We thought these were the only two possible futures:

— if we prove selfish and short-sighted — mass death,

— and if we bend all our efforts, working together, applying every ingenuity — then a genteel decline to a sort of threadbare equilibrium.

But was there a third choice? Another type of social singularity? Stan’s stick hovered over the sand. When each generation owns more books than its father’s, the volumes don’t accumulate arithmetically or even geometrically. Knowledge grows exponentially.

Stan recalled the last time he and Alex and George had gotten drunk together, when he had complained so about the lack of new modalities. Now he laughed at the memory. “Oh, I was wrong. There are modalities, all right. More than I ever imagined.”

Those youngsters back in the encampment were talking about making gravitational transistors! It was enough to make a man cry out, “Stop! Give me a minute to think! What does it all mean?”

Knowledge isn’t restrained by the limits of Malthus. Information doesn’t need topsoil to grow in, only freedom. Given eager minds and experimentation, it feeds itself like a chain reaction.

A third type of social singularity, then, would be a true leap, some sudden, jarring shift to a completely undefined state — where changes manifest themselves in months, weeks, days, minutes… Still climbing, the rocket attains escape velocity.

With a sigh, Stan wiped away the rude figures. We’re caught up in our own close view of time. A human life seems so long. But try on the patient outlook of a glacier.

His eyes lifted to the white continent of ice, only a few kilometers away and stretching from horizon to horizon. Ice ages are geologically rapid events. And yet we’ve flashed from caveman to world wrecker in just three hundred generations. One moment there are these barefoot Neolithic hunters, bickering over a frozen caribou carcass. Turn around, and their children’s children talk about tapping energy from pulsars.

Stan sat down on the convenient boulder, which had been dragged hundreds of miles only to be dropped here by the retreating glacier. It was a good place to watch late autumn’s early twilight usher onstage the gauzy curtains of the aurora borealis. He loved the way the colors played across the glacier, causing its rough corrugations to undulate in time to the sizzling of supercharged ions high above. It was starting to get chilly, even in his thermal coat. Still, this was worth savoring for a while.

Stan heard a soft clunk and saw a stone roll across the sand, coming to rest near his foot. Not far away, two other rocks quivered.

Well, I guess we’re at it again.

But it was more than a typical tremor. He realized this as a deep groan seemed to fill the air… apparently strongest toward the ice. He started to rise, but changed his mind when a sudden trembling made it hard to gain his feet. Whether it was in the ground or his legs, Stan decided to stay put.

After all, what can harm me out here in the open?

Sparkling fireflies were the next phenomenon, dancing within his eyes.

This must be what it’s like to be near a beam when it exits, he thought bemusedly. A level-six harmonic at about twenty kilowheelers should do it, coupling with my own body’s bag of salty fluid. If the frequency dispersion isn’t too…

But then Stan blinked, remembering. No beam was scheduled to exit so near—

He didn’t finish the thought. For at that moment the glacier began to glow directly opposite him, and not from any outside illumination this time. Deep inside the vast ice flow a fierce luminance throbbed. Shapes and dim outlines warped what seemed to be a series of columns, set far back in the frozen mass.

Shafts of brightness pulsed…

Then the east exploded with light.

Teresa stared at the display, watching a vivid simulation of events taking place halfway round the world.

Glowing numbers told how much mass had suddenly departed the planet. She had to swallow before speaking.

“H-how did you do that?”

Alex looked up from his controls. “How does a musician play?” He cracked his knuckles. “Practice, practice.”

Teresa knew better. Alex grinned, but he had a tremor under his left eye and a pale, bloodless complexion.

He’s scared half out of his wits. And who wouldn’t be, after what he’d just pulled off?

“Telemetry coming in,” a tech announced. “Our beam emerged on target, missing the settlement by six point two klicks, with a surface coupling impedance of eighteen kilowheelers… at point oh niner Hawkings, metric. That’s a ninety-eight hundredths match with water ice of surface thickness…”

Another voice cut in. “Beat frequencies on the sixth, ninth, and twelfth harmonics, dominant. Very gentle. Maximum dynamic load during each throb-pulse never exceeding six gees…”

“Target trajectory calculated,” a third worker announced. “On screen now.”

A spot glowed on the map-globe, near the west coast of Greenland. From that point a thread of light speared radially into space. Arrow straight at first, it eventually curved as Earth’s more sedate gravitostatic field grabbed the small mountain their beam had ripped from the ancient glacier. The dot representing the hurtling iceberg still moved very fast, though, and the planetary sphere had to shrink in compensation.

As if impatient with even this fleeting pace, a dashed line rushed ahead of the dot, tracing the frozen missile’s predicted path. Earth diminished toward the lower left corner of the tank and into view, at the upper right, a pearly globe sedately swam onstage.

Teresa let out a cry. “You can’t be serious!”

Alex tilted his head. “You object?”

“Whatever for? There’s no one living on the moon.” Teresa clapped her hands. “Do it, Alex! Get a bull’s-eye!”

He grinned up at her and then turned back to watch as their projectile passed the halfway mark and sped on toward its rendezvous. Teresa unselfconsciously laid a hand on Alex’s shoulder.

No one had ever tried to manipulate the gazer on such a scale. Sure, Glenn Spivey’s people had lain instrument packages where beams were scheduled to emerge. But no one had ever made a beam couple so powerfully and purposely with surface objects. Others were sure to note how closely the beam had missed one of Spivey’s resonators. They’d also notice how accurately Alex had thrown his snowball.

“Phone call from Auckland!” The communications officer announced,

Not far away, Pedro Manella made a show of consulting his watch. “The colonel’s late. They must have dragged him out of bed.”

“Let him wait a few minutes longer then,” Alex said. “I’d rather talk to him after he’s mulled things over.”

Spivey must be watching a display like this now. So, no doubt, were his bosses. The dashed line filled in as the glowing pinpoint converged toward the familiar cratered face of Earth’s dwarf sister. No one breathed as it accelerated and then struck the moon’s northern quadrant, vanishing in a sudden, dazzling glitter of molten spray.