Oceanic by Greg Egan

business?”
    He shrugged. “Then I’ll work harder. I know you’ve screwed that laptop, and maybe the other computers in my house, but I’m not so broke that I can’t get a new machine.”
    Which would be a hundred times faster. He’d re-run every search, probably with wider parameter ranges. The suitcase nuke from Sparseland that had started this whole mess would detonate again, and for all I knew it could be ten times, a hundred times, more powerful.
    I said, “Have you ever wanted to join a secret society?”
    Campbell gave an incredulous laugh. “No!”
    “Neither did I. Too bad.”
    I told him everything. The discovery of the defect. Industrial Algebra’s pursuit of the result. The epiphany in Shanghai. Sam establishing contact. The treaty, the ten quiet years. Then the sudden jolt of his own work, and the still-unfolding consequences.
    Campbell was clearly shaken, but despite the fact that I’d confirmed his original suspicion he wasn’t ready to take my word for the whole story.
    I knew better than to invite him into my office for a demonstration; faking it there would have been trivial. We walked to the local shopping center, and I handed him two hundred dollars to buy a new notebook. I told him the kind of software he’d need to download, without limiting his choice to any particular package. Then I gave him some further instructions. Within half an hour, he had seen the defect for himself, and nudged the border a short distance in each direction.
    We were sitting in the food hall, surrounded by boisterous teenagers who’d just got out from school. Campbell was looking at me as if I’d seized a toy machine gun from his hands, transformed it into solid metal, then bashed him over the head with it.
    I said, “Cheer up. There was no war of the worlds after Shanghai; I think we’re going to survive this, too.” After all these years, the chance to share the burden with someone new was actually making me feel much more optimistic.
    “The defect is dynamic ,” he muttered. “That changes everything.”
    “You don’t say.”
    Campbell scowled. “I don’t just mean the politics, the dangers. I’m talking about the underlying physical model.”
    “Yeah?” I hadn’t come close to examining that issue seriously; it had been enough of a struggle coming to terms with his original calculations.
    “All along, I’ve assumed that there were exact symmetries in the Planck scale physics that accounted for a stable boundary between macroscopic arithmetics. It was an artificial restriction, but I took it for granted, because anything else seemed ... ”
    “Unbelievable?”
    “Yes.” He blinked and looked away, surveying the crowd of diners as if he had no idea how he’d ended up among them. “I’m flying back in a few hours.”
    “Does Bridget know why you came?”
    “Not exactly.”
    I said, “No one else can know what I’ve told you. Not yet. The risks are too great, everything’s too fluid.”
    “Yeah.” He met my gaze. He wasn’t just humoring me; he understood what people like IA might do.
    “In the long term,” I said, “we’re going to have to find a way to make this safe. To make everyone safe.” I’d never quite articulated that goal before, but I was only just beginning to absorb the ramifications of Campbell’s insights.
    “How?” he wondered. “Do we want to build a wall, or do we want to tear one down?”
    “I don’t know. The first thing we need is a better map, a better feel for the whole territory.”
    He’d hired a car at the airport in order to drive here and confront me; it was parked in a side street close to my house. I walked him to it.
    We shook hands before parting. I said, “Welcome to the reluctant cabal.”
    Campbell winced. “Let’s find a way to change it from reluctant to redundant.”
    #
    In the weeks that followed, Campbell worked on refinements to his theory, emailing Alison and me every few days. Alison had taken my unilateral decision to