By Matt Lefebvre

This post is a continuation of the teleological argument. Please see Part 1, Part 2 if you have not read them yet.

To read along with audio for this article, click here Teleo-Part3

The Sun

Though the Sun is in the center of the solar system, it is not in the center of the universe.  In addition, the Sun is not a particularly large star, by quite a significant margin.  It is also not the smallest, but occupies the mid-range among stars that have been observed.  This has led to the suggestion that the Sun is not especially significant, being just an average star, both in terms of qualities and size.  Is this the case?  Well, it should first be pointed out that mid-range is not the same as average.  Gonzalez and Richards illustrate this difference well when they write,

“Suppose we want to estimate the average adult male weight.  If we consider the extreme ranges, and just take the mid-range value, we will get an answer just under 1,000 pounds; the average, however, will be somewhere between 150 and 200 pounds.  Very rare extreme cases dominate the mid-range value.  In the same way, the average star mass and luminosity are actually much smaller than the corresponding solar values.” (The Privileged Planet, p.137).

Temperature and luminosity of different types of stars

In other words, being a mid-range star does not equate the Sun with mediocrity, but simply states the fact that there are bigger and smaller stars.  The question to be answered is what an ideal star would look like and how the Sun would measure up.  One aspect of a star is the length of its main sequence (the longest phase of its life), in which a star’s luminosity (light and radiation) changes very little proportional to the rest of their lifetime.  Considering those stars that are compatible with life, the best stars would be those with a relatively long main sequence, because this would provide both light and energy over a long period of time.  This is crucial for aspects of life such as photosynthesis in plants, atmospheric cycles, and stable temperatures.  The thing is, though, not just any star will provide this without significant side-effects.  To take more massive stars, even just 50% bigger than the Sun, they spend relatively little time in the main-sequence, and even while in it, their luminosity changes quicker than stars the size of the Sun.  This would lead to rapid climate changes, more hostile orbits, and more asteroid threats.  Less massive stars fair no better, however, for while they spend much longer in the main sequence, it may not do the planet any good.  If the Circumstellar Habitable Zone is closer to the planet, as it would have to be for adequate conditions, the close proximity would stop the planet’s rotation.  The planet would orbit the star as our Moon orbits Earth (without rotating), and thus there would be a “dark side” of the planet, just as there is a dark side of the Moon.  This would lead to a severe temperature differential between the sides, which would not only lead to the dark side freezing out, but the illuminated side being hot and dry, because of the integration of a planet’s atmosphere as a whole.  Furthermore, in terms of solar flares, Earth is at a safe distance, but in addition to a planet having to orbit closer to a smaller star, the intensity of the flares compared with the star’s intensity is much greater than solar flares.  Also, terrestrial planets orbiting a smaller star would perturb each other’s orbits, whereas the planets orbiting the Sun have maintained fairly stable orbits for the duration of the main sequence of the Sun so far.  So smaller stars would only allow smaller orbits, and therefore shorter lifetimes for the ideal conditions on the planets.

“Ironically, then, the shortest dynamical lifetimes of terrestrial planets in habitable zones should be found around the longest-lived stars.” (The Privileged Planet, p.135).

So, even though smaller stars last longer, the habitability of their planets does not.  Moreover, it is also unlikely that the right kind of planet will be at the right distance from the star, irrespective of the mass.  George Wetherhill produced simulations of planet formulation that indicated that the most massive terrestrial planets (which would be about the size of Earth, as indicated above) would form at around the distance Earth sits relative to the Sun (give or take 50%).  This means that terrestrial planets of the right size would in any case form outside the Circumstellar Habitable Zone for a smaller star and inside it for larger stars.  “This suggests that fairly large terrestrial planets, like Earth, will reside in the CCHZ [Continuous Circumstellar Habitable Zone] only when their host stars are similar in mass to our Sun.” (The Privileged Planet, p.136).  This at least places stars of similar mass in an elevated place among the various types of stars, but there is more.

“At some level, of course, all stars are variable.  Among Sun-like stars of similar age and sunspot activity, however, the Sun’s light varies much less than average, preventing wild climate swings on earth.” (The Privileged Planet, p.137).

