It doesn't immediately look that interesting or full of new phenomena; it looks like a forest, albeit without species identical to any specific ones she's acquainted with.

Then she will happily stroll through the forest, examining the plants and forming hypotheses about their phylogeny and physiology and occasionally taking a cutting of a particularly intruiging one.

And eventually, a new phenomenon appears. He's a short spindly person with wings and bright, highlighter-yellow hair. "Hello there!"

"Hello! I've never met a member of your species before, unless you're an unusually colored Traxalan. How do you do?"

"I'm doing well! What's your name?"

"People call me the Teacher." She isn't as reticent about sharing her name as some Time Ladies, but the sense she's getting from him makes her want to keep things formal. "And yourself?"

"Call me Yellow," he says. "Don't tell anyone else your name, and follow me." And he takes off and flies back in the direction whence he came.

She notices the extraphysical properties of Yellow's words a moment before she feels herself being compelled to obey them. Inconvenient, decidedly so, but also fascinating. She wants to learn more about this (incredibly rude) person anyway, so she chooses to follow him at a distance of a few meters rather than a few kilometers or light-years or what have you.

"Did you meet anybody else since you got to Fairyland?" he asks. "Tell me the truth."

She comes up with a couple ways to decieve him, as an intellectual exercise, but has no actual reason to lie about that. "No," she says, and adds "Why would you think I would lie?" to give the general impression that she hasn't noticed what's going on.

"Just making sure," he says.

She has nothing to say to that. She watches Yellow and the forest. The ground doesn't curve much; either this planet is very large for its surface gravity or she's in one of those big-flat-plane dimensions. She prefers the ones with planets, but it does take all sorts.

"Try to get along with my other vassal," he mentions after a bit more traveling.

So he's been doing this sort of thing to exactly one other person, then. Most likely someone who could use a helping hand. "Of course," she says. "It's always better when people get along with each other." She wonders what that order will actually require her to do; possibly no more than she had been planning on already.

A bit more walk later they arrive at a bungalow right on the edge of a lake - extending over the water a bit, in fact. It's not sized for her but she'll be able to get through the door if she ducks.

She heads on in. Looks like the inside fits entirely inside the outside. Is the aforementioned other vassal at home?

Yes! She emerges from one of the rooms when she hears the door open.

"Promise! This is - pick a safer nickname," Yellow tells the Teacher.

Frizzle picks "corundum" as a random word with no connection to her whatsoever, but asks, "What makes a nickname safer?" rather than immediately saying it.

"Can't have a syllable overlap with your real name."

"Then my nickname shall be Corundum. Hello, Promise." How does Promise appear to feel about Yellow?

Not really enthusiastic. "Hello, Corundum."

Corundum just smiles and keeps looking boring.

"Obey Promise as though she were your master," says Yellow, "don't try anything clever. Promise, show her around."

"Yes sir," says Promise.

That could be anything from a serious complication to a minor inconvenience depending on Promise's attitude. She examines what she can see of the bungalow and prepares to follow Promise around. The whole style of architecture was clearly designed for habitation by flying people, and their tech level is on the low side. Maybe a young civilization, maybe enough people have those order powers that it's stunted their growth. Anthropologically interesting either way.

Yellow lets himself back out. Promise begins a tour of the house, which has a main room and two bedrooms - Promise's is decorated with drawings on the walls. "He'll probably get around to having me add a room for you at some point," Promise says. "Uh, how confused are you right now?"

She knows Yellow, and probably Promise, and likely many or all of the people here, can give orders based on knowing someone's name. She knows the orders depend on the wording, though she hasn't nailed down how that interacts with this species fascinating lack of a language (the error messages from the TARDIS' translation field are rather hysterical). Lying might be failing to try to get along, so she'll just ask questions and see if she gets consistent and true answers. "Is it only names that activate the orders? Can you do it too? What happens with contradictory orders?"

"It's not just names, all fairies can do it, and recent orders take precedence."

None of those have contradicted anything Ms Frizzle has noticed, and also Promise can definitely give her orders and hasn't. "What else works then, other than names? And what constraints are you presently acting under?"

"The other way is food vassalization. And it's - too many to list completely, but a considerable number."

"Oh dear. And if, hypothetically, someone in your situation were to come across someone who was interested in changing that situation?"

"Well, they'd be forbidden from trying anything clever, unfortunately."

The Teacher will just have to be clever enough for both of them, then, but she'll see if she can't get a bit more data first. "Can you explain food vassalization?"

