Collected Stories Of Arthur C. Clarke (190 page)

‘Spaceguard reports that the probability of impact on Earth is 99.9%. Operation ATLAS will begin immediately.’

The task of the mythological Atlas was to hold up the heavens and prevent them from crashing down upon Earth. The ATLAS booster that
Goliath
carried as an external payload had a more modest goal: keeping at bay only a small piece of the sky.

It was the size of a small house, weighed 9,000 tons and was moving at 50,000 km/h. As it passed over the Grand Teton National Park, one alert tourist photographed the incandescent fireball and its long vapour trail. In less than two minutes, it had sliced through the Earth’s atmosphere and returned to space
.

The slightest change of orbit during the billions of years it had been circling the sun might have sent the asteroid crashing upon any of the world’s great cities with an explosive force five times that of the bomb that destroyed Hiroshima
.

The date was August 10, 1972
.

Spaceguard had been one of the last projects of the legendary NASA, at the close of the 20th century. Its initial objective had been modest enough: to make as complete a survey as possible of the asteroids and comets that crossed the orbit of Earth – and to determine if any were a potential threat.

With a total budget seldom exceeding $10 million a year, a worldwide network of telescopes, most of them operated by skilled amateurs, had been established by the year 2000. Sixty-one years later, the spectacular return of Halley’s Comet encouraged more funding, and the great 2079 fireball, luckily impacting in mid-Atlantic, gave Spaceguard additional prestige. By the end of the century, it had located more than one million asteroids, and the survey was believed to be 90% complete. However, it would have to be continued indefinitely: there was always a chance that some intruder might come rushing in from the uncharted outer reaches of the solar system.

As had Kali, which had been detected in late 2212 as it fell sunward past the orbit of Jupiter. Fortunately humankind had not been wholly unprepared, thanks to the fact that Senator George Ledstone (Independent, West America) had chaired an influential finance committee almost a generation earlier.

The Senator had one public eccentricity and, he cheerfully admitted, one secret vice. He always wore massive horn-rimmed eyeglasses (nonfunctional, of course) because they had an intimidating effect on uncooperative witnesses, few of whom had ever encountered such a novelty. His ‘secret vice’, perfectly well known to everyone, was rifle shooting on a standard Olympic range, set up in the tunnels of a long-abandoned missile silo near Mount Cheyenne. Ever since the demilitarisation of Planet Earth (much accelerated by the famous slogan ‘Guns Are the Crutches of the Impotent’), such activities had been frowned upon, though not actively discouraged.

There was no doubt that Senator Ledstone was an original; it seemed to run in the family. His grandmother had been a colonel in the dreaded Beverly Hills Militia, whose skirmishes with the LA Irregulars had spawned endless psychodramas in every medium, from old-fashioned ballet to direct brain stimulation. And his grandfather had been one of the most notorious bootleggers of the 21st century. Before he was killed in a shoot-out with the Canadian Medicops during an ingenious attempt to smuggle a kiloton of tobacco up Niagara Falls, it was estimated that ‘Smokey’ had been responsible for at least 20 million deaths.

Ledstone was quite unrepentant about his grandfather, whose sensational demise had triggered the repeal of the late US’s third, and most disastrous, attempt at Prohibition. He argued that responsible adults should be allowed to commit suicide in any way they pleased – by alcohol, cocaine or even tobacco – as long as they did not kill innocent bystanders during the process.

When the proposed budget for Spaceguard Phase 2 was first presented to him, Senator Ledstone had been outraged by the idea of throwing billions of dollars into space. It was true that the global economy was in good shape; since the almost simultaneous collapse of communism and capitalism, the skilful application of chaos theory by World Bank mathematicians had broken the old cycle of booms and busts and averted (so far) the Final Depression predicted by many pessimists. Nonetheless, the Senator argued that the money could be much better spent on Earth – especially on his favourite project, reconstructing what was left of California after the Superquake.

When Ledstone had twice vetoed Spaceguard Phase 2, everyone agreed that no one on Earth would make him change his mind. They had reckoned without someone from Mars.

The Red Planet was no longer quite so red, though the process of greening it had barely begun. Concentrating on the problems of survival, the colonists (they hated the word and were already saying proudly ‘we Martians’) had little energy left over for art or science. But the lightning flash of genius strikes where it will, and the greatest theoretical physicist of the century was born under the bubble domes of Port Lowell.

Like Einstein, to whom he was often compared, Carlos Mendoza was an excellent musician; he owned the only saxophone on Mars and was a skilled performer on that antique instrument. He could have received his Nobel Prize on Mars, as everyone expected, but he loved surprises and practical jokes. Thus he appeared in Stockholm looking like a knight in high-tech armour, wearing one of the powered exoskeletons developed for paraplegics. With this mechanical assistance, he could function almost unhandicapped in an environment that would otherwise have quickly killed him.

Needless to say, when the ceremony was over, Carlos was bombarded with invitations to scientific and social functions. Among the few he was able to accept was an appearance before the World Budget Committee, where Senator Ledstone closely questioned him about his opinion of Project Spaceguard.

‘I live on a world which still bears the scars of a thousand meteor impacts, some of them
hundreds
of kilometres across,’ said Professor Mendoza. ‘Once they were equally common on Earth, but wind and rain – something we don’t have yet on Mars, though we’re working on it! – have worn them away.’

Senator Ledstone: ‘The Spaceguarders are always pointing to signs of asteroid impacts on Earth. How seriously should we take their warnings?’

Professor Mendoza: ‘Very seriously, Mr Chairman. Sooner or later, there’s bound to be another major impact.’