At this point, perhaps you have heard enough about the Sun, as I am giving more space to the question of the right star than to anything discussed so far, but there is one more crucial aspect of the Sun that I must mention, because it has implications for all the examples I have produced above as a necessary, though not a sufficient, cause.  Added to the fact that the Sun provides a situation that makes a place in the solar system more habitable for life, the Sun also provides essential elements for life itself!  So when we talk about cooking up life, it is not just a matter of using the Sun’s kitchen, but of taking the ingredients from what the Sun itself produces.  As Alister McGrath explains,

“All the heavier elements of the universe, from carbon upward, are believed to be the result of nuclear fusion within stars, and not to be a direct outcome of the primordial fireball.  Without the formation of stars, the universe would have been limited to hydrogen and helium, with only a tiny percentage of other elements, such as lithium and beryllium.  The nucleosynthesis of carbon, nitrogen, and oxygen must therefore be regarded as essential to the emergence of life.” (A Fine-Tuned Universe, p.133).

To phrase the matter differently, without the production of elements in stars, the universe would have about 5 elements instead of over 100.  Considering the importance of carbon for life as shown above and the fact that oxygen is a crucial part of a compound in water as shown above also (not to mention that oxygen is crucial as an element itself), it was critical that this synthesis, or production, of elements be carried out.  So, what we can see is that this must happen in stars to produce the aspects of the universe we have already discussed (carbon, water, the various metals and gases that make the Earth and the Moon the way they are), but where does the Sun fit in specifically?  Could any other star have given us the same fighting chance for life?  Well, in addition to having already pointed out other conditions a star must meet, even this criterion can be seen to be narrow, irrespective of the other elements a star would need to support life.  The amount of heavier elements (from carbon upward, remember) is referred to as metallicity, but do not confuse this with elements that somehow have to be metals.  The Sun obviously had a metallicity that produced a solar system with both giant planets (like Jupiter) and terrestrial planets (like Earth), and both of these are important for life in the solar system, but how do other stars compare?  Well, on one side, around stars with less than 40% of the Sun’s metal content, astronomers are not finding giant planets.  On the other side, the more the metal, the more the planets.  In a system with more planets, including more giant planets, they would be more likely to disturb each other’s orbits, and especially in the case of giant planets, they might either send the smaller planets into the path of the host star or throw them out of the system completely.  In addition to more planets, a more metal-rich star would produce more comets and asteroids, increasing the impact threat beyond what would be helpful to life to the point of possibly extinguishing whatever chance of life there was, however slim it may have already been based on the other factors (The Privileged Planet, p.132-137, 154-156, 159-161).  Again, many crucial variables of a star influence the habitability of its system.  Unlike Hollywood, even though the Sun is not the biggest star in town, this is not something to be ashamed of, but is rather a particularly privileged status.

The Galaxy

We live in a galaxy called the Milky Way, which was once believed to be the entire universe, but the fact that it is just one of billions of other galaxies obviously negates that idea.  “The word galaxy, by the way, derives from the Greek words for Milky Way.” (The Privileged Planet, p.143).  So, if our galactic habitat is just one among so many of the same kind of groupings of stars and systems elsewhere in the universe, should we then think that our place is of no consequence?  Well, I would hope at this point that you would expect my answer to be no.  Though we again find that we are not situated at the center of even our own galaxy, we should be very thankful for this, for in any given galaxy, you do not want to be the center of attention.  As we saw above, stars are responsible for the production of heavier elements, some of which are crucial for life.  We also saw above, that the Sun is the ideal type of star to produce a terrestrial planet with a mass similar to Earth.  However, before this could happen, there would need to be sufficient basic elements for the Sun to convert them into the heavier elements.  As it turns out, the inner regions of the galaxy are the places where there would be enough basic elements, whereas the edge of the galaxy contains much less gas density, so the rate of star formation decreases.  Basing a location purely on this question, it would stand to reason that a star would be better off forming in the inner regions and not in the outer, but it is not based purely on this question.  Because we are interested in the question of sustaining life, it is not enough to just be where the greatest potentiality of forming elements is.  A reporter might try to get himself right in the middle of an intense military battle because that is where the action is, but the question of his safety is less than optimal to say the least.  In the inner regions, there are greater radiation threats and impact threats, including the very likely possibility that at the very center of the galaxy is a relatively dormant black hole, which will hopefully not be fully awoken anytime soon.

