My claim is that it is exactly in areas where life and science develop were expect to see science discover a correlation between habitability and measurability. Without habitability we would not have been here, without measurability we would not have science to lead us to this conclusion. Does this mean that there was purpose involved, or just a matter of fact statement?
Isn't a beach well adapted for sun bathing, digging holes in the sand, beach volley ball and wading. Isn't it miraculous that we go to beaches, which provide for easy access to the ocean, with sand allowing us to spend our sun bathing in relative comfort and play beach games. In addition a slowly deepening bottom allows us to wade in the ocean without the immediate risk of drowning. As icing on the cake, the waves seem to approach the beach in perpendicular to the coast line adding to our enjoyment. And in addition to all this, what surely must seem to be a miraculous environment, also provide us with protection from flooding (dunes). One cannot escape the conclusion that these beaches were designed with a purpose in mind. (I would like to thank my unnamed colleague who came up with these excellent observations).
[size=150%]Opacity, habitability and measurability[/size]
Assume that a habitable environment exists with an opaque atmosphere, or at least opaque to ï¿½visible' light (visible to us that is). Would it not be reasonable to expect that the local life forms might evolve a ï¿½vision' in a range in which the atmosphere is not opaque? What exciting discoveries could such an organism make in these wavelengths? And how would they lament these poor creatures on planets with opaque atmospheres. So is measurability not in the eyes of the beholder?
[size=150%]A review of critiques[/size]
In 2002, a five-part debate on the hypothesis of 'Rare Earth' took place on Space.com website. One of the participants, David Grinspoon remarked
David Grinspoon: I think it is a mistake to look at the many specific peculiarities of Earth's biosphere, and how unlikely such a combination of characteristics seems, and to then conclude that complex life is rare. This argument can only be used to justify the conclusion that planets exactly like Earth, with life exactly like Earth-life, are rare.
My cat "Wookie" survived life as a near-starving alley cat and wound up as a beloved house cat through an unlikely series of biographical accidents, which I won't take up space describing but, trust me, given all of the incredible things that had to happen in just the right way, it is much more likely that there would be no Wookie than Wookie. From this I do not conclude that there are no other cats (The Rare Cat Hypothesis), only that there are no other cats exactly like Wookie.
Life has evolved together with the Earth. Life is opportunistic. The biosphere has taken advantage of the myriad strange idiosyncrasies that our planet has to offer. Not only that, life has created many of Earth's weird qualities.
So it is easy to look at our biosphere, and the way it so cleverly exploits Earth's peculiar features, and conclude that this is the best of all possible worlds; that only on such a world could complex life evolve. My bet is that many other worlds, with their own peculiar characteristics and histories, co-evolve their own biospheres. The complex creatures on those worlds, upon first developing intelligence and science, would observe how incredibly well adapted life is to the many unique features of their home world. They might naively assume that these qualities, very different from Earth's, are the only ones that can breed complexity.
Darling published a detailed criticism of the 'Rare Earth' hypothesis in his book "Life Everywhere: The Maverick Science of Astrobiology." Much of his comments apply to the Privileged Planet claims as well. But there are some differences between the arguments in Privileged Planet and Rare Earth, which I will discuss.
Darling quotes Athena Andreadis, a neuro surgeon at Harvard Medical School who points out that:
In science, theories cannot be identical to their predictions, nor can that prediction be trivial. In fact, the Rare Earth theory is neither hypothesis nor prediction, but a description of how life arose on earth... Their (Ward and Brownlee's) oft repeated statement that both Earth and humans are unique is neither novel not contested - nor helpful in predicting life elsewhere.
While these objections are about Ward and Brownlee's book 'Rare Earth' they appear to apply equally well to the "Privileged Planet".
Darling continues to argue that
But Ward and Brownlee go further, they actually pick and choose the factors that best suit their case.
In "Privileged Planet" the authors argue that a large moon is both required for habitability and measurability. A claim which I intend to more in depth show to be erroneous.
