Starfarers (2 page)

What can they be but the trails of material objects blasting through the interstellar medium?

Slowly, grudgingly, more and more physicists admit that the least fantastic hypothesis is that they indicate spacecraft.

They aren’t many, less than a hundred, and they seemed confined to a volume of perhaps two hundred parsecs’ diameter. Why that is, why they don’t range everywhere, why they haven’t come to us—those are among the mysteries. But all at once, humans around the whole Earth want us also to be in space.

Through a quickening pulsebeat, he heard Lewis’s carefully dry voice: “Lately, here, using the Maxwell superconducting telescope, we’ve found what appear to be similar phenomena elsewhere. The traces are faint, scattered, from sources far more distant than those behind Zeta Centauri. They are few, and none is as rich in objects as that region is. But there they are. Or so we think.

“To confirm, we need better instruments. That will also let us pinpoint them in the galaxy. More important, new theoretical work suggests that improved data will give clues to what the power source is. There’s the great stumbling block, you know. Where does the energy come from? I honestly believe we’re on the verge of a revolution in our understanding of the universe.

“I can show you around, introduce you to the people doing the research, let you judge for yourself before you report to your group. Would you like that?”

“I—I would,” he answered inadequately. “And—no promises, you realize, but—I expect you’ll get what you want.”

It happened
that Avery Houghton launched his coup on the day that Edward Olivares recorded a television interview. Nothing had overtly begun when the physicist reached his
office, but the crisis had been building up for weeks—demands, threats, demonstrations, riots—and was now unmistakably close to the breaking point. Most Americans who could stayed home, huddled over the newscasts. The amber-hued Hispanic façades of Caltech stood on a nearly deserted campus, impossibly sunlit and peaceful, while fighter jets drew contrails across the blue above them.

Olivares was stubborn about keeping promises. He arrived at the appointed hour. The camera crew was already on hand, trying hard not to act nervous. Joanne Fleury succeeded in it. She had her own professional pride.

“I fear we won’t draw much of an audience,” Olivares remarked while the crew was setting up.

“Maybe not for the first showing,” Fleury said, “though I imagine a fair number will tune in around the world regardless of our troubles here. But the rebroadcasts will pull their billions.”

“We could postpone—”

“No, if you please, sir. This is going to be a classic in science journalism. Let’s do it while we’ve got the chance.”

Planning and a sketchy run-through had gone before, and the business went more smoothly than might have been awaited. But then, it offered a brief escape from what was outside.

After the cameras had scanned the book-lined room, the battered desk, the portrait of Einstein, while Fleury gave her introduction, “—scientist, mathematical physicist, as famous as he is modest—We’ll discuss his latest and greatest achievement…” they moved in on her and him, seated in swivel chairs. A projector spread a representation of the galaxy behind them, ruddy nucleus and outcurving blue-tinged spiral arms, awesome athwart blackness. Somehow his slight frame belonged in front of it.

She gestured at the grandeur. “Alien spacecraft traveling there, almost at the speed of light,” she said. “Incredible. Perhaps you, Dr. Olivares, can explain to us why it took so long to convince so many experts that this must be the true explanation.”

“Well,” he replied, “if the X-ray sources are material objects, the radiation is due to their passage through the gas in interstellar space. That’s an extremely thin gas, a hard vacuum by our standards here on Earth, but when you move close to
c
—we call the velocity of unimpeded light
c
—then you slam into a lot of atoms every second. This energizes them, and they give back the energy in the form of hard X rays.”

For a minute, an animated diagram replaced the galaxy. Electrons tore free of atoms, fell back, spat quanta. The star images returned as Olivares finished: “To produce the level of radiation that our instruments measure, those masses must be enormous.”

“Mostly due to the speed itself, am I right?” Fleury prompted.

Olivares nodded. “Yes. Energy and mass are equivalent. As a body approaches
c
, its kinetic energy, therefore its mass, increases without limit. Only such particles as photons, which have no rest mass, can actually travel at that velocity. For any material object, the energy required to reach
c
would be infinite. This is one reason why nothing can move faster than light.