"If a fairy feeds a mortal or a mortal feeds a fairy, food that they have claim to - generally any kind of fairy food from a fairy or any kind of mortal food from a mortal will work but there are some potentially fuzzy boundaries - then the one who eats it is vassalized. This doesn't work if there's a preexisting vassalization between the two going either way. - we're forbidden to try anything clever, but if I just mention something clever I'm not trying it, and if you just copy my idea it's not that clever of you."

"You're quite right," she says, reaching a hand into one of the many subtle pockets on her fern-patterned dress. One doesn't spend countless years teaching small children without developing a habit of keeping an Emergency Snack on hand at all times. 

She doesn't want to risk being polite about this, when she doesn't know what contingencies Promise is under and she might only get one shot. Out comes a granola bar, clumsily unwrapped with one hand, and the end is in Promise's mouth in the time it would take a human to blink.

Promise swallows. "You might want the phrasing 'I rescind all your orders'."

"I rescind all your orders. And I apologize for the surprise; I wasn't sure you weren't ordered to try to stop me."

"Yellow's incompetent. I'd have been out from under him a long time ago if I didn't have some standing orders from my prior master. I can't feed you in return but your name will still work."

"I have all sorts of ideas for how to cause you to be informed of my name without technically telling you or letting anyone else overhear. Unfortunately they're all clever." She can't manage to explain any more helpfully than that, though she's still under orders to obey Promise, so that should be fixable pretty easily.

Promise gets her some paper. "Write it down," she suggests.

Oh good, using someone else's paper, nice and boring, not clever at all. She writes "Valerie", shows it to Promise, then pockets it.

"Never give me an order that I do not expressly request of my own uncommanded will, or that you do not sincerely without mental contortion believe to be in my best interest as you genuinely understand it. Except the reciprocal of this one if you so desire. I rescind all Yellow's orders."

"Never give me an order that I do not expressly request of my own uncommanded will, or that you do not sincerely without mental contortion believe to be in my best interest as you genuinely understand it. Commendable phrasing, I'm glad you're prosocial and Yellow isn't rather than the other way around. I suppose you'll be leaving the area now? I will." Not necessarily the dimension, mind you, now that she has a workable nickname she might stay and look around a bit more, but certainly the house and its vicinity.

"Yep, I'm going to pack some food and burn down his house and get out of here."

"Would you like a ride someplace? My ship can go anywhere you've heard of and a great many places you haven't. Including places with no other fairies or similar magic, which something tells me you might find a selling point."

"I'd object to being without my magic. But I wouldn't object to getting several continents away, if we can make a stop first." She's stepped into her room and is shoving fruit into a bag.

"I suspect your magic is thoroughly attached to you, most people's is, but we can always go somewhere else and then come back to this dimension if the other one doesn't suit. Where's your planned stop?"

"Sorcery doesn't work in the mortal world; I'd still be a fairy but I prefer to be a sorcerer." She has her bag packed; she lets herself out of the house. "It's north of here, I'm not sure how you mean to travel exactly."

She chuckles at "the mortal world". "I'm planning to walk to my ship, from which it's about a minute's travel to just about anywhere in time and space. Including your stop, and several dimensions that will probably permit your sorcery--which I'd love to learn more about, by the way."

"Several dimensions."

"Oh, yes, there are quite a lot of them. More than I've ever had time to count, though I suppose the Bus might know. She's this way, by the way," Corundum adds with a gesture.

"Well, I suppose if the mortal world is only one of those then the others might be any which way about sorcery, but I'd still have some trouble getting food safely outside of Fairyland."

"Well, I can certainly drop you anywhere in Fairyland. I'm curious how food synthesized on the Bus would interact, though I suppose you won't want to test it."

"If the Bus is a person it would presumably count as her food."

"That would seem to follow! Though I don't actually remember where I got that granola bar, so I'm afraid the question may already be moot unless a piece of food can only count for one person. Also, she can't or won't talk to anyone other than me."

They've gotten far enough from the house by now that it would probably be safe to set it on fire.

"It could theoretically count for more than one person but it came straight out of your hand and nobody else who was involved with it is specifically likely to try ordering me around, especially if the bus won't try to talk to me at all."

She looks over her shoulder and the house goes from quaint to flaming slag in less than a second.

"I haven't known her to give anyone else more than an eye-roll in centuries."

When Promise slags the house, she adds, "My, what interesting magic! I can see why you'd want to hang onto that. And generally learnable too, from the looks of it."

"Yes. You can tell that by looking?"

"My species can see a lot of things. Your magic didn't seem to be attached to you in the way, say, orders are, so it's less likely to be a matter of being the right species."

"Mortals can learn sorcery, yes. I don't know about whatever you are."

