Then they were out in space, up above the plane of the solar system, so far that the sun itself was hardly larger than an eyeball. One by one, Niall was made aware of the planets in their elliptical orbits: of Mercury, that tiny ball of red hot iron whose surface is as cracked as a wizened apple, of Venus, swathed in its atmosphere of sulphurous mist, of Mars with its frozen red deserts, of Jupiter, the vast red giant made of bubbling liquid, of the grey wanderer Saturn, whose immense bulk consists mainly of frozen hydrogen, and of Uranus, Neptune and Pluto, whose temperatures are so low that they are little more than floating balls of ice. Niall felt chilled and overawed by the sheer size of the solar system. From the orbit of its outermost planet, Pluto, the sun looked the size of a pea, while the earth was an almost invisible pinhead. Yet the nearest stars were still as far away from him as the earth’s equator is from its polar caps.
When Niall’s attention returned to the present, he realised with a shock that he had forgotten who he was. This experience had absorbed him so completely that his identity seemed slightly absurd. In the past, he had frequently lost himself in daydreams, or in stories told by his mother or grandfather. These had ignited his imagination; but compared with this experience, they seemed no more than a spark compared to a bonfire. It left him stunned and breathless, feeling like a man who has suddenly awakened from a dream. Immense forces were stirring inside him. He longed to ask a thousand questions, to be allowed to visit every planet in turn, then to voyage through space to other stars and solar systems. He experienced something like despair at the thought that knowledge was infinite and his own life so short.
As these thoughts disrupted his inner peace like an earthquake, the wordless voice inside him seemed to advise him to be patient. The negative emotions were dissolved away; instead, he experienced a consuming appetite for knowledge, a desire to devote the rest of his life to learning and understanding
“Ask any questions you like,” the old man’s voice said. “The Steegmaster contains the sum of all human knowledge. It is for you to decide what you want to know.”
“Could you tell me about the earth before the spiders came, and about the men who built this city?”
“For that we need to go back nearly five thousand million years, to the birth of the solar system. . .”
As he closed his eyes again, the voice was no longer coming from the old man but from inside him. Now he was watching a blinding explosion that seemed to fill all space, and that hurled great spirals of gas away from its centre like the arms of an octopus. The explosion seemed to go on forever, sending wave after wave of searing, destructive energy into space. Then, very slowly, it subsided, and its own gravity turned the initial explosion into an implosion. The remaining gases, sucked back together again, began to rotate in an immense whirlpool. Gradually, in the freezing cold of space, it lost its heat until the gases condensed into drops of liquid. Half a billion years later, these droplets had condensed into ten planets. Some, like Mercury, were too hot to retain an atmosphere; some, like Mars, were too small and too cold. Only the earth, nearly a hundred million miles away from the sun, was neither too hot nor too cold.
The formation of the planet was as violent as its birth. Comets and fragments of planets crashed into it, churning it into a mass of boiling mud. It took two billion years for the earth to cool from a seething inferno into a planet with seas and continents. By then, it had shrunk to about a thousandth of its original size. And the sun had also been shrinking steadily, until it reached a point where nuclear reactions began and it turned from a dark globe into a dull red mass, then into a raging atomic furnace. Its ultra-violet rays penetrated the earth’s thin atmosphere — mostly of hydrogen and ammonia — and caused violent electrical storms. And as the gases and water vapour were subjected to this bombardment, the first complex molecules began to form — the sugars and amino-acids. There also appeared a molecule called DNA — deoxyribonucleic acid — which had the peculiar property of duplicating itself. It was DNA that created the first form of life on earth — the bacteria. The bacteria possessed only one simple instinct — to gobble up the organic compounds floating around them in the warm seas, and so steal their energy. Life began as an energy-vampire.
