What Happened before the Big Bang?
Adnan balboa19@idt.net
Sat, 27 Sep 1997 02:43:53 -0700 (00875375033, 3.0.1.32.19970927024353.006c2854@idt.net)
Steve Stokes:
>Well they don't have much choice...there has always been a universe,
>eternally.
>I define the universe as the "set of all things". Even if the set of all
>things where empty, i.e., there are no things in the universe, the universe
>would still conceptually exist.
>When would there have been a time when the set of all things did not exist?
Adnan:
I do not know where Steve Stokes studied his physics or astronomy. Sadly,
he even doesn't' know what is the "universe." Haven't he ever heard
something like "universe is some 10 billion years old", or that the
"universe is expanding"?
Anyway, I recommend that he should check out the site :
"Ask the Astronomer"
http://www2.ari.net/home/odenwald/qadir/acosm.html
It has answers to 100 questions about Big Band and the universe.
Here I quote few of them which Steve should consider.
**************************
If the universe is finite, what is outside it?
When we stand outside and look at the sky, it is hard to believe that there
shouldn't be some very simple explanation for what we are seeing. But after
a century of delving deeply into the laws of physics, we now know that much
of the underpinning is probably destined to remain intuitively
incomprehensible. There are no known simple explanations for why nature
obeys quantum
mechanical laws, why special relativity is the only explanation for the
phenomena seen at high speeds. And then there is the universe itself.
Einstein's theory of general relativity is the only existing theory we have
that guides us in thinking about physical space. So far as possible, it has
been put to a variety of diverse tests and found to give an accurate
picture of how gravity operates. But it asks us to also forget about common
sense
in the particular domain in which it works. General relativity is the
premier theory of how gravity works. It says that space and time are a
4-dimensional 'thing' whose overall shape is dictated, nay, defined by
gravitational fields themselves.
General relativity shows that if we looked at a spacetime whose
3-dimensional space sections were finite ( the case of our universe as a
closed, finite one destined to recollapse in the far future) we would
discover that the paths of particles and light rays would be closed curves.
If the universe could hold this particular spatial shape long enough as in
Einstein's original cosmological model in 1917, a rocket could
circumnavigate the universe by always traveling exactly straight ahead.
There is no edge to such a space for much the same reason that if surveyors
were to map the 2-dimensional surface of the earth they, too, would not
find an edge to it ( well, there are of course
the Atlantic and Pacific Oceans, but I think you know what I mean). Gravity
has distort 3-dimensional space to such a degree that it has seamlessly
folded over itself through the fourth dimension to form a closed spatial
universe. This business only sounds strange to us because we have never
experienced anything other than life in a 3-dimensional world since we
emerged out of the oceans 500 million years ago.
Since the mathematical space in which this finite, closed universe is
embedded is outside our physical spacetime, it will never contain events
that can be experienced by anyone within our spacetime....ever. This means
that since we can never observe this exterior space, it lies outside
science. On the other hand, it does not lie outside mathematical deduction
since mathematics is
controlled by logical necessity not physical testability.
There are many philosophical attitudes that can be taken about this
question. None of these can be strictly proven on the basis of hard data
since the arena of interest lies outside of our spacetime. The first
attitude is that our spacetime, our universe, is absolutely all there is.
It extends beyond our
visible horizon, there is no 'embedding space' to account for because it
simply doesn't exist. The second attitude is that nothing is forbidden in
nature so if a mathematician can imagine it, it actually exists. The
embedding space is as physically real as our spacetime, and in it, all
possible universes
exist including ones with drastically different physical laws, particles,
forces and dimensionality.
The difficulty in thinking about the embedding space is that we persist in
asking "What is happening in it?" and "How do events evolve in time?" when
in fact time is only a phenomenon experienced when one of the 4-dimensional
spacetimes that inhabit it is sliced in a particular way. Each of these
closed universes is like a coconut floating in the vaster ocean of the
embedding space. From the perspective of the embedding space, all
structures in it are seen from their timeless perspective. They are not in
the process of becoming or changing, they simply exist.
If you have trouble visualizing what this embedding space looks like, you
are in good company. John Wheeler confesses in his 1990 book A Journey into
Gravity and Spacetime that "I confess I have never been able myself to
picture directly this mythical, flat, infinite 4-space and the 3-space
universe embedded in it...This flat, 4-dimensional space has nothing
whatsoever directly to do with our real physical world as spacetime, even
though that also is four-dimensional. Almost all of this [embedding] space
is totally out of our reach, quite untouchable, pure talk... Only
[3-dimensional space] itself is real [to us]".
I know this sounds as if I am dodging the question by playing on the
limitations of the human mind, but these limitations seem to be real. The
human mind is perpetually puzzled by the rules of the quantum world, the
constancy of the speed of light for all moving observers, and a host of
other properties of the physical world. According to general relativity,
the universe is a 4-dimensional thing which requires us to visualize it as
a complete 4-dimensional object. You can never appreciate a sphere by only
looking at one of its circular cross sections.
********************
Does infinity mean that space goes on forever?
Infinity in physics isn't just confined to a spatial definition. There are
many conditions which our mathematics say lead to 'infinities'. Generally,
physicists consider infinities cropping up in their theories a sign that
they have done something wrong and the theory is no longer useful.
Theoreticians spent decades getting rid of 'infinities' in their field
theory of quantum electrodynamics before they developed 'QED' in the late
1940's which no longer gives infinity as an answer, but provides perfectly
finite answers that agree with experiment to one part in a trillion!
As for cosmology, it may turn out that the gravitational field of the
universe is strong enough to deform space into a closed shape. This would
mean that no matter how old the universe gets, space will never be
infinite, but like the surface of a sphere, will close back upon itself
making a surface
with a finite area ( 3-D volume). If this is the case, a true spatial
infinity in nature doesn't exist and is only a mathematical fiction. There
are, however, cosmological models that predict the universe will grow in
size without bound so that after the passage of eternity ( an infinite
number of years) the size
of the universe will become infinite. This means that space goes on
forever. The way that one interprets this physically, however, is that even
at the moment of creation, space-time was already infinite! Our experience
of space unfolding to become infinite is just a limitation we have that
prevents us from seeing space and time as a complete 4-dimensional object
which has an infinite
size.