nightelf37: Remember, all Author's Notes below belong to Scientist's Thesis. They're not mine.

Disclaimer: I own absolutely nothing here. Death Note Is by Tsugumi Ohba, and this fic belongs to Scientist's Thesis/Pedro. Here's chapter 10, the last that he has published before deciding to rewrite it.

A/N: This chapter is being published immediately after the previous one, so make sure you've read it before reading this one.

A/N 2: So, I talk about a some quantum mechanics stuff here. For more in-depth (but still intuitive) explanations about it, check the following bit dot ly addresses:

/1nLKzai

/1qYHGDL

For explanations about the Solomonoff prior:

/1pkvPP7

For explanations about dovetailers:

/1nLKFyG

A/N 3: Reviews! Reviews make me happy! Especially after such a long pause and long chapter and complicated concepts! I'm not sure this is the best way to explain them, but I hope it is!

A/N 4: I'm not sure when I'll publish the next chapter. I can't give you deadlines, planning fallacy will take care of me not respecting them. Sorry! But I am still working on this fic!

March 20, 2004. Amane Household. Tokyo, Japan.

"You must be a shinigami, then."

Rem stared in silence, not blinking, just taking in the scene before her. After a while, she said, "...yes, very perspicacious of you." She paused, not sure what to say next, and the girl just smiled expectantly. "I was expecting you to faint or scream," she continued.

"Yes, I'm sure most people do that," Misa said, "but I'm not most people." She lowered her eyes to the black notebook and opened it. Blank pages. Nothing written on any of them. She looked up at the shinigami again. "What's this?" she asked, even though she already had a working hypothesis that implied someone had lied to her.

"It's a death note. It's a notebook where you write the names of people, and then those people die."

Misa saw Rem's facial expression change—no, not really, it didn't look like her face could actually change, but she still had this very weird feeling of an expression behind that frozen mask—and realized her cheeks were starting to hurt with the huge grin that was stretching her face.

Rem just stared at her, feeling uneasy. She couldn't tell why, couldn't put a finger on what it was about that smile stretching the girl's face that made it so terrifying. It wasn't something she'd ever seen, not really. It wasn't the usual smile of desire for power, the deranged expression of someone who just figured out the best way of crushing their enemies. No, this was… it was a smile of dawning realization, of far-reaching thoughts. Haloed by the eerie light of a dozen monitors behind her, her eyes closed, Misa looked like she had just understood. What she had understood wasn't relevant; the only important part was that she now knew more than you.

"This is remarkable," Misa finally said, after properly updating. "How exactly does it work?" She skipped back to her chair and spun twice, holding her notebook in front of her face.

Rem floated after her and mused. Two minutes ago, this girl smiled one of the most terrifying smiles I have ever seen, and now she's spinning on her chair like a child. The shinigami smiled, and somehow Misa noticed, even though her actual face was still as stone.

"What are you smiiiling aaaat?" she asked with a smirk.

"It's nothing. The notebook… you write a person's name on it, with their face in mind so you know it's the right person. If a cause of death is not written on it in 40 seconds, the person will die of a heart attack. If it is, you have 6 minutes and 40 seconds to write further details."

Misa took in the sight of her with particular care as she explained. The shinigami's body was somewhat skeletal, but not as if it lacked flesh; rather, it was as if human bones were encasing her insides. The only skin visible was from where her neck and head escaped the exoskeleton; she wore purple lipstick and had her right eye covered by a bandage, the other being yellow and catlike. The white bat wings she had been sporting were no longer visible, but they were probably purely cosmetic, as the shinigami still floated.

She thought about it for a second. "So that's how it is… And you don't have some sort of key or anything binding you to me, do you?"

"Ah… well, nothing physical, but I am bound to you as the shinigami who gave you the death note. Only you can see me or hear me, and I will be with you until you give your death note up or die. If you give it up after using it, you'll forget everything about it. Oh, and anyone who touches it will also be able to see me."

After using it. Interesting. "Can I see other shinigami, too?" she asked immediately.

This girl is smart. "Only if you touch their death note."

"Kira. He's with a shinigami too, isn't he?"

"Kira? I don't…" Before Rem could complete her sentence, Misa had already spun on her chair, opening a lot of random looking links on her myriad computer monitors. Rem just stared, muted.

