GHZ and God
(Galactic Habitable Zone)
The most basic concept that we present in the Does God Exist? program is that science and faith are friends and not enemies. Those in the religious and scientific establishments who approach the two areas of study as enemies do a huge disservice to both. One of the problems that we face in this work is staying up to date with all of the new discoveries which impact the relationship of science and faith. What is rewarding about staying up to date is that new discoveries and understandings in science always add support for evidence of the existence of God. Sometimes this happens by destroying mistaken scientific concepts that had been opposed to the existence of God, and sometimes it destroys a mistaken religious idea.
In the 1960s and 1970s, there were a number of scientific proposals which seemed to suggest that the nature of the cosmos was such that there should be massive numbers of earth like planets throughout our galaxy and certainly throughout space. In many college classrooms, students were exposed to the Drake Equation, a mathematical statement of odds of chosen variables necessary for life. One textbook wrote it this way.
N = RfnghkL where N is the number of civilizations in our galaxy, R is the rate at which stars form, f is the fraction of these stars that have planets, n is the number of planets in the solar system that are suitable for life to survive, g is the fraction of these planets on which life actually arises, h is the fraction of these lifeforms that develop intelligence, k is the fraction of the intelligent species that choose to communicate, L is the lifetime of civilization. (The symbol letters have been changed to assist the non-science person in comprehension.)
Also presented in 1966 was a book by Carl Sagan and I. S. Slavsky entitled Intelligent Life in the Universe in which they suggested that there were thousands of inhabited earth-like planets in our Milky Way galaxy. All of this was gobbled up by UFO and SETI proponents as proof of the validity of their claims. Many atheists used these proposals to ridicule any notion that human or any kind of life was the product of intelligence and planning.
Since those early days there has been a wide range of discoveries in space and on the earth. Some of these discoveries have debunked claims of the origin of life and how prevalent life can be expected to be in the cosmos. Studies of the earth's crust, for example, have shown that the assumptions of the Miller-Urey experiment are totally incorrect. That experiment assumed anaerobic conditions existed on the primitive earth, but we now know there was a great deal of oxygen. The experiment also assumed that methane, ammonia, and water vapor dominated the earth's early atmosphere with little or no carbon dioxide. Strong evidence has been found that carbon dioxide was the dominant gas in the earth's early atmosphere and that methane and ammonia were not present in large quantities.
Another field of rapid scientific advancement has been in studies of the conditions of various geographys of the solar system and the galaxy in which we live. Our understandings of galaxies have grown enormously during the past fifty years. When galaxies were first discovered, they were assumed to be stable islands of stars floating independently in space. New discoveries have shown us that galaxies are dynamic interacting changing objects, not stable dead regions of space. In the picture to the left, different things are happening throughout the galaxy. The center of the galaxy, called the bulge, is made up of a very active part of space. Most, if not all, galaxies have at least one black hole in this area, and massive energy processes are taking place in this area.
The processes that operate in a galaxy become less active as one moves out away from the bulge. That means that there are very few heavy elements in the outer regions of galaxies, there are no planets made of rock, and no life could be found in such an area. Astronomers have now given four prerequisites for complex life to exist in a galaxy:
The above drawing shows where such conditions exist within the Milky Way galaxy. The green area where these conditions exist is called the Galactic Habitable Zone (GHZ). In our galaxy the GHZ is 25,000 light years out from the center of the galaxy. If that was all there was to it the green area would hold as many as 10% of all of the stars in the galaxy. New research has shown that forces along the galactic plane make the GHZ even smaller. Because most of the mass of the galaxy is along the green zone in the side view, there are huge gravitational forces pulling on any object in that zone. This makes that zone unstable. This shrinks the GHZ by a significant amount.
As surveys of other galaxies in space has continued, it has become obvious that many galaxies have no GHZ at all. Some are too young and are totally dominated by hydrogen with no heavy elements having formed yet. Others have massive amounts of astronomical explosions taking place making them too unstable to support a life-bearing planet. Planetary astronomers have developed a model of a Solar Habitable Zone (SHZ). This is the same concept as the GHZ, but it deals with the kind of star, its stability, the distance it is away from a planet, whether heavy elements are in the system, and a variety of other newly discovered requisites for a life-bearing planet to exist in the right geographic place. Even with all of this we are a long way from having a place where life can exist. The GHZ and SHZ do not include such things as planet size, orbital eccentricity, rotation rate, tilt, atmospheric composition, magnetic field, and similar factors. They also do not deal with the creation of life and all that it takes to sustain life.
All of this simply shows that creating a place for life to exist is far more difficult than anyone could have imagined 50 years ago. Instead of the Drake Equation containing seven variables, it is more realistic that it contain twenty-five to one hundred variables. Long after Sagan and Slovsky wrote their book, Slovsky wrote another manuscript titled, We Are Alone. The number of things we now know need to exist for life to survive on a planet has grown to such an extent that suggesting that there are massive numbers of inhabited planets throughout space is not a reasonable idea.
It is important to notice that all of these numbers and calculations are based upon the assumption that chance is the only operative in what happens. If intelligence is added to the discussion then the numbers are meaningless. When Francis Crick (the Nobel Prize winning biologist) wrote his book on the origin of life (Life Itself: Its Origin and Nature), he showed that it was not possible for life to occur by chance. Recognizing that intelligence was involved, Crick suggested that alien astronauts seeded the cosmos with packets of DNA--something called directed panspermia.
We applaud Crick for being willing to think "outside the box," but we would also suggest that there is a great deal of evidence that the intelligence was not a physical alien but rather God. The evidence of a beginning, of there being a cause of design features seen in all life, and man's uniqueness as being in the image of God, all provide additional evidence that God is the Source of all life, wherever it may be.
"In the beginning God created the heavens and the earth" may sound pretty simple, but the more we discover about space and about the earth, the more evidence there is that God is the author and creator of all we see.
Back to Contents Does God Exist?, NovDec04.