"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."