Today’s New Reason To Believe

by Jeff Zweerink

I enjoy traveling, whether taking a trip to visit relatives for Christmas or a summertime vacation to witness the beauty of creation. However, any trip with my family (wife and five kids) requires lots of preparation in order to achieve success. Clothes must be packed, bills paid, lodging reserved, and the list goes on. These tasks must also be accomplished in the proper order. Trying to pack clothes after a trip begins is highly unadvisable. Likewise, when the solar system formed, certain events needed to take place before others in order to establish a life-friendly cosmic habitat.

As described in Rare Earth, advanced life depends on plate tectonics. In order for a planet as small as Earth to experience long-standing plate tectonics, it must have a large supply of radioactive nuclei that will emit the heat that drives tectonic activity. These nuclei form in the massive supernova explosions that occur as stars die. However, like packing for a trip, the nearby supernovae that seed the planets with radioactive material must take place at the proper time. If they occur too early (or too close) the supernovae might blow the solar nebula apart and prevent the formation of the solar system. If they occur too late, the planets will have already formed without incorporating the necessary radioactive elements. I have detailed some of the evidence about this fine-tuning in a previous TNRTB.

Astronomers and geophysicists have discovered evidence of such “fine-timing” by looking at meteorites that formed in the early solar system and recently landed on Earth. Some of these meteorites, known as chondrites, record the conditions present in the early solar system because they have not been melted or otherwise processed since their formation. They include different components such as calcium-aluminum inclusions (CAIs) and chondrules. According to most models that incorporate finely timed supernova explosions in the early solar system, these components form at different times. In particular, the chondrules should form later than the CAIs.

The research measured ages of the chondrules at 1.66 million years younger than the CAIs. This number supports models where the aluminum enters the solar nebula shortly after a nearby supernova explosion occurs. It also provides further evidence that the solar system formed between 4.57 and 4.56 billion years ago. The proper timing of events in the early solar system ensured that Earth had all the necessary “clothes” so that the life-essential plate tectonics would continue for the duration of Earth’s trip through this universe.

David H. Rogstad, Ph.D.

Since its inception 22 years ago, Reasons To Believe has held the position that our Solar System is extremely unusual, probably unique in the observable universe. We base this view on the Solar System’s various characteristics required to provide the long-term conditions necessary for life in general and especially for the advanced life on Earth. On the other hand, it is the contention of the naturalistic scientific community, for the most part, that there is nothing unique about our Solar System or Earth. This viewpoint is usually referred to as the Principle of Mediocrity (an extension of the Copernican Principle), the idea being that since the Earth is not at the center of the Solar System, we are not special like once thought. In the words of Carl Sagan from his PBS series Cosmos,

For most of human history we have searched for our place in the cosmos. Who are we? What are we? We find that we inhabit an insignificant planet of a hum-drum star lost in a galaxy tucked away in some forgotten corner of a universe in which there are far more galaxies than people.

While this is the prevalent view, there are some nontheist scientists who have argued an approach not too different from that of Reasons To Believe; namely that Earth is rare. However, the growing body of evidence for exoplanets—planets orbiting stars other than our Sun—seemed to provide support for the non-uniqueness of our Solar System.

A recent report on computer simulations of the birth of planetary systems appears to put the ball back into the “uniqueness” court. E. Thommes and his colleagues at Northwestern University examined the more than 250 planetary systems, including our own, and developed a sophisticated model for the formation of planetary systems from beginning to end. They have numerically simulated this model using a variety of boundary conditions to reproduce results that are in agreement with some of the key trends observed in the properties of the exoplanets. These same simulations demonstrate that our own Solar System represents a rare case where the gas giants form but do not migrate into the inner parts of the planetary system, and all the planets achieve stable circular orbits. In the words of one of the authors,

We now better understand the process of planet formation and can explain the properties of the strange exoplanets we’ve observed. We also know that the Solar System is special and understand at some level what makes it special.

Undoubtedly, skeptics will remain and certainly this model will require development and improvement, but RTB scholars remain convinced that the more we learn about the special characteristics of our Solar System, the more we will discover the “fingerprints” of its Designer.

David H. Rogstad, Ph.D.

What if we could exchange our Sun for another star? Would we still have an environment that supports advanced life? Or would the change prevent the continuation of that life?

A few months ago, Hugh Ross discussed efforts by various astronomers to find a twin of the Sun using six different star properties. Only four or five stars out of more than 100,000 had characteristics similar enough to fit this category, and those few still had differences that disqualified them. I was so impressed with this work that I voiced the opinion on our Creation Update webcast that it wouldn’t surprise me if, as more data came in, the uniqueness of the Sun would be more firmly established, providing us with another fine-tuned characteristic for our solar system. (Hugh made the same argument.)

My enthusiasm was somewhat dampened, however, by a soon-to-be-published study by J. Robles and colleagues where they performed a comprehensive comparison of the Sun to other stars. In this study the authors established 11 relatively independent star properties that are thought to affect whether a planet orbiting the star can support simple (as opposed to advanced) life for a short time (as opposed to simple life for billions of years). In such cases, the likeness of a supposed twin can be more relaxed.

Ideally, one would like to measure these properties for a large collection of stars in order to obtain the distributions in each property. The Sun would then appear as a point in this 11-dimensional distribution and measurements would show whether the Sun was out on the edge of this distribution (indicating rarity) or somewhere in its middle (indicating ordinariness). Of course, to get a proper measure of the uniqueness of the Sun, some kind of a chi-squared statistical test should be applied, from which various probabilities can be derived.

Unfortunately, the number of stars possessing all 11 of the properties is very limited, so the authors of the study had to use limited sets of stars that were parts of other surveys, and in many cases these sets were not overlapping. To see what this limitation could do to bias the study, imagine a comparison for just two properties with the stars being completely nonoverlapping so we don’t know if the stars in one set have skewed values for the other property. It is possible for the Sun to appear in the middle of both property distributions but not be in the middle of the joint distribution for stars where we can obtain both properties. In practice the nonoverlapping distributions are not likely to be so skewed, but it does reveal a weakness in the conclusions of the study.

The authors conclude that the Sun is not unique. If the study is free from the non-overlapping bias, one would expect to be able to find stars that are twins of the Sun in many, if not all, of the 11 properties. However, based on the studies Hugh Ross mentioned above, finding such a twin, even for a limited number of properties, has proved difficult, at least for the more restrictive advanced-life case.

Perhaps in the end the Sun will not prove to be unique, but based on the results so far, that appears to be the case. Future deep surveys with accurate measurements for all the relevant stellar parameters hold promise to help settle the matter.