Do Parallel Universes Really Exist? (good science article)

note: nice clear summary of the gradual merging of physics and metaphysics of the multi-verse. Michael

PARALLEL UNIVERSES: ARE THEY MORE THAN A FIGMENT OF OUR IMAGINATION?
Daily Galaxy
November 13, 2008

http://www.dailygalaxy.com/my_weblog/2008/11/parallel-univer.html

The Hollywood blockbuster, The Golden Compass, adapted from the first volume
of Pullman’s classic sci-fi trilogy, “His Dark Materials” portrays various
universes as only one reality among many, but how realistic is this kind of
classic sci-fi plot? While it hasn¹t been proven yet, many highly respected
and credible scientists are now saying there¹s reason to believe that
parallel dimensions could very well be more than figments of our
imaginations.

“The idea of multiple universes is more than a fantastic invention — it
appears naturally within several scientific theories, and deserves to be
taken seriously,” stated Aurelien Barrau, a French particle physicist at the
European Organization for Nuclear Research (CERN).

There are a variety of competing theories based on the idea of parallel
universes, but the most basic idea is that if the universe is infinite, then
everything that could possibly occur has happened, is happening, or will
happen.

According to quantum mechanics, nothing at the subatomic scale can really be
said to exist until it is observed. Until then, particles occupy uncertain
“superposition” states, in which they can have simultaneous “up” and “down”
spins, or appear to be in different places at the same time. The mere act of
observing somehow appears to “nail down” a particular state of reality.
Scientists don¹t yet have a perfect explanation for how it occurs, but that
hasn¹t changed the fact that the phenomenon does occur.

Unobserved particles are described by “wave functions” representing a set of
multiple “probable” states. When an observer makes a measurement, the
particle then settles down into one of these multiple options, which is
somewhat how the multiple universe theory can be explained.

The existence of such a parallel universe “does not even assume speculative
modern physics, merely that space is infinite and rather uniformly filled
with matter as indicated by recent astronomical observations,” Max Tegmark,
a cosmologist at MIT in Boston, Massachusetts concluded in a study of
parallel universes published by Cambridge University.

Mathematician Hugh Everett published landmark paper in 1957 while still a
graduate student at Princeton University. In this paper he showed how
quantum theory predicts that a single classical reality will gradually split
into separate, but simultaneously existing realms.

“This is simply a way of trusting strictly the fundamental equations of
quantum mechanics,” says Barrau. “The worlds are not spatially separated,
but exist as kinds of ‘parallel’ universes.”

Partly because the idea is so uncomfortably strange, it¹s dismissed as
sci-fi by many critics. But there are also many credible, respected
proponents of the theory — a group that is continuously gaining new
adherents as new research unveils new evidence. Some Oxford research — for
the first time — recently found a mathematical answer that sweeps away one
of the key objections to the controversial idea. Their research shows that
Everett was indeed on the right track when he came up with his multiverse
theory. The Oxford team, led by Dr David Deutsch, showed mathematically that
the bush-like branching structure created by the universe splitting into
parallel versions of itself can explain the probabilistic nature of quantum
outcomes.

The work has another strange implication. The idea of parallel universes
would apparently side-step one of the key complaints with time travel. Every
since it was given serious credibility in 1949 by the great logician Kurt
Godel, many eminent physicists have argued against time travel because it
undermines ideas of cause and effect. An example would be the famous
³grandfather paradox² where a time traveler goes back to kill his
grandfather so that he is never born in the first place.

But if parallel worlds do exist, there is a way around these troublesome
paradoxes. Deutsch argues that time travel shifts happen between different
branches of reality. The mathematical breakthrough bolsters his claim that
quantum theory does not forbid time travel. “It does sidestep it. You go
into another universe,” he said. But he admits that there will be a lot of
work to do before we can manipulate space-time in a way that makes ³hops²
possible. While it may sound fanciful, Deutsch says that scientific research
is continually making the theory more believable.

“Many sci-fi authors suggested time travel paradoxes would be solved by
parallel universes but in my work, that conclusion is deduced from quantum
theory itself.”

The borderline between physics and metaphysics is not defined by whether an
entity can be observed, but whether it is testable, insists Tegmark.

He points to phenomena such as black holes, curved space, the slowing of
time at high speeds, even a round Earth, which were all once rejected as
scientific heresy before being proven through experimentation, even though
some remain beyond the grasp of observation. It is likely, Tegmark concludes
that multiverse models grounded in modern physics will eventually be
empirically testable, predictive and disprovable.