Senator Ledstone was impressed, and indeed charmed, by the young scientist, but not yet convinced. What changed his mind was not a matter of logic but of emotion. On his way to London, Carlos Mendoza was killed in a bizarre accident when the control system of his exoskeleten malfunctioned. Deeply moved, Ledstone immediately dropped his opposition to Spaceguard, approving construction of two powerful orbiting tugs,
Goliath
and
Titan
, to be kept permanently patrolling on opposite sides of the sun. And when he was a very old man, he said to one of his aides, ‘They tell me we’ll soon be able to take Mendoza’s brain out of that tank of liquid nitrogen, and talk to it through a computer interface. I wonder what he’s been thinking about, all these years …’

Assembled on Phobos, the inner satellite of Mars, ATLAS was little more than a set of rocket engines attached to propellant tanks holding 100,000 tons of hydrogen. Though its fusion drive could generate far less thrust than the primitive missile that had carried Yuri Gagarin into space, it could run continuously not merely for minutes but for weeks. Even so, the effect on the asteroid would be trivial, a velocity change of a few centimetres per second. Yet that might be sufficient to deflect Kali from its fatal orbit during the months while it was still falling earthward.

Now that ATLAS’S propellant tanks, control systems and thrusters had been securely mounted on Kali, it looked as if some lunatic had built an oil refinery on an asteroid. Captain Singh was exhausted, as were all the crew members, after days of assembly and checking. Yet he felt a warm glow of achievement: they had done everything that was expected of them, the countdown was going smoothly, and the rest was up to ATLAS.

He would have been far less relaxed had he known of the ABSOLUTE PRIORITY message racing toward him by tight infrared beam from ASTROPOL headquarters in Geneva. It would not reach
Goliath
for another 30 minutes. And by then it would be much too late.

At about T minus 30 minutes,
Goliath
had drawn away from Kali to stand well clear of the jet with which ATLAS would try to nudge it from its present course. ‘Like a mouse pushing an elephant,’ one media person had described the operation. But in the frictionless vacuum of space, where momentum could never be lost, even one mousepower would be enough if applied early and over a sufficient length of time.

The group of officers waiting quietly on the bridge did not expect to see anything spectacular: the plasma jet of the ATLAS drive would be far too hot to produce much visible radiation. Only the telemetry would confirm that ignition had started and that Kali was no longer an implacable juggernaut, wholly beyond the control of humanity.

There was a brief round of cheering and a gentle patter of applause as the string of zeros on the accelerometer display began to change. The feeling on the bridge was one of relief rather than exultation. Though Kali was stirring, it would be days and weeks before victory was assured.

And then, unbelievably, the numbers dropped back to zero. Seconds later, three simultaneous audio alarms sounded. All eyes were suddenly fixed on Kali and the ATLAS booster which should be nudging it from its present course. The sight was heartbreaking: the great propellant tanks were opening up like flowers in a time-lapse movie, spilling out the thousands of tons of reaction mass that might have saved the Earth. Wisps of vapour drifted across the face of the asteroid, veiling its cratered surface with an evanescent atmosphere.

Then Kali continued along its path, heading inexorably toward a fiery collision with the Earth.

Captain Singh was alone in the large, well-appointed cabin that had been his home for longer than any other place in the solar system. He was still dazed but was trying to make his peace with the universe.

He had lost, finally and forever, all that he loved on Earth. With the decline of the nuclear family, he had known many deep attachments, and it had been hard to decide who should be the mothers of the two children he was permitted. A phrase from an old American novel (he had forgotten the author) kept coming into his mind: ‘Remember them as they were – and write them off.’ The fact that he himself was perfectly safe somehow made him feel worse;
Goliath
was in no danger whatsoever, and still had all the propellant it needed to rejoin the shaken survivors of humanity on the Moon or Mars.

Well, he had many friendships – and one that was much more than that – on Mars; this was where his future must lie. He was only 102, with decades of active life ahead of him. But some of the crew had loved ones on the Moon; he would have to put
Goliath
’s destination to the vote.

Ship’s Orders had never covered a situation like this.

‘I still don’t understand,’ said the chief engineer, ‘why that explosive cord wasn’t detected on the preflight check-out.’

‘Because that Reborn fanatic could have hidden it easily – and no one would have dreamed of looking for such a thing. Pity ASTROPOL didn’t catch him while he was still on Phobos.’

‘But
why
did they do it? I can’t believe that even Chrislamic crazies would want to destroy the Earth.’

‘You can’t argue with their logic – if you accept their premises. God, Allah, is testing us, and we mustn’t interfere. If Kali misses, fine. If it doesn’t, well, that’s part of Her bigger plan. Maybe we’ve messed up Earth so badly that it’s time to start over. Remember that old saying of Tsiolkovski’s: “Earth is the cradle of humankind, but you cannot live in the cradle forever.” Kali could be a sign that it’s time to leave.’

The captain held up his hand for silence.

‘The only important question now is, Moon or Mars? They’ll both need us. I don’t want to influence you’ (that was hardly true; everyone knew where he wanted to go), ‘so I’d like your views first.’

The first ballot was Mars 6, Moon 6, Don’t know 1, captain abstaining.

Each side was trying to convert the single ‘Don’t know’ when David spoke.

‘There is an alternative.’

‘What do you mean?’ Captain Singh demanded, rather brusquely.

‘It seems obvious. Even though ATLAS is destroyed, we still have a chance of saving the Earth. According to my calculations,
Goliath
has just enough propellant to deflect Kali – if we start thrusting against it immediately. But the longer we wait, the less the probability of success.’

There was a moment of stunned silence on the bridge as everyone asked the question, ‘Why didn’t I think of that?’ and quickly arrived at the answer.

David had kept his head, if one could use so inappropriate a phrase, while all the humans around him were in a state of shock. There were some compensations in being a Legal Person (Nonhuman). Though David could not know love, neither could he know fear. He would continue to think logically, even to the edge of doom.