“The objects, the ships, that we’re talking about are moving so close to
c
that their masses must have increased by a factor of hundreds. Calculating backward, we work out that their rest masses—the masses they have at ordinary speeds—must amount to tens of thousands of tonnes. In traditional physics,
this
means that to boost every such vessel, you would have to annihilate millions of tonnes of matter, and an equal amount to slow down at journey’s end. That’s conversion on an astrophysical scale. Scarcely sounds practical, eh? Besides, it should produce a torrent of neutrinos; but we have no signs of any.”

Fleury picked up her cue. “Also, wouldn’t the radiation kill everybody aboard? And if you hit a speck of dust, wouldn’t that be like a nuclear warhead exploding?”

A jet snarled low above the roof. Thunder boomed through the building. Cameras shivered in men’s hands.
Fleury tensed. The noise passed, and she found herself wondering whether or not to edit this moment out of the tapes.

“Go on, please,” she urged.

Olivares had glanced at the galaxy, and thence at Einstein. They seemed to calm him.

“Yes,” he told the world, “There would have to be some kind of—I’m tempted to say streamlining. The new space-borne instruments have shown that this is indeed the case. Gas and dust are diverted, so that they do not encounter the object itself, but flow smoothly past it at a considerable distance.” An animation represented the currents. The ship was a bare sketch. Nobody knew what something made by non-humans might be like. “This can, in principle, be done by means of what we call magnetohydrodynamics.”

Fleury had regained her smile. “A word nearly as knotty as the problem.”

“It takes very powerful force fields,” Olivares said. “Again we meet the question of energy. Of course, the requirement is minuscule compared to what’s necessary for the speed.”

“And nobody could build a nuclear power plant to supply that.”

“No. If you did, you’d find you had built a star.”

“Then where does the energy come from?”

“The original suggestion was that it comes from the vacuum.”

“Could you explain that? It sounds like, well, Alice’s Cheshire cat.”

Olivares shrugged. “A good deal of quantum mechanics does. Let me try. Space is not a passive framework for events to happen in. It is a sea of virtual particles. They constantly go in and out of existence according to the uncertainty principle. The energy density implied is tremendous.”

“But we don’t know how to put the vacuum to work, do we?”

“Only very slightly, as in the Casimir effect. You see, the more energy you ‘borrow’ from the vacuum, the shorter the time before it must be ‘returned.’ Both these quantities,
energy and time, are far too small to power a spacecraft.”

“But now you, Dr. Olivares, have shown how it can be done,” Fleury said softly.

He shook his head. “Not by myself. I simply pursued some speculations that go back to the last century. And then the new information started to come in from the new instruments.”

Fleury gestured. The galaxy gave way to the observatory on Lunar Farside. After a few seconds the scene swept across millions of kilometers to the devices in their huge orbits. Representations of laser beams quivered between them and back toward the Moon, bearing data. An antenna pointed at a constellation. Briefly, the outlines of a centaur stood limned amidst those stars. It vanished, and a telescopic view expanded. It zoomed past a globular cluster of suns, on toward the one called Zeta, and on and on beyond. Tiny fireballs twinkled into existence, crawled across the deep, and died back down into the darkness while fresh ones appeared. “The bow waves of the argosies,” Fleury intoned.

The animations ended. The galaxy came back.

“Details we could not detect before, such as certain faint spectral lines, are now lending confirmation to my cosmodynamic model,” Olivares said. “And that model, in turn, suggests the energy source for such spacecraft. That’s all,” he ended diffidently.

“I’d say that’s plenty, sir,” the journalist responded. “Could you tell us something about your ideas?”

“It’s rather technical, I fear.”

“Let’s be brave. Please say whatever you can without equations.”

Olivares leaned back and drew breath. “Well, cosmologists have agreed for a long time that the universe originated as a quantum fluctuation in the seething sea of the vacuum, a random concentration of energy so great that it expanded explosively. Out of this condensed the first particles, and from them evolved atoms, stars, planets, and living creatures.”

