09 Conifer Village / A Computer of Light, Pt 2

Previously, on Usagi Days: The girls enter the mysterious warehouse. Inside is a large computer that miraculously works. The girls are dumbfounded as to how such a thing can exist …

- 9.1 - Professor Kay Introduces Herself -

The woman in the white lab coat made her way down to Misa and the Usagis.

"You must be the girls who delivered my package the other day. I've been meaning to thank you personally, but it's been crazy over here the past few days. Trying to keep up with demand, lots of maintenance and bugs. In fact, I don't think I've slept in … oh, three days?"

Violet and Ivy shared a look. Telepathically, between each other: Did she say bugs? Like … spiders?

"But your delivery arrived just in time, really saved my butt." The woman extended her hand to Ruby. "So thank you. Really. I'm Professor Kay. Pleasure to meet you."

Ruby shook her hand, and one by one the girls introduced themselves to the professor.

- 9.2 - Professor Kay and Probabilistic Integrity -

Prof K: "First, let's start with a basic question—why don't electronics work under the SDF? Why don't machines of any complexity work?"

Ruby and the girls looked around. Feeling that the professor was about to tell them anyway, they remained silent.

Prof K: "The problem is not really in the inherent complexity of any system. A pistol is pretty simple. But it fails to shoot. A lightbulb connected directly to a battery is pretty simple. But it fails to light up. Well, you might get a brief flash, before it sputters out.

"But let's talk about what does work under the SDF. A bow and arrow still works. A simple wooden waterwheel will still turn under a waterfall, and we can mill grain with it. But we start bringing in magnets to turn that mechanical energy into electricity—suddenly we start seeing problems. Why?

"The answer is simple. If there is the slightest possibility that something can go wrong in a system, the SDF will pounce on it, make it into reality. But there has to be some kind of …"—she searched her head for the right word—"… plausibility to how improbable a Gestaltzerfall event is.

"A bullet fails to fire? Sure, that's within the realm of 'plausibility'. A laptop PC fails to start? Plausible. The SDF can make that happen.

"Where would a bow and arrow go wrong? The arrow leaves the bow and turns to … steam? The arrow fails to leave the bow entirely? The bow just snaps in your hand? There's no plausibility to those results. The probabilistic integrity remains intact. If the SDF has no advantage to take, it cannot act.

"Now. If you swab a bit of poison on tip of your arrow, did you know that in most cases, the SDF will actually inactivate that poison? The same applies for blowgun darts. You can't see the viability or effectiveness of a poison by sight alone. That fact alone gives the SDF the 'plausibility' to act.

"The larger a system is, and the less quote-unquote 'plausible' the probability of its failure is, the higher its probabilistic integrity is."

The professor paused, blinking as if snapping out of a trance. She looked as though she had been somewhere else during her talk, and had just now returned to Earth.

"Sorry, that was a lot. You girls following so far?"

Violet, Ivy: "Yeah, totally." (Not understanding at all.)

Ruby: "Kinda."

Anemone was deep in thought.

- 9.3 - Anemone on Subjective Plausibility -

Anemone: "But this plausibility—isn't that a bit subjective? You say plausibility as though it's a fact. But events are really only plausible by our definition, right? You've defined a clear separation between plausibility and probability. An arrow turning into steam is implausible, but what about … I dunno, the arrow tip flying off? That's rare, but it happens. Probably about as often as a gun misfiring. So why do bullets consistently misfire, but arrow tips aren't flying off all the time?"

The professor smiled. "That's a good observation. And you're right. An arrow tip can fly off. A bowstring can snap. Both plausible—on improperly maintained or worn equipment. The arrow tip can be secured properly. We can verify this with our naked eye. Just like the bowstring can be observed to be new and tightly woven. The act of taking these precautions itself reduces the plausiblity index of a Gestaltzerfall event. If I tie twenty-thousand knots on a long piece of rope, it's not going to untie itself. It's just too implausible. It's all in the observable plausbility of the action.

"A microchip that refuses to work properly looks the same as a microchip running without issue. It's in that microscopic, particle-level world where the SDF hides, where it works best."

