Formation of the Sun and Solar System

We as scientists do not fully understand all the details about the history of the universe or how the universe works. I don't think that statement would surprise anyone. Yet, some Christians will portray certain scientific proposals as being completely untrustworthy because there are certain processes and details we can't fully explain. Its as if I were to try to explain how an internal combustion engine works but because there are some details I don't understand you were to claim that my entire explanation is false.

In my previous post I quoted a reader who stated, "You did not address the supposed problems with Star Formation and Planet Formation and Moon Formation. Problems include: the Angular Momentum of our sun, the Accretion of gas clouds, and the Accretion of planets and moons. In line with this is the distant mature galaxies." This reader then directed me to a video on the web where a Christian who believes the universe is only a few thousand years old (a young earth creationist) brought up these and other supposed problems in an attempt to discredit the current scientific understanding of how stars, planets, and our solar system formed. The lecturer was implying that since there were some unsolved problems with our understanding of the formation of these objects, then the entire scientific proposal of star and solar system formation was unreliable. I disagree with the lecturer and the premise of the question. From my perspective it is possible that the overall big picture about a scientific process could be completely reliable and substantiated even if some of the details are not yet understood. I would think that most reasonable people would agree with me.

Let me give a very simple explanation of how scientists think our sun and solar system was formed and why we think our conclusions are valid. The universe is filled with regions of interstellar dust and gas which we can observe in our telescopes. The dust and gas is attracted to other dust and gas by gravity and so it will coalesce into denser regions. As the gas coalesces in the most dense region of the gas cloud its gravitational attraction to other objects becomes greater thus sucking in more and more gas to the dense region. As the gas falls into this denser region it gains energy (just like a falling ball gains energy) and this energy is found in the form of heat. The gas continues to heat up and becomes so hot that eventually a nuclear reaction starts at the center of the dense gas region. This ball of gas with a nuclear furnace at its core is a new star.

Around the star is still a disk of dust and gas that did not fall into the star by gravity. However the gravity from the star and the momentum of the gas causes it to swirl around the star. The dust also begins to coalesce into clumps that grow in size as their gravitational attraction increases. Clumps of dust eventually grow larger to maybe a meter in size and then by more gravitational attraction continue to clump together and grow larger and larger into planets. Some planets are composed of dust and debris that is rocky and become planets like the earth and Mars, and some are composed mostly of gas and become the gas planets like Jupiter and Neptune. Throughout the history of the solar system these planets do not stay in a single constant orbit but actually move farther and closer to the star as gravity shifts their positions. Finally, we end up with a solar system with a star burning in the center and planets orbiting the star.

How do we know all of this? First of all, we understand the scientific principles from physics that control these processes so we can run computer simulations of the various stages of solar system and star formation. This computer simulation compiled from a number of various scientific groups shows a very beautiful model of the formation of the solar system after the sun was formed at the center. Notice how detailed the simulation is and how well it works. The overall big picture produces a solar system like ours. We understand the big picture with no problems at all.

The second way that we know this is a correct model of how stars and solar systems form is that we see many various stages of star and solar system formation throughout the universe. We see regions of dust and gas where there are many very new and young stars. We see young stars with planar dust clouds surrounding them, some of the clouds having regions where we believe planets have recently formed even as the dust still exists and is forming more planets. Critics will argue that we have never actually seen a star form so we don't really know that our models are correct. Let me provide an analogy of the situation to illustrate that we can understand the complete process even if we haven't observed a small part of the process. Suppose an alien race visited the earth for a few hours and stealthily observed humanity. The aliens saw people of all ages including infants, toddlers, teenagers, elderly, and maybe even a pregnant woman or two. But because the actual birth process is so short compared with a human lifetime the aliens never actually see a birth in their short visit to earth. Would it be valid for the aliens to postulate that humans are born, live, and die even though they never saw the very brief moment of birth? Of course that would be a valid hypothesis. This is exactly analogous to the situation we observe when we study the cosmos. We see stars and solar systems in all stages of development, young, middle aged, and old. Even though we haven't seen a birth, it is perfectly valid and reasonable to infer their existence from all the observations.

Now let me get back to the reader's question. If you looked at the video linked above you will see how much we do understand and can model about the development of the solar system. Our computer models match the observations we make of the universe including observing stars and solar systems in various stages of development. But even though our models and observations agree with each other and give a consistent picture, there are a few details we don't fully understand and can't fully model. Of course, we have possible ideas about how to fix these problems, but the solutions are not yet completely satisfactory. Some of the problems include the things mentioned by the reader, though other things mentioned by the reader have already been completely solved in principle. We don't yet fully understand a few details of how the first meter sized objects are formed from dust (the accretion of asteroid sized objects). Once we get objects that size we do understand the accretion of planets contrary to the reader's statements. We do pretty much understand the accretion of gas clouds with very few problems so that is not really a very big issue. We do also pretty much understand how our moon was formed when a large object collided with the earth. There are some details of that collision not fully worked out but the overall picture works very well and describes what we see.

The angular momentum of the sun seems to now be fairly understood. As the gas of the sun coalesced it would have spun faster and faster to conserve angular momentum. A naive estimate would then conclude that the sun should have a lot more angular (rotational) momentum than it does. But we know of processes that remove angular momentum like interactions with magnetic fields and in fact we see evidence of angular momentum reduction of stars throughout the universe. The other "problem" brought up by the reader is that we've discovered two distant (and ancient) galaxies that appear to be more mature than first predicted. Most ancient galaxies are not so mature and we don't fully understand why two (out of millions or billions) are more mature than we originally thought could be possible.

So out of all the problems mentioned by the reader, they seem to all have plausible explanations, some of them have actually been resolved, and one or two remain unsolved and are still being studied. None of the problems are insurmountable or cast any doubt on the overall big picture of stellar and solar system formation that works so well in our computer models and agrees with the various ages and stages of star formation and solar system formation that we see throughout the cosmos. If you read literature and web sites written by young earth creationists you might think that these problems are much bigger than I have portrayed them because the young earth creationist will sometimes quote a scientist who is talking about one or more of these unresolved problems. The scientist may say something like, "We don't really understand planet formation" which sounds quite indicting. Within context, however, the scientist will mean that maybe we don't fully understand how the first meter-sized asteroids were formed but the quote will be portrayed as making the whole process seem unreliable and not understood. I guarantee that is not the intent of the statement made by the scientist.

Finally, I'd like to comment on our remarkable solar system. We live in a solar system unlike any that we have discovered so far. The large gas giant planets like Jupiter and Saturn are far from the earth and orbit the sun in nearly circular orbits which is necessary for our existence. Our single large moon that likely formed through an unusual collision with a Mars-sized object is also necessary and probably rare. A colleague of mine at the University of Oklahoma studies the formation and development of solar systems. He develops computer simulations that try to model the formation of a solar system like ours. He finds that it is possible to do so, but it is very challenging and requires special initial conditions and circumstances. It requires migration of some of the gaseous planets toward and away from the sun over billions of years and probably the existence of another planet early in our solar system that was ejected out of the solar system millions or billions of years ago. In other words, we need a solar system like ours for us to live and thrive on earth, and although our solar system can be modeled by our computer simulations, it requires very specific fine-tuning to get it to work. I was talking with my colleague about this and I said that to me as someone who believes in God it is amazing all that had to happen to create a solar system that we could thrive in. His response was that to him as a scientist it was equally amazing. The heavens declare the glory of God. They do so through God's creation and through the remarkably finely-tuned development of the universe, sun, and solar system over the billions of years God used to create.