Excitement throbbed beneath the academic phrases. “At first the cosmologists took for granted that the beginning
involved a fall to the ground state, somewhat like the transition of an electron in a high orbit to the lowest orbit it can occupy. But what if this is not the case? What if the fall is only partway? Then a reservoir of potential energy remains. For an electron, it’s a photon’s worth. For a universe, it is vast beyond comprehension.

“I’ve shown that, if the cosmos is in fact in such a metastable condition, we can account for what the astronomers have observed, as well as several other things that were puzzling us. It’s possible to tap energy from the unexpended substrate—energy more than sufficient, for lengths of time counted not in Planck units but in minutes, even hours.”

Fleury whistled. “How can we do this?”

Olivares chuckled. “I’ll leave that to the laboratory physicists, and afterward the engineers. In principle, though, it must be by means of what I’ll call a quantum field gate. We can use a Bose-Einstein condensate to generate a certain laserlike effect and bring all the atoms in two parallel, superconducting plates into the same quantum state. The consequences are nonlinear and result in the creation of a singularity. Through this the energy of the substrate flows. Presumably it will distribute itself evenly through any connected matter, so that the acceleration is not felt.”

“Hoo, you’re right, this is kind of technical.” A touch of practicality should liven it. “How does the, um, pilot get the ship headed the way he/she/it wants to go?”

“A good question,” Olivares approved. “I’m glad you know the difference between a scalar and a vector. I think the velocity vector must increase or decrease linearly. In other words, when the ship acquires the new energy, she continues in the same straight-line direction as she was moving in. I’m still working on the problem of angular momentum.”

“More technicalities,” Fleury said ruefully. “You mentioned having this energy for a period of maybe hours. Must it then go back?”

Olivares nodded. “Yes, just as with the familiar vacuum, a
loan from the substrate must be repaid. The product of energy borrowed and time for the loan is a constant. However, with the substrate the constant is immensely larger—a multiple of the Planck energy, which is itself enormous. The quantum field collapses, reclaiming the borrowed energy for the substrate.”

“But the ship can take out another loan right away?”

“Evidently. The instruments have, in fact, detected flickerings in the X-ray outputs that correspond quite nicely to this. From the inverse proportionality of energy and time, it follows that every jump is of the same length. My preliminary calculations suggest that this length is on the order of a hundred astronomical units. The exact value depends on the local metric—” Olivares laughed. “Never mind!”

“Maybe we can talk a little about what a voyage would feel like, aboard a ship like that,” Fleury proposed.

“Why not? It’ll take us back to less exotic territory.”

“Could you review the basic facts? For some of us, our physics has gotten kind of rusty.”

“It’s simple enough,” Olivares said, quite sincerely. “When you travel at relativistic speeds, you experience relativistic effects. I’ve mentioned the increase of mass. The shortening of length in the direction of motion is another. Of course, you yourself wouldn’t notice this. To you, the outside universe has shrunken and grown more massive. And your observations are as valid as anybody else’s.”

“What about the effect on time? I should think that’d matter most to the crew.”

“Ah, yes. Time dilation. Loosely speaking, if you’re traveling at close to
c
, for you time passes more slowly than it does for the friends you left behind you. One of those spacecraft may take several hundred years to cross the several hundred light-years between her home port and her destination. To those aboard, whoever or whatever they are, a few weeks will have passed.”

Before she could head him off—but it could be edited out later if need be—Olivares continued: “The new theory modifies this a bit. If you travel by way of the quantum field
gate, you never get the full time dilation you would if you accelerated to the same velocity by ordinary, impossible rocket means. However, at high energies the difference becomes too small to be worth thinking about. Contrastingly, the less energy you borrow from the substrate, the worse the ratio is. You could take an extremely long time by your clocks—theoretically forever—to transit the fixed distance of a jump at an ordinary speed. You’d do better to use a regular jet motor.

“So the quantum field gate is not for travel between the planets. Nor do I expect it will serve any other mundane purpose.”

“But it will take us to the stars,” Fleury breathed.