“Like a giant dragon sleeping in the heart of a mountain, a massive black hole probably dwells in the center of our galaxy, though at the moment it’s fairly inactive…Presumably, a dormant black hole ‘wakes up’ when a star or cluster wanders too close and becomes disrupted.” (The Privileged Planet, p.162).

Black holes are so dense that not even light can escape its horizon, and are thought to drive other sources of galactic radiation.  Considering this extreme threat to life in the inner regions of the galaxy, it might be thought that a star could try its luck in the outer regions, where it is certainly safer.  However, from what we pointed out above, if a star cannot produce enough heavy elements, the results are detrimental to life, both in terms of forming a terrestrial planet big enough to support life and in having the very essential elements that life is based on.  This line of thought includes the same kind of criteria that led to the notion of the Circumstellar Habitable Zone, so in thinking about where would be the ideal place for a system to support life in our galaxy, the region between not too far out and not too far in could be called the Galactic Habitable Zone.  I assume that it will not be a surprise, in the tone that this article has taken, to be told that our solar system occupies a place inside the Galactic Habitable Zone.  It is not just the fact that we are the right distance from the center, though, for there are other factors that could be a threat to habitability for a system within the zone.

Galaxies come in 3 basic types (spiral, elliptical, or irregular) and the Milky Way just happens to be a spiral galaxy, which in turn just happens to be less hostile to life than an elliptical galaxy (I left out irregulars, because the type is not specific and thus hard to characterize).  Giant elliptical galaxies seem to be the favoured host for the most massive black holes and the stars within these galaxies have less ordered orbits, causing various problems that are hostile to life.  A spiral galaxy has spiral arms made up of stars and dust.  This might not seem so threatening, but it depends on how a system is passing through.  Giant clouds of dust, for example, could cause the extinction of whatever life might be on a planet, if such a system were making its way through the spiral arm.  It is significant that the Sun has a more circular orbit than most other stars of the same age and its vertical motion (relative to the rest of the galaxy) is less extreme.  If the Sun’s motion paths were more exaggerated, or if it was located in a globular cluster (a collection of stars that orbit the galactic center like a moon), or in the bulge (where older stars are located), it would pass through the spiral arms at greater speeds.  This would produce deadly radiation and cosmic dust storms.  As it is now, though, in the case of the solar system, the interstellar dust (dust between stars) and gas actually offer protection from radiation threats.  Furthermore, it is important to compare our galaxy with other galaxies.  Remembering the importance of metallicity for the formation of a terrestrial planet able to sustain life and to have life itself on such a planet, it is significant that 98% of the galaxies in the local universe have lower metallicity and luminosity than our universe.  Thus, it is possible that entire galaxies could be completely without the right sized terrestrial planets.  In addition, interaction with other galaxies can hinder habitability, because when galaxies come close together, orbits can be upset, but worse still, whole groups of stars can be dislodged and thrown out into deep space.  This might also be an effect that would activate a central black hole.  As far as the position of the Milky Way is concerned, the concentration of galaxies around us is somewhat sparse compared with the concentration of galaxies in the local universe.  In fact, some bigger clusters of galaxies get bigger by swallowing other smaller galaxies, but this does not somehow make them more habitable, but less, since there is intense nuclear activity in these super galaxies (The Privileged Planet, p.143-145, 158-168).  In view of the above, I agree with Gonzalez and Richards in their assessment of the Milky Way.

“In many ways, ours is the optimal galaxy for life: a late-type, metal-rich, spiral galaxy with orderly orbits, and comparatively little danger between spiral arms.” (The Privileged Planet, p.167).