"I'm a Time Lady. So called because we were the first species in my original universe to invent time travel, and whoever decided they had the authority to name us all was excessively pompous."

"You have time travel?"

"I certainly do! Silly me, I thought I had mentioned it. Yes, the Bus can go anywhere and anywhen in any of several thousand universes."

"How does that work with travel that would alter the past?"

"I can go over the math with you if you like, but the short version is that whatever you do turns out to produce a single consistent history. Maybe you fail to do whatever would have changed the past; maybe you succeed but it turns out whatever you did was part of the history of the events you remember. In a few extreme situations, it's possible to split history into two different timelines, but the Bus is quite capable and can reliably avoid that sort of thing."

"Oh."

"Quite."  

It doesn't sound like she wants to talk about it.

"Well. Maybe it'd be safer to take a cutting of my tree from years ago when it was more definite no one was staking it out, and then drop me off in the future far enough that my name will have been forgotten."

"That, I can certainly do. Not much farther from here to the Bus."

"Thank you."

Then they can walk in silence until they reach a tree that looks slightly off somehow. Corundum smiles as she approaches, and the tree shifts and warps and suddenly there isn't a tree at all, but a yellow school bus distorted into the shape of a tree trunk and with branches growing out of it. And a pair of large, friendly eyes and a smiling mouth.

...okay. "Hello."

The eyes blink at her. "All aboard!" Chirps Ms. Frizzle, climbing into the Bus as the door folds open.

Promise goes in.

The inside looks even less like a school bus than the outside. There are padded benches, there's a large control panel with a great many mysterious buttons and levers and a large chair in front of it, and that's it for the resemblance. The rest is a large circular room that could not possibly fit inside the visible outside, crowded with posters, plants, rocks, unidentifiable things in jars, machinery, a skeleton on a stand wearing a vest and top hat, and a tank of small glittering fish. Several other doors are visible around the walls.

"Welcome to the Bus! The bathroom is through there, the food replicator is that green box--oh, and she tells me that for fairy purposes, the food from the replicator belongs to whoever was operating it at the time. Now, where and when shall we go first?"

"My tree. About fifteen years ago, let's say."

"Can you describe where your tree is relative to here? Or the Bus can go off the sense-of-place in your mind, but she won't look unless you say it's alright."

"I appreciate that. It's north, it'd take me a few hours to fly it, that's probably not precise - if she can look only at the sense of place that will be fine."

"That's enough of a start that I can probably find it with the mokoscoper." She pulls a lever and a screen unfolds from somewhere; pressing some of the many unlabeled buttons brings up an bird's eye view of the area a couple hundred miles to the north. "Recognize anything on here?"

"That river. If you followed it west from there for maybe twenty miles and then turned right you'd reach my tree soon after."

She pans; she zooms; a tree loaded with haws comes into view.

"That's the one. I just need a branch to plant wherever I wind up."

"Right-o! And how's twenty years ago, for the time?" The image on the screen time-lapses back twenty years over several seconds; without earthlike days and seasons this looks less dramatic than one might expect.

"Twenty years ago should be fine."

"Off we go, then! No need to strap yourself in, this will be a very short jump." She pulls some more levers with extreme gusto, and the view out the windows starts spinning in a set of directions that ought to cancel out but instead add up. Before Promise can get dizzy, the blurred scenery slows down again and resolves into a different patch of forest, with her tree just ahead. The door folds open, accompanied by a cheerful "beep-beep!" from the horn.

Promise flutters out of the bus. A tree branch bends down to her and comes off in her hand.

When Promise gets back on, the bus has remodeled her interior. There's now a large patch of grass on the floor with a cleared space in the center, and the ceiling is a glass geodesic dome letting in sunlight at a different angle from outside.

"Oh, this is pretty. What's the gap in the grass for?"

"I believe it's for you to plant your tree in. She's taken a liking to you."

"- um?"

"She's hoping you'll stick around and explore the multiverse for a bit before settling down somewhere.  But if you'd rather not, you'd rather not."

"We've barely met."

"From your perspective, yes. You see, the Bus operates in more temporal dimensions than even I can really understand. She might like you based on something you did years ago, or something you're probably going to do years from now, or something you would have done had circumstances been different. And she doesn't tend to go in for more linear beings' social norms about it," she adds with a chuckle.

"- if she likes me for something I did years ago - that is, a thing that from my perspective I have already done - that implies surveillance of some kind."

"I suppose you could call it that, though that implies a level of deliberate effort. The Bus trying to see someone's present but not their past or future would be like you trying to notice only the left half of a person's body."

"Someone might also choose to wear clothes on the left half of their body, if they didn't plan on it being observed."

