The Interval

The Interval is the separation between one cosmic membrane and the next — that is, between two universes — measured across the Common Manifold rather than through either universe's own space. Two universes can be adjacent across a narrow Interval while being unreachably far apart by every ordinary measure of distance either one has.

The Interval exists only between membranes. A Concordant Zone is a region inside a universe, so two adjacent zones are separated by an ordinary internal edge and no Interval at all. Everything below is therefore inter-universe by definition.

It is not a place. Nothing is native to the Interval, nothing lives in it, and nothing travels through it under its own power. No vessel has been in one. It is a distance term, not a medium — closer in kind to a gap between two pages than to the space between two stars.

Its one operationally interesting property is that it varies. Everything Survey Corps documents at a boundary zone is a consequence of a narrowing Interval:

• Under a wide Interval, adjacent membranes are functionally inert to each other.
• As it narrows, effects begin to couple across it — Membrane Resonance, then Intermembrane Bleed in the Etheric channel, and Membrane Shadows in the Physical one.
• At the Type III extreme, and rarely, a transient gravity tunnel briefly opens a genuine through-conduit. This is the only documented circumstance in which anything crosses an Interval at all. A certified fold transit into a neighbouring membrane is not a second one: a fold compresses the separation to adjacency and releases it, so nothing traverses a standing Interval on the way.

What crosses is field structure, not matter. A Membrane Shadow is gravity leaking across a narrowed Interval while every gram responsible for it stays on the far side. Intermembrane Bleed is template admissibility competing across one. In neither case has anything travelled.

Example: Threshold Station's Dock Seven chronometer discrepancy is an Interval measurement that nobody on the station was equipped to read as one. Recalibrating instruments on this side of a narrowing Interval does not widen it, which is precisely why the discrepancy returned after every correction.

See also: Concordant Membranes and Intermembrane Bleed, The Common Manifold, Membrane Shadow, Boundary Zones and Concordant Edges.