The Necessity of Cosmic Design
Back in my younger years when I was an atheist and arguing that the cosmos
had to be an accident, one of my suggestions was that there is too much
waste in the cosmos to believe that any being with intelligence and purpose
could have created it. "All you need is the sun and the earth," I said.
"All the rest of the creation is superfluous fluff." As the years have
gone by and I have become better educated, I have realized that what I called
"fluff" is vital to our survival. We now know that the tilt of the earth
on its axis is only possible because of the moon.1 The stability
of the elliptical orbit of the earth around the sun is only possible because
of the effects of the other objects in the solar system.
As astronomers search the galaxy for other solar systems, more and more
factors are being found which are directly related to the ability of a planet
to sustain life. New data from studies of galaxies and star systems are
also showing us that the complexity of life supporting planetary systems
is far greater than anyone imagined even a few years ago. In simple terms,
there are two things that must exist--the right material to produce and sustain
life and protection from those things that would destroy life. Both of
these are more difficult to achieve than anyone would have imagined even
five years ago.
GHZ
GHZ is an abbreviation for galactic habitable zone. It has been known for
a long time that certain regions of our galaxy could not sustain a stable
solar system capable of supporting any kind of life. The cores of galaxies
contain black holes and areas of enormous energy outbursts that would produce
too much instability for the stability necessary for life to exist. As
new studies are being released concerning planets orbiting other stars,
it is becoming obvious that something called metallicity is critical to
being able to produce life and the places where it can exist. Metallicity
is the ratio of metal atoms to hydrogen atoms in a star. Metallicity determines
whether planets can exist, what size planets can form, and what their properties
will be. Every star that a planet has been found going around has a metallicity
close to our sun, and no planets have been discovered around any star with
25% of the value of the sun or lower. Recent studies of our Milky Way show
that only 2% of the stars in our galaxy possesses metal richness that would
allow planets to form.2 Each of the 67 planets that have been
found orbiting other stars are orbiting metal-rich stars.3 High
metallicity will also prevent a life-sustaining planet from existing due
to stronger gravity, more volatile compounds, and more interference between
stars.
The interesting thing is that studies of the Milky Way and of other galaxies
show that metallicity varies in the different parts of galaxies. Moving
out from the cores of galaxies, metallicity decreases at about 17% every
14,000 light years. This means that the part of the galaxy where the materials
would exist to produce life and a planet to put it on is extremely small.
Studies of globular clusters which have stars with metallicities of about
25% have not found any planets at all.
Having the right materials is only half of the GHZ story. The other
part of the story is being protected from dangerous objects in space. Galactic
nuclei, super novas, gamma ray bursts, and black holes all hold the potential
to destroy terrestrial planets and any life that might exist on them. Very
high metallicities exist near the cores of galaxies, producing black holes.
Some kinds of galaxies have large numbers of gamma ray bursts, making them
inhospitable for life. When all of these factors are more fully understood,
it is obvious that the GHZ is going to be a very small percentage of the
volume of the entire galaxy.
CHZ
CHZ is an abbreviation for circumsteller inhabitable zone. Like the GHZ,
it is the region around a star where a life-supporting planet and where life
itself can exist. This concept has been understood longer than the GHZ, but
in recent years, more data has shown that the earlier proposals about CHZ
were more valid than anyone knew. The earlier proposals were that the CHZ
was the zone where liquid water can persist for a very long period of time.
As more and more data has been collected, the necessity of water for life
to exist has become more and more obvious, and it is now clear that water
must exist in the liquid state. Studies of Venus have shown that water will
boil off of planets too close to the sun and be lost to space due to not only
the closeness of the sun, but also of a runaway greenhouse effect. Planets
outside the CHZ will be frozen over and again prevent life forms from being
able to survive. Green area is the habitable part.
Studies of planets orbiting other stars have shown the shape of planetary
orbits are a major issue. A vast majority of the planets that have been
discovered have elliptical orbits that are so eccentric that the planets
spend part of their orbit outside the CHZ, part of it inside the CHZ, and
a relatively small amount of its orbit in the CHZ. These planets not only
could not have life on them, but they would radically alter any other planets
that might be in the CHZ.
Over the past 50 years, we have seen many claims that life is abundant
in the cosmos, with popularizers like Carl Sagan maintaining numbers in
the thousands when referring to inhabited planets in our own galaxy. As
more data has been obtained, and more has been understood about the dynamics
of the solar system and the galaxy, it has become obvious that the conditions
needed to have a planet that can sustain life are very hard to come by.
The miracle of the planet Earth is just that--a miracle. Our planet is
not one of many places where an accidental series of reactions produced a
life-supporting planet and then life itself. Complex life is incredibly
rare in the galaxy by all measurements available to us, and that rareness
suggests that intelligent purpose and design is part of the process that
makes it happen wherever that might be.
1. Neil Comins, What If There Were No Moon (New York: Harper
Perennial, 1995).
2. Hugh Ross, "Exotic Life Sites," Facts for Faith, page 22.
3. Ibid.
--Reference: "Refuges for Life in a Hostile Environment," Guillermo
Gonzales, Donald Brownlee, and Peter Ward, Scientific American, October
1, 2002, page 60-67.
--John N. Clayton
Back to Contents Does God Exist?, MayJun02.