July 08, 2006

The Heavens Declare His Glory (part 3)

It's in the Stars
(Part 3 in a 4 part series)

Now that we know where we need to be positioned in this universe, let's look at the kind of local habitat we would need to support life.

The first thing that life needs is a safe and stable home. It needs to be warm enough to facilitate chemical reactions, but not so hot that complex molecules break down. It needs a usable energy source, yet protection from damaging energy sources like cosmic and high-energy radiation. It needs a diverse source of key materials, but the ability to isolate from volatile materials. And it needs this environment to be stable for a long period of time (an enormous period of time if you insist on presupposing evolution).

Now, I don't wish to be accused of begging the question here. I'm not just implying human life or "life as we know it"; I'm talking about any kind of complex, sentient life that would be a candidate for (or result of) God's special attention. We do, after all, have a fairly good grasp of chemistry and the kind of general conditions that must prevail in order to support complex chemical bonds and reactions. And unless God wished to "ensoul" a molecular cloud (which would lead to interesting problems of where one "person" ends and another begins), then we must look to certain constraints.

The obvious solution to the habitat problem is a planet, which, of course, would be dependent upon a star for its energy supply. An alternative might be something like an interstellar dust cloud or nebula. But while these may be candidates for the formation of simple materials upon which life is based, they offer nothing like the kind of stability, protection, and concentration of resources that can be found on a planet.

So a solar system it is then, but first we need a proper star. Unfortunately, not all stars are created equal. We know by example that our own kind of star is a good host, but when astronomers call our sun "average," it is not that the majority of stars are like it; it is more due to the fact that our star falls right in the middle of some important stellar classifications. Indeed, our sun is anything but average. To begin with, 90% of all stars are smaller than our own. If anything could be said to be an average star it would be a red dwarf, the most common type. But for several reasons, these are bad candidates for a parent star.

These smaller stars output far less energy, so a habitable planet that hoped to maintain a reasonable average temperature (and liquid water) would have to hold a close orbit. Unfortunately, close-orbiting bodies have the effect of putting the least massive partner into gravitation (or "tidal") lock. This is where one side of the satellite body always faces what it is orbiting. For instance, the same side of our moon always faces us, and this is true for nearly every other moon in our solar system. Having a planet tidally locked to its sun would be devastating to the climate of both sides of the planet.

Being close to your sun also means that you are susceptible to greater exposure to its miscellaneous undesirable emissions, like solar winds, flares, and general radiation. Just because a star may give off less of the energy you need does not mean that every other emission is proportionately smaller. In fact, these red dwarf stars have been found to have a rather erratic and volatile nature. At worst, these common stars are unsuitable for life. At best, life would be downright nasty under their dominion.

Of course, not all stars are smaller than ours. Stars can be up to 150 times the mass of our sun. Unfortunately, larger stars are even worse candidates as a host star. I'll mention just three reasons why.

First, large stars tend toward the blue end of the spectrum, which means a greater abundance of ultraviolet radiation, among other things. This would not only have an adverse effect on life's biochemistry, but would cause toxic chemical reactions in the very atmosphere of a planet (like ionizing it).

Second, adding mass to a star does not proportionately increase its energy output, it exponentially increases it. This means that even if it were possible to maintain a hospitable planet around one of these infernos, it would have to be positioned in a distant orbit that would nullify the temperature-balancing effects of short seasons (assuming the planet is even tilted on its axis). More on this later.

Third, contrary to what you might expect, the larger the star the shorter its life-span. This is because the increased gravitational pressure causes the star's fusion engine to run more efficiently. (Of course, I am assuming that the reader knows that stars are nothing more than giant fusion reactors, which spend the bulk of their lifetimes fusing hydrogen into helium). In the same way as the energy output increases, and for the same reason, the lifespan exponentially decreases with mass. So a star only 1/4 again the size of our sun may have its lifespan reduced by half. And the largest stars number their years in the millions (or hundreds of thousands), rather than 10 billion like our own.

A shorter star life is not only bad news in the general sense that shorter is worse, but it is bad because a shorter lifespan serves to condense the lifecycle of the star in a way that causes a briefer possible sweet-spot. You see, during a star's main sequence burn phase it grows progressively hotter, brighter, and larger. Where a planet may once have rested comfortably within the habitability zone it could quickly find itself on the inside of it if its star were too large. Our own planet has been slowly "moving" from the outer edge of its zone to the inner edge. But because of the smaller size of our sun this progression has happened slowly enough to give us a long life-window and to permit complex planetary adaptations (e.g., the reduction of carbon dioxide so as not to trap the increasing level of solar energy).

