For the female Taur had suddenly gone down on her knees, mooing in misery. She had dropped the tray of dishes, and when she turned to look at the three humans, the broad bovine face was racked in misery.
"She's sick," Sork declared.
But his brother was shaking his head. "No," he whispered, listening.
And Sue-ling heard it too. There was another sound, barely heard—a wordless keening from far away. It climbed in volume and pitch, and it was dire.
Sue-ling blinked at the brothers, suddenly afraid. "Is that the Turtles who are making that awful noise?" she whispered.
Kiri nodded somberly. Sork said, his voice taut, "If we can hear this much, this far away, they must be screaming up a storm." He didn't have to say that most of the vocal range of Turtle sounds was well outside the frequencies audible to humans.
"I've never heard anything like it," Sue-ling said.
Sork, whose entire life had been spent in the Turtle compound, nodded slowly. "Nor I. Not even when they worship their goddess. This is something brand-new."
"It must be something really terrible to get them so upset," Sue-ling said, gazing at the Taur, now drunkenly picking herself up and staggering out of the room.
And Sork, his eyes suddenly gleaming with a savage light: "You bet it must—and, oh, God, I hope so!"
Where do the aiodoi sing? If one must ask that one may never know, for the aiodoi are not in a "where." Still, their songs are heard everywhere, except in a few places where those who dwell there have never learned to listen, while the aiodoi themselves hear everything, always, even the faint old songs from distant Earth.
"If you remember when we talked about Hawking's idea of what we called 'the eternal anaconda of time,' you probably also remember that we mentioned that the universe was born out of'vacuum fluctuations.' What we didn't do was tell you what was in the vacuum to fluctuate, or how it fluxed.
"There's a good reason for that. The reason is that we don't know the answer.
"Still, we do know quite a lot about vacuum fluctuations in general, and that's what we're going to take up today. To begin with, there's no such thing as 'empty space.' There isn't
any such thing as a law of conservation of matter and energy any more, either, except perhaps statistically, over time. The ironclad bookkeeping limitations were repealed by Werner Heisenberg, as a logical consequence of his uncertainty principle.
"According to the uncertainty principle, the conservation of energy doesn't have to be exact at every moment. 'Borrowing' is allowed. At some point temporary particles can be created out of nothing at all. However, they have to be 'paid back' later on by disappearing. The new law allows that they can last for a period, which is written as delta-T, in an amount, delta-E, such that delta-T times delta-E is roughly equal to Planck's constant, which you all of course remember is written as h.
"We don't usually see these particles appearing and disappearing before our eyes. There are several reasons for that: they are tiny; they don't last very long; and we don't usually look in the right place. It would be possible for us to see them, I think, or at least to see very clear proof that they exist, if we had some stable superheavy elements to look at. The heaviest natural element we have is uranium, with ninety-two protons. Even the artificially created elements, the ones that are called 'transuranic,' aren't very much heavier. If we had some really massive elements—say, with atomic numbers of two hundred protons or more—the particles we're looking for could be counted on to appear inside those atoms, and they would have definite, measurable effects on the atoms so we could detect them. As it is, they appear only randomly—but they do it everywhere, and all the time.
"Space, all space, is literally filled with these particles, winking in and out of existence. And that is why space is not truly empty.
"That's another reason why a good many physicists refuse to use the term 'empty space' any more. They even go back to the old idea of the 'luminiferous ether'—well, not really to that; but at least to the notion that there is some sort of universal frame, or what we call a rigging vector field, which pervades all of space. You remember, I hope, that some of those scientists, particularly the old Jagiellonian group, in Krakow, Poland, have ventured to use the. word 'neoether' to describe just what the invisible something is that fills the universe.
"I suppose you are now beginning to think that next week we'll be reviving phlogiston and the Philosopher's Stone. No. We don't go that far. But all the same, we have to admit the notion that there is something that exists everywhere."
But the aiodoi simply sang on, for that song, like all other songs, they had been hearing forever.
3
Four thousand kilometers from the Turtle compound at Kansas City, Captain Francis Krake looked around him and felt almost at peace.
That was a blessing he had longed for, for a long time. Just being on an air field revived some wonderful, aching old memories—the memories of that almost forgotten Second Lieutenant Francis Krake of World War II. Nineteen years old. The world before him then. There was the memory of basic training in Miami Beach, flight cadet school in Mississippi, two-engine transitional training in Oklahoma—and, in all of those places everywhere, the dayrooms with their jukeboxes blaring That Old Black Magic and My Reverie and all those other soppy, sentimental, wonderful songs of parted lovers and joyous reunions. There had been real reunions in Krake's memories, too; the precious forty-eight hour passes with a friendly pilot to take you home for a day; that last overseas leave when Madeleine had promised to wait for her airman to come safely back home from the war. . . .
It did not do to think about Madeleine. Krake knew that, at last, the wait would have turned out to be too long.
It didn't do to think of the end of it, either, when Krake had known for certain that he was going to die . . . until that incredible stub-winged Turtle scout ship had appeared miraculously to pull him from the waters of the Coral Sea. They had certainly saved his life. . . .
Or they had stolen it from him, one or the other.
Now here he was, at an air field again. It was his kind of field. It certainly was not an "airport," like that crowded, crazy place at Kansas City where he'd boarded the commercial flight to take him here to New Mexico. This place was relaxed, slow-moving—no giant liners inching toward a takeoff strip, just a few dozen parked light planes and a sign that said "rentals." And when he had phoned that pretty doctor at the Turtle compound to make sure nothing new had come from the orbiter, he entered the rental office. Inside, a shapely young woman looked him over appreciatively and said, "An aircraft? Certainly, sir. You'll want a low-speed, hover-capable two-seater, I suppose? Any particular model?"
Krake shrugged. "Whatever you think best," he said, and glanced away as she gave him a warm smile before leading the way out of the rental shack. He felt embarrassed. It wasn't that he didn't recognize the interest in her eyes. It wasn't that he was no longer sexually functional, either. At least, he didn't think he was—though with all those long space voyages since the Turtles had picked him up, and no human companionship except for Marco and Daisy Fay—and Daisy Fay, though certainly female, being what Daisy Fay was these days—he was no longer entirely sure.
Anyway, there was one thing decisively wrong with this pretty woman. She did not look in the least like Madeleine.
But he followed her with a spring in his step—caused, maybe, by the idea of flying a real airplane again after all the subjective years in Turtle spacecraft. He was prepared to find that these new planes would be a little tricky to fly. You had to expect that, after all these years. Krake thought he might have to taxi around the field for a while, until he got used to the new controls. But it couldn't be too hard. The planes were sure to have wings, flaps, an engine and landing gear; and if you could fly a P-38 in aerial combat in the Pacific you could fly anything. . . .