"It varies widely, depending on the source, likely due to impurities and inclusions - I believe the fundamental operation produces a rather stark white light, uniform across the entire visual spectrum.

One of its advantages over conventional light sources is that water does not particularly affect it, other than the usual refraction effects you would naturally expect."

"...well, it's probably not radioactive, then.  ...I really fucking hope it's not radioactive.  Because I am very fucking uncertain why there are graphite inclusions in rod shapes in lightstone, and my best guess is 'I don't know of anything else that uses graphite rods except nuclear fission, because graphite doesn't occur in rods naturally - I'm not sure if it occurs naturally at all, if I remember and understand anything about crystal deposition, I have vague feelings about it coming mixed with clay for some reason - so there must be something fucky going on, and it could be a surprise crashed spaceship that for some godforsaken reason had a fission reactor on it - why the fuck they'd do that I haven't a clue, you want a radiothermal generator for lastingness and fusion for power and also refueling' - but if it was a nuclear fission reactor...

"We'd be kind of turbofucked!

"Well, no, it depends upon the age of the spaceship...

"But the rocks are still glowing...

"...Do they fade, whatsoever?"

"Only if you disrupt the crystal lattice - not just by itself. Sometimes people complain of them going out unexpectedly, but usually it transpires that they have dropped it and are trying to pretend they didn't break it.

The graphite occurs like any other mineral inclusion, it's just that large enough inclusions can be carefully chipped into rods convenient for pencils."

...She very carefully exhales, in relief.

"Okay.  It's Magic Bullshit.  I can work with magic bullshit."

"There is a considerable quantity of Magical Bovine Excrement loose in the world, alas. One simply has to make do around it.

I believe you were going to explicate the secrets of capacitance, before we meandered to talk of magical excreta?" 

"Yeah.  So.  Capacitance.  ...First, we need to talk about resistivity.  Might even need to talk about thermodynamics, but if you'll take as given the idea that - much like objects fall down, there is a sort of gravity to the states of being where everything's mixed together, when the universe is engaged in normal operations.  Even if that's really entirely backwards of the model my world's scientists use.

"...Magic obviously fucks with this, because the probability of a spontaneously appearing off-brand polymath is so close to nil as this entire house jumping three feet in the sky is, but.

"In general, and there's a bunch of equationy shit I'm leaving out because I don't know it very well - things move towards a state where the average energy within the universe is equally distributed, when not perturbed by an outside force.  (Such as magic.)

"Except that sometimes, that is hard.

"Your roof would not break if you dropped a sheet of paper on it, unless something very weird was happening.  ...And the sheet of paper would hardly be recognizable as one, at that point, but I digress.  Your roof probably would break if you dropped an anvil on it.

"That making sense?"

"Spontaneously appearing people are considerably more likely around here than jumping houses, especially if they might in fact be tulpas.

You are referring to entropy, yes? It is harder to unmix pigments than mix them, that kind of thing?"

"...Honestly, that the word for it is tulpas is going to rub me the wrong way the entire time I'm here even if I am one on the merits, which I have no idea how you'd actually go about testing other than seeing if I spontaneously dis-appear later; it's honestly probably closer to the original 'some sort of mental entity that either is in the way of or induces revelation and I've forgotten which actually but probably the former' that I-don't-know-who-came-up-with-the-meditative-practice defined, but I constructed my own dang self and 'the universe' as mostly represented by this planet's collective unconscious as-reified doesn't get to take credit for me.

She nods when he mentions entropy.  "Didn't know if you had the word for that yet, so I figured I'd better explain it from first principles.  Anyway.  Entropy is also - constrained by degrees of freedom; it's possible to construct a system that creates a region of very high energy that is nonetheless not producing entropy in the area under consideration...

"Oh, excuse me, I appear to be getting sidetracked.  We were talking about electrical resistance.  ...I don't think that needs to get into quantum anything...

"...Maybe it's worth explaining anyway, though.

"So!  The thing about those very small individual particles that all substances are presumptively composed of, is that -

"To observe them, you must change them.  Now, maybe magic is magic and lets you do magic bovine excrement - but imagine a world composed of - bouncy balls like so."

She actually has one in one of her pockets, in a garishly neon pink and white swirl; it bounces back to her hand when she throws it at the floor.

"It's actually magnets, mostly - but we'll get to that later.

"Anyway.  You're trying to figure out where one of these bouncy balls is, or how fast it's going, and your only tool for doing so is bouncing a ball off of it.

"That's going to alter your results!  There is a fundamental uncertainty in quantum matters precisely because of the nature of observation.  Don't even get me started on the double-slit experiment, I don't think I know how to reconstruct the requisite 'observer' and if I'm making claims like 'light is a wave and a particle' I want to be able to prove...huh, I wonder if that is also magnets.  ...Probably not.  Photons aren't charge-bearing.

"Anyway.  That weird and fascinating diversion into quantum mechanics aside, there's a relevant concept of...

"...Why am I going off about probability, anyway, wouldn't that mostly only explain leakage and not the underlying principle of capacitance...Well, I don't really know the underlying principle of capacitance, E-E isn't a field I specialized in, which you would think would be pretty stupid considering that everything I did relied on electricity, but it was so far below my level of abstraction.  I worked on things built on things built on things built on electricity, and that's a short stack of mostly the hardware and not anything I'd have to explain in and of itself.  It's like concerning yourself with the mining process of the metal gears you've bought to make clocks with, except that in this case I'm not a clockmaker but someone who assembles functioning clocks into hellaciously complicated musical instruments.

