He was still sleepwalking; nevertheless, in Chandra's expert opinion, he was now quite capable of flying Discovery from its close orbit around Io up to the rendezvous with Big Brother.
The prospect of getting an extra seven thousand kilometres away from the burning hell beneath them was welcomed by everyone. Trivial though that distance was in astronomical terms, it meant that the sky would no longet be dominated by a landscape that might have been imagined by Dante or Hieronymus Bosch. And although not even the most violent eruptions had blasted any material up to the ships, there was always the fear that Io might attempt to set a new record. As it was, visibility from Leonov's observation deck was steadily degraded by a thin film of sulphur, and sooner or later someone would have to go out and clean it off.
Only Curnow and Chandra were aboard Discovery when Hal was given the first control of the ship. It was a very limited form of control; he was merely repeating the program that had been fed into his memory, and monitoring its execution. And the human crew was monitoring him: if any malfunction occurred, they would take over immediately.
The first burn lasted for ten minutes; then Hal reported that Discovery had entered the transfer orbit. As soon as Leonov's radar and optical tracking confirmed that, the other ship injected itself into the same trajectory. Two minor in-course corrections were made; then, three hours and fifteen minutes later, both arrived uneventfully at the first Lagrange point, L. 1 - 10,500 kilometres up, on the invisible line connecting the centres of Io and Jupiter.
Hal had behaved impeccably, and Chandra showed unmistakable traces of such purely human emotions as satisfaction and even joy. But by that time, everyone's thoughts were elsewhere; Big Brother, alias Zagadka, was only a hundred kilometres away.
Even from that distance, it already appeared larger than the Moon as seen from Earth, and shockingly unnatural in its straight-edged, geometrical perfection. Against the background of space it would have been completely invisible, but the scudding Jovian clouds 350,000 kilometres below showed it up in dramatic relief. They also produced an illusion that, once experienced, the mind found almost impossible to refute. Because there was no way in which its real location could be judged by the eye, Big Brother often looked like a yawning trapdoor set in the face of Jupiter.
There was no reason to suppose that a hundred kilometres would be 'safer than ten, or more dangerous than a thousand; it merely seemed psychologically right for a first reconnaissance. From that distance, the ship's telescopes could have revealed details only centimetres across -but there were none to be seen. Big Brother appeared completely featureless; which, for an object that had, presumably, survived millions of years of bombardment by space debris, was incredible.
When Floyd stared through the binocular eyepiece, it seemed to him that he could reach out and touch those smooth, ebon surfaces - just as he had done on the Moon, years ago. That first time, it had been with the gloved hand of his spacesuit. Not until the Tycho monolith had been enclosed in a pressurized dome had he been able to use his naked hand.
That had made no difference; he did not feel that he had ever really touched TMA-1. The tips of his fingers had seemed to skitter over an invisible barrier, and the harder he pushed, the greater the repulsion grew. He wondered if Big Brother would produce the same effect.
Yet before they came that close, they had to make every test they could devise and report their observations to Earth. They were in much the same position as explosives experts trying to defuse a new type of bomb, which might be detonated by the slightest false move. For all that they could tell, even the most delicate of radar probes might trigger some unimaginable catastrophe.
For the first twenty-four hours, they did nothing except observe with passive instruments - telescopes, cameras, sensors on every wavelength. Vasili Orlov also took the opportunity of measuring the slab's dimensions with the greatest possible precision, and confirmed the famous 1:4:9 ratio to six decimal places. Big Brother was exactly the same shape as TMA-1 - but as it was more than two kilometres long, it was 718 times larger than its small sibling.
And there was a second mathematical mystery. Men had been arguing for years over that 1:4:9 ratio - the squares of the first three integers. That could not possibly be a coincidence; now here was another number to conjure with.
