape, and use the projector ourselves?"
Sarto Sen shook his head. "It's impossible," he told the big engineer. "If we escape from here at all it will be by night, for by day the rooms and corridors outside are thronged with globe-men. And by night we could do nothing, for Alto, the sun itself, would not then be in the sky. Nor could we wait for its rising, there on the platform, since our escape would soon be discovered, and we should be attacked there. Our only chance is to get out of here by night, make our way up to the platform, and make a dash for our ship. If we can do that we can flash back to our own universe and get the help we need to crush these globe-people."
"But when shall we make the attempt?" I asked, and my heart leaped at Sarto Sen's answer. "Tonight! The sooner we get out the better. A few hours after dark we'll try it." He went on, then, to unfold his plan for escape, and we listened intently, while big Hal Kur's eyes gleamed at the prospect of action. Our plan was simple enough, and likely enough to fail, we knew, but it was our only chance. What course we would follow after getting free of our cell we did not even discuss. There was nothing for it but to make our break and trust to luck to bring us through the thousand obstacles that lay between us and the tower-platform which held our ship.
The remaining hours of that day were the longest I have ever experienced. The slanting shafts of light from the loopholes seemed to move across the room with infinite slowness, while we awaited impatiently the coming of night. At last the light-bars darkened, disappeared, as the dying crimson sun sank beyond the rim of the world outside. Darkness had descended on that world, now, and here and there among the buildings, and streets of the weird city outside flared points of red light. Still we waited, until the vague, half-heard sounds of soft movement and thrumming speech outside had lessened, ceased, until at last the only sound to be heard was an occastional shuffling movement of the guard outside the door.
Sarto Sen rose, making to us a signal of readiness, and then threw himself flat on the floor of the room's center. At the farther side of the cell lay Hal Kur and Nar Lon, as though sleeping, with a thick roll of garments between them which resembled another sleeping figure. These preparations made, I stepped to the door and stationed myself directly inside it, to one side, my heart pounding now as the moment for action approached.