Gray Goo

“This is thermodynamically impossible.”

“No one was particularly scared of these things, since they’re so small.”

“And no one particularly should be, since they cannot dissipate Brownian energy, nor can they reproduce on such limited raw materials.”

“All true,” remarked the speaker, somewhat disgruntled. “But that doesn’t change the fact that one of our orbital research facilities has—and quite otherwise inexplicably, I might add—dissolved into a perfect sphere of uniform color.”

The slide changed. A red ball stood superimposed against the stars, a sinister crescent moon.

“Why!” Someone gasped. “That was the I.S.S Clarke!”

The speaker nodded. “Indeed, Clarke was painted red, for better visibility to near-IR scanners.”

“My condolences, Charlie.”

“So they don’t operate on individual atoms,” someone muttered.

“Speak up.”

“They operate and exist on the molecular—not atomic—level. Or else they’d have simply decomposed the pigments, and it would take some unpredictable appearance. It’d form a nanoscale metastructure, so I guess it’d be some kind of an iridescent panoply.”

“Correct. Notice that operating at a higher spatial level obviates the major energy constraints. The material-limitations ones did not apply, as Clarke is—was—made primary of steel nanofoam and composite volatiles.”

“So,” the speaker continued, “we have a real gray goo situation on our hands. So far, it shows no signs of stripping the extremely tenuous atmosphere in LEO, but eventually it will fall to Earth, and this crisis will become, quite possibly, an apocalypse. Any suggestions?”


“This isn’t really safe, is it.”

“That’s good on paper. What about practice?”

“Of course, we won’t know anything until we try.” John shot her a quizzical look, then went on: “It’s not like the academy is fully cognizant of the potential significance of this work.”

“They’re barely cognizant of their own financial security, which, by the way, is still rather tenuous. Research cuts, you know.”

“Don’t I know it.”

“Well let’s try it, then. We’ve been ready for a while. Months, really.”

John nodded. And, without further ceremony, a small red button was pushed. Somewhere, machinery hummed, and two enormous drums of titanium alloy began spinning in a perfect vacuum.

Faster and faster the enormous drums spun, until sheer strength was insufficient to hold them together, and the radial artificial gravity fields began crushing them inward.

Their outer surfaces were racing past each other now at thousands of kilometers per second, separated by a tiny vertical strip just millionths of a meter wide. To the naked eye, the two atomically perfect, titanic disks touched in a single, unbroken line.

But of course no human would risk his life from being so near to such contained energy. And of course, the Earth couldn’t be risked either, so that was far away too.

“We should see something by now,” Casey observed, searching without success for that something.

“Well, frame dragging is within predicted measures.” said John.

“The cylinders are warping spacetime past 0.5 c. Something’s going to have to give, and it’d better be space. There’s already more than a quadrillion joules of kinetic energy in those wheels.”


“It’s a wash, then.”

“3 trillion , wasted.”

“Wasted?” Casey smiled furtively. “No; we’ve only just begun.”

Scrawled Note

Based on a heartwarming true story.

Inside the labyrinthine corridors of the Center for Advanced Neural Study in Cambridge, England, a certain graffitied message was once messily scribbled in Sharpie on a vacant wall:

Computers can’t think. Submarines can’t swim. I don’t know who I am anymore.

The wall was not repainted.


I.T. isn’t better in the future.

“Apparently, they use some kind of subspace.”

“That doesn’t make sense.”

“Ugh. No. Wrong word. More like, spacetime is some . . . thing, kindof? Since it has all these associated properties. Think of it like a ribbon. The thing they use is sortof like the ‘hangers’ that the ribbon is hanging on. See?”

“Vaguely. What’s the effect, anyway?”

“The effect is they can project radio-band white noise, from any point, to any point, using a ‘sublight’ wave traveling about one light-year per second.”

“‘Point!’—Ha!—Try: ‘a planet!‘ . . . Why white noise, though?”

“Yeah. Apparently that’s about the only thing. Anything structured gets scrambled immediately. Not especially useful, although you could probably rig some kind of ansible.”

“Doesn’t that violate something?”

“Sortof, but nothing is going faster than light; it’s just there’s less distance it has to cover in ‘subspace’.”

“Regardless, this interstellar denial-of-service attack is pretty awful, I’ll say. Can’t we send some spaceship back the other way? Make them stop?”

“It’s hard because subspace is seething with activity. That’s what corrupts any heterodyned signal. However, we tried sending a one kilogram test mass through.”

“. . . and?”

“Sir, I know you have family in Pittsburgh . . .”

Niven Ring

“You got a problem with relativity, son?”


“Sir! The ring has become destabilized! She’s dipped 50 km down!”

“Already? Get me Morgenstross!”

“Right away!”

The functionary fiddles clumsily with his communicator, then slams it onto the desk, where it squawks, as if in protest. Over the radio, Morgenstross is shouting something. Slowly. Very slowly.

“I couldn’t pick it up directly, sir. I had to go through four relays around the ring. Four!”

“From a certain perspective, we’re racing into the future.”

“Quiet! I can’t hear!”

“. . .”

“Morgenstross! Enable emergency RCS in your segments! I can’t do it from here. Everything’s shot!”

Morgenstross continues shouting, his voice audibly lower and slower.

