But, while it remained close to the Sun, the star made certain that the inner planets became well aware of its passage. While just within the combined Roche Limit of the two stars—further inside and total tidal disruption would have occurred—it drew hydrogen gas from the surface of the Sun. This gas fell onto the white dwarf and exploded outward, causing a nova outburst.
This was but a pale echo of the supernova which had precipitated its own flight, but still it emitted more than 10,000 times more light than normal, and the star became wreathed in a halo of fluorescing gas as great jets and streamers of red-glowing hydrogen were torn from the tortured skin of the Sun, reaching out for the stranger like grasping fingers.
Mars was fortunate. It was on the far side of its orbit when the star approached the Sun, and, while its inhabitants saw everything, they felt only relatively minor ground tremors. The ozone layer which had been created high in the Martian atmosphere protected them from most of the brief burst of radiation.
Earth did not fare so well. The angle of the white dwarf’s approach was such that it passed within a few million kilometers, and the tidal forces were fearsome. Earthquakes reduced buildings and whole cities to rubble; great cracks opened in the ground, belching flame and steam; ancient volcanoes came to life and blackened the sky with clouds of ash and dust, while pouring out rivers of red-glowing lava which devoured everything in their path.
Giant waves—tsunamis—reared up from the oceans and created more havoc, sweeping away buildings and trees and drowning many millions of people and animals. These were accompanied by the rush of mighty winds, bringing their own forms of destruction.
As if this were not enough, soon afterwards a blast of radiation from the nova outburst engulfed the Earth. The storm of particles lasted for well over the Biblical forty days and forty nights, until the visitor began to move away from the Sun and its brilliance diminished. It was, by cosmic standards, a modest outburst, but it held danger enough. Only the fact that, by the time the radiation arrived, Earth was almost completely shrouded in a thick blanket of cloud, smoke, and dust prevented greater harm from being perpetrated.
The star retreated, gloating. It was watched by the Martians, who had not abandoned astronomy completely, though they now concentrated on the more esoteric aspects of cosmology and were engaged on a search for the answer to the great mystery of the origin and destiny of the Universe. A white dwarf would be invisible beyond a hundred light years even to their sensitive instruments; but such a tiny, insignificant object would never have interested them anyway, had they deigned to notice such a minuscule change in the normal star-patterns when it first became visible.
Communication between the two worlds had been rare in recent centuries. There was little to talk about. But the means for communication still existed. Once some semblance of normality had returned to Earth, its Council of Twelve (now reduced by casualties to seven, until its missing members could be replaced) contacted Mars, requesting asylum.
Before its transformation by terraforming, the surface area of Mars had been almost as great as that of the dry land on Earth. Even now that water occupied the lower portions of the terrain, the few millions living there had plenty to spare. Once upon a time its inhabitants might have held onto that land avariciously, but in this enlightened age they gladly welcomed their cousins from Earth. The spaceships which, thousands of years ago, had lifted their ancestors from the home planet were intact, cocooned in great hangars.
True, there was no one who knew how to pilot them, but records and implanted memories remained, and it was not difficult for young men and women to learn. Indeed, to them it was an exciting and unexpected challenge.
The ships, containing the pitiful remnants of Earth’s great final civilization, crossed the abyss between the two worlds in a matter of weeks. The whole migration took many months. But at last the home planet was nearly empty of all but plant and animal life—and even some of the latter, unique to Earth, had been ferried to the new world. A few, mainly older, people chose to remain. They would die naturally long before the star’s second coming, and preferred to live out their allotted spans in their own homes.
The people who left Earth took with them crystals on which were stored as much as remained of the home world’s art and literature, and even some of its science. It was unlikely that they would ever return.
What remained behind them would be safe for centuries, for the white dwarf was still on its way into the depths of space, still at an angle which kept it clear of the outer planets. But its elliptical, comet-like orbit would bring it back to the inner system again and again. And each time it flung its invisible arms around the Sun and danced its deadly jig it would seize more material from the bigger star and hurl much of it into space. But much it would hug to its own chest, miser-like, growing more massive with each passage. As long as the output of light and radiation remained no more than one-fifth above normal, Earth would be scorched but Mars should escape.
Even so, Martian astronomers knew that each return would shorten the period before the next. One day in the far distant future, enough material would have been transferred from the Sun to the white dwarf that it would have absorbed more helium into its core than it could comfortably contain. It too would erupt in a supernova explosion—and the Sun, now itself nothing but a stripped helium core and so effectively itself a white dwarf, would be hurled away like a cast-off lover. Perhaps to wander one day, millions or billions of years hence, into some other unsuspecting star system....
The Martians, who over the years had assimilated the immigrant culture from Earth—both groups benefiting from the intermixture, and indeed the interbreeding—began to discuss very seriously the possibility of leaving the Solar System altogether in order to find a safer world orbiting another star. A few probes had been sent into interstellar space, millennia ago, but various historical disturbances had prevented further progress in that direction. Finally, the sending of probes had no longer seemed a necessity, or even particularly desirable. Instruments in space, or on the Moon, could provide all the information required.
