Beq’qdahl’s voice betrayed interest. <What of it?>

<Noble Beq’qdahl, I have in mind an amusing game….>

THREE

Killeen fell.

It had taken him years to truly get used to the sensation of free-fall, and that had been outside Argo, in the silent enormity of open space. It had been possible then to convince his reflexes that he was in some sense flying, airy and buoyant, oblivious to gravity’s cruel laws.

But here…Here he plunged downward between mottled glowing walls that rushed past with dizzying speed. He felt the silvery rim of New Bishop thrusting up to meet him as the planet flattened into a plain. Crinkled mountains grew, detail getting finer with every moment. Through the gauzy sheen of the whirling cosmic string he watched the planet grow.

The polar region still held a few rivulets of white, snow from what must have once been an icecap. The land had a naked look, pale and barren, as though recently exposed. It stretched away, filling half his sky beyond the glowing translucent walls of the hoop-tube. The ravaged land was rutted by fresh rivers that poured over jagged scarps. He could see rough roads cut by treads, broad tracks of churned mud.

The ground hurtled up, a vast hand swatting at him, and he flinched automatically. He plunged toward a broad hillside—

—braced himself for the impact—

—and felt nothing.

Instantly he shot through into a dim golden world, alone.

Glowing walls gave some light but he could see nothing beyond them. Far below, between his boots, was a glaring yellow point. Arthur’s voice came to him:

I have conferred with Grey. She unfortunately knows nothing more of this than I. We are left with only educated guesses. This tube is indeed empty, free even of air. We are inside the planet now. I estimate our speed at 934 meters per second.

Dark mottled shapes soared up toward him and flashed soundlessly past in the walls. “Headed for what?”

If the alien cyborgs have constructed this miraculous planet-coring device with the precision I would expect of them, I predict we shall plunge entirely through the center and out to the other side.

“What’s a cyborg?” Killeen asked, to focus his mind. His Grey Aspect answered faintly:

Half-organic being…half-machine…I could not ascertain…exact proportions…from such hasty observation…historical records…spoke of such a race…in very early days…the Great Times…

“Skip that! How can I get out?”

Arthur replied crisply:

We cannot. By thrusting the cosmic string to very near the planetary axis, the cyborgs ensured that there is no spin along this tube. Matter coming up from the core—or down from outside, as we are—will suffer no slow drift, and so should not strike the walls. In addition, uniquely to this choice they have adroitly made, there is no Coriolis force which would deflect us.

Killeen could not follow the jargon but he understood it was all bad news.

Despite the glowing walls the light around him was dimming.

He fought down rising panic. Part of his fear came from the simple fact that he was falling at greater and greater speeds, and sheer animal terror threatened to engulf him. Against this consuming fear he fought like a man hammering at a dark wave which loomed ever higher. His breath caught. He forced his throat to open, his lungs to stop their spasmodic heaving.

Grainy, blurred shapes flashed past. These were features in the rock, illuminated by the thin barrier of the rotating hoop.

The yellow glare below had swollen to a brilliant disk. He could feel now through his sensorium a bone-deep bass whuum-whuum-whuum-whuum of the spinning magnetic fields.

“Maybe…maybe I can reach the walls. Is there any way I can slow down?”

Killeen felt Arthur’s sharp, pealing laugh. A circle appeared in his left eye. It billowed into a sphere—the planet—with a red line thrust along the axis of revolution. A small blue dot moved inward near the top of the axis, just below the surface.

We have now acquired a speed of 1,468 meters per second. The hoop material, remember, is extremely dense—many millions of tons per kilometer. All packed into a thread which hardly spans an atom’s width, whirling at immense speed. If you were to strike that matter at our present speed, your hand would vaporize.

Killeen’s breath came in fast, jerky pants. “Suppose they get some core metal in here, comin’ out, and we meet it.”

I don’t suppose I have to analyze that possibility for you.

“No, guess not.”

Killeen cast about for some idea, some fleeting hope. The walls were nearly dark now, the radiance of the hoop somehow absorbed by the rock beyond. Smoldering orange-brown wedges shot past—lava trapped in underground vaults, great oceans of livid, scorching rock.

I would suppose that the hoop-tube is left to stand empty at times. Perhaps the cyborgs are now working on some minor repairs. Or perhaps they simply pause to let the orbited teams which are fashioning the first batch of core metal do their work. In any case, assuming the cyborg above did not simply throw us in to see us boiled away by a gusher of iron, there is another fate.

Killeen tried to calm himself and focus on Arthur’s words. The walls seemed closer as he fell, the tube narrowing before him. He pulled himself rigid and straight, arms at his sides, feet down toward the yellow disk below that grew steadily. He blinked back sweat and tried to see better.

I believe we have passed through the crust and are now accelerating through the mantle. Note that the occasional lava lakes are getting larger and more numerous. Temperature increases here by about 10 degrees centigrade every kilometer we fall. This will continue until the temperature exceeds the melting point of simple silicate rocks. Then—drawing on studies of similar planets—we will enter an increasingly dense and hot core. At this point the rocks will be fluid and at about 2,800 degrees centigrade.

“Howcome rock doesn’t fill up this tube?”

The hoop pressure, which is truly immense. Grey calculates—

“And the heat? The hoop stops that?” Killeen asked, seeking reassurance, though he already suspected the answer.

Heat is infrared electromagnetic radiation. The hoop is transparent to it. All light passes through it—which is why we see now the dark rock beyond. Soon, though, the silicates will begin to glow with the heat of their compression.

“What’ll we do?”

The heat radiation exerts a pressure. But this is symmetric, of course, acting equally in all directions. So it cannot push us toward one wall in preference to another. But it will cook us quite thoroughly.

“How…how long?”

Passage through the core…about 9.87 minutes.

“My suit—it’ll silver up for me.”

True, it already has. And I calculate we might survive one entire passage if we seal up completely, close your helmet visor, damp all inputs. Perhaps the cyborg understood that; it may know a good deal about our technology. Yes, yes…I am beginning to see its devilish logic.

Killeen shut down his suit inputs. He left only a slight lightpipe for optical images. His suit skin reflected the blur of thickening light around him with a mirror finish. The walls rushing past were turning ruddy, sullen. “Where are we?”

We must be approaching the boundary at which iron melts. This reddening probably signals the transition from the mantle to the outer core. We can expect some varying magnetic fields now, since this is the region—so theory says—where the planet’s field is born. Large currents of molten metal eddy about, carrying electrical currents, like great wires in a generator station. New Bishop’s spin serves to wrap these around, creating current vortexes, which in turn stir up magnetic whorls.