[size=200%]The arguments in more detail[/size]
First some definitions
Habitability: A habitable planet is a "terrestrial planet that supports complex carbon- and water-based life", a "planet in "Circumstellar Habitable Zone"" and "Planetary system in "Galactic Habitable Zone""
The main argument proposed is that:
"Habitability correlates with measurability". Or in other words "The same narrow circumstances that allow us to exist also provide us with the best overall setting for making scientific discoveries."
"Therefore, there is a God." or "A More Modest Conclusion: The universe is fine-tuned so that environments habitable to observers will provide the best overall conditions for observation and discovery. The universe is designed for discovery"
Examples of these correlations include
1. Perfect solar eclipses
2. Layering processes
3. Plate tectonics
4. Transparency of atmosphere
5. Planetary neighbors
7. Galactic location
8. Cosmic time
9. Fine tuned cosmos
Gonzalez and Richards argue that the following requirements need to be met for a habitable planet
1. Right terrestrial planet
2. Stabilizing moon
3. Right atmosphere
4. Right planetary neighbors
5. Right single star
6. Galactic location
7. Right cosmic time
8. Universe fine tuned for life
A side claim
What does design tell us about God? Design confirms theism:
The correlation is more likely given theism than given naturalism.
[size=200%]A devastating rebuttal[/size]
Kyler Kuehn has presented a very compelling thesis why the arguments proposed by Gonzalez and Richards should be rejected.
Kuehn's primary thesis is
Habitability + Measurability do not warrant an inference to design (Divine or otherwise).
His secondary Thesis is
Habitability + Measurability cannot provide warrant for a design inference.
Habitability + Measurability are not the right tools for empirically detecting design.
Kuehn argues that optimal measurability is trivially true, in other words science will use the best observations/measurements and thus will be biased. In order to know the true distribution one needs to know good/bad measurability examples and show that there is a preponderance of good. By its nature however measurability is biased because we are ignorant of those things that are NOT measurable.
Kuehn then argues that based on physical law "constraints on measurability are entailed by constraints on habitability"
Habitability requires appropriate stellar (and electromagnetic energy) density--necessarily, we can see more than if we were located in a globular cluster or the galactic center
Kuehn then argues that several generations of stellar nucleosynthesis are required to form biologically relevant and necessary elements thus we can by definition observe a lot of stellar history.
Kyler then pursues the possibility that the correlation is law like? Thus a regularity pathway blocks a design inference. ID can of course argue that the designer designed the laws but Kyler argues:
Specific design input in the initial stages of the universe would then have to be proven (beyond simply the ontological or cosmological argument for God).
Such an argument does not pass through Dembski's design filter--is there a better design detection algorithm for this job?
Kuehn then argues that measurability may not even be measurable
Optimality Measure = Nopt/Ntot
But if Ntot is unknown then we cannot argue that a particular value of Nopt is 'special'
Then of course there are many confounding factors such as Nopt being a measurement of intrinsic properties of the universe or Nopt is biased by sociological factors such as funding.
And then Kuehn gives the final blow:
Science flounders towards truth:
Many physical objects are hideously difficult to observe properly (e.g. neutrinos).
Many measurements require significant manipulation of our environment (e.g. placing satellites beyond the absorption effects of Earth's atmosphere).
How are quantities optimally measurable if most of humanity's scientific knowledge has been accumulated only recently?
A Design Inference based on the correlation of measurability and habitability is at best only trivially true.
Quantifying measurability is a formidable (impossible?) task which must be completed prior to any potential design inference based on the Privileged Planet Hypothesis.
A Critique of the Privileged Planet Hypothesis by Kyler Kuehn presented at the "The Heavens Declare the Glory of God" ASA Annual Meeting, July 25-28, 2003 Colorado Christian University
[size=200%]Well positioned earth[/size]
Mankind is unusually well positioned to decipher the cosmos.
From: Gonzalez and Richards, The Privileged Planet: How our place in the cosmos is designed for discover.
But Gonzalez et al provide no quantifiable measures that help us determine if their claim is correct. What they do argue, again without much supporting evidence, is that habitability and measurability correlate in zones that are called galactic ï¿½habitable zones". They argue that these zones are ï¿½rare' but present no quantifiable information as to how many stars would be involved. The statement that habitability and measurability correlate in (significantly sized) zones in the universe undermines the argument that habitability and measurability are improbable and even seems to argue that measurability and habitability naturally correlate.
