# Footnotes and Explanations

## MWI

The Many Worlds Interpretation of Quantum Mechanics. See the FAQ
for more details.
## Life and Information

"Life" is an ill defined term, but seems in general to apply to some kinds
of self-sustaining dissipative systems able to self-reproduce and evolve.
Tipler (and me) argue that essentially life can be seen as patterns of information (even emotions have an informational content and have to be put in relation to other experiences to exist), which is the Strong AI Postulate in another (slightly stronger) form.
## Mixed Strategies in Games

In some games between two or more players the optimal strategy
is a random mixture between some moves, with as little pattern
as possible.
## Future-Endless

A worldine that does not end in the future direction except at the c-boundary.
## Timelike

A curve through spacetime whose velocity at no point becomes greater
than the speed of light. Matter moves along timelike curves.
## Eternal Return

The Eternal Return is Tipler's term for a state where a system repeats
its states endlessly, without ever changing. All systems with a finite number of states will eventually get into such a loop, and through the ergodicity theorem it can be shown that the same goes for all systems with a finite phase space(although in classical mechanics its possible to enter a strange attractor and thus never repeat a previous state *exactly*, although the system will get infinitely close to a certain state an infinite number of times). The only way to avoid it is to expand the phase space.
## Shear Energy

If spacetime isn't isotropic, then the anisotropy can at least theoretically be used as an energy source. Since the anisotropy of spacetime increases, it will be dominant in certain forms of collapses of closed universes, which is what Tipler counts on in his scenario.
Currently the cosmic background radiation is isotropic, but in some cosmological models the universe will expand or contract in an anisotropic way. This will lead to temperature differences of the background radiation in different directions as it is blue- or red-shifted, and from this a heat engine could be set up to extract energy.

The idea that intelligent reasoning and experience can be emulated by
a mathematical system (especially a program running on a Turing Machine).
## No Clone Theorem

Two systems that are in identical quantum states are identical; the "identity
of indistinguishables". This can be generalized to mean that two objects that have the same structure are identical (which essentially implies that an emulation and the original are identical).
## Economic Argument

There seem to be a fairly well established economic tendency for goods to
become cheaper (as compared to wages) in time as economy and technology develops. Today a person can own books, a car or a computer, which in the past was far too expensive for most people. If this trend continues (and Tipler argues that the "laws of economics" hold for most expanding technological civilizations), then eventually any device or service will eventually become available to the private citizen (barring restrictions etc.).
## Empty universes don't exist

Tipler thinks that universes without conscious observers do not exist, at
least not in an observable sense (since they cannot by definition be observed). Tipler seems to regard this as ontologically true, which may be a bit extreme (but it follows from the Omega Point Boudnary Condition - which is partially based on this view!).

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Anders Sandberg / asa@nada.kth.se