Astronomy has come a long way in the last 100 or so years. We’ve gone from thinking the Milky Way galaxy is the only galaxy to Edwin Hubble discovering that other galaxies are out there to the knowing of over 100 billion galaxies. But just as our universe is fine-tuned for life to exist so also is our solar system is fine-tuned for advanced life to exist. To sum up the fine-tuning of a solar system, there are 137 parameters that have to occur in a planetary system for advanced life to exist (the probability that this would occur is 1 in 10^112 (10 to the power of 112)) and there are 140 parameters for a star that have to occur for advanced life to exist (the probability that this would occur is 1 in 10^108 (10 to the power of 108)). But wait, there’s more! Both our galaxy and the location of our solar system within the galaxy is also fine-tuned for advanced life to exist. There are several factors to consider.
The galaxy that our solar system resides in is called the Milky Way, and it is of a shape that is called a barred spiral galaxy. In regards to the shape of the galaxy, J Warner Wallace, in his book God’s Crime Scene: A Cold-Case Detective Examines the Evidence for a Divinely Created Universe, sums it up this way:
THE SHAPE OF THE MILKY WAY IS FAVORABLE TO LIFE
The Milky Way galaxy is an elegant spiral, while the vast majority of galaxies (approximately 95% percent of them) are elliptical or irregular. This spiral shape makes a difference. If our galaxy were larger and irregular (rather than spiral), its nucleus would release destructive radiation (and matter) harmful to the existence of life. On the other hand, dwarf elliptical galaxies are metal-poor (metals are heavy elements) so they are unlikely candidates for life. As it is, the spiral shape encourages the early formation of stars before this formation can be threatened by the presence of heavy elements in the interstellar environment.
He then quotes Astrophysicist Hugh Ross in his footnotes:
In elliptical galaxies star formation ceases before the interstellar medium becomes enriched enough with heavy elements…The problem with large irregular galaxies is they have active nuclei. These nuclei spew out life-destroying radiation and material. Meanwhile, most small irregular galaxies have insufficient quantities of the heavy elements essential for life.
Another way that Hugh Ross says this is that if the galaxy type is too elliptical, the star formation would cease before sufficient heavy element build-up for life chemistry. And that if the galaxy type is too irregular, the radiation exposure on occasion would be too severe and heavy elements for life chemistry would not be available.
In addition to the shape of the galaxy, we also have to consider is the size of the galaxy. The largest known galaxy is a barred spiral galaxy named NGC 6872, and it is five times the size of our Milky Way galaxy. There are a number of galaxies that are larger than our Milky Way, and a number that are smaller. Astrophysicist Hugh Rose says that if a galaxy size is too large, the infusion of gas and stars would disturb the star’s orbit and ignite too many galactic eruptions. And if the size of the galaxy is too small, there would be an insufficient infusion of gas to sustain star formation for long enough time. He also reports that if the galaxy mass distribution if too much in the central bulge, that a life-supportable planet would be exposed to too much radiation. And that if the galaxy mass distribution is too much in the spiral arms, that a life-supportable planet would be destabilized by the gravity and radiation from adjacent spiral arms.
J Warner Wallace sums up the information:
THE SIZE OF THE MILKY WAY IS FAVORABLE TO LIFE
The Milky Way is also within the proper size ranges to permit life; it is large and spare enough to prevent gravitational disruption from (and collisions with) other star systems, and yet small and dense enough to allow star formation from gas infusion.
Hugh Ross says that there are 200 parameters for a galaxy that each have to fall within a required range for advanced life to exist. The probability for all 200 parameters to occur within a galaxy is 1 in 10^135 (10 to the power of 135). Mind you, the number of subatomic particles in the known universe is 10^80.
We’ve covered the shape and size of a galaxy. But the location of the galaxy in relation to other galaxies is also important. Galaxies can congregate in clusters.
J Warner Wallace says this:
THE POSITION OF THE MILKY WAY IS FAVORABLE TO LIFE
In addition, the Milky Way is separated by just enough distance from other large galaxies and dense galactic clusters to guard against gravitational interference.
Hugh Ross says that if the galaxy cluster type if too rich, galaxy collisions and mergers would disrupt solar orbits. And that if the galaxy cluster is too sparse, there would be an insufficient infusion of gas to sustain star formation for a long enough time. He also says that if a galaxy’s location is too close to a rich galaxy cluster, the galaxy would be gravitationally disrupted. And that if a galaxy’s location is too close to very large galaxy(or galaxies), the galaxy would be gravitationally disrupted. Furthermore, if the galaxy’s location is too far away from dwarf galaxies, that there would be an insufficient in fall of gas and dust to sustain ongoing star formation.
All in all, Hugh Ross says that there are 99 parameters for galaxy clusters that each have to fall within a required range for advanced life to exist. The probability for all 99 parameters to occur within a galaxy cluster are 1 in 10^53 (10 to the power of 53).
We’ve looked at the shape and size of a galaxy, as well as the location of that galaxy in relation to other galaxies that must be fine-tuned for advanced life to exist. Now let’s look at another factor: the location of a solar system within the galaxy. This is called the Galactic Habitable Zone. J Warner Wallace describes it like this:
Our position within the Milky Way is of critical importance. Our proximity to the spiral arm of the galaxy protects us from the core radiation at the center of the Milky Way. In fact, our distance from this center is critical for a number of reasons. If we were farther from the core, there wouldn’t be enough heavy elements to make terrestrial planets; if we were closer, the radiation would be too severe and the gravitation influence of the numerous stars would be too strong.
Hugh Ross says that if the parent star distance from the center of the galaxy is farther, the quantity of heavy elements would be insufficient to make rocky planets and that there would be the wrong abundances of silicon, sulfur, and magnesium relative to iron for appropriate planet core characteristics. And that if the parent star distance from the center of the galaxy were closer, the galactic radiation would be too great, the stellar density would disturb planetary orbits, and that there would be the wrong abundances of silicon, sulfur, and magnesium relative to iron for appropriate planet core characteristics.
But it’s not just the distance from the galactic core that is critical, it’s also the proximity to the spiral arm. Hugh Ross says that if the parent star distance from the closest spiral arm is too large, the exposure to harmful radiation from the galactic core would be too great. In addition to being not too far and not too close to the galactic core, we are in just the right spot between the spiral arms.
We also have to consider the star’s rotation around the galactic core. Our sun revolves around the galactic core at the same rate as the spiral arms. This helps us from crossing over into the spiral arms. If our Sun’s rotation were more elliptical, like 95% of the stars, then we would cross over into the spiral arms.
All of these factors, as well as those covered in my previous blog, and many more, have to be taken into consideration. Of the fine-tuning of a solar system and of a galaxy that is necessary for advanced life to exist, Hugh Ross has compiled a list of 402 quantifiable characteristics that must fall within narrow ranges. A slight increase or decrease in the value of each characteristic would impact that possibility.
I’d also recommend watching The Privileged Planet by astrophysicist Guillermo Gonzalez.
In my next blog, I will cover the fine tuning of a planet that is necessary for advanced life to exist.