His Arthur Aspect seemed remarkably collected, given the hysteria which had beset it only minutes before. “How…how ’bout that cooling thing?”

You mean our refrigerator? It can only function by ejecting waste heat at a cooler sink. As yet there are no colder surroundings, as you can see.

“So we wait till we get out?” It seemed an impossibly long time. Between his boots he could see the blackness of the planet’s mantle, thousands of kilometers of dead rock they must shoot through before regaining the dark of space itself. And there he would somehow have to make good this attempt, or else he would slow and pause and then plunge again. He wished again that he had saved his thruster fuel. It would give him some freedom, some hope of being something other than the helpless, dumb test particle in a grotesque experiment.

We do have some fluids we could eject, but…

“But what? Look, we try everything. Got no hope otherwise.”

The refrigerant fluids. We could bring them to a high temperature and vent them.

“Think it’ll help much?”

To lose the coolant meant he would have no chance whatever if he failed up ahead and fell back into the tube. He would fry for sure.

I cannot tell how much momentum we picked up from that maneuver. Pushing a large mass such as ourselves with mere light pressure…

Killeen gave a jittery laugh. “I’m the mass here—you weigh nothin’ at all. And don’t you worry ’bout calculatin’ what’ll happen. Time comes, up at the top of this hole, I’ll have to grab whatever’s in sight. Fly by the seat of my pants, not some eee-quation.”

Then I should vent the refrigerant fluids?

“Sure. Bet it all!” Killeen felt small icy rivulets coursing along his neck as he let the Aspect take fractional control of his inboard systems.

I am warming the poly-xenon now.

“And when you spray it, just use the spinal vents. That’ll give us another push in the right direction. Could make the difference.”

Oh, I see. I did not think of this possibility.

“Trouble with you Aspects is you can’t imagine anythin’ you haven’t seen ’fore.”

Let us not debate my properties at quite this time. We are rising toward the surface and you must be ready. I believe the wall you face is nearer now. Notice the sparkling?

“Yeasay. What’s it mean?”

That is where the mantle rock is forced by sidewise pressure against the passing cosmic string. It is disintegrated on impact. I cannot see whether it is somehow incorporated into the string, or whether it is simply forced back. For whatever reason, the rock is held back. Clearly, the cyborgs must relax this hoop pressure somehow, down in the core, in order to fill this tube with the liquid iron we saw before.

“Maybe they just slow it down some? Let the iron squish in a li’l ’fore the next time the string comes whizzin’ by?”

In the midst of techtalk he lapsed back into the short, clipped speech of his boyhood in the Citadel. The carefully assumed veneer of Cap’n rubbed away under the press of action. Killeen fumbled with the suit refrigerator controls. He knew he had to understand more about the hoop.

Possibly. Clearly the rotating string exerts great pressure against these rocks.

Killeen watched the quick flashing in the walls. For him to see these sparks at all, they must be enormous, since his speed took him by kilometers of the ruby-red rock in an instant. He had no bodily sensation of speed, but knew from the 3D simulation Arthur ran in his left eye that he was rising toward the surface, slowing as gravity asserted itself.

He had to find a way to escape the tube, but no idea came to him. He had nothing he could throw to gain momentum. The coolant jet throbbed behind him, but relative to the blur of motion in the walls he could not tell whether it did any good. It occurred to him that if he was too successful he would crash into the speeding wall and be torn to pieces in an instant. Somehow the abstract nature of these things, the dry, distant feel of science, frightened him all the more.

The tube is flaring out. We are approaching one side of it, but I cannot judge our velocity well. As we rise, the hoop curves away to make its great arc outward. The majesty of it is impressive, I must say. No mechtech I have ever heard of matches this. Grey says the historical records suggest even greater works near the Eater.

“Forget that. What can I do?”

I am trying to see how we can use our situation, but I must say that a solution continues to elude me. The dynamics—

“We’re gettin’ close. Come on!”

The rock around him had already ceased glowing. Beyond the walls lay complete darkness. He could not understand how he could be moving up from the center of New Bishop and yet still feel that he was falling. No matter; science was a set of rules to him, and this was simply a rule he did not comprehend.

The tunnel was broadening. A shimmering golden passage flared gradually as he gazed between his boots at shards of light that rushed toward him. More vast lava lakes, brimming with angry reds. The injury to the whole axial length had brutally shoved great masses together, making the walls around him froth with the planet’s jagged orange wrath.

Again he thought of what would happen if he could do nothing up ahead. The cool logic of dynamics would, Arthur said, fling him back into the core. The heat would kill him on the next pass. Or if it managed only to send him into delirium, there would be another cycle, and another, and another…. He would bob endlessly, a crisp cinder obeying simple but inexorable laws.

Instantly he was swimming in light.

Stars bloomed beneath his feet. A bowl of brilliant gas and suns opened as he shot free of the planet’s grasp, above the twilight line. After the sultry darkness this sky was a welcoming bath of colors and contrasts.

Out, free!

He could feel his suit cool as it lost heat to the cold sky. It went ping, pop as joints contracted. Wrinkled hills rose above his head, the whole landscape stretching as it drew away. Here, too, was the stripped look, as though the polar ice had only recently been vanquished.

The golden walls fell away from him on one side, but in front of him the radiance did not fade or recede. It was much closer. He had gained some significant speed, then.

But now he was losing his speed along the tube. He watched the planet above his helmet turn into a gigantic silvery bowl. The dawnline cut this bowl in half. A ruby sky-glow of dustclouds and stars dominated the wan day.

As he rose the world’s curve brought into view a far-off scruff of woodland and stark, jutting mountains. Fluffy white clouds clung to shallow valleys.

His rate of rise dwindled. The far side of the hoop-tube was bending away. In front of him the glow was brighter. He took a few moments to be sure he was in fact curving over along with the hoop walls. Could he see the flicker of motion from the rapidly rotating string? He had begun to think of the walls as solid, and now he became aware of their gauzy nature.

The cosmic string can exert pressure only when it is very near you, of course. You will not in fact strike the cosmic string itself, I judge.

“Thought you said it’d take off my hand.”

I have conferred further with Grey. She believes that normally a string would function like a scythe. However, this highly magnetized string is different. Until now you were moving with respect to the string at high speeds. Now you will have a low relative velocity, but only for a brief moment. At such speeds the string’s magnetic fields will repulse your metallic boots and suit.

“Huh.” Killeen supposed this was good news, but the Aspect spoke as though this was just another dispassionate physics problem. “Look, you save any that cooler stuff?”

Yes, I had anticipated that we might need another push. But there is very little. I needed it all to keep us from losing consciousness back there, and so—