Free Schild's Ladder by Greg Egan

module—continuing along its arc of rotation, yet dropping from the zenith in front of him rather than disappearing behind his head—scrambled his sense of balance and direction completely. At first he felt as if he was tumbling backward, which would at least have explained what he was seeing, but when his inner ears failed to confirm the motion, the illusion vanished—only to return a moment later, to take him through the same cycle again. The lurching fits and starts that followed might have made him less queasy if they'd actually been happening; it was the inability to make sense of his perceptions that was disturbing, far more than any direct, physical effect of the lack of gravity.
    He began to get his bearings once the whole ship was visible, edge-on. A minute later it had shrunk to a sparse necklace of glass beads, and the newly fixed stars finally crystallized in his mind as cues worth taking seriously. The infinite plane of whiteness on his right might have been a moonlit desert seen through half-closed eyes. He'd once flown a glider high over sand dunes at night, on Peldan, nearly free-falling at times in the thin air. There'd been no moonlight, of course, but the stars had been almost as bright as these.
    Yann, sitting beside him, caught his eye. “You okay?”
    Tchicaya nodded. “In the scapes you grew up in,” he asked, “was there a vertical?”
    “In what sense?”
    “I know you said once that you didn't feel gravity...but was everything laid out and connected like it is on land? Or was it all isotropically three-dimensional—like a zero-gee space habitat, where everything can connect in any direction?”
    Yann replied affably, “My earliest memories are of CP4—that's a Kähler manifold that looks locally like a vector space with four complex dimensions, though the global topology's quite different. But I didn't really grow up there; I was moved around a lot when I was young, to keep my perceptions flexible. I only used to spend time in anything remotely like this”—he motioned at the surrounding, more-or-less-Euclidean space—“for certain special kinds of physics problems. And even most Newtonian mechanics is easier to grasp in a symplectic manifold; having a separate, visible coordinate for the position and momentum of every degree of freedom makes things much clearer than when you cram everything together in a single, three-dimensional space.”
    So much for being a seasoned traveler . Tchicaya didn't envy Yann's upbringing, but it probably rendered the world behind the border less exotic to him than the notion of a jungle had been to Tchicaya as a child. It shook his confidence to be reminded that there were measures by which his millennia of experience had been laughably narrow.
    He couldn't have it both ways, though: he couldn't claim that the embodied needed the shock and the strangeness of this burgeoning universe, and then wish it could be no more daunting to confront than one more mundane planetary surface.
    Kadir turned around and interjected testily, “I can analyze the flows in a symplectic manifold perfectly well without pretending to inhabit it. That's what mathematics is for. Imagining that you need to float through every last abstract space that shows up in a physics problem is just being literal-minded.”
    Yann smiled, unoffended. “I'm not going to argue with you. I haven't come here to proselytize for acorporeality.”
    Zyfete, seated in front of Tchicaya, muttered, “Why bother, if you can render embodiment just as barren?”
    Tchicaya bit his tongue. He'd been forewarned about the level of acrimony, and at some point everyone on the Rindler was going to have to wade waist-deep through their opponents' venom on their way to a resolution, but spur-of-the-moment bickering in a confined space wasn't his idea of productive disharmony.
    The shuttle's drive kicked in, delivering a mild push that Tchicaya succeeded in interpreting as a precipitous dive, rather than a complete