Location from remembrance-of-earths-past by
A collapsing bubble of higher-dimensional space encountered by Blue Space and Gravity en route to NH558J2 — a place where every 3D object opens like a flower into impossible interiors, where the Ring waits among the wrecks, and where droplets can be undone from a direction that does not exist in our geometry.
The 4D bubble is one of the trilogy's most hallucinatory passages. The crews of Blue Space and Gravity learn — from a sentient tomb-craft called the Ring — that the universe used to have more dimensions and that civilizations in dimensional war have been folding it down for billions of years. The 4D collapse is the cousin of the dual-vector foil's 2D collapse. It is also where humans first learn to attack a droplet from a fourth direction and disable it from the inside.
A region of space that, from outside, looks like an unremarkable patch of vacuum. From inside: every familiar 3D object reveals itself as cross-sections of a much larger 4D form, organs and crystals folded into unseen directions. The eye does not know what to do. Wrecked spacecraft from a dozen civilizations drift inside the bubble, all unfolded, their hidden interiors exposed.