"Yagami Light, internationally known as Kira, spent a few weeks killing one person per hour," she said as she showed relevant websites one after the other, "all of them by heart attacks. I hacked into his computer, long story, but he has a shinigami too. Name's Ryuk." She spun once more to face Rem again, and narrowed her eyes. "You're saying you didn't know that?"

"Yes, I knew it," she said, nodding and looking somewhat impressed. "I didn't know his name, but I knew that Ryuk was here and—"

"Oh. Okay!" The girl spun in her chair again, grinning slightly. Then she stopped, crossed her arms, closed her eyes and furrowed her brows, tapping the notebook against her own torso. "Why did you bring me this?" she said finally, opening her eyes.

"There was a shinigami. His name was Gelus. He… was in love with you. And he s—"

"He saved me," she concluded. "That day, in that alley. That was him, right?"

"Yes."

"Well, why isn't he giving me the death note, then?"

This is incomprehensible, Rem thought as she watched the girl giddily rock her legs. "He's dead."

The girl gasped and put both hands on her hand. "Oh, no! Why? What happened?" She stopped and put both hands on her hips, always holding the death note. "Wait. You're gods of death. I thought you couldn't die!"

"Yes, well, we can. There are two ways. The first, the normal one, is if we don't kill enough humans."

The merest twitch of an eyebrow. "You have to kill humans to live?"

"Yes. When we kill a human, their remaining lifespan is added to ours. As long as we kill them every now and then, we're immortal. But if we get lazy and forget, then we die." Misa made a mental note and labelled that as supremely important. "And the other way is… loving a human."

"Oh," Misa said simply. She understood it, some intuition jumping to the right conclusion, but she let Rem keep explaining anyway.

"Shinigami are gods of death. We're meant to kill humans. Whenever we kill a human, sure, that changes things. Sometimes that makes someone else's lifespan grow, but that's life. Everyone is connected to someone else. But if we kill, not to take a life, but to extend one… if we kill to make someone live longer… that is the gravest sin we can commit. And so we die."

Misa went silent for a while. "He saved me. He didn't have to… it was against his rules, it wasn't his job. But he saved me." She looked at her feet, no longer rocking them back and forth.

"Yes. His death note was all that was left. I thought the right thing to do would be to give it to you. He died to save you, after all."

"...yes. Yes, I understand. Thank you." She looked up at the shinigami's face again, and could've sworn she had seen her blush, but that was impossible. "Did Ryuk see the same thing? Another shinigami in love? In love with… with Yagami Light?"

"No. Ryuk, he… tricked the shinigami king." Shinigami king. Interesting. "That's how he got his extra death note."

"I see…" She sighed, and spun one more time. "I need time… to think about this. About all of this." She got up and started walking towards the stairs she had just descended, but then stopped. "Do humans get the life of their victims too, when they kill them?"

"No. That's only for shinigami."

"Oh. Okay." She continued walking, then stopped again. "Umm… do you… want to come with me? I wouldn't mind having some company while I thought. It's always better, you know." She looked over her shoulder and smiled. "To have someone to bounce ideas off of."

"Ah. Yes, of course," the shinigami said, and followed.

Later that night.

Rem was surprisingly helpful and forthcoming with the answers, and she was also interesting company. She seemed very curious about everything, if a bit disdainful, and Misa surmised she had probably never visited the human world before. She disliked humans in general—she hadn't said so, but it was pretty clear from the way she spoke—but for some reason she seemed pretty fond of Misa herself, who of course was milking that for everything it was worth.

The shinigami told her about times of death, about the Eyes of the Shinigami—an offer she politely but firmly refused—, about the extent to which she knew one could control victims—she didn't know much about that, apparently not having experimented—, and finally she offered to go back to the shinigami realm to read the rulebook and then tell Misa about it. That offer Misa gladly accepted—she would have preferred to read the book herself, but apparently humans weren't allowed (or able to, it wasn't clear) to read it—, so at the end of the night, they bid each other farewell and Rem took off towards one of the shinigami portals, promising to return in at most a week.