It might be worth mentioning here that, for the reason I just discussed, these planetary habitability zones are not as broad as they may at first appear. In reality, any planet with the hope of long-term habitability must begin at a very narrow position on the outer portion of the zone so that it will stay within it as long as possible while the star progressively increases in luminosity.

But what about the stars with approximately the same mass as our sun? Surely there are plenty of these out there in such a big galaxy. Well, that may be, but there is more to making a star than mere mass. The amount and mix of heavy elements it contains — its "metallicity" — controls its burn rate, energy output, and variability. And its spin rate affects things like its magnetic activity, which drives its flare intensity and frequency.

When looking for twins of our own star (which SETI scientists seem to think very important) there are a lot of sensitive variables that we are only beginning to understand. In fact, even using the criteria that we can understand and measure we have found, to date, precisely zero solar twins, that is, unless you wish to loosen up the criteria for "twin" (which they intentionally do for solar "analogs"). The closest contender of the thousands of candidates reviewed is 46 light years away, but even this one has its problems. Here are just two quotes that point out some of the notable differences.
"HD146233 [also known as '18 Scorpii'] is the only star in the ELODIE library which merits the title of solar twin because it has passed the filter of all methods [of identification]. It is not however a perfect twin and differs from the Sun by its higher [Lithium] content [3 times as much], slightly higher age (6 Gyr against 4.6 Gyr for the Sun) and higher luminosity (Mv = 4.77 against Mv⊙ = 4.82)." (Source)

"18 Scorpii's activity cycle [it has actually been classified as a variable star] may be of greater amplitude than Sol's and that its overall chromospheric activity level is noticeably greater than Sol's. Hence, this otherwise excellent solar photometric twin therefore may be a less perfect spectroscopic twin." (Source)
At 46 light years away, and being a relatively small star, 18 Scorpii is too dim to see with the naked eye. Even assuming that this star were a solar twin, thus being a prime candidate for a habitable system, this means that of all the stars you can observe in the night sky not a one of them is much like our own. Even extending your vision with binoculars and low-powered telescopes, you will only include a couple of possible candidates (the runner up is 126 light years out).

There's just one other very important thing I'll mention by way of requirements for the host star itself: it must be a loner. If it has one or more companion stars, then any planet's hope of maintaining a long-term, regular orbit (i.e., constantly remaining in a habitability zone) is slim to none. This further narrows the field of available parent stars in that more than half of all solar systems are binary, or greater (the percentage being lower for red dwarves and higher for large stars).

So far we've seen that when considering the ideal home for life we not only must consider the galactic neighborhood, the kind of galaxy, and the position within the galaxy, but the very details of the star as well. All factors make a dramatic difference to the stability, longevity, and energy output. It is no mere bias that leads us to consider our own Sun as the benchmark of habitability; it is the perfect star on theoretical grounds, by comparison, and by experience. Either ours is the only possible kind of star able to support complex life like our own, or God simply delights in exceeding requirements.

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17 Comments:

At 7/10/2006 9:28 AM, Blogger Psiomniac said...

This was an interesting and detailed exposition Paul.
Although you say that 18 Scorpii has some differences such as its lithium content you did not say that its inability to support a lifebearing planet system could be deduced from these. Do you think it is conclusive? Also, if a near comparison has been found within a radius of a mere 46 lightyears, what estimate for the number of candidates for our galaxy does that give? I realise, as you have pointed out in detail, that there are other hurdles to leap but it might start to give an indication about whether we are likely to be alone in our galaxy, or our galaxy cluster or completely alone in the universe.

 
At 7/10/2006 5:17 PM, Blogger Jeff said...

One sad thought, when contemplating the possibility of other life in our universe, is that due to the rare nature of hospitable locations, if one is out there it's very likely to be hundreds of thousands of light years away making contact impossible

 
At 7/11/2006 1:06 PM, Blogger Paul said...

Psio,

Thanks for the compliment. Astronomy is one of my great loves, and I've enjoyed getting caught up in the state-of-the-art in this field in preparation for these articles. I've enjoyed this since my college days, and it only increases my passion to realize that what I'm seeing is not just the result of the random confluence of particles, but, instead, is the product of design down to the very laws of physics that permit such things as atoms, fusion, the electromagnetic spectrum, complex molecules, and even a universe that survives for an extended period of time and coalesces into discrete objects. The universe moves me profoundly in a way that seems most consistent with theism.

