Multiverse Theory

Multiverse Theory is a theoretical attempt to impose a structure on the known characteristics of the Multiverses. It is, of course, untestable by any normal beings, and the Flowers aren't telling.

The Theory
Put briefly, the Theory runs like this: a world will usually consist of three spatial dimensions (height, width and depth), and one temporal (time). In most cases, the world is locked into moving on a determined vector along the temporal dimension, while moving freely in the spatial ones. Multiverse Theory states that there are in fact three temporal dimensions, to match the three spatial ones. One, the observed one, is time as we know it, or depth-time. The other two, commonly rendered height-time and width-time, are not observable by normal spatial beings, as they are incapable of moving in them, and (this is important) do not have a constant motion in them, unlike depth-time.

The Theory therefore states that width-time consists of innumerable Alternate Universes based on the continuum one occupies at the time. This may be identical with the fifth dimension named "probability" by the Flowers, or it may not. Height-time provides access to the different continuua -- in other words, moving time-up may move you from Lord of the Rings to Harry Potter, whole moving time-right will take you from a Legomance into a slashfic.

It is unclear where the Mirror Multiverse falls in this theory. Some claim it is a separate Multiverse in its own right, where everything started off reversed (as opposed to the normal Multiverse, in which all variations started identically but split off at various points). Others say that the extreme time-left of the Prime Multiverse is identical with the extreme time-right of the Mirror Multiverse, and thus that they are merely widely separated sections of a single Multiverse. To test this theory would require a great deal of time and expense, and the use of PPC portal technology; thus far, the Flowers have not granted permission for this to occur.

Travel
Travel within a Multiverse is possible by many means. PPC portal technology is able to move Agents through both height-time and width-time. Most other means only affect width-time; for example a malfunctioning TARDIS may land its operater in an alternate universe (as in the Rise of the Cybermen episode of Doctor Who), although one instance (Inferno) may rather be a manifestation of the Mirror Multiverse. Travel between multiverses is less common; the best known occurances occur by accident, as did the Inferno trip for the Doctor. However, it appears that Mirror Makes-Things succeeded in developing a machine that can travel between multiverses at will.