“Morgenstross, listen to me!”

“. . . I don’t think he can hear you, commander.”

“Then patch me through!”

“No; I mean, I think he cannot, because the time slip between here and lower is so high. Relative to us, he’s so far down the gravity well by now that our sectors are, from his perspective, racing into the future.”

“Speak English, cadet.”

“Time slows down for objects falling into black holes. The Niven ring is lost. We must get to the pods. We must also warn the people behind us in the ring before it’s too late.”

“. . .”

“And sir, we should hurry. Morgenstross was probably trying to do just that.”


I guess there’s time for sightseeing.

“No Visitors”, reads the scrawled lettering on the thin, corrugated metal. Beth grimaces remorselessly and turns the handle.

Inside is static chaos. Everything bolted down bent. Everything stacked or hanging fallen. The table, the lamp, the picture frame with the occupant’s daughter, all lie in a broken heap. Chaos.

And covered with dust.

The thin, fine, dangerous dust that you get from manufacturing defects, from micrometeorite punctures in your ventilation system, leaking precious, life-giving air into the clutches of nothingness. From monopropellant from ruptured tanks coating the suffocated interior of a small freighter, one of thousands spinning lonely in the dark.

Beth plays her flashlight over the rubble. Nothing here. No Tellurium on the engine deck either. Already picked over.

On a whim Beth reaches for the picture frame. Then smiles. The girl would be about 230 now. Still, she’s a pretty echo of the long dead.

Angular Momentum

Advantages of tumbling pigeons.

“Tell me straight, skipper. What’s wrong?”

“We’re dead. That’s what’s wrong.”


“Even as we stand here, we’re dead men. That last bomb pumped us full of a whole soup of radiation. I’m surprised the hull hasn’t shattered from neutron embrittlement. But the gamma rays are what did us in.”

In the background, someone clutches his abdomen in sudden pain.

“Well, do something!”

“Detonate this warhead in the null-G section amidships.”

“You’re mad!”

“I will be, unless you get on it. I’ve already notified engineering.”

The young lieutenant stands for a moment, petrified.

“Oh fine. Since understanding might make you more obedient. We spin end-over-end for gravity, and right now our plane of rotation is lined up with their vessel. They’re about 15 klicks away, so if we break in half at the right moment, we might get the tail end flung close enough to detonate our atomic drive right next to them before they notice.”

“But! We’ll all die!”

“We’re already dead. Now move it.”


Not exactly diplomacy.

“Lemme get this straight—at the bottom of that mineshaft is a thermonuclear warhead. And at the top of that mineshaft is a steel plate. In 41 seconds, their warship is going to pass by in orbit overhead and we light it off?”

“That’s about the size of it. Any questions?”

“. . .”

“. . .”

“Well, I mean, isn’t the plate kindof . . . you know . . . not aerodynamic?”

“That turns out not to matter. At the speed it will be going, it will be in the atmosphere, oh, only about 130 milliseconds.”

Peter’s mind boggled.

“That’s like a hundred kilometers per second!”

“Yeah. Through their hull. Neat, huh?”

Somewhere in the distance . . .


Orbit Guard

Kratocide or capitalism?

“Don’t tell me you’re busy?”

“Crushingly. Important?”

“No. I’ll be back later.”

The U.F.P. Justice hung in null-G, poised, as its burdened commander labored over the ship’s supercomputer terminal. Two hours ago, the call had come in: “Unauthorized asteroid deflection burn, Dec. -5.419°, R.A. 41.17°, class ξ asteroid 1999 RQ36 ‘Bennu’. Deflection Δv = 0.26±0.03 m/s.”

Small deflections make big changes. Even the emission of absorbed heat makes asteroids move unpredictably, unless their surfaces are mapped in detail. But with literally millions of asteroids, the Yarkovsky effect is not worth the bother.

But now someone has gone and moved one of them. A pretty big one, maybe half a kilometer on edge. That would probably utterly destroy one of Earth’s megacities, should it hit one.

Which means someone landed on it, did a thermographic survey, plotted its orbit to high precision, and then nudged it deliberately, in a particular direction, an exact amount.

So, the question—was it some unhinged terrorist bent on the obliteration of Los Angeles? Or a miner secretly moving a motherlode of priceless volatiles back to base?

In 51 years, he’d know for sure. For now, there’d be only guessing.

A Monte-Carlo Simulation

Because really, how long is “short” for a galaxy?

“We’re alone.”


“Ran a sim. It’s really obvious. I don’t know why I didn’t think of it before. See these green dots?”

The visualization in front of her swam with millions—probably billions—of green fireflies.

“Yeah hmm?”

“Each is a planet in the sim. 1011-ish. Let’s say there are 103 civilizations, starting within 108 years of each other, technologically. Once a civilization attains spaceflight, each of their planets colonizes a vacant one every 500 years.”

“So how long does it take?”

“12 500 years for half the galaxy, and no one else has even started. See where I’m going?”

“Exponential growth is a bitch?”

“Ha. Try again.”

“It seems to me that if you pick a random point in time, chances are, either the galaxy will be empty, or else full. 20 000 years should be enough to colonize the whole thing, and that’s a very short time in galactic terms.”

“Exactly. So the fact we still haven’t heard from anyone?”

“It means either we’re alone, or we’re the first.”