The Multiverse

The universe described in the Alt Earth Background section is one of many parallell universes that make up the Multiverse. The Multiverse operates according to principles loosely based on the Everett-Wheeler Interpretation of Quantumn Mechanics, sometimes called the Many-World Interpretation or MWI.

Everett-Wheeler Interpretation

MWI is an interpretation of quantum mechanics which holds that the subjective impression of having observed one and only one outcome of a given experiment is an illusion and that there exist other parallel universes, said to be equally real, in which the unknown outcomes are realized.

Terminology

The terms below are not all MWI terms; some have been created for purposes of the Multiverse and do not reflect actual scientific terms or concepts.

Multiverse

The term Multiverse refers to everything that exists; it incorporates many universes that exist in parrallel. There is only one multiverse.

Universe

A universe is the totality of (macroscopic) objects: stars, cities, people, grains of sand, etc. in a definite classically described state.

A "definite classically described state" is one in which the position and state (e.g. alive, dead, smiling, etc.) of an object/being is maximally defined according to our ability to distinguish between the alternatives. That is to say, someone is either alive or they are dead. Objects in a universe cannot be both dead and alive (although they can, on AltEarth at least, be "un-dead").

Tangent Universe

A way of identifying a universe in relation to some previous universe. A tangent universe is one that has split from some previous universe that is used as a reference point.

Divergence Threshold

The threshold beyond which an irreversible event generates a tangent universe. Events that do not cross this threshold produce temporal static

Divergent Event

An irreversible event intense/significant enough to cross the divergence threshold and, therefore, create a tangent universe.

Temporal Static

A "vibration" throughout the Multiverse resulting from irreversible events which do not, however escape the force of their own discrete universes to create tangent universes. This static is more intense based on the relative proximity to the time-space locus of the event.

Significance of MWI to the Multiverse

Effectively, the fact that the Multiverse is governed by the principles of MWI means that there is no one reality; reality is composed of very many, increasingly divergent, non-communicating parallel universes.

If the Multiverse strictly adhered to MWI, there would be possibly infinitely many universes for each irreversible thermodynamic event. Since MWI is being appropriated here from dramatic purposes, we depart from strict science and make the bold leap into science fiction.

In the Multiverve, divergences of less than a certain intensity do not actually reach the divergence threshold, but create, instead a kind of "ripple effect" that "vibrates" across/between/through the Multiverse. This temporal static is subjectively imperceivable to all but a very few (the supervillain Downtime's danger sense is the result of an attunement to these vibrations), but can be measured as a kind of transdimensional "static" by some extremely advanced instruments and magical artefacts.

Thus, irreversable events that cross the divergence threshold in a given universe spawn a new universe, resulting in the creation of one or more tangent universes, each with a different outcome for the event. This results in a continual splitting of the Multiverse into a multitude of mutually unobservable, but equally real, tangent universes. Tangent universes with different outcomes for the same event in a shared parent universe exist simultaneously, but do not interfere further with each other (beyond the diffuse impact of temporal static). Each single prior universe then has the possibility of generating divergence events that split that universe into further, mutually unobservable but equally real tangent universes.

Thus, the present universe of AltEarth corresponds to a unique universe with a single History, but corresponds to a multitude of tangent universes at a time in the future. The Age of Destroyer, for example, is one such tangent universe.

Although universes may split, they can never fuse, as this would require all the atoms, subatomic particles, photons, etc. in each universe to be in the same state simultaneously. This kind of convergence is possible only in small microscopic systems, but not in more complex systems.

Probability in the Multiverse

At first glance, the mutliple nature of the 'verse may seem to hopelessly muddle notions of probability. If many possible outcomes of an irreversible event that crosses the divergence threshold are realized in some tangent universe, what is the meaning of saying that one outcome is more or less likely than some other outcome? This is explained by the probability postulate.

What the probability postulate means for the Multiverse is that in cases of divergent events, probability can be explained in terms of the number of tangent universes created. The probability of a particular outcome is proportional to the number of tangent universes with this outcome. A very improbable outcome will be realized in only a small number of tangent universes; a very probably one in many.

Impact of Time Travel in the Multiverse

What this means for the notion of time travel within the Multiverse is that there is not a single timeline which can be changed retroactively in order to irrevocably change the future.

