The Standard Big Bang Cosmology (SBBC)
would rank as a successful scientific theory. Yet it has some rather peculiar
defects. To explain these difficulties some astronomers have introduced an even
more peculiar principle - the Anthropic Principle.
The Flatness Problem
Why is the geometry of the universe almost flat? This seems like a harmless enough
question. Observations, while not at all conclusive, lead us to believe that the
universe is very nearly flat. This "nearness" is so unlikely that it has lead
some to speculate that the universe is EXACTLY flat. This means that the
density of matter is precisely the critical density that we spoke of earlier.
Why? The reason is quite simple. If the universe had been any denser than the
critical value than it would have collapsed back on itself before now - we wouldn't
be here to wonder... On the other hand, if the earlier universe was not dense
enough then the galaxies would never have formed - space would have thinned out
too rapidly and again we wouldn't be here to wonder ...
Calculations have shown that the only way for our universe to have formed
and be this "close" to flatness is if the original conditions governing the
formation of the universe were very precisely tuned to better than one part
in 1049 ! This means that the universe must have started out close
to its critical density. If it was too dense then the universe would have stopped
expanding and re-collapsed: NO YOU AND ME! If it was not dense enough then the
universe would have expanded too fast for stars to form: NO YOU AND ME!
Another way of putting this is that the odds of the universe starting "randomly"
and ending up as we are today is about 1 in 1049 . These odds are
about as good as winning 7 consecutive lotteries with single tickets each time!
In fact it may even be less likely than this. If Roger Penrose is correct the
odds would be more like winning 150 lotteries in row!!
The Smoothness (or Horizon) Problem
A related problem has, ironically to do with the back ground radiation -
long considered crowning proof of the SBBC. The trouble is that the back ground
radiation is too uniform. Uniformity means that the universe was at the exactly
the same temperature everywhere at the end of the radiation dominated era. But,
this requires that every part of the universe be able to exchange heat and reach
equilibrium with every other part of the universe. The problem? By the time of
recombination the universe was too large to permit this. The only way the universe
could appear so smooth today is if it began in an incredibly ordered fashion which
again means that the initial conditions had to be tuned to almost incredible precision.
Proof for God's Existence? or The Anthropic Principle
Yes, the initial conditions of the early universe were so unlikely that it is
reasonable to believe that God must have ordered and guided the formation of the
universe. It wasn't chance at all and only a designing God could have created
the necessary initial conditions. Well, maybe.
On the other hand consider this. Even as unlikely as these odds are,
given enough time even the most unlikely event will occur. Another way of putting
it is anything that is not absolutely prohibited must eventually happen . This
is the tack that some scientists have taken. They go further to suggest that
the very fact that we exist to observe this universe means that it is the only
possible universe in which we could be. Infinities of universes have come and
gone - ours is the only one in which we would be conscious. There is nothing
at all surprising in the numbers. This is known as the Anthropic Principle .
Which do you find most reasonable? Perhaps the point is that a proof
of God's existence really seems to beg the question. Further, how do I as a
Christian astronomer find my way here? If I simply assert that God created the
universe I have gone no further than I was before. Of course God created the
universe - but how? How does God prepare so special a set of conditions that
our present universe unfolds?
The Inflationary Universe
In the late 1970's the young physicist Alan Guth heard about the flatness problem.
He was researching the early history of the universe when the temperature was
so extreme that all the forces and particles were essentially unified into one
particle, one force. What Guth began to realize was that as the universe expanded
and cooled there would be events much like phases changes in chemistry. For example,
when water turns to ice a phase change occurs and the structure of the water changes
rapidly. Guth hypothesized that as the universe cooled it underwent the equivalent
of a phase change. A consequence of this was extremely rapid expansion of the
universe from a point to the size of a grapefruit - all within about 10-35 s!! This phase has been called inflation . It very effectively solves the problem
of flatness and smoothness. Prior to inflation the universe was small enough to
reach thermal equilibrium. Also, any "wrinkles" or departures from flatness would
be smoothed out and the overall curve of the universe would be rapidly driven
down to zero. The Inflationary Model has now become an essential feature of the
BBC.
The Large Scale Structure of the Universe
The Inflation Model has many successes to its credit. It solves the problem of
flatness and smoothness as well as a number of more technical problems relating
to the existence of certain kinds of particles. One vexing problem, however, has
been a satisfactory explanation of the formation of galaxies, clusters, superclusters,
walls, voids, etc. Within the past 3 years a promising theory has been put forward. While the theory
is quite mathematical it does have a simple analogy. Imagine an ice cube forming.
As the ice freezes it is streaked by thin lines or sheets. These are defects in
the crystal structure. In the very early universe a similar process is thought
to have taken place. In the mid 1990's the Cosmic Background Explorer Satellite
(COBE) and more recently the Wilkinson Microwave Anisotropy Probe (WMAP)has succeeded in detecting the very minute deviations in isotropy of the background
radiation that could be attributed to the first nascent structures of the universe.
The pink "blotches" in this all sky image taken in the microwave region (after
a considerable amount of image reduction) show regions that are a few micro-degrees
warmer than the blue regions. We now have data that will allow us to test models
of "structure formation" within the very early universe.
|
A roll-over image comparing the resolution of COBE abd WMAP |
The early universe was extremely hot and perfectly symmetric. As it cooled
"defects" in the structure of space appeared. Sheets of immense size and mass
developed. These are believed to be very strange objects being essentially 2
dimensional or even 1 dimensional in the case of cosmic strings . Detailed calculations
show that such structures could form. Furthermore, they would represent regions
of strong gravitational attraction - the necessary seeds for the formation of
galaxies and the other large scale structures observed in the universe. In a
tantalizing way the largest structures in the universe may be the result of
quantum fluctuations during the big bang. We explain the largest structures
by using the physics normally reserved for a discussion of the smallest of structures!
The Inflation Model has many successes to its credit. It solves the problem of
flatness and smoothness as well as a number of more technical problems relating
to the existence of certain kinds of particles. One vexing problem, however, has
been a satisfactory explanation of the formation of galaxies, clusters, superclusters,
walls, voids, etc. Within the past 3 years a promising theory has been put forward. While the theory
is quite mathematical it does have a simple analogy. Imagine an ice cube forming.
As the ice freezes it is streaked by thin lines or sheets. These are defects in
the crystal structure. In the very early universe a similar process is thought
to have taken place. In the mid 1990's the Cosmic Background Explorer Satellite
(COBE) and more recently the Wilkinson Microwave Anisotropy Probe (WMAP)has succeeded in detecting the very minute deviations in isotropy of the background
radiation that could be attributed to the first nascent structures of the universe.
The pink "blotches" in this all sky image taken in the microwave region (after
a considerable amount of image reduction) show regions that are a few micro-degrees
warmer than the blue regions. We now have data that will allow us to test models
of "structure formation" within the very early universe. 
Seeds:
Chp18