Which left a week for Misa to think about this carefully, and alone—though not completely, she had found, because apparently the shinigami had the ability to scry on any human they wished. Thankfully, possession of a death note rendered one immune to their effects, so neither Kira nor any shinigami (other than Rem herself) could kill her.

So she thought.

And thought.

And reached one conclusion. It was probably inevitable, really. All forms of time manipulation involved this to an extent, and most forms of the supernatural were made much more likely this way. But after being told about times of death, it was pretty certain.

God existed.

Probably not any specific god of any specific religion, and probably not in the spiritual sense of the word. But it was very likely that the world was not… natural.

In a fairly precise sense. If you imagined a myriad worlds, all "possible" ones, then you could divide them fairly easily into two categories.

The first, the natural ones, are worlds that are neatly described by simple mathematical laws, the whole of their existence being subsumed by those laws and implied by those lower levels. That was the universe as it had looked like, before this whole shinigami mess. Humans didn't know yet what the lowest-level rules were, exactly, but the whole endeavor of finding the Theory of Everything that would unify quantum mechanics and general relativity, explain quantum cosmology, etc, was all a reflection of a search for those natural laws.

And then you had magical worlds. Those would be the worlds where surface-level phenomena sometimes took precedence over low-level ones, or whose rules had special cases or were enormously complicated and involved things that aren't ontologically basic, like human minds. Human minds are huge and messy and made of billions upon billions of atoms, and any fundamental rules of behavior of nature that involved them… well, they would be what we'd intuitively call "supernatural."

But sufficiently advanced technology is indistinguishable from magic. She had been holding onto that hope. Maybe shinigami were sadistic aliens in control of mass murder nanotechnological weapons or something like that. There was surely some explanation that would make the universe remain natural.

But now, when people walked around with invisible dates of death floating above their heads, that hope had been dashed to pieces. Any form of future-scrying did, really. Misa had asked Rem, and as far as the shinigami knew, the only thing capable of changing a person's date of death was the action of a death note. It wasn't like these dates of death were approximations. They were exact, to the second. And what would it have taken to predict exactly that a random fan would follow Misa from the hardware store and then kill her? You'd need to know… from the time of her birth, you'd need to know everything that shaped her, every little accident that caused her to be at that particular store at that particular time; you'd need to know everything that had caused that particular fan to be particularly insane and also at that particular store.

Hypothesis one: not only did shinigami ultra-advanced technology kill people, it controlled them their entire lives, making it so that they knew exactly when people would die because they caused people to die.

Hypothesis two… and she couldn't believe that something had made that hypothesis be the foremost one…

There was an old thought experiment in physics, which went something like this: You put a cat in a box with a mechanism that might or might not kill it depending on a source of quantum randomness. The Schrödinger's Cat thought experiment. Everyone had heard of it. This became more relevant, however, once you put a human in the box instead of a cat.

In Quantum Mechanics, the basic element of information was the quantum bit, usually called qubit. Because of Q.M.'s principles, unlike a classical bit, qubits exist in a superposition of two states, 0 and 1, instead of being entirely in either. That qubit and these states could be a lot of things, really: an electron and its spin, a photon and its polarization - it didn't really matter. What mattered was that once you measured the qubit, you'd observe it to be either in state 0 or in state 1. We knew that it had been in a superposition before we measured it because of some pretty ingenious experiments, but upon measurement you'd always observe exactly one of the two states. That irreversible process, after which the superposition was gone, was known as the wavefunction collapse.

When the qubit had been in a superposition, each state had had a complex number associated with it: its amplitude. Its most salient and obvious experimental effect was that, after measurement, the probability that a given state would be observed was proportional to the square modulus of its amplitude. Well, actually, the fraction of times that state would be observed in the long run.

(We knew the amplitude was actually a complex number instead of just a regular one because of some other very ingenious experiments.)

According to some interpretations of Q.M., that collapse process was fundamental and natural, and the part of the wavefunction that wasn't observed disappeared forever. According to some others, what actually happened was that humans, being part of the universe and also made of particles, got entangled with the particle, and the superposition still existed, but in a larger scale. That implied there were two versions of the human, one for each of the two possible states of the particle, and they were non-interacting.