Even more mysterious than the fact that our location is so congenial to diverse measurement (what is so mysterious about this? Other than that the authors have failed to make their case that the earth is uniquely congenial to diverse measurements) and discovery is that these same conditions appear to correlate with habitability (appear to correlate. That's the risk of not really providing for hard estimates). This is strange because there is no obvious (to the authors at least) reason to assume that the very rare (unsupported) properties that allow for our existence (anthropocentric) would also provide the best overall (and yet the authors provide NO evidence for this optimality) setting to make discoveries about the world around us.
So lets look at some of the examples of measurability they quote from a variety of disciplines. Their article include perfect solar eclipses (astronomy), ice cores in Greenland and Antarctica (geology), deep sea cores (geology), tree rings (biology), stellar trigonometric parallax (astronomy). Stars as isotropic emitters of highly specific information (any ID paper seems to have as a requirement a reference to information and specificity J), supernovae and Cepheids (astronomy), our place in the Milky way and dust extinction (astronomy), the capacity to observe the maximum diversity of star types and the distant universe (astronomy) background radiation (astronomy) and the particle and event horizons of the universe (astronomy). Not as diverse as one may have hoped for and in fact the authors fail to show that the earth is somehow unique in these aspects
So is the earth ï¿½the best overall bench in the lab'? The authors do little to support this conclusion other than by pointing out that the earth has certain characteristics but are they optimal? Are they the best bench in the universe? How will we know? Little guidance is provided here.
[size=150%]Big Moons and solar eclipses[/size]
Gonzalez suggests that there is a link between life (on earth) and perfect solar eclipses. The moon and sun appear to be of similar size in the sky allowing ï¿½perfect' solar eclipses to occur. Not only is a big moon essential for stabilizing the planet (helpful perhaps but not necessarily essential)but it also was essential for the validation of Einstein's theory of relativity and the study of the solar corona. Thus linking habitability with measurability.
But was the solar eclipse of 1919 required for the scientific discover of Einstein? It's hard to argue that this confirmation hurt Einstein's case but lest point out that first of all, Einstein did not base his theory on the solar eclipse so the origins of the theory are not dependent on the solar eclipse but what about its verification?
To understand the relevance of the 1919 solar eclipse we need to remember that Einstein provided in his 1915 paper three experimental tests.
Would the precession of the perihelionof Mercury not have been sufficient? Would the solar eclipse data have been sufficient without the Mercury prediction? In fact to Einstein "This discovery was, I believe, by far the ]strongest emotional experience in Einstein's scientific life, perhaps in all his life. Nature had spoken to him." Abraham Pais (EM, p. 202)" ".
These equations, which proceed, by the method of pure mathematics, from the requirement of the general theory of relativity, give us, in combination with the [geodesic] equations of motion, to a first approximation Newton's law of attraction, and to a second approximation the explanation of the motion of the perihelion of the planet Mercury discovered by Leverrier. These facts must, in my opinion, be taken as a convincing proof of the correctness of the theory.
The same link reports that
To his friend Paul Ehrenfest in January 1916 he wrote that "for a few days I was beside myself with joyous excitement", and to Fokker he said that seeing the anomaly in Mercury's orbit emerge naturally from his purely geometrical field equations "had given him palpitations of the heart".
But of course Mercury and habitability arguments just do not seem to be as impressive as trying to present a case that the moon provides for stability of the earth axis (habitability) and allows for discovery (measurability). Certainly the perihelion of Mercury was an earlier event than the 1919 solar eclipse. We may never know to what extent the solar eclipse data sealed the case for Einstein's theory but it does show how the data appear to be carefully selected to support the thesis.
Here we also encounter another peculiarity of Earth namely that the requirement for habitability (nearly circular orbit) made the earth orbit unreliable for perihelion precession measurements.
Mercury 43.0 43.1 +/- 0.5
Venus 8.6 8.4 +/- 4.8
Earth 3.8 5.0 +/- 1.2
Icarus 10.3 9.8 +/- 0.8
The large tolerances for Venus and Earth are mainly due to the fact that their orbits are so nearly circular, making it difficult to precisely determine the axes of their elliptical orbits.