You are right that I did not explore the difference that higher lithium content would make, which, by the way, the other star (HD 98618) also has in addition to 11% more iron. However, my overall theme is that a different mix of starting materials can make a significant difference in the stability (and suitability) of a star. And this is exactly why they are so keen to find "solar twins" as the starting point for astrobiological studies. Additionally, since 18 Scorpii is more variable than our own star it is reasonable to conclude that something like its higher lithium content is a contributing factor to that difference.

As far as the odds are concerned when taking the vastness of space into consideration, my effort so far has served to divide those numbers through progressive waves of issues that must be taken into consideration. Where that puts us at this point (down to the star) by way of probability I cannot say, though I would not be at all surprised if there were no more than 100 solar twins positioned in the right locations throughout our own galaxy. And if you were to increase that by one or two orders of magnitude, what I have to say regarding planetary conditions will make those numbers of little encouragement.

 
At 7/11/2006 3:40 PM, Blogger Psiomniac said...

Paul,
And even if we were optimistic with regard to the 100, as Jeff pointed out they would very likely be so far away as to never be practically contactable, barring profound revisions of our present scientific paradigms.
I think your view as regard all the variables being 'just right' being compatible with theism is understandable. Many people have advocated the Strong Anthropic Principle within the scientific community, for example Professor Paul Davies of the The Australian Centre for Astrobiology.
As you can imagine, I have a somewhat different view.

 
At 7/11/2006 7:27 PM, Blogger Paul said...

Paul Davies is an enigma to me. Often when I hear him talk about these things he sounds indistinguishable from a theist, but he seems very keen to avoid classical theism and opts instead for some rather esoteric views about Gaia theory and self-organizing principles. I haven't been exposed in great detail to his metaphysical views (or his latest ones, anyways), but he seems to me to be ignoring the elephant in the room.

I wonder if you think him just as wrongheaded as us full-blown theists.

 
At 7/12/2006 12:09 PM, Blogger Psiomniac said...

I'm tempted to say that he is more wrong headed than full blown theists. At least most theists admit that some faith is required whereas Davies seems to think his conclusions are completely rational.

 
At 7/12/2006 8:50 PM, Blogger Paul said...

You bring another question to mind: What do you think Christians mean by the word "faith?" That is, aside from its use as a noun.

 
At 7/12/2006 8:52 PM, Blogger Paul said...

Oh, also, do you think Davies is wrong to see something to be explained by the order and precision in the laws of physics?

 
At 7/13/2006 4:12 PM, Blogger Psiomniac said...

Paul,
From my point of view I would say that Christians regard faith as a kind of ongoing process of trust. For a Christian, faith is not blind but is informed by evidence and argument to form a coherent world view. Does that come close to what you mean by faith?

I do not think that Davies is wrong to see something to be explained, I just think he hasn't actually found an explanation, rather, he has found an explanatory fiction, which is a different thing altogether.

 
At 7/14/2006 1:04 PM, Blogger Paul said...

Psio,

Pretty good description of faith — better even than most modern Christians would define it. I like that you used the word "trust." That's the most common synonym chosen when trying to clear up misconceptions about this. You've also captured the active component of it (an "ongoing process"). "Faith" is beyond mere "belief." There is a "so what"ness to it; a consequence and application of that belief. You may "believe" that there is an Oort cloud surrounding our solar system, but it would be odd to claim that you had "faith" in that fact. Now, if some astronomer claimed that one of the objects (a comet) from that cloud were due to strike earth next year, you might believe that and choose to exercise "faith" in that belief by digging a bomb shelter and stocking up on provisions.

The Christian faith is just a matter of acting upon what we believe to be true about God and Judeo-Christian history. We certainly believe that we have good reasons to exercise that faith and reorder our lives and minds according to it, though not all can articulate their reasons in a tangible way.

The reason I asked you about faith was because you said that Davies thinks he is being "rational," whereas theists admit that there is some "faith" aspect to their belief. This implied to me the old reason vs. faith dichotomy, which we Christian thinkers reject. We simply believe that there is good reason to invest ourselves in Christianity (and then we do so), and that something like atheism attracts a similar following of the "faithful."

I don't know if Davies has actually exercised "faith" in his belief that there is "something going on behind it all." Maybe only insomuch as he devotes his energy to thinking and writing about it. I doubt that it affects his politics, ethics, and his social dynamics though.

I'm not sure why you say that Davies' explanation is only a "fiction" though. Is that just because you don't buy it, or is that because you just think he's left the boundaries of what you would classify as science and reason?

 
At 7/14/2006 9:06 PM, Blogger Psiomniac said...