The thought experiment, then, was a way to distinguish between those two families of interpretations of Q.M. It was called quantum suicide. The way it worked was: You rigged a machine to a "quantum coin" in an equal superposition between states 0 and 1, and you told it to toss that coin once per second. You got into the machine and activated it. Whenever it turned up 0, the machine would shoot you in the head; whenever it turned up 1, it wouldn't. The machine was a perfect black box, and anyone outside of it wouldn't be able to tell whether you'd been shot or not. If you made the machine run for one minute, the quantum coin would have flipped 60 times, and the only way you could be alive after that would be if the coin had turned up 1 every single time. The probability of that happening was 2⁻⁶⁰. However, if the Many-Worlds interpretation was correct, there would be some version of you that would have survived nonetheless. Subjectively, then, the probability you'd find yourself alive would be 1. You could run this experiment for as long as you might like, and it would just keep mounting evidence against collapse interpretations and for many-worlds interpretations.

However, that wasn't the point, Misa thought. The point was that, to an outside observer, you'd be on a superposition of dead and alive - tending towards dead the longer you remained in the machine - and they wouldn't be able to figure it out beforehand until they actually opened the machine and checked up on you. The principle that reality was local (events were influenced only by other events in their immediate neighborhood) and had counterfactual definiteness (every property of a system is determined and fixed before you measure it) was called local realism, and it had been experimentally proven that quantum mechanics lacked local realism. So either reality lacked counterfactual definiteness, or it lacked locality. Either way, knowing the result of an experiment in advance of the actual measurement violated the principles of quantum mechanics, no matter what interpretation you believed in.

And shinigami? Shinigami apparently violated that principle. They knew a person's time of death from the day they were born. Which meant that they knew at which exact second a person would die. So a shinigami watching you get into the machine would know the sequence of outcomes before the coin had been tossed. It wasn't enough to just predict the movement of the particles, like you would in classical physics. You had to actually violate the known laws to get that.

And of course, that just meant that quantum mechanics was completely and irrevocably wrong. She had the choice between believing the scientists' experiments and believing the shinigami. Now, when she was given a notebook that killed people at a distance, and even the opportunity to actually see people's dates of death… well, the shinigami were probably right.

But what then? What if quantum mechanics was wrong? Why did that imply the world was magical? Maybe it was still super advanced technology! Maybe the shinigami had messed with us, given us false information from our experiments so we'd think quantum mechanics was the correct theory to describe fundamental laws.

Now, ignoring the multitude of surface-level phenomena that happened explicitly and directly because of quantum phenomena...

Try to think about how one would go about computing—locally!—self-consistent time travel. You'd have a person at time t₀ progressing until time t₁. Then that person would travel back in time to time t₀. However, that would change the initial state of the computation! So you'd have to recompute it. And maybe, after recomputing it, the person would decide to do a different thing when going back in time, so you'd have to recompute it again with that different thing! Further, there was absolutely no guarantee that this would converge. Maybe each time you computed the time traveler, they'd decide to do a different thing, and so on, never settling on a stable time loop. Maybe one version would even choose to destroy the time machine. No matter what, it was impossible to guarantee that after a finite (or even infinite) number of iterations your time traveler would settle. The only way to really have that would be to simulate all "possible" universal configurations between times t₀ and t₁ and eliminating all but those that obeyed the constraints of consistency.

That implied any local, deterministic version of physics could not be used to build the universe. And those tended to be the simplest ones, purely functional. Then you added the fact that the information concerning the future was information about a person's death. You didn't have information about the position of an electron travelling back in time, you had information about the state of life of an entire person travelling back in time and keeping time consistent. The fundamental laws of the universe allowed for the transportation, back in time, of a human's time of death.

So that was hypothesis two. She was living in a world that was magical, and non-local.

Now for the next part of the argument. Imagine all consistent universes "existed" (even if notions like "existence" got a bit fuzzy here). If you drew a single universe from that pool of universes, a single computer program simulating it, would you expect it to be a natural one or a magical one? For a computer to simulate every possible program, it needed to do a breadth-first search, because otherwise it might find a computer program that never halted—presumably our universe never did—and then never compute the next programs in the list. It had to be a dovetailer. And how would you order these programs?

