“What causes them?”
“The most reasonable assumption is that they are light reflected from small, solid particles — meteors. Apparently a cloud of such matter extends outward for some distance past the Earth's orbit, though just how far, it is hard to say. It grows fainter with distance from the Sum, as would be expected, except for the patch we call the Gegenschein.”
“Why the exception?”
“I think one of you can answer that.”
“Would it be for the same reason that the full Moon is so much more than twice as bright as either quarter? Simply because the particles are rough, and appear dark in most positions because of the shadows of irregularities on their own surfaces — shadows which disappear when the light is behind the observer?”
“I think you will agree that that would account for it,” Wright said. “Evidently the meteors are there, are large compared to wavelengths of visible light, and form a definite part of the Solar System. I believe it was once estimated that if the space inside the Earth's orbit contained particles one millimeter in diameter and five miles apart, they would reflect enough light to account for what we are observing. They might, of course, be smaller and more numerous. Only that amount of reflecting surface is necessary.”
“You had me worried,” another voice broke in. “I'd been hearing for years that there would be little reason to fear collisions with meteors when we finally get a rocket out of the atmosphere. For a moment, I though a cloud such as you were working up to would riddle anything that got into space. One pinhead every five miles isn't so bad, though.”
“There is a fairly good chance of collision, I would say,” returned Wright, “but just what damage particles of that size would do, I am not sure. It seems rather likely that they would be volatilized by impact. How the hull of a rocket would react, we will have to find out by experience. I wouldn't mind taking the risk myself. I think we can sum up the greatest possibilities by saying that the meteoric content of the Solar System has and will have nothing but nuisance value to the human race, whether or not we ever leave our own planet.”
A streak of white fire arced silently across the sky, putting a fitting period to the subject.
Wright wondered whether it would appear on his friend's photographic plate.
The Foundling Stars
“All right — perfect. You're the most nearly motionless thing in the universe.”
Hoey's words were figurative, of course; whether they were accurate or not depended entirely on point of view. Rocco Luisi and his Ymyrgar were indeed at rest with respect to Hoey and the Anfforddus, after more than four hours of maddening effort, but neither machine was motionless with respect to much else. Both were travelling at about four kilometers a second, roughly galactic northward, with respect to their home port on Rhyddid, seventy-five parsecs away. They were moving at a much greater velocity with respect to the far more distant Solar System. With respect to each other, however, velocity had been whittled down to somewhat less than five centimeters a year.
How long this would last was problematical. An automatic tracker was now on duty in Hoey's ship, trying to hold steady the fringe pattern produced by combining two ultraviolet laser beams, one originating in his own vessel and the other in Luisi's, in one of the most precise interferometers ever made. Since the crafts were about a light-hour apart, however, corrections tended to be late in time and, in spite of a computer's best efforts, erratic in amount and direction.
“Nineteen decimals” had been a proverbial standard of accuracy for well over a century; but achieving it on any but the atomic size and time scale was not yet standard art.
“That seems to be it,” Hoey repeated. “That means that you and I stay strapped in our seats, with no more motion than we can help, for the next four hours or so. If either of the instrument platforms on our ships moves more than half a micron with respect to the other, a lot of time and money go down the drain.”
“I know — I've had it hammered into me as often and as hard as you have.” Luisi's voice was undistorted, and the responses instant, on the medium communicator.
“Sure you have,” retorted Hoey, “only a lot of people wonder whether you really believe it.”
“Well, it depends on what you mean by believe. I can figure as well as anyone where the center of mass of my ship would go if I stood up; I…"
“I know you can. Your trouble is that you can't believe it would make as much trouble as they say. Just remember that they were even concerned about tidal forces from Cinder over there” — he gestured, rather uselessly, at the grossly misnamed o6e star glaring at them from half a parsec away—“and even went to the trouble of finding a part of this neighborhood where the wind was steady—
“Right there I break connection. Space is space. You only worry about wind when you're close to a sun, and then it's only a hard-radiation problem.”
“True enough, as a rule. The trouble is that the usual run of stellar winds involves a mass density of around ten atoms to the cubic centimeter; here it's a couple of thousand. It turned out that even that much mass wouldn't accelerate the ships seriously unless the relative velocity were very high indeed, but it was something the planners had to check on. You see what I mean; so stay put. Let's cut the chatter. The sooner the folks in 'Big Boy' can get to work, the sooner we can breathe comfortably. I'll call 'em.”
Hoey's finger tensed on a button, replacing the microscopic crystal in the activity field of his communicator with another, whose twin was aboard. “Big Boy” — more formally, the Holiad. He spoke without preamble, knowing that someone would be listening.
'We're in position, and my tracker says we're holding. Get the job going while the going's good.”
“Right.” The answer was terse, but not casual. The speaker, a heavy-set, middle-aged man with an almost fanatically intense stare in his blue eyes, leaned forward over the console in front of him and began punching buttons in an intricate sequence. He paused every second or two to interpret the patterns of light which winked at him from the board. After half a minute or so the pattern became fixed, and he leaned back, more relaxed.
“Program A is running.” A younger man, seated at a similar console a few yards away, nodded at the words. At first he did not answer aloud; then he decided to speak, though for several seconds he was obviously trying to make up his mind what to say. It was easy to make the wrong remark to Elvin Toner.
“D'you think we'll get full time out of it?” he ventured at last. “Those pilots are good, but I still wish it had been possible to use robotships for the key stations. A man can't hold still forever.”
“So do I.” Toner answered without obvious irritation, and his eyes remained fixed on his console, to the younger man's relief. “I also wish,” the director went on, “that it were possible to use the medium communicator system directly for automatic control of such things as distance, so as to get away from light-lag. But until some genius in your generation works out a way to measure the frequency, wavelength, and propagation velocity of medium waves — or at least, furnishes some evidence that a wave phenomenon is involved — we'll have to stick with electromagnetic radiation and, at times, with human beings. You may not like it, but by the time you reach my age you'll have learned to put up with it.”