EGS Fan Factbook

On The Nature Of The Multiverse

Here There Be Spoilers!

The Big Picture

We appear to be lucky, blessed with an author who doesn't flinch away from the unblinking eye of infinity.

EGS's multiverse appears to use the many-worlds model(a la quantum physics), wherein each universe splits into an infinite number of universes(or maybe an analog continuum of universes) every planck, resulting in a very large infinity of universes. Indications: In the many-worlds model, each possible decision on a quantum level splits into two universes. Except you have an infinite number of possible decisions at each instant(for example, 94% of the particles in the universe could all spontaneously move three plancks to my left), so it's more like a "reality volume", composed of infinite numbers of universes, each of which splits into an infinite number of universes every planck. The result is a massively infinite number of universes, which can have very subtle differences(like one electron, hurtling through deep space, being one planck to your left). They can also have fairly important differences, like our galaxy not existing in any recognizable form due to snowballed changes from billions of years ago.

In reality, this is our current best theory. Reality also appears to feature a set of 3-D universes within each many-worlds universe; these should be finite in number(IIRC in the quad digits), being generated by a pair of branes colliding in a higher space. (There may be more branes generating more clusters of universes.) Due to many-worlds variations in the action of these branes, there can be different numbers of 3-D universes in each many-worlds universe; EGS appears to only use alternates(see below) of our 3-D universe, in at least some sense, but it's not like we bunnies would note a few extra orders of magnitude on the large infinities.

Alternates

An objective definition of "alternate" is a sticky subject. There is one possibility provided by many-worlds, being the you in any universe that split from this one since your birth; these individuals can trace a common origin, yet had different events during their lives(even if they're of the "one electron over" variety). However, while all of these are alternates, we recognize other people as obviously alternates, due to extreme similarity; for example, Beta Ellen is considered Main Elliot's alternate, despite obvious genetic differences. The universe recorded for Second Life had even larger differences(including a time offset of one sort or another), which appear to reach back at least a generation… yet SL Ellen is considered Main Elliot's alternate. So we can say any pair that're "similar enough" are alternates, with "enough" being defined by the individual. (Including different changes being valued differently.)

This is complicated(or perhaps simplified) by the possibility of some sort of mystical connection. This post by Dan mentions an attractor in universes with an Elliot and a Tedd, which may simply mean they're very suited for each other, or may indicate some destiny pattern - and a destiny pattern could be used for a strict in-character definition of alternate. If and only if you share destiny patterns, you're alternates. (Personally, I believe it's just tendencies, but I could easily be wrong.)

Most universes with what we'd recognize as humans on Earth should have a common origin, and thus they will be of the same species(aside from possible allopatric speciation). However, there will also be a small(though still infinite) number of universes with what appear to be humans, yet are different and incompatible in some way.

The Interference Effect

When universes interact, they tend to become more unique. This is described here and here(same thread), and may be entirely a question of unlikely events. (If it is, this would affect the definition of "more unique".)

The interference effect is also another possible mystical connection I don't believe in but could be wrong about.