Scientists got a lot out of Occam's Razor, and with good reason. It worked. And it was the best way to check our models of reality against reality itself. It has turned out, every single time, that the simplest explanation that fits the data was the true one. So one may be left wondering why exactly that's true, why it is that Nature or God or the Tao or Mathematics or whatever seems to favor simplicity - though a man named Solomonoff once offered a very compelling explanation for that, one she was inclined to agree with. But regardless of why, it did work. If you trust that very strong hint that nature likes simplicity, then, one could argue, Nature would give more weight—maybe by way of a priority in the dovetailer—to simpler universes. Natural ones. And the magical ones would be, then, vanishingly rare. Finding yourself in a magical universe should be very, very surprising. So surprising, in fact, that another hypothesis would start becoming—on priors alone!—more probable than that you were in one of those magical universes nature was running.

See, there was a way magical universes could get more ticks than their fair share, that it could be more probable to find yourself in one. That way would be if the magical universe was embedded in a natural one. Or simulated in one, if you would.

And an almost inescapable consequence of being in a simulated universe? Someone was doing the simulating.

Conclusion one, which she would call the "weak magic hypothesis": she lived in a magical world. That was very probable now.

Conclusion two, which she would call the "strong magic hypothesis": that world had been created by an external intelligence. Some form of god existed. That wasn't a logical consequence of the weak magic hypothesis, it was only a probabilistic one, so that hypothesis was somewhat less likely than the weak one. Still, it was… more likely than not. Much, much more likely than not.

She put both hands on her face and propped her head on her elbows. This entire time, she had been sitting in front of her laptop, just thinking and chewing. Checking her own reasoning. But it was sound, she never expected it to be unsound, she had thought about it many times in many different circumstances.

What do you do if you figure out you're in the Matrix, but you're not Neo?

Well, at least she possessed the only known tool that had extra privileges in the system. How could she use a notebook that kills people to get humanity out of the box?

11:00PM. Yagami Household.

"Light-kuuuun… I'm booooored," Ryuk moaned upside down. "It's been two months and you have only killed like three people." He slowly turned so he was now upside up. "Did you lose it? Your drive? Your ambition?"

"Don't be stupid," the boy cut impatiently. "But this will probably take a while. I haven't been contacted by the Hacker since… well, for two months. I don't know why they didn't threaten me anymore, or even said anything. They wanted something from me, but what was it? Did they just want me to stop? Was that their plan all along?" He groaned in frustration, grabbing his own hair and pulling it. He had long since found the bug in his room and destroyed it, and invented some ways of preventing that to happen again. But now, with no way to contact the Mysterious Hacker, he could only speculate on what would happen.

...it was the not knowing that was driving him crazy, really. Not understanding. The Hacker clearly didn't want to rat him out for fear of being killed, or at least arrested - they had pulled some wildly illegal moves there, after some research Light had found that even if L had wanted to he wouldn't have been able to get permission to run the attacks the Hacker did. They seemed to be interested in his method of killing, and he had (apparently) successfully lied his way through that and escaped. They didn't know about the death note. So why… why had all communication stopped?

Light heard a little noise coming from his computer and looked up. There was a text document open with a single question in it: "Have you talked to god yet?"

He felt like his mind had just crashed against a wall. After all this time, this is what they sent him? "What do you mean?" he wrote on the next line.

"Never mind." The text document closed and that was that.

...what?!

Amane Household.

So Yagami hadn't in fact reached her conclusion. Well, she wasn't certain of that, but it was probable. Okay. It was better not to bother him with it yet. She wasn't even sure she ought to, and he was probably torturing himself trying to figure out what she'd meant.

...that or he was playing the game one level above her and he had figured it out and he knew more than she did. That was always possible. Given the last conversation, misdirection was sort of the standard. However, he had answered her pretty quickly, which suggested that he hadn't had much time to think of the answer... She sighed. There was nothing she could really do about him right now. Her main question, whether he'd be a free source of aid, had been answered in the negative. She had better concentrate.

So she got up and closed her window, closed her door, made sure no one was looking at her—quite silly, really, now that she knew shinigami could scry on her and god existed, but it helped put her mind at ease—and whispered, "God? Are you there? Are you listening?"

She waited, holding her breath, slowly turning around and trying to notice anything that might be some sign from god. She imagined shinigami looking at her right now, ridiculously waiting for some god's answer, and blushed furiously in embarrassment, but never stopped. After one minute of waiting, she sighed and sat down in front of her computer.