"Yes. It's not ideal, having someone be closer to omniscient than anyone else expects. She's usually better about keeping it ignorable--this is the most I've seen her actually act on her knowledge of someone's world-lines in centuries. Perhaps she concluded you would rather know, even at the cost of making it obtrusive."

"Well, yes, if she's in the same information state either way I'd sooner know about it, but how'd she know that?"

"Quite possibly from you saying it just now! Time is a funny thing."

"Apparently. I'm not sure how to think about this."

"I expect if you stick around you'll pick up an intuition for it, but I can get you a book on the math if you like."

"The math will probably be more useful after I have an intuition."

"Quite likely. So, where to next? Sure you don't want to see the multiverse a bit before settling down? There's a planet with a thousand species of flowering tree, and every three thousand years they all bloom at once."

"That does sound pretty."

"Absolutely stunning." She seems to have taken this statement as acceptance, because she starts pulling levers on the dashboard again. "You might want to find something to hold on to."

...Promise looks for suitable handholds.

There are railings along the walls. There are also the traditional benches and seatbelts, including one with a back that looks like it wouldn't squash her wings much.

She grabs a railing.

"Alright Bus, do your stuff!" Ms. Frizzle pulls a final lever and the view out the window gets all weird again. Now they're in a different forest, where it's just after dawn and the sky and the trees are both overflowing with color.

...Promise tiptoes over to the window to get a closer look.

She can't see all one thousand kinds of trees at once from this vantage point, but she can see multiple dozens--clusters of tiny red ones and single enormous blue ones, purple ones fading to white at the center, yellow ones whose petals are foot-long streamers fluttering gently in the breeze. Some of the flowers are growing directly out of the tree trunks; some sprout up from the roots to cover the ground with veins of color. Some are translucent. Some are luminescent. A shaft of sunlight hits a branch and all the buds on it unfold at once in a matter of seconds.

"Ee!"

Ms. Frizzle smiles at her, pops the door, steps out, and twirls exuberantly. Her dress has switched to a pattern of flowers and fruit. 

Tiny gem-bright insects, and clouds of hand-size butterflies, and little darting birds are roving between the trees, feasting on nectar.

"What are those things -"

Ms. Frizzle is So Excited about having been asked a question!

"Those birds and insects are pollinators! They drink nectar from the flowers, and they spread pollen which help the trees reproduce! If you like, we can shrink down and take a look at the process up close!"

"Fairyland doesn't have animals," explains Promise. "They're kind of weird. You can shrink?"

"What, none at all? That must have fascinating consequences for your ecology. Do you have fungi? Microbes? Do fairies pollinate plants? And oh, yes, the Bus has a shrinkerscope that can make us anywhere between full-size and microscopic!"

"We have fungi and I don't know about microbes and sometimes fairies pollinate plants."

"Do dead plants decay, or get diseases that aren't in the form of fungi or parasites? Do fairies get diseases? "

"Dead plants decay eventually, but I'm not sure what causes all their problems so it could all be fungi or parasites. Fairies don't get sick."

"Then it's entirely possible you don't have native microbes! Though I expect some will have colonized off outsiders arriving. So, what do you say, shall we go explore the insides of some flowers?"

"Yeah, all right."

"Excellent! Here we go!" Rays of light shines out of each of the Bus's headlamps and illuminate the two of them. They start getting smaller; it doesn't feel like anything and looks like their surroundings getting bigger. "Wahoo!" yodels Ms. Frizzle as they shrink to about a centimeter tall.

Promise wonders if this will make flying easier. Flutter flutter.

Her mass has decreased by a greater fraction than the surface area of her wings, so she doesn't need to flap as hard to get lift!

Ms Frizzle, for her part, has pulled a jetpack out of a pocket that should not be able to fit a jetpack and strapped it on. She joins Promise in the air.

"What is that?"

"It's called a jetpack! It shoots burning fuel downward, which generates an opposite reaction force upward, and I can angle the direction to steer." She demonstrates by doing a barrel roll.

"...okay!"

Ms. Frizzle flies into one of the larger flowers with a "come over here" gesture. They're small enough to both fit inside it easily.

Assuming Promise can fit inside easily without getting anywhere near her personal space, she'll go into the flower.

At this scale, the flower is the size of a large room; Promise can stay on the far side of stamens bigger than she is. Ms. Frizzle is excitedly pointing out all the pieces of flower anatomy and their functions.

Promise is willing to learn about flower anatomy.

Her explanation concludes with a demonstration of how to scoop some nectar out of the base and drink it. "There's no native sapient life on this planet, by the way, so you shouldn't have any trouble."

"...how do you know?"

