If you could see the notes they’re taking . . .

As time increases without bound, the probability of
existing within a simulated reality approaches unity.

There are exactly two possibilities: either we exist in a simulated reality, or we do not. If we’re simulated, this almost certainly evidences a creating group of entities in the enclosing universe with a reason for doing it.

At this point, you can speculate on motive. For example, maybe they’re doing a simulation: a group of cosmological grad students. (The idea of a “god” in the classic sense seems cretinous; what depraved being would build a toy universe and then have trite interactions inside of it for eternity?) But these lines of inquiry become dull rather quickly.

More interesting is to speculate on the existence of the parent universe itself. By applying the same logic recursively, we find that they’re probably simulated too. So you have us, inside a parent universe, inside a parent universe, inside, inside, and so on until you reach some root universe. It will always reach a root universe in a finite number of nested universes. (Why? Because by assumption, the probability of existing in a simulated reality only approaches unity. And even if we were to know we’re in a simulated universe, you toss the problem to the next one up, and so on until an assumption breaks. Anyway, you can’t have turtles all the way up.)

For example, let’s say that we think the probability of existing in a simulated reality is ps=0.93. Assuming this is constant for each universe (each universe likes simulating universes approximately the same as itself), we’d expect on average to be the 14th or 15th universe down. If it’s ps=0.5, on average we’re the first universe down.

What’s fascinating is that this implicitly involves a problem: we can’t define time very well. If you observe a universe right at the big bang and then live through until its end, your ps grows monotonically from 0 to 1 but the truth remains constant. What the original conceit really is saying is about time in the root universe. That, as time progresses, the number of recursively simulated beings collectively grows faster than the number of real-lifes. It’s a hyperexponential growth, too, since each simulated reality makes its own recursively simulated universes too.

This suggests something interesting: we can devise an a-priori experiment to see whether we’re in a simulated reality. See, this hyperexponential growth starts exactly when the root universe starts simulating things. The population growth in the root universe continues at an ordinary exponential rate, so the simulated universes very quickly outpopulate the real one.

This means that after the root universe develops universe simulation, your chances of being born in the real world drop abruptly, asymptotically, to zero.

In the absence of better data, we assume that any parent universes are like ours, since people are interested in creating applicable simulations. So:

  1. If we are simulating our own universes, then probably we are the child of a parent universe that is also simulating universes (one of which is us).
  2. If we’re not simulating universes, then we don’t have a parent universe, because that parent universe wouldn’t be simulating us either. So we wouldn’t exist (and yet clearly we do).

The intriguing thing is that the simpletons who authorize science funding get the implication backwards, reasoning that if we don’t invent universe simulation, then we’ll be living in real life (as if such post-hoc decisions could influence the very nature of reality). If this carries back up to the root universe, then no child universes will ever exist (which makes the fallacious chain of reasoning even more appealing).

Ed. note: this isn’t actually strictly fiction.

In Case of EMP . . .

Nostalgia costs mass.


Johnson broke the glass.

“The hell is this?”

“It’s a slide rule. And it’s going to save our asses.”

“Lotta fancy numbers. What’s it do?”

“It multiplies, divides, square roots, all the usual things ‘cept addition. This one does trig and exponents too. It’s more precise than your brain, but less so than a computer. That EMP means we don’t have a computer, though. Both backups are dead too.”

“Well, we had no way of knowing that that particular CME would hit us way out here at Jupiter. The chances of that must be pretty absurd.”

“Not really. Happens all the time. But our electrical shielding clearly wasn’t up to par, and this was a particularly big one. Right now, we’re dead fish in a very big sea. See if the emergency sparkgap is working. Tell Ganymede we’re scrubbing the mission—and we’ll use this thing to figure out how to burn for home.”

Ed. note: Idea from Atomic Rockets. I myself restored a K&E for work, and have another at home. They’re useful for one-off calculations that would be too slow to do in my head and too unimportant to boot a shell.

Material Science

A song, broken by tears.

“What is it, my dear? What’s wrong?”

“I . . . I broke it, mommy!”

“Well, what did you break?”

[looks up with sorrowful eyes]

“You don’t mean . . .”

“It was dirty! I tried to wash it and—”

“Show me!”

The violin lay on the bed in a crumpled, twisted heap. Traditional violin bonding is water-soluble, and modern strings put nearly 50 pounds of pressure . . .

“I’m sorry!”

[examining] “Ugh, and the wood is all warped too. You should have called me sooner!”

“I’m sorry!”