So when Gonzalez et al claim that:
The requirements for producing perfect solar eclipses, which provide scientific insight, also contribute to the Earth's habitability. This is only one example where the conditions for habitability overlap the conditions for measurability.
it seems that this overlap depends on what data we include and what data we ignore.
Now the argument for habitability. Is the moon essential for the stability of the earth and habitability?
Recent computer simulations by Eugenio Rivera of NASA AMES and his colleagues suggest that small planets with big moons are likely to be quite common. As many as one in three earth like planets in their infancy may be struck hard enough by other large objects to make big moons, and one in twelve struck at a time when its tilt is sufficiently mild for it to be stabilized at a terrestrial angle (currently 23.5 degrees) or less.
Page 97 Darling, Life Everywhere: The Maverick Science of Astrobiology
Rivera reports that
In my Ph.D. dissertation, I explored the plausibility of having five terrestrial planets for 8 -- 200 Myr, having two of them collide in this time, and leaving a planetary system with small orbital eccentricities as in the Solar System. I performed 191 N-body simulations which started with the planets Mercury through Neptune with their current orbits and masses except that the Earth and Moon were replaced with two bodies (the Earth-Moon progenitors), each in its own heliocentric orbit between the orbits of Venus and Mars, such that mass and angular momentum were conserved. I varied the mass ratio of the Earth-Moon progenitors, their initial eccentricities, inclinations, and semi-major axes. When a collision occurred, the bodies were simply merged into one. Slightly over one-half of the simulations ended with a collision between two planets before 200 Myr had elapsed, and about one-third of the systems which started with five terrestrial planets were stable for 200 Myr. Out of the 191 simulations, 16 ended with a collision between the Earth-Moon progenitors in the right time interval; four of these 16 resulting systems resembled the Solar System in that the terrestrial planets were on nearly circular, coplanar orbits. An additional 27 simulations ended with a collision at the right time which left four terrestrial planets with a mass distribution similar to that in the Solar System. Four of these 27 resulting systems resembled the Solar System. Thus, the scenario I explored does seem plausible.
But not only is the moon exactly the right 'size' for perfect eclipses, Gonzalez et al also argue that the moon is "just massive enough to stabilize this planet's 23.5-degree axial tilt. If the moon were any smaller, the tilt of our planet could vary as much as 30 degrees over the course of a year. "
But is this argument correct?
"A Moon-less Earth with the same mass, rotation rate, and orbit as today would have the direction of its spin axis vary chaotically between 0 and 90 degrees on time scales as short as 10 million years," says Darren Williams, Assistant Professor of Physics and Astronomy at Penn State University and NAI member. "At high obliquity, temperatures over mid-to-high latitude continents would reach near boiling 80 to 100 Celsius around the summer solstice under a 1-bar nitrogen- dominated atmosphere. Such temperatures would be damaging to all forms of water-dependent life on Earth today."
In addition without a moon the earth would be spinning faster, fast enough to stabilize the earth. In addition calculations have shown that the tidal friction increases the distance between the earth-moon, eventually causing the earth to come under the influence of chaos. Neron de Surgy and Laskar report in "On the long term evolution of the spin of the Earth" that in the next 5 billion years, the obliquity of the earth can reach a chaotic stage in about 1.5 billion years from now.
One may also ask why the moon adds to measurability when its dark-side has remained invisible to us from earth? But that may seem to be nitpicking, or does it?
Similar arguments for design based on the earth moon system can be found
God and Science website
A collision which would have ejected material less than the Roche limit would have formed only rings around the earth. Computer models show that a collision of a small planet with the earth must have been very precise in order for any moon to have been formed at all (coincidence or design?). (see What If the Moon Didn't Exist?, by Neil F. Comins, professor of Astronomy and Physics).
For a moonless earth, the time scales for fluctuation would be as short as 10 million years. Quite a different perspective.