"...Considering some of the hellaciously complicated musical instruments I've seen in my life I think that's giving me undue airs, honestly.  I was hardly capable of assembling a metaphorical one-woman band, let alone the several dozen instruments and autoplaying functionality of - what was the name of the thing - ugh, that's going to haunt me, I'm not sure I even ever knew - anyway, I'd barely consider myself competent to whittle out a metaphorical single-key flute.  ...There are some very complicated flutes, on Earth.  Well.  I say 'very complicated' but children could play them.  Not build them, though, there's gotta be some funky stuff going on with the hole-cover things...I've been a loyal member of my school orchestras for as long as I've been attending - some dozen-plus years, starting from...holy shit I think I could count as having played for almost two entire decades actually - but I only played strings, not winds.  ...Damn, and your violin bows are totally going to suck, the modern shape is - well, modern -"

"...Anyway.  Sidetracked again, good grief, me.  Sorry, that just sorta... ...is.  Known hazard of having my sort of brain, unfortunately.  I get rather wrapped up in whatever comes to my attention, and much falls by the wayside."

"A priest could tell you, I suppose, if you were interested in your precise nature.

The effects of witness are understood by us, although it is more of a Urizeni field of study.

It sounds as though you are acquainted with the shoulders of some considerably taller giants than we stand astride, to have conquered and tamed lightning thus.

I don't suppose you could sketch your idea of a capacitor, such as we humble folk may be able to one day construct?"

He is mostly being exaggeratedly polite, but it does rather shade into sarcasm by the end.

Oh dear gods why is that so desperately funny.  Don't laugh.  It really isn't funny whatsoever.  Okay it is a little - but still!

"Yeah.  That's, well, you got me there."

"Honestly, I bet we could bodge something together from what you have on hand, but the big problem with replicating my world's technology is that - you don't have industry - this pencil looks handmade - and that then because you don't have industry you can't really - the trick to the vast quality of life improvements of my world, is standardization.  Being able to know that there will be hundreds of thousands of the same screw, rather than having everything be custom-ordered.

"Being able to bake a hundred loaves of bread with the push of a button.

"Not having to catch lightning from the sky, but instead harnessing the motion of the world or the light of the stars to make your own."

"I'm not entirely sure what you mean by industry, I imagine you did not intend to insult our Prosperity." While quite a lot of his words sound a bit like they might be pronounced with capital letters, that definitely had one. "We have production lines and highly industrious workers. There are even some machines that build other machine parts with only unskilled operators, although they're more fashionable in Holberg."

"Right.  I stand corrected, then.  So the question becomes, why the heck is what's going on in Holberg not spreading like wildfire?  Historically speaking it rather ought to!  It's just straight-up more effective for most things!

"...Surely someone's automated spinning and weaving..."

"There's the spinning wheel and any number of varieties of loom. The Dawnish have an entire magical tradition based around it, presumably because they go through so much cloth because not a single one of them has heard of 'less is more'."

"Have they made any powered ones?"

"I'm sure I heard of a clockwork one over in Holberg, and the Urizeni obviously have their Ushabti do it? Clockwork is rather finicky, though, and it's not hard work on the modern lightweight varieties. And at this rate it's not as if the Empire is going to run out of orphans."

She winces, at the "orphans" line.

"...The Ushabti-powered ones don't count, that's just using magic to replicate man-hours.

"As for clockwork, that's also rather not my field, though it is in a sense my field's great-great-ancestor.  Wish I knew more about the first programmable looms...I know they did use punchcards, but not how.  Bah."

He appears to be completely oblivious to her facial expressions.

"Here in Temeschwar we primarily focus on fundamental advances in the control and utilisation of natural forces. When we're not busy running tawdry mining and forestry concerns, in any case."

"Watermills?  Windmills?"

"Oh, yes - not up here, mostly, a little bit in some of the mines now, mostly you'll see donkey mills instead, the wind and the water aren't predictable enough.

But the Marchers love their windmills and the Dawnish adore water wheels, and the Brass Coast do both here and there."

"Alright, then.  I'll hope you know how to convert rotary motion to back-and-forth motion, and then I'll tell you that you ought to get a big magnet, stick it on one of those, and push it back and forth through tightly coiled conductive wire to generate electricity more reliably than hoping lightning shows up.

"And the inverse is also true; electricity can be converted to motion in magnetic or magnetizeable objects.  I saw someone spin iron like that so hard it melted, once.

"...There's other ways that you can get the magnet to shove the electrons around, but I forget the precise details of them."

"...Ooh, do you have the telegraph yet?"

"Yes, we can do cog wheels and such. How big a magnet? The largest lodestone I've seen is about the size of my fist, although I have not gone specifically hunting larger specimens.

The sight lines aren't clear enough up here, but Urizen has the Heliopticon? It's only really practical in those big clear mountain ranges, or if you happen to already have a lot of widely spaced tall towers around."

"It's not really 'how big a magnet' by itself so much as how strong the magnet is and how fast you can get it moving.

"...And no, the telegraph is not the clacks.  ...'scuse me, literary reference you wouldn't get.  But - no, not a light-based system.  ...Well, maybe one of those later, but that's once we can actually do radio...Man, I wish I knew how those old crystal radios worked.  Anyway.  The Heliopticon is indubitably impressive - but it sounds like you have to actually have someone looking at the signal?  We can do better than that.

"With, of course, magnets!

"Well, actually, electromagnetism.  I don't believe there's permanent magnets involved.  Do you have some copper wire I can test with?"

"Certainly, what thickness do you need? There's the heavy duty conductive strips, the binding wire, and some very delicate wire for connecting very precise areas."

"Let me see what you've got; probably not very thick, though.  And a dowel to wrap it around?"