The Universe

It would certainly be a striking omission to come this far in our journey outward from where we stand, and yet, not discuss the fundamental behaviour of the universe as a whole.  The reason I chose to travel from the inside out is that I have shown you what is at stake, so you can fully appreciate how the universe is just right for life.  I hope this will be your experience in this section.  I would like to focus on what could be called the fundamental forces: the strong nuclear force (which holds protons and neutrons together in the nuclei of atoms), the weak nuclear force (which controls the conversion of protons to neutrons and neutrons to protons), the electromagnetic force (which causes interaction between electrically charged particles), and the gravitational force (which attracts bodies of particles together, increasing as mass increases).  These forces determine what the universe can and cannot have, what it can and cannot do.  They affect various aspects of the universe as we know it, but I find it sufficient to just mention one factor for each force that could not stand to be different.  If the strong nuclear force were half of what it is, not only would many life essential elements not exist, but some that would exist would be fairly unstable, because the interiors of atoms would not be held together well enough.  Thus, life would not be able to even start in a universe where there was nothing worth living on or living by for that matter.  If the weak force were decreased thirty-fold, stars would be composed of almost entirely helium, which would mean that the stars would burn a lot faster than hydrogen stars, like the Sun, do.  This would not give an adequate window of time for life on a terrestrial planet, assuming that one could even form in this kind of universe, which is uncertain.  The electromagnetic force would have the same effect on the stability of elements that decreasing the strong force had.  If the electromagnetic force was increased fourteen-fold, the stability of elements would be compromised and if it was a little stronger, all elements except hydrogen would be non-existent.  If the gravitational force were to be altered by increase or decrease, it would have devastating effects on the universe, such that the universe would not be hospitable to life.  The limits of how gravity could be changed are conceptualized by Gonzalez and Richards.

“…the expansion of the universe must be carefully balanced with the deceleration caused by gravity.  Too much expansion energy and the atoms would fly apart before stars and galaxies could form; too little, and the universe would collapse before stars and galaxies could form.” (The Privileged Planet, p.204).

As important as the right kind of galaxy and right kind of star is, as we saw above, it does not do anyone any good if there are no galaxies and stars in the first place.  Individually, these examples (and I only shared one of the consequences for each) are impressive, but when things really start to get interesting is when you consider the relationship of the forces to each other.  Sometimes people think of changing only one of the forces at a time, just to keep things simple.  The truth is not only that these forces could have had very different values, but also that the ratios between the forces could also be different, which is especially significant if the same forces exert influence on the same particles.  For instance, even if there was some explanation for the strong force taking the value that it does, the weak force would also have to be in the right place along with the electromagnetic force, so this could just as easily be wrong (and I would say more easily, but we will get to that) (The Privileged Planet, p.198-208, William Lane Craig in God and Design, p.155-158, Reasonable Faith, P.158-159, Robin Collins in God and Design, p.182-194, The Anthropic Cosmological Principle, p.326-327).  In other words, even if the strong force could not be blamed for the lack of heavier elements, some other force could be, if the values did not line up in relation to each other.  That may be true, but what about the possibility of compensating for a change in one of the forces through adjusting another force?  Well, as promising as this might initially seem, those who have tried are less optimistic.

“Don’t pour water on a grease fire.  It won’t help, but will only make things worse.”

“Efforts to avoid one problem by changing several of the constraints at once generally produce some other problem.  Thus we apparently live in a rather delicately balanced universe, from the point of view of hospitality to chemical life.” (Astronomer Virginia Trimble, quoted in The Privileged Planet, p.206).

“If we modify the value of one of the fundamental constants, something invariably goes wrong, leading to a universe that is inhospitable to life as we know it.  When we adjust a second constant in an attempt to fix the problem(s), the result, generally, is to create three new problems for every one that we ‘solve.’  The conditions in our universe really do seem to be uniquely suitable for life forms like ourselves, and perhaps even for any form of organic chemistry.” (Astronomers John Gribbon and Martin Rees, Cosmic Coincidences, p.269).

There are various other examples of what might be called cosmic fine-tuning, at the level of the universe as a whole, and some are more impressive than others.  The point is that there is general agreement that the universe is in fact just right for the existence of complex life, such as ourselves.  Alister McGrath pin-pointed the issue among most who study in the relevant fields when he wrote,

“The debate in the literature mainly concerns the interpretation of these phenomena, whose existence is generally conceded.  The essential point is that if the values of certain fundamental constants which govern the development of the universe had been slightly different, its evolution would have taken a different course, leading to a cosmos in which life would not have been possible.” (A Fine-Tuned Universe, p.118).

While many agree that there is fine-tuning in the universe, and therefore, that it cries out for explanation, whatever that may be, there are still some voices skeptical of the fact that the universe is really fine-tuned for our existence.  It is to this that we turn, before moving on to discussing the possibilities for the best explanation.

Click here to see part 4 of the article


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