Lets say a time traveler goes back in time to avert a catastrophe that has destroyed 99% of all human life on Earth (leaving only the time traveler and some of his friends). Let’s say the catastrophe could have been averted by preventing a man from pushing a big red button. Going back to the moment in the traveler’s universe in which the button was about to be pressed and stopping the man from pressing it will not change the future tangent universe from which the traveler came.

Instead, at the moment a divergent event occurs as a result of the intervention of the time traveler (e.g., preventing the button from being pressed and saving most of humanity), a new tangent universe will be created.

This tangent universe will follow its own path, splitting in turn into a multitude of tangent universes. We can imagine, however, that this could be perfectly satisfactory to the time-traveler with the capability of reaching these newly-created tangent universes. He could occupy a newly-spawned, equally real, tangent universe where his loved ones were not killed. He would have to confront the fact, however, that he had left friends and loved ones behind in another, far-less hospitable, universe in order to secure a more comfortable existence for himself (in a universe in which versions of these people also exist, perhaps living happier lives). He also faces the problem of having entered a tangent universe in which a version of himself never had a need to depart; he would have to decide how to deal with his own double. Any of these issues, in addition to being disorienting, would undoubtedly cause some ethical, existential, and psychological problems for the traveler.

Time Travel Technology

How it works

Time travel is achieved by turning a journey through Time into one through Space. This can be accomplished by means of dimensional travel to Dimension X. Dimension X is a dimension in which every point of Space and Time is suffused with rotation. In a rotating dimension, a journey through space, but reaching the past or future, is possible. Dimension X is extraordinarily dense; it is as dense everywhere as the nucleus of an atom and rotates at an incredible speed.

Time travel involves entering Dimension X for a fraction of a second and taking advantage of its axis-twisting to travel along a loop into the past or the future, and then returning to the dimension of origin.

Technical Requirements

Time Travel requires several kinds of technology:

• Extra-dimensional Travel. Vehicles or persons must enter into Dimension X to spiral through time.

• Nonlinearity Engine or Nonlinearity Driver. Once a traveler reaches Dimension X, he will require a nonlinearity engine or driver to effect travel through time. These devices provide the massive amount of propulsive force needed to travel through Dimension X. A nonlinearity engine makes up a part of the time travel vehicle and, with enough fuel, can effect multiple voyages through time. For one-way trips through time, an alternative to a nonlinearity engine is a nonlinearity driver. A nonlinearity driver launches an object, vehicle, or even a traveler into and through Dimension X to a pre-plotted location. These devices are more dangerous than nonlinearity engines, for rather than being contained in a vehicle, they essentially launch the traveler like a projectile through time. Despite the dangers, one advantage of the driver is its ability to propel a traveler through time (in a protective capsule) without the added mass of a vehicle, thus allowing for considerable fuel conservation.

• Anti-Protons. The massive energy required for nonlinearity engines can only be feasibly produced by antiproton drives. Antiproton “fuel” is held in a magnetic field that is then brought into an annihilation reaction with protons. Fuel is expended in proportion to the mass transported and the relative “distance” to the destination.

• Computation Capacity. The mathematical equations required for accurate time travel within the Multiverse are immensely complex. Thus, one or more advanced supercomputers is required for plotting courses. Plotting a course can, depending on the level of technology, take weeks, months, years, or even longer. Temporal navigation equations are relative and probabilistic and the “position” of “points” in time in the Multiverse are indeterminate; a traveler must plot a new course after each journey through time. Further, the time traveler’s arrival at another point in time itself produces temporal static and, in some cases, new tangent universes—thus impacting variables used in the plotting of future courses. A traveler, then, cannot simply travel to a point in time with a pre-plotted course home (or anywhen else for that matter).

Given these requirements, those who do not wished to be stranded in the tangent universe in which they arrive, must bring with them technology, fuel, and computational capacity capable of meeting the requirements of further time travel or he must obtain these in the destination universe.

Within the physical bounds of AltEarth, this practically limits time-travel without the immediate means of return to the early 21st century. The capability to meet the requirements for time travel is at lest nascent in the technology of AltEarth in this age.