Collected Stories Of Arthur C. Clarke (146 page)

He found the astronomer in the Torture Chamber – the tiny gym, squeezed between the technical stores and the bulkhead of the main propellant tank. Each member of the crew had to exercise here for an hour a day, lest his muscles waste away in this gravityless environment. Martens was wrestling with a set of powerful springs, an expression of grim determination on his face. It became much grimmer when Pickett gave his report.

A few tests on the main input board quickly told them the worst. ‘The computer’s insane,’ said Martens. ‘It can’t even add or subtract.’

‘But surely we can fix it!’

Martens shook his head. He had lost all his usual cocky self-confidence; he looked, Pickett told himself, like an inflated rubber doll that had started to leak.

‘Not even the builders could do that. It’s a solid mass of microcircuits, packed as tightly as the human brain. The memory units are still operating, but the computing section’s utterly useless. It just scrambles the figures you feed into it.’

‘And where does that leave us?’ Pickett asked.

‘It means that we’re all dead,’ Martens answered flatly. ‘Without the computer, we’re done for. It’s impossible to calculate an orbit back to Earth. It would take an army of mathematicians weeks to work it out on paper.’

‘That’s ridiculous! The ship’s in perfect condition, we’ve plenty of food and fuel – and you tell me we’re all going to die just because we can’t do a few sums.’

‘A
few
sums!’ retorted Martens, with a trace of his old spirit. ‘A major navigational change, like the one needed to break away from the comet and put us on an orbit to Earth, involves about a hundred thousand separate calculations. Even the computer needs several minutes for the job.’

Pickett was no mathematician, but he knew enough of astronautics to understand the situation. A ship coasting through space was under the influence of many bodies. The main force controlling it was the gravity of the sun, which kept all the planets firmly chained in their orbits. But the planets themselves also tugged it this way and that, though with much feebler strength. To allow for all these conflicting tugs and pulls – above all, to take advantage of them to reach a desired goal scores of millions of miles away – was a problem of fantastic complexity. He could appreciate Martens’ despair; no man could work without the tools of his trade, and no trade needed more elaborate tools than this one.

Even after the Captain’s announcement, and that first emergency conference when the entire crew had gathered to discuss the situation, it had taken hours for the facts to sink home. The end was still so many months away that the mind could not grasp it; they were under sentence of death, but there was no hurry about the execution. And the view was still superb …

Beyond the glowing mists that enveloped them – and which would be their celestial monument to the end of time – they could see the great beacon of Jupiter, brighter than all the stars. Some of them might still be alive, if the others were willing to sacrifice themselves, when the ship went past the mightiest of the sun’s children. Would the extra weeks of life be worth it, Pickett asked himself, to see with your own eyes the sight that Galileo had first glimpsed through his crude telescope four centuries ago – the satellites of Jupiter, shuttling back and forth like beads upon an invisible wire?

Beads upon a wire
. With that thought, an all-but-forgotten childhood memory exploded out of his subconscious. It must have been there for days, struggling upward into the light. Now at last it had forced itself upon his waiting mind.

‘No!’ he cried aloud. ‘It’s ridiculous! They’ll laugh at me!’

So what? said the other half of his mind. You’ve nothing to lose; if it does no more, it will keep everyone busy while the food and the oxygen dwindle away. Even the faintest hope is better than none at all …

He stopped fidgeting with the recorder; the mood of maudlin self-pity was over. Releasing the elastic webbing that held him to his seat, he set off for the technical stores in search of the material he needed.

‘This,’ said Dr Martens three days later, ‘isn’t my idea of a joke.’ He gave a contemptuous glance at the flimsy structure of wire and wood that Pickett was holding in his hand.

‘I guessed you’d say that,’ Pickett replied, keeping his temper under control. ‘But please listen to me for a minute. My grandmother was Japanese, and when I was a kid she told me a story that I’d completely forgotten until this week. I think it may save our lives.

‘Sometime after the Second World War, there was a contest between an American with an electric desk calculator and a Japanese using an abacus like this. The abacus won.’

‘Then it must have been a poor desk machine, or an incompetent operator.’

‘They used the best in the US Army. But let’s stop arguing. Give me a test – say a couple of three-figure numbers to multiply.’

‘Oh – 856 times 437.’

Pickett’s fingers danced over the beads, sliding them up and down the wires with lightning speed. There were twelve wires in all, so that the abacus could handle numbers up to 999,999,999,999 – or could be divided into separate sections where several independent calculations could be carried out simultaneously.

‘374072,’ said Pickett, after an incredibly brief interval of time. ‘Now see how long
you
take to do it, with pencil and paper.’

There was a much longer delay before Martens, who like most mathematicians was poor at arithmetic, called out ‘375072.’ A hasty check soon confirmed that Martens had taken at least three times as long as Pickett to arrive at the wrong answer.

The astronomer’s face was a study in mingled chagrin, astonishment, and curiosity.

‘Where did you learn that trick?’ he asked. ‘I thought those things could only add and subtract.’

‘Well – multiplication’s only repeated addition, isn’t it? All I did was to add 856 seven times in the unit column, three times in the tens column, and four times in the hundreds column. You do the same thing when you use pencil and paper. Of course, there are some short cuts, but if you think
I’m
fast, you should have seen my granduncle. He used to work in a Yokohama bank, and you couldn’t see his fingers when he was going at speed. He taught me some of the tricks, but I’ve forgotten most of them in the last twenty years. I’ve only been practising for a couple of days, so I’m still pretty slow. All the same, I hope I’ve convinced you that there’s something in my argument.’

