'Yes, like that, exactly.' She nods eagerly. 'It's possible for anyone, to some extent, but brains are most adaptable in younger people. They can change dramatically, whether that's to compensate for an injury or...' no, that part will take further explanation.

'Let me explain about space travel. Our hard limit, so far as we know, is the speed of light, but even at speeds close to it, it takes a long time to get anywhere. The slow ships used to put colonists in stasis and travel for decades, and... well, sublight travel has all sorts of problems, but in the old days it was the best people had. Then Stanley Lorentzen and his team discovered L-space. It's another set of dimensions. Shift your ship into L-space, travel a while, and when you come out you've gone much further in ordinary space than you would have without the shortcut.

Problem is, human brains weren't designed to perceive L-space. Different geometries, sounds and colors - even smells that the human mind has to interpret through best-guess perception. Trust me, it gets weird. And for most people? That's completely incapacitating. Severe space sickness. Test people at twenty standard years, hardly any can handle it. So our regular spacers who start older, they take a pill, sleep through that part of the flight - but a Tradeline officer has to be L-space capable. So we start young. Most twelve-year-old candidates adjust quickly. Their brains can adapt. That's what made spacer culture develop the way it did. Sure, some planetsiders don't like it, but it's how we do things, and like I said, nobody's ever forced. Voluntary contract, always.'