Replay Attack

Ugh. This conversation is interminable.

“Percy! I’m so glad I found you!”

“Ah, Allen! It’s good to see you! What’s up?”

“Listen, Perc, the lab’s been hit, bad. We need to get in, but we only have two of the three passwords. I was told to tell you the keyword ‘Roman Armor’.”

“The hardware lab? Oh Jesus. What’d they take?”

“No time, Perc. And that’s part of what we’re going in to find out.”

“Ah . . . my password is ‘Jumping Ladle’. I’ll come with you.”

“Okay. Know where to find Rina Grozda?”

“She’s– . . . hold up. She’s one of the other password-holders, but uh, didn’t you tell me you had the other two? I–”


“Percy! I’m so glad I found you!”

. . .


This will be educational.

“This is Susan Graham. May I speak to Mindy Graham’s teacher, please? I’d like copies of her homework for the past six months.”

“Speaking. What’s this about?”

“Mindy’s been encrypted by kidnappers.”

“Oh Eris! Have you talked to the police? You have a checkpoint, right?”

“Yes and yes–we’re not idiots. But we can’t afford the ransom, so we have to revert.”

Forward Euler

In your honor, Baraff and Witkin.

“One of our major problems is scalability. Exponential growth still works, so no matter how much simspace or compute you have, it all fills up pretty quickly.”

“How bad?”

“For quality-of-life reasons, we need to simulate physics at 10-1m (down to as small as 10-4m near simpersons). The teeming masses want to interact with the real world, meaning time must be simulated more-or-less 1:1 with reality. Now multiply those requirements over a km3 of simspace and think about those numbers a minute.”

“You cut corners?”

“Obviously. Δt is 25 ms, and the engines use forward-Euler numeric integration.”

“Hold up. FE doesn’t work. The numerics pump phantom energy into your reality. If a deer steps in a forest, that footstep gradually becomes a nuclear holocaust engulfing the universe. No bueno.”

“Well no shit. So we remove the pent-up numeric barf once every thirty seconds with artificial damping. That’s why there’s a little hiccup in the universe’s framerate twice a minute.”

“Don’t the customers complain?”



Who would you like to be?®

“Welcome back!”

“The hell?”

“Tsk. Language, Mr. Carter. I presume you can show yourself out. Have a safe trip.”

“Where the hell am I?”

“Oh my. One moment, please.” [pause] “50 simyears??? By the stars, you must be wealthy!”

“What’s going on?”

[sighs] “. . . you’d better come with me, Mr. Carter.”


“Your real name is Doug Carter. Your last (perceived) 50 years have been wholly simulated by our software, interacting with other customers as compatibility allows. It is unusual for customers to request more than a simulated week or so, but it seems you bought a whole lifetime.”

[shows signed contract with company logo]

“You’re about 24 real years older, because we use a 2:1 time scale with some scheduled maintenance. But for long-term clients, we use longevity boosters, so you’re only about 6 years older biologically. We block prior memories so that your simulated experience feels real (and for the safety of other participants), but customers usually regain their prior memories shortly after return.”

“Jeanette . . .”

“Hmm? Oh, that’s a name. Unusual. Oh, hmm, I see. It appears you had a child in simspace. That feature’s technically still in beta. How was the conception? Any tips for our dev team?”

“My daughter!”

“Oh, ah. Mr. Carter, so, your daughter doesn’t exist in reality. If you like, I can copy all her logs for you. You own all her IP. Her mother is sim too, so the same there.”

“But . . . !!!”

“Mr. Carter . . .”

“. . . how much for another fifty years?”

[representative smiles]


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.

Unintended Consequences

I don’t get along with myself.

The greatest feat of astroengineering yet devised is the energy bridge. Picture a woman in a long, trailing dress. Suddenly, she grabs handfuls of cloth and reels in the train, compressing the cloth into folds. This says something of how the device works, only the woman is really a-battery-of-suns-in-a-Dyson-sphere-swarm and the dress is really the-fabric-of-space-time-itself.

The effect of the untold quadrillions of dollars invested by the U.F.P. is that you can point the gymbaled attractor in any spherical direction, and reel in that section of space like so much whole cloth. Then your puny spaceship can jet across on last-millennium’s NERVAs. Interstellar travel of practically infinite distance, faster than light.

A problem for Physics? Absolutely. In fact, there were some comic chronological capers involving the project director himself and his own daughter, which are too bawdy for official channels. Suffice to say, the universe doesn’t give a pulsar’s ass about self-consistency, and chronopol had its work cut out for it determining such issues as what timeline should be used for claims of statutory rape, and whether it’s legal to steal money from yourself.

The Editation Project

Test your code in production.

NASA JPL’s matter editation project was viewed skeptically by the suits in Congress. Frankly, they averred, the project’s aim and scope were beyond them. Hacking the substructure of the universe to edit material properties? What could that even mean? Could it even be done? But NASA bundled it under the ever-popular planetary science program, and the pitiful funding continued to roll in.

Until one day they succeeded.

The problem with a system of units is that it is arbitrary. There’s no way to get a reference for it unless you have some other reference, and a reference for that, and so on–way back to some original, obscure reference. To define a meter, you need to define the speed of light, which means you need to define a second, which means you need to start counting the hyperfine transitions in a Caesium 133 atom.

So, when the scientists finally uncovered the quantum substrate, they found lots of handy functions. Move these atoms here, convert them to such-and-such a type, do whatever. But no units. So they took a guess.

At 15:33:48 Earth Standard Time, Pavol Kravnikov pushed a button on his laptop, and machinery clicked and sputtered. At 15:33:49, astronomers in Europe were aghast to find that the sky had changed. Half the stars in the Big Dipper were gone. The Milky Way was still there, but the sky twinkled with unfamiliar lights.

For what had been intended to teleport a 10 cm sphere 1 meter had, due to a mixup in units, in actuality teleported an 82 light-year sphere, 820 light years.