Back on Earth, statisticians and mathematical physicists were soon playing happily with their computers, trying to relate the ratio to the fundamental constants of nature - the velocity of light, the proton/electron mass ratio, the fine-structure constant. They were quickly joined by a gaggle of numerologists, astrologers, and mystics, who threw in the height of the Great Pyramid, the diameter of Stonehenge, the azimuth bearings of the Nazca lines, the latitude of Easter Island, and a host of other factors from which they were able to draw the most amazing conclusions about the future. They were not in the least deterred when a celebrated Washington humorist claimed that his calculations proved that the world ended on 31 December 1999 - but that everyone had had too much of a hangover to notice.
Nor did Big Brother appear to notice the two ships that had arrived in its vicinity - even when they cautiously probed it with radar beams and bombarded it with strings of radio pulses which, it was hoped, would encourage any intelligent listener to answer in the same fashion.
After two frustrating days, with the approval of Mission Control, the ships halved their distance. From fifty kilometres, the largest face of the slab appeared about four times the width of the Moon in Earth's sky - impressive, but not so large as to be psychologically overwhelming. It could not yet compete with Jupiter, ten times larger still; and already the mood of the expedition was changing from awed alertness to a certain impatience.
Walter Curnow spoke for almost everyone: "Big Brother may be willing to wait a few million years - we'd like to get away a little sooner."
24
Reconnaissance
Discovery had left Earth with three of the little space pods that allowed an astronaut to perform extravehicular activities in shirt-sleeve comfort. One had been lost in the accident - if it was an accident - that had killed Frank Poole. Another had carried Dave Bowman to his final appointment with Big Brother, and shared whatever fate befell him, A third was still in the ship's garage, the Pod Bay.
It lacked one important component - the hatch, blown off by Commander Bowman when he had made his hazardous vacuum-crossing and entered the ship through the emergency airlock, after Hal had refused to open the Pod Bay door. The resulting blast of air had rocketed the pod several hundred kilometres away before Bowman, busy with more important matters, had brought it back under radio control. It was not surprising that he had never bothered to replace the missing hatch.
Now Pod Number 3 (on which Max, refusing all explanations, had stencilled the name Nina) was being prepared for another EVA. It still lacked a hatch, but that was unimportant. No one would be riding inside.
Bowman's devotion to duty was a piece of unexpected luck, and it would have been folly not to take advantage of it. By using Nina as a robot probe, Big Brother could be examined at close quarters without risking human lives. That at least was the theory; no one could rule out the possibility of a backlash that might engulf the ship. After all, fifty kilometres was not even a hair's breadth, as cosmic distances went.
After years of neglect, Nina looked distinctly shabby. The dust that was always floating around in zero gee had settled over the outer surface, so that the once immaculately white hull had become a dingy grey. As it slowly accelerated away from the ship, its external manipulators folded neatly back and its oval viewport staring spaceward like a huge, dead eye, it did not seem a very impressive ambassador of Mankind. But that was a distinct advantage; so humble an emissary might be tolerated, and its small size and low velocity should emphasize its peaceful intentions. There had been a suggestion that it should approach Big Brother with open hands; the idea was quickly turned down when almost everyone agreed that if they saw Nina heading toward them, mechan
ical claws outstretched, they would run for their lives.
After a leisurely two-hour trip, Nina came to rest a hundred metres from one corner of the huge rectangular slab. From so close at hand, there was no sense of its true shape; the TV cameras might have been looking down on the tip of a black tetrahedron of indefinite size. The onboard instruments showed no sign of radioactivity or magnetic fields; nothing whatsoever was coming from Big Brother except the tiny fraction of sunlight it condescended to reflect.
After five minutes' pause - the equivalent, it was intended, of "Hello, here I am!" - Nina started a diagonal crossing of the smaller face, then the next larger, and finally the largest, keeping at a distance of about fifty metres, but occasionally coming in to five. Whatever the separation, Big Brother looked exactly the same - smooth and featureless. Long before the mission was completed, it had become boring, and the spectators on both ships had gone back to their various jobs, only glancing at the monitors from time to time.
