The left hand hovered over a keyboard of buttons resembling those of a computer input. It probably was the computer input, Ivo reminded himself. There was a strap over the wrist to prevent the hand from drifting away in the absence of gravity; buttons could be awkward to depress without the anchorage of bodily weight. The right hand held a kind of ball mounted on a thin rod, rather like an old-fashioned automobile gearshift. As the left fingers moved, a large concave surface glowed over Brad’s head.

“I’ll cut in the main screen for you,” Brad said. “Notice that my fingers control the computer settings; that covers direction, range and focus, none of it simple enough for human reflexes to handle. The vagaries of planetary motion alone, when that planet is not our own, are complicated to account for, particularly when we want to hold a specific focus on its surface.”

“I’m aware of planetary motion.” He remembered one of his old pet peeves. “I had to work it out when I wanted to criticize the concept of time travel. If a man were granted the miraculous ability to jump forward or backward in time, with no other travel, he’d arrive in mid-space or deep underground; because the Earth is always moving. It would be like trying to jump off a moving rocket and jump on again.”

“Nevertheless, we do travel in time, with the macroscope,” Brad said, smiling.

“Oh, so you’re going back to supervise your grandfather’s conception?”

“Delicacy forbids.” Brad’s hands flexed. “I’ll center on a precoded location: the planet Earth. The computer uses the ephemeris to spot all the planets and moons of the solar system exactly, and a good many of the asteroids and comets as well. The right-hand knob provides our personal tuning; once the difficult compensations have been made, we use this control to jog over several feet at a time, or to gain different angles of view. Right now we’re orbiting the sun about nine hundred thousand miles from Earth — right next door, as interplanetary distances go. Just out far enough to reduce the perturbations of the moon. There.”

The screen was a mass of dull red. “If that’s Earth, the political situation has deteriorated since I left,” Ivo observed.

“That is Earth — dead center. Per the coordinates.”

“Center? Literally?”

“Definition, problem of, remember. Our corrected coordinates nail the heart of the body. The image is on a one-to-one ratio.”

“Life size? It can—”

“The macroscope can penetrate matter, yes. As I told you, this isn’t exactly light we’re dealing with, though the time delay is similar. That’s a representation of the incandescent core of our planet as it was five seconds ago, muted by automatic visual safeguards and filters, of course. We’ll have to drift about four thousand miles off that point to hit the surface, which is what most people seem to assume is all the scope looks at. Right there, you can appreciate the implications for geology, mining, paleontology—”

“Paleontology?”

“Fossils, to you. We’ve already made some spectacular finds in the course of routine roving. Lifetime’s work there, for somebody.”

“Hold on! I ain’t that ignorant, perfessor. I thought the bones were widely spaced, even in good fossiliferous sediments. How can you tell one, when you’re in the middle of it, not looking down at it in a display case? You certainly couldn’t see it as such.”

“Trust me, junior. We do a high-speed canvass at a given level and record it on tape. The machine runs a continuous spectroscopic analysis and trips a signal when there’s anything we might want. And that’s only the beginning.”

“A spectroscopic analysis? You said the macroscope didn’t use light.”

“It doesn’t, exactly, but we do. We keyed it in on samples: every element on the periodic table. Thus we are able to translate the incoming impulse into a visual representation, much as any television receiver does. The truth is, the macrons are far more specific than light, because they don’t diffuse readily or suffer such embarrassments as red shift. Spectroscopy is really a superfluous step, but we do it because we’re geared to record and analyze light, here. Once we retool to orient on the original impulse, our accuracy will multiply a hundredfold.”

“It grinds that fine?”

“That fine, Ivo. We’re just beginning to glimpse the potential of this technique. The macroscope is a larger step toward universal knowledge than ever atomics were toward universal power.”

“So I have heard. But I’m sort of stupid, as you know. You were about to tell me what makes superior definition so difficult to adapt to, even with the computer guidance.”

“So I were. Here is the surface of Earth, fifty feet above sea-level, looking down. Another keyed-in location.”

The screen became a shifting band of color.

“Let me guess again. Your snoop is stationary, right? And the globe is turning at the equivalent of a thousand miles an hour. It’s like flying a jet at low altitude near the equator and peering out through the bombsight.”

“For a pacifist, you have violent imagery. But yes, just about. Sometimes over ocean, sometimes land, sometimes under mountains that rise above the pickup level. And if we move higher—” He adjusted the controls, and the scene jumped into focus.

“About a mile up,” Ivo said. “Makes the scene clear, but too far for intimate inspection. Yes.” He watched the land sliding by. “Why don’t we just see a panel of air? What we have now is a light image, perspective and everything.”

“What we see is the retranslation of the macronic image sponsored by visible radiation passing through that point in space. Maybe I’d better give you the technical data after all.”

“Uh-uh. Just answer me this: if it’s that sharp on planet Earth from five light-seconds, can it also handle other planets? Can it look at Jupiter from one mile up, or even Pluto? If it can—”

The headgear tilted as Brad nodded somberly. “You begin to comprehend what a magnificent tool we have here. Yes, we can explore the other planets of our solar system, from one mile above ground level — those that have ground — or one inch or anywhere inside. We can also explore similarly the planets of other systems, with so little loss of definition that distance can be ignored.”

“Other systems…” This was distinctly more than he had anticipated. “How far — ?”

“Almost anywhere in the galaxy. There is interference from overlapping images near the galactic center that complicates things tremendously, I admit, but the evidence is that there is more than enough of interest elsewhere to hold us for a few centuries of research.”

Ivo shook his head. “I must be misunderstanding you. As I make it, our Milky Way galaxy is over a hundred and ten thousand light-years across, and we’re about thirty-five thousand light-years from the center. Are you claiming that you can get a life-sized image from ground level of a planet orbiting a star, oh, fifty thousand light-years away?”

“Yes, theoretically.”

“Then that’s the key to interstellar exploration — without the need for physical travel. Why drive to the show when you can see it on TV?”

“Precisely. But we are hampered by those mundane practicalities just discussed. We can compensate to a considerable extent for rotary and orbital and stellar motions — but not every planet is the sitting duck Earth is.” He twitched a finger and the fifty-foot elevation resumed, this time motionless. “Properly programmed, the computer can direct a traveling focus and follow the dizzy loops of a particular planetary locale, as it is doing now, and provide a steady image. It’s a pretty fine adjustment, but that’s what the machinery is for. At least we know the necessary compensations.”

“And you don’t know the motions of planets the regular telescopes can’t pick up. But you should be able to figure them out soon enough from the—”