The Long Earth

He laid her gently on the bed in her stateroom. She looked younger when she slept. He felt an unreasonable stab of protectiveness, and was glad she wasn’t awake to notice it.
    There was no sign of Lobsang, no sound of his voice.
    And the trolls, it turned out, had left of their own accord. Joshua thought, troll see elevator button. Troll think about button. Troll press button. Goodbye troll … Lobsang had wanted to get more out of his contact with the trolls. But evidently the trolls had got all they wanted out of
him
.
    Alone, Joshua lay down on his couch on the observation deck, looking at the stars.
    At dawn, with all its passengers asleep, the ship rose gently, gaining height until it was above the tops of the highest forest giants, and then stepped, disappearing with a small thunderclap.

40
    IN THE MORNING Lobsang was back. Joshua could sense him, sense that a kind of purposefulness had returned to the ship, even before the ambulant unit joined him on the observation deck, as he drank the first coffee of the day. Sally was evidently still asleep.
    They were stepping gently, and worlds washed beneath them. As ever the Long Earth was mostly trees and water, silence and monotony. Joshua was glad to be free of the hard-to-pin-down oddness of Happy Landings, but as they headed West once more that gathering pressure in his head had returned. He tried and failed to ignore it.
    The two of them sat in silence. There was no mention of Lobsang’s departed friends the trolls, or of his offline episode. Joshua couldn’t read Lobsang’s mood. He wondered vaguely if he was
lonely
without the trolls, disappointed they had chosen to leave, frustrated that his research was evidently unfinished. It was faintly disturbing that Lobsang seemed to be becoming more unstable, more unpredictable. Overloaded by new experiences, perhaps.
    After an hour of this Lobsang said, out of nowhere, ‘Do you ever think about the future, Joshua? I mean the far future?’
    ‘No. But I bet you do.’
    ‘The diffusion of humanity across the Long Earth will surely cause more than mere political problems. I can foresee a time where mankind is so dispersed across the multiplicity of worlds that there will be significant genetic differences at either end of the human hegemony. Perhaps there will have to be some kind of enforced cross-migration to make certain that mankind remains sufficiently homogeneous to be united …’
    A burning forest below made the ship dance briefly on turbulent thermals.
    ‘I don’t think we need worry about that just yet, Lobsang.’
    ‘Oh, but I do worry, Joshua. And the more I see of the Long Earth, the more its scale impresses itself on me, and the more I fret. Mankind will be trying to run a galactic empire, effectively, on one ever-repeating planet …’
    The airship shivered to a halt. The world below was shrouded in low cloud.
    Sally wandered on to the deck, wrapped in a robe, her hair in a towel. ‘Really? Do we have to copy the mistakes of the past? Must there be Roman legions marching into endless new worlds?’
    ‘Good morning, Sally,’ Lobsang said. ‘I trust you are rested?’
    ‘The best thing about the beer at Happy Landings is its purity, like the very best German brews. No hangover.’
    Joshua said, ‘Although you did your best to test that theory to destruction.’
    She ignored him and looked around. ‘Why were we travelling so slowly? And why, in fact, have we stopped?’
    Lobsang said, ‘We travelled slowly in order that you might sleep late, Sally. But also I took on board your criticism. It pays to inspect the small details, and so I have slowed the flight of our flying penis, as you so amusingly described it. Small details, such as the relic of an advanced civilization just underneath us. Which is why we have stopped.’
    Joshua and Sally, electrified, exchanged a glance.
    As the ship lost height they peered down through the haze.
    ‘My radar scanner is returning images through the cloud,’ Lobsang said, apparently staring into empty space. ‘I see a river valley, evidently long dry. A cultivated flood plain. No recognizable electromagnetic or other high technology. Signs of purposeful construction on the riverside – including a bridge, long ago broken. And rectangles on the ground, my friends,
rectangles
of brick or stone! But no signs of complex life surviving. I have no idea who the builders were. This may be a diversion from our main goal, but I am sure I speak for all of us