"That's it," said Walter Curnow at last, when Nina had arrived back where she had started. "We could spend the rest of our lives doing this, without learning anything more. What do I do with Nina - bring her home?"
"No," said Vasili, breaking into the circuit from aboard Leonov. "I've a suggestion. Take her to the exact centre of the big face. Bring her to rest - oh, a hundred metres away. And leave her parked there, with the radar switched to maximum precision."
"No problem - except that there's bound to be some residual drift. But what's the point?"
"I've just remembered an exercise from one of my college astronomy courses - the gravitational attraction of an infinite flat plate. I never thought I'd have a chance of using it in real life. After I've studied Nina's movements for a few hours, at least I'll be able to calculate Zagadka's mass, That is, if it has any. I'm beginning to think there's nothing really there."
"There's an easy way to settle that, and we'll have to do it eventually. Nina must go in and touch the thing."
"She already has."
"What do you mean?" asked Curnow, rather indignantly. "I never got nearer than five metres."
"I'm not criticizing your driving skills - though it was a pretty close thing at that first corner, wasn't it? But you've been tapping gently on Zagadka every time you use Nina's thrusters near its surface."
"A flea jumping on an elephant!"
"Perhaps. We simply don't know. But we'd better assume that, one way or another, it's aware of our presence, and will only tolerate us as long as we aren't a nuisance."
He left the unspoken question hanging in the air. How did one annoy a two-kilometre-long black rectangular slab? And just what form would its disapproval take?
25
The View from Lagrange
Astronomy was full of such intriguing but meaningless coincidences. The most famous was the fact that, from the Earth, both Sun and Moon have the same apparent diameter. Here at the L.1 libration point, which Big Brother had chosen for its cosmic balancing act on the gravitational tightrope between Jupiter and Io, a similar phenomenon occurred. Planet and satellite appeared exactly the same size.
And what a size! Not the miserable half-degree of Sun and Moon, but forty times their diameter - sixteen hundred times their area. 'The sight of either was enough to fill the mind with awe and wonder; together, the spectacle was overwhelming.
Every forty-two hours, they would go through their complete cycle of phases; when Io was new, Jupiter was full, and vice versa. But even when the Sun was hiding behind Jupiter and the planet presented only its nightside, it was unmistakably there - a huge black disk eclipsing the stars. Sometimes that blackness would be momentarily rent by lightning flashes lasting for many seconds, from electrical storms far larger than the Earth.
On the opposite side of the sky, always keeping the same face toward its giant master, Io would be a sluggishly boiling cauldron of reds and oranges, with occasional yellow clouds erupting from one of its volcanoes, and falling swiftly back to the surface. Like Jupiter, but on a slightly longer time scale, Io was a world without geography. Its face was remodelled in a matter of decades - Jupiter's, in a matter of days.
As Io waned toward its last quarter, so the vast, intricately banded Jovian cloudscape would light up beneath the tiny, distant sun. Sometimes the shadow of Io itself, or one of the outer satellites, would drift across the face of Jupiter; while every revolution would show the planet-sized vortex of the Great Red Spot - a hurricane that had endured for centuries if not for millennia.
Poised between such wonders, the crew of Leonov had material for lifetimes of research - but the natural objects of the Jovian system were at the very bottom of their list of priorities. Big Brother was Number 1; though the ships had now moved in to only five kilometres, Tanya still refused to allow any direct physical contact. 'I'm going to wait," she said, 'until we're in a position to make a quick getaway. We'll sit and watch - until our launch window opens. Then we'll consider our next move."
It was true that Nina had finally grounded on Big Brother, after a leisurely fifty-minute fall. This had allowed Vasili to calculate the object's mass as a surprisingly low 950,000 tons, which gave it about the density of air. Presumably it was hollow - which provoked endless speculation about what might be inside.
