(Physics) Interstitial Space
Interstitial Space(IS). Literally the Space Between Dimensions.
In really simple terms; think of this like the water in an Ocean, where Space itself floats on top.
As you can transit in three dimensions in both; this allegory breaks down a little, but it's good enough for the fundamentals.
Interstitial space itself has it's own currents & eddies, much like a real Ocean, and it's own positive/negatively charged energy, which is what allows [[Interstitial Drive]]s to transit in/out of this realm and move around it.
Interstitual Space being non Euclidian isn't bound to the same rules as normal space. 1M =/= 1M in real-space. a Given Distance of transit in IS does not equal the same given distance in real space, and the ratio is not certain.
For this reason the navigation through Interstitual Space is more like Stellar Triangulation - Known star systems or obvious Stellar Phenomena used to place exactly what you're currently moving through/past.
IS isn't inherently hostile to any matter there, although anything that can't conduct IS energy tends to have a very rough time as it gets battered & tossed by the currents within, however unpowered vessels will eventually be "Rejected" back to their source, in a very lose term.
All matter will "Float" up towards the universe in which it was created, however when & where it returns to the surface is very much luck of the draw more than it is any art or science to predict.
(//Codex Entry Author: Alex Lee)