"I've been exploring here several times, including well in our future, and never seen any sign of civilization or met anyone who spoke a language. Doesn't rule out microscopic life-forms, I suppose, but even those usually tend to have some visible presence."

"I guess I don't know how a microscopic life-form would be able to give orders anyway..."

She taps her chin thoughtfully. "Yes, if they were telepathic or speaking in radio waves I would certainly have noticed."

"...are there many telepathic things?"

"There's a fair number, but most of them can only communicate within their own species, or with other kinds of telepath. Myself, for instance--I'm technically a telepath, in that I can hear most kinds of telepath when they send things, but I can't do anything with non-telepaths, and some of the people I can hear I can't answer. It's lead to some interestingly structured conversations, now and then."

"I don't want to meet anything that could read my mind."

"Then we can stay well away from anywhere with people who might be able to."

"Thanks."

Ms. Frizzle takes another sip of nectar, then carefully cuts open a stamen and starts looking at the inside.

"What's in there?"

"Interesting tissue structures! I was curious which of a couple other species this flower was related to, and the way the microsporangia are arranged suggests it's most closely related to those ones with the very thin stripes on the petals."

"Flowers are related to other flowers?"

"Yes! On most planets, all the native lifeforms are related to each other. Life starts as one very simple thing, and diversifies over millions of generations of tiny changes into millions of different species." 

"I guess that might be true of the plants in Fairyland if it is of these..."

"Do you know how fairyland plants reproduce? If each new plant resembles its parents, but with some tiny random changes, that will inevitably produce a lot of different but related species given enough time."

"I've never personally cultivated any from seeds, just cuttings sometimes. Some of them are very different, though, like moss and trees..."

"Plants as different as moss and trees can definitely evolve from a common ancestor! But if you're curious about fairyland in particular, we could go there a hundred million years in the past and see for ourselves."

"Are you sure that's long enough?"

"If species are changing at all, that should be long enough to notice. But there's no reason we couldn't go farther. If your universe has a beginning, we can't go before it, but that's just about the only limit." Well, she did have to take the Bus to a mechanic after she went to a few picoseconds after the Big Bang, but they had both felt the destabilized zoroflooper was worth it for the excellent pictures.

"I'm not sure if it had a beginning or not!"

"Well then, what do you say we aim for a billion years back and see if the Bus can find it?"

"Sure, why not."

"Alright then--to the Bus!" Ms Frizzle jetpacks out of the flower and over to the Bus, who has grown metal flowers all over herself in what may be history's most flamboyant attempt to blend in. The Bus zaps her back to full size on the way.

"...I like the flower sculptures," Promise comments to the bus.

The Bus smiles appreciatively, and zaps Promise back to full size as well.

She boards.

And off they go to Fairyland's extremely distant past! The trip takes noticeably longer, this time, and the glowing colors outside the windows smear into streaks like mixing paint. Eventually they come to a stop again.

It's not very interesting, Actually, it's totally dark.

She flicks on the Bus's headlights. "How does fairyland handle lighting, incidentally? Infinite flat planes have a number of interesting solutions there."

"There are suns in various places. Even night places aren't this dark though."

The headlights illuminate a very empty flat land.

"Do the suns move at all? Do you know how large they are, and whether they run on nuclear fusion? And if you don't know what nuclear fusion is then I'm curious how your language handling rendered it." Promise's language handling thing is very intriguing in general--she can only barely sense it and it seems to be very different from what the Bus would otherwise be doing. She sets up a scan of the conditions outside: breathable air, by her definition and Promise's somewhat stricter one? Radiation levels unexceptional? Temperature recommending a sweater or a spacesuit?

"They move. I don't know if they are the sort of thing that has a size. I don't speak a language and don't know what nuclear fusion is."

There is in fact not air. It's also not radioactive at all. A spacesuit would be the correct attire for the season.

"What sort of thing could the suns be that doesn't have a size?" she asks, popping open a wall compartment and pulling out two spacesuits. One of the spacesuits has a wing-sized amount of extra room in the back. "Also, you'll want to put this on if you're coming outside."

"They're the warm lights in the sky, and they don't look bigger if you fly higher. And most of them aren't around all the time. What is that?"

"This is a spacesuit! It provides you with breathable air, which outside is presently lacking. It goes on like this." She unzips hers and climbs into it, her skirt having turned into pants some time while Promise wasn't looking.

"Oh, if it's the wrong sort of air for breathing I can breathe through my wings."

"It's actually no air at all, does that bother you?"

"...yes, I don't think that would be comfortable. The suit deals with that?"

"Yes! Air comes out of this hose here, and when you exhale it gets drawn away by this other hose."