Until now.
The brains of the Martian scientists were quite capable of designing theoretical drives that would produce speeds close to that of light. Some even wove dreams of there being tunnels through space, evading the need for such a finite and physical limitation. But the technological base, the industrial infrastructure, for the manufacture of starships no longer existed—especially ships capable of effecting the sort of massive evacuation which would be required. At last they rejected the idea of any massive exodus by mechanical means. Should a more elegant method of travelling to another star present itself—such as a matter transmitter—they would embrace it.
In the course of their researches, one scientist came across an ancient plan for another type of vehicle. A ship to cross not space but time.
The older and more entrenched scientists shook their heads in disbelief. Time had long been regarded as the one barrier that would never yield to humankind’s probings. Yet...the theory behind this proposed machine did seem to be sound. It gave promise of being able to travel backward in time, though never forward, so anyone who attempted such a journey could never return, and those who sent that person would never know for certain whether he or she had succeeded.
Unless it proved possible to tamper with the past.
To change it.
THE JOURNEY
Themor and Anela laid their girlchild gently in her capsule. “We should have waited until after the Naming Ceremony,” said Anela, not for the first time.
“It is better that she takes up a new identity in the twentieth century,” he replied aloud. Sometimes a voice was comforting, if not necessary. “She will carry her name to her death, for she cannot return here. None of us can.”
The timeship stood inside a low metal building surrounded in all directions by kilometers of sand—“in case of accidents,” the Martian scientists had said. Its circular, domed shape gleam
ed dully in the sourceless lighting. The man and woman had arrived on Mars nearly two hundred years before in the mass exodus from Earth, and they hoped to return to their original world, but in a much earlier time.
In order for them to do so, the timeship had to be a spaceship also. For they would go back to arrive on their present world—Mars—as it had been 20,000 years before: barren and lifeless. Then they would have to cross interplanetary space to the Earth, arriving in the year 1969 by the reckoning of that time. That year had been chosen because then, the year of humanity’s first landing on the Moon, the world’s consciousness had been attuned to the potentials and benefits of the exploration of space in a way that it would not be again for centuries. It also happened to be exactly a century before that first major agent of destruction—the comet—would arrive.
Or as close to that year as possible: travel through time was an unknown science. It was impossible to check results by any experimental or empirical method, only by theory and extrapolation, so calibration was difficult and guidance likely to be imprecise. They tried to ensure that any error would make their arrival early rather than late, because the date of 2069 was crucial; Earth had to be warned of the true nature of this particular coming calamity. Its inhabitants should know, too, of the natural catastrophes which were still thousands of years in the future, so that perhaps technology could be maintained at a level which could defeat these, or at least avoid them. An audiovisual projection had been prepared to help them to communicate the danger. Perhaps even the human errors could be avoided by forewarning—though the history to date of humankind made this seem unlikely....
And if the generations of the early twenty-first century were able to solve the problems, then perhaps the future could be changed. There lay the paradox. If the future had been changed, surely the time travelers would not be here to go back to an earlier time to alter it? Or were the strands of time somehow interconnected in such a way that the action and the result occurred “simultaneously”—in which case the future would change and no one would ever know that it had? Or did time constantly subdivide, so that one stream or branch would continue from a twentieth century in which mankind escaped the trials which destroyed them in another stream? The scientists and philosophers argued, but had no answer.
All that mattered was that they had to try.
A model could not be tested, because the vehicle that had been built was the smallest practicable size that could function. Some of the spaceships used in the evacuation of Earth had been cannibalized to help construct the timeship. Neither of its crew understood its workings. The scientists had tried to explain, simply, how a loop of cosmic string whirling inside the torus which surrounded the ship, and a mini black hole at its center, would distort space so that the ship was forced to escape into the fourth dimension of time, but to the temponauts themselves it was meaningless. Just as long as it worked!
Thirty-six babies, aged between two and six months, had been chosen to make the journey along with the two adults. These were the children of parents who were among the most talented of the species, and who had the most powerful psi powers—many of them rare. There was no longer any official genetic program, but it was natural and logical for those with particular strengths to mate and breed. This was the only way currently known that might give their (perhaps even more talented) offspring a chance to live and continue their line.
The majority of the inhabitants of Mars accepted philosophically—even with resignation—the incontrovertible fact that their world would within a few millennia be vaporized by fire. Some hoped that a method might be discovered that would save them or move them to a new location; already, a faction was advocating a crash program to rediscover the means to build starships, using minerals from the relatively close asteroid belts.
