Charged Vacuum Emboitement

A Charged Vacuum Emboitment or CVE was a violent pathway between universes. CVEs provided a transit point between N-Space and E-Space. (TV: Full Circle)

Physics
They were the rarest of space-time events and almost undetectable, entities containing layers of highly charged quantum particles suspended in pockets of super-vacuums. They occupied the space between realities (either the Void or interstitial time) and were so violent in their physics that when they formed they punched a hole between universes, pushing space aside to insinuate themselves into reality, releasing massive waves of energy in the process. Passing through one was a disorienting experience. They had no external energy signature and made no detectable footprint in the three primary dimensions, yet could be as large as a moon. (AUDIO: The Invasion of E-Space)

CVEs operated passively, drawing both physical objects and entropy through them. Because of their special function, the closure of the CVEs would threaten the physical integrity of N-Space and all life within. (TV: Logopolis)

History
The Logopolitans created CVEs using Block Transfer Computations in order to save N-Space, their universe, the existence of which was threatened by entropy. (TV: Logopolis)

While all complex systems eventually break down, the Logopolitans reasoned that if they opened a closed system (N-Space) into a smaller one (E-Space) they could extend the life of the larger one. By the year 1981, N-Space would have already passed the point of no return into heat death without the CVEs keeping it still viable. Also that year, only one CVE (located in Cassiopeia) was left, eventually closing in the far future. (TV: Logopolis, PROSE: Timewyrm: Apocalypse)

While in flight, the Doctor's TARDIS travelled through a CVE into E-Space by accident. (TV: Full Circle) They wandered this universe for months searching for another. (AUDIO: The Invasion of E-Space) In the middle of the 22nd century a similar event may have happened to the human ship Hydrax, which passed into E-Space, though the King Vampire had some involvement in bringing them through. (TV: State of Decay / PROSE: Lucifer Rising)

Charged Vacuum Emboitment