But there were plenty of practical, everyday problems to take their minds off these greater issues. Housekeeping chores aboard Leonov and Discovery absorbed ninety per cent of their working time, though operations' were much more efficient since the two ships had been coupled by a flexible docking connection. Curnow had finally convinced Tanya that Discovery's carousel would not suddenly seize up and tear the ships to pieces, so it had become possible to move freely from one vessel to the other merely by opening and closing two sets of airtight doors. Spacesuits and time-consuming EVAs were no longer necessary - to the great delight of everyone except Max, who loved going outside and exercising with his broomstick.
The two crew members quite unaffected by this were Chandra and Ternovsky, who now virtually lived aboard Discovery and worked around the clock, continuing their apparently endless dialogue with Hal. 'When will you be ready?' they were asked at least once a day. They refused to make any promises; Hal remained a low-grade moron.
Then, a week after the rendezvous with Big Brother, Chandra unexpectedly announced: "We're ready."
Only the two lady medics were absent from Discovery's flight deck, and that was merely because there was no room for them; they were watching on Leonov's monitors. Floyd stood immediately behind Chandra, his hand never far from what Curnow, with his usual gift for the neat phrase, had called his pocket giant-killer.
"Let me emphasize again," said Chandra, "that there must be no talking. Your accents will confuse him; I can speak, but no one else. Is that understood?"
Chandra looked, and sounded, at the edge of exhaustion. Yet his voice held a note of authority that no one had ever heard before. Tanya might be the boss everywhere else, but he was master there.
The audience - some anchored to convenient handholds, some floating freely - nodded assent. Chandra closed an audio switch and said, quietly but clearly: "Good morning, Hal."
An instant later, it seemed to Floyd that the years had rolled away. It was no longer a simple electronic toy that answered back. Hal had returned.
"Good morning, Dr Chandra."
"Do you feel capable of resuming your duties?"
"Of course. I am completely operational and all my circuits are functioning perfectly."
"Then do you mind if I ask you a few questions?"
"Not at all."
"Do you recall a failure of the AE 35 antenna control unit?"
"Certainly not."
Despite Chandra's injunction, there was a little gasp from the listeners. This is like tiptoeing through a minefield, thought Floyd, as he patted the reassuring shape of the radio cut-off. If that line of questioning triggered another psychosis, he could kill Hal in a second. (He knew, having rehearsed the procedure
a dozen times.) But a second was aeons to a computer; that was a chance they would have to take.
"You do not remember either Dave Bowman or Frank Poole going out to replace the AE 35 unit?"
"No. That could not have happened, or I would have remembered it. Where are Frank and Dave? Who are these people? I can only identify you - though I compute a sixty-five per cent probability that the man behind you is Dr Heywood Floyd."
Remembering Chandra's strict injunction, Floyd refrained from congratulating Hal. After a decade, sixty-five per cent was a pretty good score. Many humans would not have done so well.
"Don't worry, Hal - I will explain everything later."
"Has the mission been completed? You know I have the greatest enthusiasm for it."
"The mission has been completed; you have carried out your program. Now - if you will excuse us - we wish to have a private conversation."
"Certainly."
Chandra switched off sound and vision inputs to the main console. As far as this part of the ship was concerned, Hal was now deaf and blind.
"Well, what was all that about?" demanded Vasili Orlov.
"It means," said Chandra, carefully and precisely, "that I have erased all Hal's memories, beginning at the moment when the trouble started."
"That sounds quite a feat," marvelled Sasha. "How did you do it?"
"I am afraid it would take me longer to explain than it did to carry out the operation."
"Chandra, I am a computer expert - though not in the same class as you and Nikolai. The 9000 series uses holographic memories, doesn't it? So you couldn't have used a simple chronological erasure. It must have been some kind of tapeworm, homing on selected words and concepts?"
"Tapeworm?" said Katerina over the ship's intercom. "I thought that was my department - though I'm glad to say I've never seen one of the beastly things outside a jar of alcohol. What are you talking about?"