At this early stage, life was almost destroyed by its own success. Bacteria flourished so abundantly that they had soon eaten up most of the organic compounds in the sea. Life would have vanished as quickly as it started if one of these bacteria had not discovered a new trick: manufacturing its own food by absorbing the energy of the sun. By this process — known as photosynthesis — the bacteria learned to make sugar from carbon dioxide and water. They absorbed the sunlight through a chemical called chlorophyll, and the chlorophyll gave these tiny organisms a green colour. Soon, the rocks around earth’s continents — there were four immense continents at this time — were stained with a green, slimy substance, the first algae. And the blue-green algae drank the carbon dioxide from the earth’s atmosphere and turned it back into oxygen.
Another immense period of time drifted past, during which the earth’s atmosphere became increasingly rich in oxygen. Once more, life was in danger of destroying itself through its own success — for to plants, oxygen is a poison, and an earth that contained only plants would die from lack of carbon dioxide. But before this could happen, a new life form appeared — a form that could absorb oxygen and change it into carbon dioxide. These tiny blobs of swimming jelly were the first animals.
As Niall looked down on the earth of a billion years ago, he saw a peaceful and static planet whose warm seas lapped gently on the shores of the barren continents — or rather, on the shores of the barren continent, for the four continents had now drifted together to form one immense land mass known to geologists as Pangaea. On this placid globe, nothing ever changed. For, oddly enough, there was no death. These primitive amoebas and worms and algae shed their old cells and grew new ones, and went on living for ever.
And then, somehow, life invented death, and all the amazing complexities of evolution became possible. What happened is that these simple living creatures learned how to reproduce themselves, so the parent could die, and the young take over.
A creature that goes on living for millions of years falls into a lazy rhythm of existence. It knows how to survive, and that is enough. But when a new creature is born, it knows nothing whatever. It has to fight to establish a foothold. And it has to develop the power to remember what it has learned. An immortal creature has no need of memory; it learned the basic tricks of survival millions of years ago. . . A new-born creature has to pack its learning into a very short period, otherwise it will not survive. The ancient, immortal organisms were mere vegetables; the new life forms were fighters and learners.
And with the invention of death, history begins. These new organisms were no longer identical; they had individuality. And their individuality meant that they explored new environments, and so began to change in themselves. New types began to evolve, new species. Sometimes, an accidental change in the DNA — some careless piece of duplication that gave the creature an extra eye or a finger — made it better able to adapt to its environment than its brothers and sisters; so it survived while they died out. Blobs of jelly turned into worms and fishes and molluscs. And some of those fishes were so spectacularly successful there was no need for further change. The giant shark arrived on earth nearly four hundred million years ago, and his descendants resemble him in every particular.
But it is a basic law of life that, in some paradoxical sense, the less successful species are the most successful. For they go on struggling and evolving while the successful ones remain static. At roughly the same time the giant shark appeared on earth, certain fishes with large fleshy fins made a habit of struggling up onto the beach to escape their enemies and relax in the sunlight. They were not particularly well adapted to life out of water; if the tide went out, their fleshy fins were hardly powerful enough to enable them to struggle back to the sea. And their lungs found a diet of undiluted air painfully difficult to cope with — many of them lost consciousness and suffocated before they could regain the sea. Yet the land was so much safer than the sea — for it had no other living creatures — that these early amphibians preferred to risk exhaustion and death to taking their chance among the sharks. They became the first reptiles. And after another two hundred million years of evolution, the reptiles had become the lords of the earth. The plant-eating dinosaurs were the largest creatures the earth has ever known — the brontosaurus was often twenty-five yards long and weighed thirty tons. The meat-eating dinosaurs — like tyranosaurus — were the fiercest creatures the earth has ever known. And the flying dinosaurs — the archaeopteryx and the pterodactyl — became the most mobile creatures the earth had ever known. For a hundred and fifty million years, the dinosaurs dominated. And then they became the victims of their own success. Some great catastrophe — probably a giant meteor — ploughed into the earth sixty-five million years ago and threw up a cloud of steam that turned the atmosphere into a greenhouse. The temperature soared, and the plant-eating dinosaurs, with their huge bodies, died of excess heat. The flesh-eaters, which lived off the plant-eaters, died of starvation. And, for the first time, the warm-blooded animals had a chance to multiply and flourish. The death of the dinosaurs set the scene for the appearance of man.