The professor's face had darkened at the last part. She seemed to have been drawn into her own mind again, perhaps grappling with ideas she couldn't quite yet reconcile. Then she snapped out of her reverie, as she did the first time, and smiled.

"Of course, I'd be deluding myself if I claimed to understand how the SDF truly works. At the end of the day, I'm just an engineer with a dream. And a working computer." She gestured to her machine. "And I believe one day we will understand the invisible chains the Orcs left us with. We might even free ourselves from it."

- 9.4 - Prof K Introduces the Fundamental Unit of the SOLA9in3 -

Prof K: "So that brings up back to our problem. How do we stop the SDF from pouncing on any chance it can get for Gestaltzerfall? Well, we take inspiration from the bow and arrow. We work in the observable world."

The professor brought the girls over to one section of the machine.

Prof K: "What you see here, all these winding tubes that the machine comprises—they're actually made up of smaller tubes themselves." She pulled out a small, black tube, about the length of her outstretched hand. "This is the fundamental unit of the SOLA9in3. Whereas the computers of yore used transistors—or vacuum tubes, if you went farther back—we use these."

- 9.5 - Prof K Explains a Logic Gate #1 -

The girls then followed the professor to a window, through which a beam of sunlight shone into the warehouse.

She held up one end of the tube to the girls. "See how there's two openings here?" She swung the tube around to show the other end. "And there's just one opening on this end?"

They nodded.

Prof K: "If I shine light into both receptors"—she moved the end with the two openings directly into the stream of the sunlight—"the light comes out the other end. The output aperture.

"But if I close just one receptor"—she covered one of the two openings with her finger—"the light at the other end disappears. In other words, both openings need to have light shining through to have light on the other end."

- 9.6 - Prof K Explains a Logic Gate #2 -

Prof K: "Now this tube, on the other hand—it looks the same. And indeed, if you hold both receptors up to the light, you see it on the other end, like before. The difference on this one is, if I block one receptor, like so … The light still comes out the other end through the output aperture. See?"

- 9.7 - Prof K Explains a Logic Gate #3 -

Prof K: "This is the third and last tube. See how it has an opening in the middle of the tube, unlike the others? For this one, a light is always shining in through this middle hole. This light gets redirected through to the end." She tapped the right end of the tube. "But! If I happen to shine a light on here"—she tapped the left end—"the two light beams will cancel each other out, and the light at this end will turn off. Destructive interference. This one is a bit hard to demonstrate, so you'll just have to … take my word for it."

- 9.8 - Prof K Concludes Her Primer on Digital Logic -

Prof K: "But now you have the building blocks of digital logic. With enough of just these three gates, you can build … well, anything. Anything you can dream of."

- 9.9 - Prof K Explains the Device on the Roof -

Prof K: "Essentially, we've blown up the structure of a computer. All this you see here"—she motioned toward the SOLA9in3—"used to fit on something the size of a postage stamp."

(Violet: "What's a postage stamp?" Ivy: "They're like little stickers. I used to know someone who collected them in a book.")

Prof K: "And by doing so, we've exponentially reduced the plausibility of it the mechanism failing. Because what can the SDF do to a beam of light? The light will not fail. No. The light will not fail.

"Ah! You probably noticed a strange device on top of the warehouse, didn't you? That's the solar collector array. It concentrates all the sunlight down into the SOLA9in3. So, as you might imagine, it doesn't work on rainy days."

Anemone: "… Or at night."

"Or at night," repeated the professor.

- 9.10 - The Girls Leave the Warehouse -

Misa escorted the girls out of the warehouse.

The Usagis thanked her for the tour, and made their way back to the inn, talking about what they had seen.

Violet: "My head hurts. I need to … I need to lie down."

Ivy: "Same. I feel dizzy after all that. I need a sugar bun or something."

Violet: "You always need a sugar bun."

Ivy, choosing to ignore that last comment: "To think that the professor has managed to find a way to successfully work around the SDF … That's quite a feat. I think it's a testament to human persistence and engineering."

Ruby, not paying attention, distracted by the sight of a stray orange cat on the road cleaning itself: "Hear, hear."

The girls walked in silence for a bit.

Ivy: "… I wonder what Eimi's serving at the inn tonight."

Anemone, deep in thought, her eyes on the ground in front of her, said nothing.