‘You certainly have: I’m quite impressed. Can you divide just as quickly?’

‘Very nearly, when you’ve had enough experience.’

Martens picked up the abacus, and started flicking the beads back and forth. Then he sighed.

‘Ingenious – but it doesn’t really help us. Even if it’s ten times as fast as a man with pencil and paper – which it isn’t – the computer was a million times faster.’

‘I’ve thought of that,’ answered Pickett, a little impatiently.

(Martens had no guts – he gave up too easily. How did he think astronomers managed a hundred years ago, before there were any computers?)

‘This is what I propose – tell me if you can see any flaws in it …’

Carefully and earnestly he detailed his plan. As he did so, Martens slowly relaxed, and presently he gave the first laugh that Pickett had heard aboard
Challenger
for days.

‘I want to see the skipper’s face,’ said the astronomer, ‘when you tell him that we’re all going back to the nursery to start playing with beads.’

There was scepticism at first, but it vanished swiftly when Pickett gave a few demonstrations. To men who had grown up in a world of electronics, the fact that a simple structure of wire and beads could perform such apparent miracles was a revelation. It was also a challenge, and because their lives depended upon it, they responded eagerly.

As soon as the engineering staff had built enough smoothly operating copies of Pickett’s crude prototype, the classes began. It took only a few minutes to explain the basic principles; what required time was practice – hour after hour of it, until the fingers flew automatically across the wires and flicked the beads into the right positions without any need for conscious thought. There were some members of the crew who never acquired both accuracy and speed, even after a week of constant practice: but there were others who quickly outdistanced Pickett himself.

They dreamed counters and columns, and flicked beads in their sleep. As soon as they had passed beyond the elementary stage they were divided into teams, which then competed fiercely against each other, until they had reached still higher standards of proficiency. In the end, there were men aboard
Challenger
who could multiply four-figure numbers on the abacus in fifteen seconds, and keep it up hour after hour.

Such work was purely mechanical; it required skill, but no intelligence. The really difficult job was Martens’, and there was little that anyone could do to help him. He had to forget all the machine-based techniques he had taken for granted, and rearrange his calculations so that they could be carried out automatically by men who had no idea of the meaning of the figures they were manipulating. He would feed them the basic data, and then they would follow the programme he had laid down. After a few hours of patient routine work, the answer would emerge from the end of the mathematical production line – provided that no mistakes had been made. And the way to guard against that was to have two independent teams working, cross-checking results at regular intervals.

‘What we’ve done,’ said Pickett into his recorder, when at last he had time to think of the audience he had never expected to speak to again, ‘is to build a computer out of human beings instead of electronic circuits. It’s a few thousand times slower, can’t handle many digits, and gets tired easily – but it’s doing the job. Not the whole job of navigating to Earth – that’s far too complicated – but the simpler one of giving us an orbit that will bring us back into radio range. Once we’ve escaped from the electrical interference around us, we can radio our position and the big computers on Earth can tell us what to do next.

‘We’ve already broken away from the comet and are no longer heading out of the solar system. Our new orbit checks with the calculations, to the accuracy that can be expected. We’re still inside the comet’s tail, but the nucleus is a million miles away and we won’t see those ammonia icebergs again. They’re racing on toward the stars into the freezing night between the suns, while we are coming home …

‘Hello, Earth … hello, Earth! This is
Challenger
calling.
Challenger
calling. Signal back as soon as you receive us – we’d like you to check our arithmetic – before we work our fingers to the bone!’

Summertime on Icarus

First published in
Vogue
, June 1960, as ‘The Hottest Piece of Real Estate in the Solar System’

Collected in
Tales of Ten Worlds

When I wrote this story, I certainly never dreamed that one day I would have an asteroid named after me: in 1996 the International Astronomical Union rescued 4923 from anonymity. As a result, I am now the proud absentee landlord of about 100 square kilometres of real estate out around Mars. It doesn’t come anywhere near the Earth, so I’m not worried about
Deep Impact
type lawsuits.

When Colin Sherrard opened his eyes after the crash, he could not imagine where he was. He seemed to be lying, trapped in some kind of vehicle, on the summit of a rounded hill, which sloped steeply away in all directions. Its surface was seared and blackened, as if a great fire had swept over it. Above him was a jet-black sky, crowded with stars; one of them hung like a tiny, brilliant sun low down on the horizon.

Could it be the sun? Was he so far from Earth? No – that was impossible. Some nagging memory told him that the sun was very close – hideously close – not so distant that it had shrunk to a star. And with that thought, full consciousness returned. Sherrard knew exactly where he was, and the knowledge was so terrible that he almost fainted again.

He was nearer to the sun than any man had ever been. His damaged space-pod was lying on no hill, but on the steeply curving surface of a world only two miles in diameter. That brilliant star sinking swiftly in the west was the light of
Prometheus
, the ship that had brought him here across so many millions of miles of space. She was hanging up there among the stars, wondering why his pod had not returned like a homing pigeon to its roost. In a few minutes she would have passed from sight, dropping below the horizon in her perpetual game of hide-and-seek with the sun.

That was a game that he had lost. He was still on the night side of the asteroid, in the cool safety of its shadow, but the short night would be ending soon. The four-hour day of Icarus was spinning him swiftly toward that dreadful dawn, when a sun thirty times larger than ever shone upon Earth would blast these rocks with fire. Sherrard knew all too well why everything around him was burned and blackened. Icarus was still a week from perihelion but the temperature at noon had already reached a thousand degrees Fahrenheit.