Paul,
I liked your comet example.
Regarding Davies and the faith/reason dichotomy I will have to think about that some more. I do not see quite the symmetry between theism and atheism in faith terms that you do. It is to do with whether ongoing processes of trust can be post-rationalised or not. I think Davies blurs some distinctions there and I agree with your second idea that he has ventured into fields that are beyond the bounds of possible human knowledge.

 
At 7/14/2006 9:09 PM, Blogger Psiomniac said...

P.S.
In terms of politics, ethics and social dynamics, it should not be overlooked that Davies' advocacy for the Strong Anthropic Principle played a part in him winning the Templeton Prize.

 
At 7/15/2006 2:59 PM, Blogger Paul said...

I wouldn't expect that you would care to see a parallel between the faith of the religious and the faith of atheism (I'm thinking you are an atheist). Generally, atheism is thought to be the shedding of false beliefs and the emotional baggage that leads to religious "faith." In this sense, it is the absence of commitment and belief in these esoteric, supernatural, and "unprovable" things. So, you are the neutral, unbiased, and rational one, while we religious types are laboring under a yoke of credulity and self-deception.

I contend that it takes just as much "faith" to be an atheist as it does to be a Christian. It takes just as much denial of plain data and affirmation of remarkable ideas to be an atheist. And do you suppose that throwing your lot in with the atheists has no impact upon your life? Tell a house full of teens that there are about 5 octillion atoms in their bodies and they will yawn and continue playing their X-Boxes (no "faith" exercised there). But tell them that there are no adults in the house for the weekend and watch the action begin.

I'm still not sure where Davies has gone so wrong. If you admit that there is something to the design problem, or Strong Anthropic Principle, then there is surely something to be hypothesized. Perhaps you believe any explanation must be a "natural" explanation in order to qualify as science. But Davies is grappling with natural explanations: that the answer is to be found in the very substance of the universe itself. Perhaps he could even manage to propose experiments to falsify his theory. I'm not sure what alternative explanation you would think more rational. The multi-verse theory, so popular these days among non-theistic scientist, seems to me to be just as "beyond the bounds of possible human knowledge" as anything Davies or us theists are proposing. I happen to think, as a Christian, that the theistic solution has the advantage that the "cause" has opened His mouth and spoken to us, thus making it very possible to have "human knowledge" on this issue.

 
At 7/16/2006 7:57 AM, Blogger Psiomniac said...

Paul,
This is a complicated area. If we use the term 'faith' in the strict and nuanced way that we have agreed upon in this discussion then I can agree that atheism requires just as much faith as theism. Where we would disagree is on the matter of the denial of plain data and on the underpinnings of the remarkable ideas involved. In this sense I regard theism as an irrational faith and atheism as a rational one, although I wouldn't use the term 'faith' because it is used by some theists to mean 'ongoing trust in something despite the balance of evidence not being in its favour'. I think we have to be careful in our exegesis regarding Bible passages that extol the virtues of faith. As a skeptic I am on the side of Doubting Thomas. It is not that atheists only believe in things that can be proven, since that leaves little or nothing, it is more that they have rigourous processes of evidence gathering and proceed on the basis that all truth regarding the physical world is contingent.

I conceded that there seems something in need of explanation but did not concede that The Strong Anthropic Principle can validly be deduced from this. Not only has David Hume effectively pulverised the arguments used for said deduction, there are as many alternative ideas that do not involve a 'designer' of the laws of physics as there are inventive cosmologists who have thought about the problem. If it is argued that these ideas are untestable and therefore lie outside science this is equally true for the S.A.P., hence all we can say is that this lies outside the bounds of possible knowledge. (Unless of course you make the separate claim that God told you, but then you can't use the S.A.P. as evidence without circularity.) That Davies thinks the S.A.P. is more rational than the other contenders for an explanation is where, in my view, he goes wrong.

 
At 7/17/2006 8:00 PM, Blogger Paul said...

It would seem that we might come to some workable agreement on the definition of faith (though I'm not sure you would prefer it), but that our main disagreement regards the strength of the rational case for theism vs atheism. You seem to think the case for Christianity to be weak, but it has been my growing experience that the case for metaphysical naturalism is fraught with every bit of the philosophical and scientific challenges that it is claimed that Christianity faces. It is not enough to say, "I don't see any God," and call oneself rational in embracing the whole messy worldview that atheism demands. And covering anomalies in foundational areas by perpetually claiming that you're still working out your theories does not make the case for atheism; it is simply descriptive of the estate of the atheist.

You said: "[Atheists] have rigourous processes of evidence gathering and proceed on the basis that all truth regarding the physical world is contingent."

