‘The main cylinder.’

‘Unlike the habitat ring – which I’ll get to – the cylinder interior was never designed for gravity, so you won’t find artigrav nets there. Everything is arranged in a circle, around a central core.’

Ghuh’loloan set down her cup. ‘Do you mean that when you go in there—’

‘We have to work in zero-g, yes.’

‘Incredible! I had no idea there were still species doing that. Not within the hull, at least!’

‘Tamsin worked there, until some years back,’ Isabel said, knowing her colleague knew her wife’s name even though they hadn’t properly met yet. ‘I’m sure she’d be happy to talk to you about it.’

‘Oh! Yes. Yes, that would be marvellous.’ Ghuh’loloan scribbled furiously. ‘Please, please, go on.’

‘At the aft end of the cylinder – as much as anything can be aft in space – we have the engines. They’re . . . they’re engines.’ She shrugged and laughed. ‘Not my area of expertise.’

‘And they don’t get much use anymore.’

‘We use them to correct orbital issues, but no, nothing like they did back in our wandering days. Now, the ring – that I can talk on for days.’ She directed the pixels into shapes she walked through every day. ‘Six hexagons, each joined to another around the main cylinder.’

‘And this used to spin, before artigrav.’

‘Right. It was a big centrifuge.’

‘Was that not unpleasant?’

Isabel shrugged. ‘I don’t know. I’ve only ever lived in artigrav. I’m sure there’s an account of how centrifugal gravity felt.’ She made a mental note to go searching for that.

Ghuh’loloan made a note as well, on her scrib. ‘So, six hexagons comprise the ring.’

‘Six hexagons. And within those, you find more hexagons. Let’s start small and work our way up.’ She thought for a moment. ‘Ah, I have just the thing.’ She accessed an animated image file intended for young kids. A lone hexagon appeared. ‘Okay, so we start with a single room. A bedroom, let’s say.’ She gestured. The hexagon shrank, and was joined by six others, creating a mathematical flower. ‘Six rooms, surrounding a seventh room. This is a home.’ The geometry expanded again. ‘Now you have six homes, surrounding a common area. We call this, predictably, a hex. You’ll hear this term a lot. Somebody’s hex is their primary address.’ Another expansion. ‘Six hexes surround a hub. This forms a neighbourhood.’

‘And in a hub, you will find . . . ?’

‘Everyday services. Grocery stands, a medical clinic, tech swaps, cafes, playgrounds, that kind of thing.’ She gestured again. ‘All right, here’s where it starts to get big. Six neighbourhoods to a district. The space in the centre is the plaza. The amenities here vary from district to district, but in general, this is where you find your big stuff: schools, recycling centres, entertainment, long-term medical facilities, council offices, marketplaces, big gardens.’

‘We are in a plaza now, yes?’

‘Yes. And from there . . .’ The image blossomed into one final shape – six triangles comprised of six districts each, arranged around a final colossal hexagon. ‘So, all of this’ – she circled it with her hands – ‘is a deck.’ The middle area is the nucleus. That’s where you get farms and manufacturing. At the centre of everything is, well, the Centre.’

‘Where you dispose of your dead.’

‘I . . .’ Isabel chose her words carefully, knowing her colleague hadn’t meant any offence. ‘I’m not sure we’d use the word “dispose”, but yes.’

‘And then above and below the residential deck, you have . . . ?’

‘Directly above, the transport deck, where you can hop from district to district in a pod. Below, waste processing. And below that, observation.’

‘Yes, I’m very excited to see your viewing cupolas. I don’t know of any other ship architecture quite like that. Most have windows on walls, not the floor.’

‘That goes right back to the need to prevent fighting over living space. If some people have rooms with a view and others don’t, you’re going to have problems. And if centrifugal gravity is pulling our feet toward the stars, then you can’t have windows on most walls. The only people who could would be the ones with homes on the edges of each deck, and that . . . well, that would invite trouble.’

‘Ahhhhh. Yes, I see. I see.’ Ghuh’loloan’s eyestalks traced over her notes. ‘Six homes to a hex, six hexes to a neighbourhood, six neighbourhoods to a district, thirty-six districts to a deck, four decks to a . . . ?

‘Segment.’

‘A segment. And six segments to a homesteader.’

‘You’ve got it.’

The Harmagian studied the children’s images again. ‘It’s rather beautiful, in a way. Nothing wasted, nothing frivolous. Simple exponents.’

Isabel smiled. ‘It’s like a . . . oh dear, I only know the word in Ensk.’ She shifted linguistic gears. ‘Honeycomb.’

Ghuh’loloan flicked her mouth tendrils. ‘I don’t know that word. My Ensk is poor enough that I’d call it non-existent.’