clifford_a-_pickover_surfing_through_hyperspacebookfi-org

addendum
As this book goes to press, I have uncovered several recent discussions dealing with
parallel universes and cosmic topology.
• Parallel Universes—Chapter 3 discussed parallel universes and the "manyworlds"
interpretation of quantum mechanics. Readers interested in a lively
and critical discussion of this topic should consult Professor Victor Stenger's
The Unconscious Quantum (Prometheus Books, 1995). For example, he
doubts very much that the parallel universes (in the many-worlds interpretation)
all simultaneously exist. He also does not believe that all branches
taken by the universe under the act of measurement are "equally real."
Stenger discusses other approaches such as the "alternate histories" theory
that suggests every allowed history does not occur. What actually happens is
selected by chance from a set of allowed probabilities.
• More on the Multiverse—Many have wondered why the hypothetical cosmological
constant (a mysterious energy that seems to be permeating space and
counteracting gravity on cosmic distance scales) is just right to permit life in
our universe. Some theories, in fact, predict that the constant should be
much larger and therefore would presumably keep galaxies, stars, and life
from forming. Uncomfortable with the idea that the cosmological constant
and other parameters are simply lucky accidents, Stephen Hawking recently
suggested that an infinity of big bangs have gone off in a larger "multiverse,"
each with different values for these parameters. Only those values that are
compatible with life could be observed by beings such as ourselves. For more
information, see James Glanz, "Celebrating a century of physics, en masse,"
Science, 284(5411): 34-35, 1999.
• Cosmic topology—Note 1 for chapter 5 discusses various topologies for our
universe. The April, 1999 issue of Scientific American suggests the universe
could be spherical yet so large that the observable part seems Euclidean, just
as a tiny patch on a balloon's surface looks flat. In other topologies, the universe
might be "multiply connected" like a torus, in which case there are
many different direct paths for light to travel from a source to an observer.
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