[sighs] “Well, there’s no way to fix this at all. The wood is cracked and the water warped it more. Even if it weren’t, there isn’t a luthier within half a light-hour.”

“. . .”

“It’s okay sweetie. You couldn’t have known. You’ve never seen wood before.”


Artwork by Dizzy Chen.

Space Bums

Immigration should do something.

“Spare change, brother?”

“Get a job!”

“That’s quite impossible.”


“Impossible: adj.: not possible; unable to be, exist, happen, etc.”

“A wise guy, eh?”

“Yeah. Everybody out here has an IQ over 110. ‘Cept you, ‘parently.”

“Why, I never!”

[sighs] “We’re all descended from Earth, one way or another, but the smartest all moved out to space. So us second- and third-gen folks are all the sons and daughters of the upper-bracket erudite—including a fair measure of genius. The funny thing about IQ is that 100 is always average, so the average Earther is 80-something and the average Belter is 120.”

“I take grave exception to—”

“Oh can it already. Where are you going anyway?”

[testily] “. . . Bureau of Careers. Just shipped in with my last dime.”

[sarcastically] “And may lady fortune herself light your path to employment.”

“I will too!”

“Nope. Yer too dumb. If I can’t get a job, then you sure as hell can’t get a job. And you’re in the same boat as I—without any cash, you can’t buy your way off this rock. Might as well take a seat next to me. Yer gettin’ no job, brother.”


We’ll get right on that, then.

From: Lt. Samuel Biggs
To: Sgt. Anton Maieux
Timestamp: 2154-07-07 06:07:11 EST
Subject: Re: (no subject)

Hey Anton,

We considered your request, but unfortunately, it must be denied. While Andromeda is in high berth, we’ll need every man onboard for inspections and extra duties. Additionally, Mars STC cannot handle any more traffic since Phobos is being developed. Advise next opportunity at Jupiter rendezvous.

-Lt. Biggs

> Lieutenant,
> Some of the boys and i were thinking of heading
> planetside for some r&r. We’ve been in spce for several
> months, and it’d improve morale
> -A
> This e-mail is confidential and may be legally privileged.
> If you are not the intended recipient or have otherwise
> received it in error, you must delete it and any and all
> copies from your comconsole and notify the sender
> immediately by reply e-mail. Any unauthorized reading,
> reproducing, printing, or further dissemination of this
> correspondence or its contents in full or in part is strictly
> prohibited and may be unlawful. Planet-net does not
> guarantee timeliness, security, or absence of self-
> replicating or self-executing code, nor does the sender
> accept liability for any such deficiencies.

Haven’s Scavengers

The best nuclear engineers are bachelorettes.

Beth nudges her tiny spaceship on RCS power the last 100 km to Haven, the orbiting metropolis dangling perilously by space elevator from Pasiphae, one of the outer retrograde moons of Jupiter.

Haven approach, U.F.P. Willow cleared for docking, junction 900 E. Advise no open-cycle nuclear propulsion within 100 klicks.”

“Duh,” Beth thinks. “Why do you think I changed orbits with docking thrusters? That’s the only other burner this thing has.”

“It’s not much,” she reflects as the dull clack, felt through the berthed ship, signals the dry dock closing behind her. She’s carrying a brown paper bag filled with treasure: Tellurium superconducting wire, spare plasmabrick for reactor lining, even a canister of propulsion-grade Xenon.

It’s a high-quality, if small, collection. It will fetch a good price, but it’s getting harder. There’s simply not much left unsalvaged. And sometimes you spend delta-V and months of transit time to intercept with a derelict that’s already been picked over. 4000s is pretty good ISP for a NTR, but after months chasing wrecks in interplanetary space, that’s still an awful lot of Hydrogen and Uranium-Hex to buy at a gas giant—to say nothing of food.

Ed. note: we first saw Beth here.

Indian Food

Grousers will be spaced.

“So I hear you like curries.”

“That’s not funny. You know I hate how space erodes your sensitivity to taste.”

“Fair enough. The rations, which are, by the way, spicy precisely to counter that effect, hit the spot for me, at least. It’s too bad there isn’t more to go around.”

“It’s a long flight and every gram counts. Cut it with water.”

“Ugh. I hate drinking our own rad shielding.”

“The rubbery taste is a bit off-putting, I’ll grant. But the ammonic tang of lightly reprocessed piss isn’t any better.”

“True enough. Pass the water. And also the aloo matar.”

Ed note: c.f. spacecoach concept IRL.


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.