Free Oceanic by Greg Egan

wasteland. After that near-disastrous first encounter, he had worked to establish communications with us, learning our languages and happily listening to the accounts we’d volunteered of our world, but he had not been equally forthcoming in return. We knew next to nothing about far-side physics, astronomy, biology, history or culture. That there were living beings occupying the same space as the Earth suggested that the two universes were intimately coupled somehow, in spite of their mutual invisibility. But Sam had hinted that life was much more common on his side of the border than ours; when I’d told him that we seemed to be alone, at least in the solar system, and were surrounded by light-years of sterile vacuum, he’d taken to referring to our side as “Sparseland”.
    Alison said, “Either way, I think we should keep it to ourselves. The treaty says we should do everything in our power to deal with any breach of territory of which the other side informs us. We’re doing that. But we’re not obliged to disclose the details of Campbell’s activities.”
    “That’s true.” I wasn’t entirely happy with her suggestion, though. In spite of the attitude Sam and his colleagues had taken – in which they assumed that anything they told us might be exploited, might make them more vulnerable – a part of me had always wondered if there was some gesture of good faith we could make, some way to build trust. Since talking to Campbell, in the back of my mind I’d been building up a faint hope that his discovery might lead to an opportunity to prove, once and for all, that our intentions were honorable.
    Alison read my mood. She said, “Bruno, they’ve given us nothing . Shanghai excuses a certain amount of caution, but we also know from Shanghai that they could brush Luminous aside like a gnat. They have enough computing power to crush us in an instant, and they still cling to every strategic advantage they can get. Not to do the same ourselves would just be stupid and irresponsible.”
    “So you want us to hold on to this secret weapon?” I was beginning to develop a piercing headache. My usual way of dealing with the surreal responsibility that had fallen on the three of us was to pretend that it didn’t exist; having to think about it constantly for three days straight meant more tension than I’d faced for a decade. “Is that what it’s come down to? Our own version of the Cold War? Why don’t you just march into NATO headquarters on Monday and hand over everything we know?”
    Alison said dryly, “Switzerland isn’t a member of NATO. The government here would probably charge me with treason.”
    I didn’t want to fight with her. “We should talk about this later. We don’t even know exactly what we’ve got. I need to go through Campbell’s files and confirm whether he really did what we think he did.”
    “OK.”
    “I’ll call you from Sydney.”
    It took me a while to make sense of everything I’d stolen from Campbell, but eventually I was able to determine which calculations he’d performed on each occasion recorded in his log files. Then I compared the propositions that he’d tested with a rough, static map of the defect; since the event Sam had reported had been deep within the far side, there was no need to take account of the small fluctuations that the border underwent over time.
    If my analysis was correct, late on Wednesday night Campbell’s calculations had landed in the middle of far-side mathematics. He’d been telling me the truth, though; he’d found nothing out of the ordinary there. Instead, the thing he had been seeking had melted away before his gaze.
    In all the calculations Alison and I had done, only at the border had we been able to force propositions to change their allegiance and obey our axioms. It was as if Campbell had dived in from some higher dimension, carrying a hosepipe that sprayed everything with the arithmetic we knew and loved.
    For Sam and his