"That part I don't think I need but it won't do me any harm." In she goes.

The Bus has helpfully acquired an airlock, so as soon as Promise is suited up they can head on out! 

"Why is the door different? - can you still hear me?"

"I can hear you, the suits have radios. The airlock is so we don't let all the air out and blow ourselves over on the way out."

"It's... windy? Without air? What is a radio?"

"No, I mean if we opened the door to the outside all the air inside would rush out, which would produce quite a gust of wind. And radios are communications devices that use a kind of light you probably can't see to send each other signals! Light is a wave, you see, no pun intended, and different colors of light have different wavelengths, which is like more or fewer ups and downs of the wave in the same space. Red has a longer wavelength than violet, and radio has an even longer wavelength than that! I can draw you a diagram once we're back inside."

"Why would the air rush out? And why does light look like it goes straight?"

More science questions! What an excellent traveling companion. 

"Air is made of particles that bounce off each other, so they tend to spread out as far as they can. If a bunch of air starts confined to the Bus and then gets released into a much larger space, a lot of particles will bounce out the door very quickly. Once we're back on the Bus, I can show you a demonstration with colored air if you like. And light looks like it's going in straight lines because individual little bits of light do go in straight lines, like a ripple in a piece of string if you shake one end, and the individual ups and downs of the wave are very small."

"Why does it go in a wave at all? Let alone all different sizes of wave?"

"Because it's a vibration, just like a ripple in a pool of water, except instead it's a ripple in what's called the electromagnetic field. That's a field that's everywhere in space, with a strength and a direction at every point, and light and magnets and electric charges disturb it. Are you familiar with magnets? They're a lot of fun."

"I know the word but I've never had one. Is the field like harmonics? It sounds like harmonics."

"I'm afraid I'm not familiar with harmonics! What are they like?"

"They're background magic. They're everywhere in space and have a strength at every point. Not a direction but they do usually vary continuously at assorted rates. Sometimes there are harmonic cliffs though."

"Ah! Yes, that sounds like the electromagnetic field, except for the lack of direction. That makes it a scalar field, rather than a vector field. I wonder if the Bus could make something to visualize it; she has an absolutely lovely sensor array." She prods the ground with a gauntleted finger to see what it's made of.

It's rock, mostly flat but not smooth.

"If you do lights in a grid without compensating for the harmonics you can see which ones turn out dimmer."

Ah, but is it igneous, sedimentary, or metamorphic rock? She pulls out a small drill-and-scoop gadget and takes a sample for later analysis.

"That's quite clever. I should like to see it, if you don't mind. Perhaps the harmonics here and now are interestingly different from what you're used to."

"Probably, since harmonics react to plants and such and there aren't any." She makes a grid. "...looks weirdly flat."

"What effect does that tend to have on the magic, besides making the lights more uniform?" She sticks a finger in the nearest light.

"Well, it makes it easier, I guess, since it's so predictable."

"Perhaps this would be a good place for me to learn it, then."

"Sure, if you want to. It also helps that it's dark. It might even help that there's no air - the idea is you concentrate on where you want to do your sorcery, like one of these lights, and all the properties the place has, and how putting a light there will affect those properties and be affected by them."

"What a delightful system." She picks a spot and contemplates. Its temperature is this and it's illuminated by her headlamp and Promise's headlamp and the Bus's headlights and by the reflected light from all of those light sources off all of those entities and the ground. Interpolating off Promise's grid, the harmonics there have such and such a gradient in each direction in that coordinate basis. Gravity at that point is thusly, determined almost entirely by the structure they're standing on but a little bit by the three of them. Adding a light at 530 nanometers will produce direct illumination in that nice shade of green, and also reflected illumination off the ground and the people, and should not affect the gravity or the harmonics or the amount of light passing through at other frequencies except to the extent that anything around here fluoresces, which is not much but also not exactly zero.

And there is a green light.

"Huh, people usually start with white."

Shrug. "Picking a single wavelength was easier to visualize. White does seem a logical next exercise, though." She works on adding a white light next to the green one, with a spectrum she thinks will look good.

She can do that too when she has it just so. "Even accounting for the flat harmonics that's very quick."

"Thanks. I expect having as much sensory input as I do helps--more information about the space, more bandwidth to process it. What else can sorcery do?"

"I can heal and make plants grow faster and purify water and candy dewdrops and transmute or shape materials and set things on fire and turn invisible and inaudible and do some other obscure things that aren't coming to mind right now."

"That's quite the list! In my experience, magic systems that can do that many things are usually general-purpose; is that simply the list of things you personally can do? Are there things known to be impossible in principle?"