Gonzalez et al reference Michael Mendillo and Richard Hart (Boston University), "Resonances," Physics Today 27:2 (1974), p. 73:
Based on the solar eclipses they reach the following conclusion
A planet/moon system will have exactly total solar eclipses only if there is someone there to observe them. As only Earth meets this requirement, there is no extraterrestrial life in the solar system.
Corollary In a system composed of nine planets and 32 moons, for only Earth with its single moon to have exactly total solar eclipses is too remarkable an occurrence to be due entirely to chance.
Similar arguments can be found in the Creation Research Society Quarterly Journal by Danny R. Faulkner (The Angular Size of the Moon and Other Planetary Satellites: An Argument For Design CRSQ Volume 35(1) June 1998)
For generations astronomers have traveled to exotic locations to observe total solar eclipses because total solar eclipses are such rare events. On average a total solar eclipse is visible from any location only once every few centuries. Therefore without planning it is unlikely that a typical person will ever view a total solar eclipse, let alone more than one. Whitcomb and DeYoung (1978, p. 132-136) and Mendillo and Hart (1974) have previously called attention to the interesting circumstance necessary for total solar eclipses as an argument for design in the earth-moon-sun system. More recently Englin and Howe concluded that the unique geometry of the earth-moon system that gives us total eclipses is no accident. No other moon in the solar system has such a close balance between the rarity and stark beauty of eclipses. Many have no eclipses at all. In the two decades since the work of Whitcomb and DeYoung the number of known satellites in the solar system has nearly doubled. At the same time the orbital parameters and measured sizes of most of the others have been greatly improved. Let us examine the latest values to determine how unique our moon is in this respect.
or in the Institute for Creation research article "THE MOON: A FAITHFUL WITNESS IN THE SKY* - IMPACT No. 68 February 1979 by Donald B. DeYoung, Ph.D.**
The combination of size and distance of the moon from the earth results in the special situation that the 0.5ï¿½ angular size of the sun and moon as seen from earth are the same. The moon is 400 times smaller than the sun but it is likewise 400 times closer to the earth. Because of this purposeful situation the moon is able to occasionally eclipse the sun exactly, providing a precise time record. Computer studies furthermore show that this perfect eclipse condition is unique among all the known moons of the solar system.5 The significance of eclipse data for Biblical studies is great, for it provides confirmation that the chronological systems employed by Old Testament scribes were perfectly accurate.
An interesting side note: Faulkner mentions that "On average a total solar eclipse is visible from any location only once every few centuries.", undermining the measurability argument proposed by Gonzalez et al.
Earth-Like Planets Common, Computer Simulation Suggests 11 December 2003
A new computer model designed to explore the range of possibilities for planet formation around other stars had no trouble coming up with worlds similar to Earth.
The simulations generated planets in similar orbits, planets with and without water, and a range of other virtual places that resemble Earth and the other inner, rocky planets.
The effort was designed to determine whether the four inner planets in our solar system, called terrestrials, represent a typical or extreme evolutionary scenario compared to what might develop around a Sun-like star with slightly different dynamics, explained said Sean Raymond, a University of Washington doctoral student in astronomy.
"We found there's a much wider possible range of masses and water content on terrestrial planets," Raymond said in a telephone interview.
"You can have planets that are half the size of Earth and are very dry, like Mars, or you can have planets like Earth, or you can have planets three times bigger than Earth, with perhaps 10 times more water," Raymond said.
43 planets formed between 0.8 and 1.5 AU with the following distribution and the authors reach the conclusion that:
1. Most of Earth's water was accreted during formation from bodies past snow line
2. Terrestrial planets have a large range in mass and water content
3. Habitable planets common in the galaxy
see original here
Scientists estimate 30 billion Earths Monday, 1 July, 2002
Scientists say they are now in a position to try to estimate how many planets may exist in the galaxy and speculate on just how many could be like the Earth. The answer in both cases is billions.
Virtually all the stars out to about 100 light-years distant have been surveyed. Of these 1,000 or so stars, about 10% have been found to possess planetary systems.
So, with about 300 billion stars in our galaxy, there could be about 30 billion planetary systems in the Milky Way alone; and a great many of these systems are very likely to include Earth-like worlds, say researchers