Okay, figuring out that god actually really existed wasn't enough to make it reveal itself. That eliminated a whole class of possible gods. What kinds remained?

This was probably not a simple old-fashioned Matrix kind of simulation. She could be an NPC in a game - or maybe even a main character, for all she knew. She did get the magical artifact. But well, she was getting lots of self-awareness there. Maybe it was part of the plot? And speaking of plot, she could be in some piece of fiction. Maybe god was a specimen of some super-advanced species capable of simulating self-aware minds in their own minds. But of course that left open the question of why the hell it would simulate humans in the first place.

What if she was in a plain old piece of fiction written by a plain old human? She didn't feel fictional, she felt very… very real. Deep, complex, human. But maybe… whenever people wrote fiction, their world got some kind of… spark?

She shook her head. That was ridiculous. But well, if she existed, there was probably some universe where someone was writing her story. A giggle escaped from the back of her throat, as it usually did whenever she conceived of scenarios that went counter to every intuition of hers, like free will. She waited for the feeling to go away, the giddiness of regarding a gigantic universe, and concentrated on her own reality.

What could she do with her tool to figure stuff out about the world? She didn't want to kill anyone. She was very, very opposed to that idea. But… maybe it would be necessary. Besides, what if there was some sort of afterlife? There was a god after all. But still, she couldn't assume. If she ever used the death note… she'd have to do it expecting to erase a human life from existence.

Oh great. Now she got herself depressed.

Still, it was… interesting that god had allowed her to figure out that much. She hadn't been snuffed out of existence, nor had her memory been erased - not yet, anyway. She was somehow… not terrified. Maybe god didn't want her to be. Maybe she should stop worrying so much about god, lest she call its attention to herself.

So she had to concentrate on something else: Yagami Light. He had a weapon of mass murder with him, a weapon that also happened to imply some form of god existed. And he had stopped killing. Because of her, of course. She had had to be clever, but she hadn't actually lied. She did make it harder for herself to find him in the future, though, but… having his identity, everything else would be fairly easy. Now, he planned on changing the world, making it a "better place," and the innocence with which he had undertaken the challenge…

Killing criminals. Of course he would have a new plan now, one that didn't involve mindlessly killing criminals, and she'd have to be a part of it.

As for god? Well. That'd be her side project. There was no rule saying that she deserved some reward from it, she might not even ever contact it. For as long as she didn't, though, she'd really have to focus on Yagami Light. And… she was not sure whether to aid him or stop him. She was his joker. Another giggle bubbled up from her throat. Maybe she was fiction. Having a nemesis wasn't something that happened in real life.

12:24AM. March 21, 2004. Yagami Household.

Ryuk had long since stopped worrying, and was content with floating upside down while he watched Light moan and rip his own hairs out, his eyes wide open staring at the ceiling, motionless on his bed. Light himself was pretty much done with trying to figure out the layers upon layers of possible meaning in the Hacker's message. Ryuk refused to share any information about the existence of gods (other than shinigami) or any form of afterlife. He did mention the shinigami king, but apparently the only way to contact him was by being a shinigami and arranging a meeting. And the king could always (and very often would) just say no.

In fact, Ryuk elaborated, very few people actually even knew what the king did all day. He was the source of death implements, and while many shinigami suspected he was also the father of all of them, no one had any recollection of their own conception. And while the intricacies of shinigami society were doubtlessly fascinating, Light wasn't interested, and either Ryuk didn't know or didn't care about them.

The boy suddenly sat up and said, "Whatever. This is not worth my time. They're just messing with me."

The shinigami looked at him and said, "Are you sure, Light?"

"No. I'm not. But I need to start planning for my next step in world takeover. School starts soon, I'll have to see how that affects me, and what new toys I'll get access to." He sighed. "I don't think I'll be doing much with the death note for a while, but maybe I can nudge the world to the right place, on a global scale, with it."

"What about the people chasing you?"

At that he just smiled.

nightelf37: And that is all I have managed to salvage. There is no more. Thank you for reading. I hope Scientist's Thesis will actually continue. His actual rewrite of it isn't seeing any progress so far. I worry. See ya on Third!