From: Spudboy100@aol.com
Date: Sat Apr 12 2003 - 22:37:54 MDT
April 12, 2003
A Brief History of the Multiverse
By PAUL DAVIES
YDNEY
Imagine you can play God and fiddle with the settings of the great cosmic
machine. Turn this knob and make electrons a bit heavier; twiddle that one
and make gravitation a trifle weaker. What would be the effect? The universe
would look very different — so different, in fact, that there wouldn't be
anyone around to see the result, because the existence of life depends rather
critically on the actual settings that Mother Nature selected.
Scientists have long puzzled over this rather contrived state of affairs. Why
is nature so ingeniously, one might even say suspiciously, friendly to life?
What do the laws of physics care about life and consciousness that they
should conspire to make a hospitable universe? It's almost as if a Grand
Designer had it all figured out.
The fashionable scientific response to this cosmic conundrum is to invoke the
so-called multiverse theory. The idea here is that what we have hitherto been
calling "the universe" is nothing of the sort. It is but a small component
within a vast assemblage of other universes that together make up a
"multiverse."
It is but a small extra step to conjecture that each universe comes with its
own knob settings. They could be random, as if the endless succession of
universes is the product of the proverbial monkey at a typewriter. Almost all
universes are incompatible with life, and so go unseen and unlamented. Only
in that handful where, by chance, the settings are just right will life
emerge; then beings such as ourselves will marvel at how propitiously
fine-tuned their universe is.
But we would be wrong to attribute this suitability to design. It is entirely
the result of self-selection: we simply could not exist in biologically
hostile universes, no matter how many there were.
This idea of multiple universes, or multiple realities, has been around in
philosophical circles for centuries. The scientific justification for it,
however, is new.
One argument stems from the "big bang" theory: according to the standard
model, shortly after the universe exploded into existence about 14 billion
years ago, it suddenly jumped in size by an enormous factor. This "inflation"
can best be understood by imagining that the observable universe is,
relatively speaking, a tiny blob of space buried deep within a vast labyrinth
of interconnected cosmic regions. Under this theory, if you took a God's-eye
view of the multiverse, you would see big bangs aplenty generating a tangled
melee of universes enveloped in a superstructure of frenetically inflating
space. Though individual universes may live and die, the multiverse is
forever.
Some scientists now suspect that many traditional laws of physics might in
fact be merely local bylaws, restricted to limited regions of space. Many
physicists now think that there are more than three spatial dimensions, for
example, since certain theories of subatomic matter are neater in 9 or 10
dimensions. So maybe three is a lucky number that just happened by accident
in our cosmic neighborhood — other universes may have five or seven
dimensions.
Life would probably be impossible with more (or less) than three dimensions
to work with, so our seeing three is then no surprise. Similar arguments
apply to other supposedly fixed properties of the cosmos, such as the
strengths of the fundamental forces or the masses of the various subatomic
particles. Perhaps these parameters were all fluke products of cosmic luck,
and our exquisitely friendly "universe" is but a minute oasis of fecundity
amid a sterile space-time desert.
How seriously can we take this explanation for the friendliness of nature?
Not very, I think. For a start, how is the existence of the other universes
to be tested? To be sure, all cosmologists accept that there are some regions
of the universe that lie beyond the reach of our telescopes, but somewhere on
the slippery slope between that and the idea that there are an infinite
number of universes, credibility reaches a limit. As one slips down that
slope, more and more must be accepted on faith, and less and less is open to
scientific verification.
Extreme multiverse explanations are therefore reminiscent of theological
discussions. Indeed, invoking an infinity of unseen universes to explain the
unusual features of the one we do see is just as ad hoc as invoking an unseen
Creator. The multiverse theory may be dressed up in scientific language, but
in essence it requires the same leap of faith.
At the same time, the multiverse theory also explains too much. Appealing to
everything in general to explain something in particular is really no
explanation at all. To a scientist, it is just as unsatisfying as simply
declaring, "God made it that way!"
Problems also crop up in the small print. Among the myriad universes similar
to ours will be some in which technological civilizations advance to the
point of being able to simulate consciousness. Eventually, entire virtual
worlds will be created inside computers, their conscious inhabitants unaware
that they are the simulated products of somebody else's technology. For every
original world, there will be a stupendous number of available virtual worlds
— some of which would even include machines simulating virtual worlds of
their own, and so on ad infinitum.
Taking the multiverse theory at face value, therefore, means accepting that
virtual worlds are more numerous than "real" ones. There is no reason to
expect our world — the one in which you are reading this right now — to be
real as opposed to a simulation. And the simulated inhabitants of a virtual
world stand in the same relationship to the simulating system as human beings
stand in relation to the traditional Creator.
Far from doing away with a transcendent Creator, the multiverse theory
actually injects that very concept at almost every level of its logical
structure. Gods and worlds, creators and creatures, lie embedded in each
other, forming an infinite regress in unbounded space.
This reductio ad absurdum of the multiverse theory reveals what a very
slippery slope it is indeed. Since Copernicus, our view of the universe has
enlarged by a factor of a billion billion. The cosmic vista stretches one
hundred billion trillion miles in all directions — that's a 1 with 23 zeros.
Now we are being urged to accept that even this vast region is just a
minuscule fragment of the whole.
But caution is strongly advised. The history of science rarely repeats
itself. Maybe there is some restricted form of multiverse, but if the concept
is pushed too far, then the rationally ordered (and apparently real) world we
perceive gets gobbled up in an infinitely complex charade, with the truth
lying forever beyond our ken.
Paul Davies, professor of natural philosophy at the Australian Center for
Astrobiology, is author of "How to Build a Time Machine."
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