‘Come the revolution,’ Prabir told Madhusree, checking for shells and coral before putting her down on the dazzling white sand.

‘What?’

‘We’ll redesign our bodies. Then I’ll always be able to lift you up. Even when I’m ninety-one and you’re eighty-three.’

She laughed at this talk of the metaphysically distant future. Prabir was fairly sure that Madhusree understood eighty-three at least as well as he understood, say, ten to the hundredth power. Looming over her, he counted out eight hand flashes, then three fingers. She watched, uncertain but mesmerised. Prabir gazed into her jet-black eyes. His parents didn’t understand Madhusree: they couldn’t tell the difference between the way she made them feel and the way she was. Prabir only understood, himself, because he dimly remembered what it was like from the inside.

‘Oh, you pretty thing,’ he crooned.

Madhusree smiled conspiratorially.

Prabir glanced away from her, across the beach, out into the calm turquoise waters of the Banda Sea. The waves breaking on the reef looked tame from here, though he’d been on enough queasy ferry rides to Tual and Ambon to know what a steady monsoon wind, let alone a storm, could whip up. But if Teranesia was spared the force of the open ocean, the large islands that shielded it — Timor, Sulawesi, Ceram, New Guinea — were invisibly remote. Even the nearest equally obscure rock was too far away to be seen from the beach.

‘For small altitudes, the distance to the horizon is approximately the square root of twice the product of your height above sea level and the radius of the Earth.’ Prabir pictured a right-angled triangle, with vertices at the centre of the Earth, a point on the horizon, and his own eyes. He’d plotted the distance function on his notepad, and knew many points on the curve by heart. The beach sloped steeply, so his eyes were probably two full metres above sea level. That meant he could see for five kilometres. If he climbed Teranesia’s volcanic cone until the nearest of the outlying Tanimbar Islands came into sight, the altitude of that point — which his notepad’s satellite navigation system could tell him — would enable him to calculate exactly how far away they were.