I would argue that theism is not contrary to the evidence; it is swimming with the current of it. It is not as though astronomers have discovered the universe to be eternal and non-contingent, or that neuroscience has discovered the electro-chemical key to consciousness, etc. I think you can only succeed in claiming that atheism holds the high ground in science if you first define science to be methodological naturalism. But I am more interested in employing science in the pursuit of truth than I am in constraining science to materialistic conclusions. Depending on how you define it, science might be only a tool in our arsenal, but not the last word on every topic. But for the atheist, the material is all there is, so science IS methodological naturalism — there can be no other — and so theists will always be seen to violate the principles of science. I guess our dispute goes beyond merely who is employing science to its best advantage; it is a dispute over the very nature of science and its proper boundaries.

I hear you agreeing that there is something curious about the fine-tuning of the universe, but I'm not hearing you say that there are any acceptable "scientific" explanations, only that you think that Davies' and my answers are not "more rational" than any other answer. I think I could make a case that a designer is a perfectly rational conclusion given an observation of "design," but I would be satisfied at this point with the admission that the materialistic explanations (I haven't heard the myriad that you imply exist) are just as rational or irrational as what the theist would propose. I think you will not be inclined to admit this, however, since I'm sure that any explanation — no matter how outlandish and untestable — that excludes a personal agent is to be infinitely preferred.

As for Hume, while I consider him someone not to be taken lightly, and to have made valid contributions to the domain of reason, I don't think he has the last word in the areas I think you are referencing. I think he has been effectively challenged from numerous quarters, but that may be another discussion.

 
At 7/18/2006 8:12 PM, Blogger Psiomniac said...

Paul,
I think you are right about the main area of disagreement being the relative strength of the rational case for theism. I think the so called 'anomalies' that you mention are either questions of detail or genuine areas of enquiry. What really matters is the methodology employed in order to conduct such an enquiry. This is where I think theism falls down. The thing is, the truth doesn't come easy. Anyone can make a miraculous claim and say they were inspired by god or whichever deity and if they are charismatic enough they may even start a cult. In this sense, rather like a rubic cube scramble, the problem is easier to set than to solve. I remember a case of a so called 'psychic' who had undergone investigation and who had produced statistically significant results under laboratory conditions. So, were we supposed to accept, against all the known precepts of physics and psychology that telepathy exists? Well, there is more than we know, so why not? At the very least we accept the possibility that it is true but further investigation is needed since we are faced with nothing short of a paradigm shift if the findings are verified. Wait a minute though. James Randi will tell you that scientists are a gullible bunch. The case I am thinking about is the Soal-Goldney experiments 1941-43 with Shackleton as 'mind reader'. What happened in fact was that the results could not be replicated. It then took thousands of researcher-hours to uncover the telltale statistical patterns that are the signature of fraud. I dare say that recent advances in phorensic accountancy software would have cut the workload. Still, the haedline would be 'Telepathy Proved!' and the disclaimer years later would be lucky to make page 5. You see the difficulty here? This is people we are dealing with. It takes one charismatic individual to set a problem and then thousands of researcher-hours to realise that the solution is fraud. Zip back now to Palestine 2000 years ago, when there were no researchers....The theistic framework doesn't even make it to first base in the methodology stakes. You KNOW the truth already, so it is obviously true that the heavens declare his glory, you just have to articulate how it decares it well enough and we will get it. Well no, here's the other thing, you say I would infinitely prefer an explanation that did not involve agency. This is not how it is. Rather, I would say that all such explanations are good insofar as they are narratives that will bolster our worldview. But if we are interested in truth, it doesn't come that easy. You cannot start from a position of knowing god loves you, deduce the way cosmology must play out if this is the case (brilliantly I must say) and expect that it will be credible that you are swimming with the current of evidence. I think that there are many processes in the universe that are observable that give rise to structure through blind algorithmic processes. Like the formation of a snowflake. So wouldn't it be more honest to admit that the generation of universes better fits this analogy than the analogy of being designed? Surely I have legitimate epistemological objections to the validity of postulating a designer as a solution, since all of a sudden we are going the wrong way in terms of explanatory gradient if we do that. The vast majority of structure we see in the world is not overtly designed (unless you want to beg the question). It is the result of the iterative application of simple rules. A designer is more likely, by analogy from what we observe, to be a product of such processes than a cause.
You say Hume has been effectively challenged. I quibble over the 'effectively' regarding natural theology.

 
At 7/21/2006 11:05 PM, Blogger Paul said...

Psio, I've finished a lengthy response to you but I've now begun to consider whether or not it warrants being reworked into a blog post. Please bear with me a bit longer.

 

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