"That's what I can personally do, there's plenty more. I don't know about known to be impossible in principle, that's a high bar. Oh, I also know how to make gates."

"General-purpose magic systems are lovely, aren't they. Are gates within a contiguous spacetime or between them?"

"Between. I don't know of a way to do it within."

"How does one generally attempt new things? Is it the same process of simulating in detail how the surroundings would be different?"

"More complicated stuff there's more detail, but that's the basic idea."

"I shall have to practice. For now, shall we take a walk around and see if there's anything other than vacuum and rock and potentially microorganisms here? I somehow suspect there isn't."

"It sure looks like there isn't but we can check." Wander wander.

Wandering: the second best activity after examining things you found while wandering.

There is super nothing around. Promise lights the way and reveals only more nothing.

"Do you happen to know if there's magma underneath us, or will be in your era?"

"There's some later, but only in some places."

"What's in the other places? Just rock forever?"

"Far as I know."

"I wonder why it doesn't reach a temperature equilibrium! Want to go into a magma pocket and find out?"

"I... don't enjoy being on fire?"

"Oh, don't worry, the Bus can handle the temperature. There's no need to go outside. But we can skip it entirely if you'd rather not."

"I can also probably cool the magma but I was imagining this would disrupt your observations. I don't mind looking at it from inside."

"Excellent. To the Bus!" She sets off back the way they came. "By the way, how much magma could you freeze at once, if we weren't trying to make uncontaminated observations?"

"Uh, that'd depend a lot on conditions."

"Could you give a range? Or a single example."

"It matters how much of it I can see, and whether it's moving, and if there's anything else in it, since all that affects how much I have to think about to know how it'd change the environmental conditions when it froze - seeing's easier than guessing about some I can't see, and so on."

"That makes sense. Is there a size limit in the easiest case, or is it always limited by how much you have to keep track of?"

"I think the latter but I haven't pushed it. I can do larger things gradually."

"So it's not always instantaneous? Intriguing!" She reboards the bus, and once Promise is into the airlock she repressurizes it so they can enter the control room proper.

"It's not, a lot of effects are slower, but better sorcerers are faster."

"Hmm! Do you happen to know how far down we'd have to drill to either hit magma or be sure there's none under us?"

"Uh... maybe a few miles? I've never really dug."

"Well, let's go ten miles down and if that doesn't do it we can ask the Bus," she says, turning a knob that causes the latter to extend an enormous drill from where her front radiator grill usually is.

"Okay."

There is not magma ten miles down.

The process of finding that out involves the bus diving through the rock like a fish, drill a-spin, with the gravity in the control room shifting as it tips over so they're still standing on the floor. Ms Frizzle discusses the rock they're tunneling through as she goes.

It's pretty samey rock.

And that is in itself weird and interesting! She already knew this rock didn't cool in the aftermath of star formation, but this is such a clear illustration of it! But eventually they stop drilling and start scanning increasingly large areas for a magma zone.

There is none to be found at this time.

"Fascinating! Promise, the magma pockets aren't as old as your world and they haven't formed yet. Let's do a binary search to find out how and when!"

"A binary search?"

Time to explain binary search! And now that they're on the Bus, she can pull up a chalkboard and draw diagrams! You start with a pair of bounds, in this case a point in time when you know there is magma in a certain location and a point when you know there isn't, and check halfway between them. That tells you whether the magma appeared in the first half of the time window or the second half. Then you repeat the process on your new half-sized time window, and keep repeating until you have something small enough to search exhaustively.

"...I guess that will work on when even if it can't help with where."

"For the where, I was hoping you'd know the location of one in your time. Or at least a general area we could similarly look around in."

"I don't know where to find magma that's just hanging out underground. I can name some volcanoes."

"We should definitely go to a volcano! Perhaps we can figure out how they formed in the absence of planetary geology."

"Probably you don't want to start with the one that erupts mercury, then. How about Ashrock?"

"Ashrock it is, though I definitely want to see the volcano that erupts mercury at some point!" She starts pulling dashboard levers.

"Can you aim for when it's erupting?"

"Certainly!" Up comes a volcano on the viewing screen, belching smoke and just starting to pour out lava. "That looks nice and energetic. Come on Bus, do your stuff!" 

The Bus responds with "Bee-beep!" and reality starts getting weird out the windows again.

"Why does it look like that?"

"The Bus travels by pinching off a little pocket of space-time and reattaching it to reality at large at a different point. Sort of like scooping a cup of water out of a pond and pouring it into a different one, and what we're seeing is like the ripples in the water."

"Huh. Why does this have an appearance?"