Other scientists proposed the use of what might once have been called particle weapons: banks of gamma-ray lasers which could be fired into the white dwarf, literally bursting its heart. An Elder from Earth preached that the answer was not technological, but lay in freeing the mind, the ka, from the chains of the body. The spirit of humanity remained indomitable.
Anela and Themor had been chosen from many applicants, all of whom had children on the timeship. Of the thirty-six babies, their own child was the thirty-sixth to be sealed into its cocoon.
Only hours before, Anela had held the tiny girl and watched her as she in turn gazed and listened with obvious pleasure as her father and his fellow Musicians played a Concert of Leaving. They had tried to make it a joyous occasion, for her sake, but inevitably it was laden with sadness.
Whether they succeeded or failed, those who left in the timeship—if indeed it worked—would never be seen by their fellows again.
* * * *
“There is nothing more to be done. Everything is prepared. All we can do now is activate the ship and hope. And pray,” said Themor now. They had to be alone out here because of the possibility of danger from this untested machine. In fact, the scientists had said encouragingly, the most probable accident, in the unlikely event that any of the safety measures should fail, was that it would tunnel its way to the center of the planet.
Both were already wearing close-fitting suits and skullcaps woven from a material that would protect them from the intense magnetic fields generated by the operation of the torus. The babies wore a similar material, although their cocoons should be protection enough. For the two adults, spacesuits and helmets could quickly be donned over these undersuits in an emergency.
They passed through the door into the control cabin, and Anela placed a palm on the tiny receptor which closed it. They seated themselves at the instrument console. Themor checked that the bubble canopy was in place, for it was so transparent that it was difficult to tell. He placed a hand on a darker panel, and mentally activated the sequence which should project them back in time. Both their faces were tense.
The black band which surrounded the upper sphere of the psibot glowed ruby red, showing that the mental pathways were clear. The crystals set in the control desk flickered briefly through a sequence of colors: violet, blue, yellow, magenta, green. All appeared to be well. Anela sent a telepathic message to the scientists at the laboratory five kilometers away, and received a mental green light.
“We cannot delay any longer,” she said, and reached for Themor’s hand.
He did not remove it from hers as he gave the command.
There was the faintest humming sound. The sequence of crystal lights changed rapidly, and then everything became insubstantial. The walls of the cabin were translucent, and through them could be seen the tiered rows of ovoid capsules containing their precious hope for the future.
Or their past. Which was it? They could no longer distinguish.
The torus which spun around the diameter of the ship glowed an impossible color, unknown to any human spectrum. Then it, too, became almost transparent. Through it, the walls of their hangar were visible only briefly before they winked out of existence; then there was just desert outside, and beyond it the green-clad cone of the Lesser Mountain, blued by distance.
They watched as blue-green plant-growth retreated down the slopes and disappeared, leaving the volcano bare and stark. The sky changed from blue to violet. Clouds flickered briefly, and now the sky became orange-pink.
On one of two rectangular black readouts, white numbers flickered, too fast to read. On the other they moved more slowly, counting not years but centuries. Simultaneously, the crystals sparkled green. There was a wrenching, lurching sensation. The walls clouded, coalesced and became substantial.
But for a moment the numbers continued to flick, backwards:
1969....
1960....
1950....
1945....
1944....
They slowed.
1943....
1942....
1941....
1940.
They stopped.
* * * *
For long minutes ne
ither said a word. Then Anela spoke:
“We have arrived too early.”
“Maybe not. We cannot be certain that the readout is accurate. The engineers tried to calibrate it by the method of dating used in this era, but who knows if they got it right? We might easily have arrived a decade or more on either side of that date. Well, we cannot go forward, and we cannot risk trying to travel further backward. We must hope that the people of 1940, if that’s indeed where—when—we’ve arrived, are sufficiently advanced to understand and heed our warning. But, if they are not, we shall just have to bide our time.
“Time is on our side, after all!”
They both laughed, more in relief at being alive and obviously on an earlier Mars than at his attempted joke.
Then Themor frowned, and pointed out through the canopy.
Beyond was only a swirling ochre fog.
Anela put her hand to her mouth. “What is it? Where are we?”
Themor searched his extensive memory. “Don’t worry. It seems that, before the planet was terraformed, dust storms were common on Mars. We must have arrived during one of those. If we wait, it may pass.”
But it did not.
Once the clouds parted for long enough that they could see the Lesser Mountain, which had once been known as Uranius Tholus but in the time in which (they hoped) they had arrived was as yet unknown by human astronomers, as were any of the volcanoes of Mars. So at least they knew they were still in the area from which they had departed.
But the dust storm raged for day after day. They did not dare open the canopy, for the cabin would have filled with dust that even the automatic extractors could not have removed.
They checked their tiny passengers, who were still safely in a mentally induced state of sedation. Checking the ship itself was both unnecessary and pointless, for it was self-regulating and, while the necessary knowledge had been implanted in their minds, they could have done little in the case of a technical problem.
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