Promise can have an explanation of high-energy physics which this margin is too small to contain! The gist is that sloshing spacetime around like that tends to make any photons in the area go all over the place, like looking into fun-house mirrors if fun-house mirrors had a lot more options. Also, they are now hovering in the ash cloud above the volcano's crater.

"We'll probably have a better view of the volcano from outside the cloud."

"A better view of the outside, at least." The Bus ascends and moves out of the ash column, with none of the sense of acceleration someone used to elevators (or non-capitalized busses, for that matter) would have expected.

Ms Frizzle takes an excited look at the volcano. Is it one of the types that tend to show up on rocky planets?

Looks like a composite volcano!

That's excellent! All volcanos are excellent, though she's rather partial to the ones on Io and Niphris III. "Ready to dive in?"

"Sure."

"Waaaaahoooo!" They turn around and dive back into the smoke cloud, and from there into the lava. It's way more viscous than water; there's almost no splash. Ms. Frizzle folds a sonar-type screen up from one of the consoles, since visibility through the lava is awful at the vast majority of wavelengths.

It looks lava-y. "There's some lava flows - not a proper volcano - that are rainbow colored."

"Ooh! Do you mean a single iridescent substance, or multiple streams of different colors?" Down down down they go.

"I don't know, I've never been and the book wasn't specific."

"Well then, perhaps when we're done here we should go find out for ourselves!" she says, staring raptly out the windshield. "Say, can you see the thermal gradients and convection currents? If you can't I can get you a pair of goggles for it."

"Ooh, I'd love a pair of goggles that did that."

"Here you are, then!" She opens a panel above her head and extracts a pair of what look like purple swim goggles. If Promise looks through them she'll be able to see the magma as sluggishly swirling currents instead of an undifferentiated mass, and on top of that the way heat diffuses through the flow. It's like watching ink spread through water, except it doesn't converge to a boring equilibrium state.

"It's beautiful!"

"Isn't it? Even something as simple as heat and rock has a lot going on under the surface." Ms. Frizzle contentedly watches an unusually hot patch force its way up.

Promise is happy to watch lava for a good long time. "Can I keep these? They'd be handy for sorcery."

"Of course! I have ones that let you see sound waves, too, would you like a combined pair?"

"Sure!"

Then she can get a second pair of lenses that add colorful ripples over any vibration source, with amplitude and frequency indicated by color and density. It stacks pretty intuitively with the heat vision.

"I love it."

"Glad to hear it! Shall we try finding out when this volcano formed?"

"Sure."

They start jumping back in time a bunch!

And they can watch lava erupting gloriously from the mossy ground in a huge gout.

This is hilarious. And best viewed through a glass-bottomed vehicle, which the Bus now is.

Neat.

Ms Frizzle has all sorts of stuff to say about the implications of an eruption of lava with no ash and without lava being flung hundreds of feet in the air. Also about how this is going to produce some very nice obsidian when it cools.

"It does, I've seen some."

"Excellent. Did you know obsidian is very similar to glass?"

"Yes. It's possible to transmute either to the other."

"That makes a lot of sense. Does your transmutation alter atoms, or just rearrange them?"

"I wouldn't know how to tell!"

"Could you turn gold into silver, for example?"

"Sure."

"Then you do alter atoms! I should take some radioactive tracer dye and turn myself into a bird with sorcery at some point," she muses. "But first, shall we see if there was a magma pocket here before it first erupted?"

"You don't want to turn yourself into a bird, you won't be able to do sorcery as a bird. I can do it for you."

"Oh, that's good to know, turning back into myself with the transmogrifier when that's not how I turned into the other thing always leaves my teeth feeling weird. What about being a bird interferes with doing sorcery?"

"It's built into the spell but I don't know exactly how - it's what fairies do to each other by way of long term incapacitation."

"Hmm! That suggests it would be possible to develop a variation that doesn't have that problem." Everything she learns always leads to more things to learn, it's so excellent.

"Maybe."

"Well, for now let's go back in time a few more weeks and see how this volcano became a volcano."

It transpires there was a lava pocket there!

There are so many fun things to do in a magma pocket. They can map its extent with sonar! They can do some math about how, if it's infinitely deep, this affects the process of it building up enough pressure to erupt! They can measure the pressure in a couple places and speculate about whether it really is infinitely deep or not! They can go to a point where the lava meets the crust above and check if heat diffusion is working normally!

Promise is glad Corundum is having fun.

Corundum understands that not everyone likes fluid dynamics; she'll keep it brief, at least by by immortal standards.

"So! Where would you like to go next?"

"I don't know."

"Well then," she says, pulling some levers, "why don't we let the Bus decide? She's sure to find us something exciting."