عصير كتاب: الكوكب المميز لـ جوليرمو جونزاليز وجاي ريتشاردز The Privileged Planet By Guillermo Gonzalez and Jay Richards

Posted: يونيو 5, 2016 in لاهوت طبيعي, الكون ونشأة الحياة, الكتابات العامة, الإلحاد, عصير الكتب

بسم الله الرحمن الرحيم

The Privileged Planet

How Our Place in The Cosmos is Designed for Discovery

By: Guillermo Gonzalez and Jay Richards

للتحميل: (DOC) (PDF)

privileged-planet

نبذة مُختصرة عن الكتاب:

مرجع في غاية الأهمية، يرجع إليه كبار العُلماء، وهو من المراجع النادرة في موضوعه، فالكتاب لا يتحدَّث فقط عن موضوع الضَّبط الدَّقيق للكون وصلاحيته لنشأة الحياة على الأرض، وإنَّما يُثبت أنَّ هذا الضَّبط سمح أيضاً بخاصِّيَّة الاستكشاف والبحث العلمي، أي قدرتنا على رؤية الكون من حولنا

لا أستطيع أن أمنع نفسي من أن أذكر قول الله تبارك وتعالى: ▬سَنُرِيهِمْ آيَاتِنَا فِي الْآفَاقِ وَفِي أَنفُسِهِمْ حَتَّى يَتَبَيَّنَ لَهُمْ أَنَّهُ الْحَقُّ أَوَلَمْ يَكْفِ بِرَبِّكَ أَنَّهُ عَلَى كُلِّ شَيْءٍ شَهِيدٌ♂ [فصلت: 53] وهي دالَّة على أنَّ قُدرتنا على رؤية ما في الآفاق ليس أمراً عبثياً جاء محض صدفة، وإنَّما بتدبير إلهي، فقد أحكم الله الكون بالطَّريقة التي أعطتنا القُدرة على رؤية ما في الآفاق من خلال مكاننا على كوكب الأرض!

هذا المرجع فريد، يرجع إليه كلّ من يُريد التَّحدُّث عن هذه المسألة التي نادراً ما يتكلَّم عنها أحد، وأوَّل معرفتي بهذا المبحث كان عن طريق كتاب «القضية الخالق» تأليف «لي ستروبل»، ففي الفصل الخاصّ بالدَّليل الفَلَكِي، كان ضيفا تحقيقه الصَّحفي مؤلِّفا هذا الكتاب، وأشهرهما «جوليرمو جونزاليز». (كتاب «القضية الخالق» لا غنى عنه لكل باحث حقيقي في مجال نقد الإلحاد وأدلة وجود الله، والكتاب مُتوفِّر على الشَّبكة، وتم عصر الكتاب في إصداره الإنجليزي الأصلي، وهو أفضل المراجع ذكراً لأنواع الأدلة على وُجُود الله من وجهة نظري، وهي: الفطرة، ثمَّ الأدلة العلمية: الكوسمولوجي، الفيزياء، والفلك، والكيمياء الحيوية، والمعلومات الجينية.)

الدَّليل الفلكي (موضوع هذا الكتاب)، يتناول الأدلة على وجود الله بعد مرحلتي الكوسمولوجي والفيزياء، فالكوسمولوجي هو المعروف بدليل الحدوث، بمعنى أن الكون حادث، فلابد من وجود مَن أحدثه، والفيزياء أول باب في دليل الإحكام والإتقان، هو الذي يبحث في مدى دقَّة ضبط الثَّوابت الكونية للسَّماح بنشأة الحياة على الأرض.

أمَّا الدَّليل الفلكي، فيتكلَّم عن موقع كوكب الأرض في الكون، وتميُّزه (عن الكتاب)، بداية من المجرَّة، مُرُوراً بصفات المجموعة الشمسية، وصولاً إلى خصائص كوكب الأرض نفسها. والجديد في هذا الكتاب الكلام عن خصائص المجرَّة نفسها، فهناك مُؤلَّفات كثيرة تتكلَّم عن خصائص كوكب الأرض (مثل كتاب «قدر الطَّبيعة» لـ «مايكل دينتون»، من إصدارات مركز براهين)، وبعض المراجع تتكلَّم عن خصائص المجموعة الشمسية، ولكن نادراً ما تجد كتاباً يتكلَّم عن خصائص المجرَّة نفسها! وهذا الكتاب هو أشهر مرجع في هذا الموضوع.

الكتاب مُقسَّم إلى ثلاثة أقسام، القسم الأول يتكلَّم عن كوكب الأرض، ومكانها المميز في المجموعة الشمسية، وخصائصها الفريدة التي تُميِّزها عن الكواكب الأخرى في المجموعة الشَّمسية، والقسم الثاني يتكلَّم عن خصائص المجرَّة، ثم القسم الثالث يتكلَّم عن بعض الآراء الإيديولوجية الخاصة بمكانة الإنسان في الكون وإشكالية «كوبيرنيكوس» فيما يخصّ مركزية الإنسان وكوكب الأرض بالنِّسبة للكون!

هذه هي النُّقطة الرَّئيسية للكتاب: الخصائص التي سمحت بنشأة الحياة على الأرض، اجتمعت مع الخصائص التي سمحت لنا بالكشف العلمي، سواء في تاريخ كوكب الأرض، أو في التاريخ الكوني كله، واجتماع خصائص الحياة مع خصائص الكشف العلمي – من حيث البرهان الرياضي الإحصائي الاحتمالي – دليل قوي جداً على التَّصميم في الكون، وأنَّه كل هذه الخصائص لم تنشأ بمحض الصُّدفة العمياء، بل من إله قدير عليم حكيم.

الكتاب في بعض الأحيان يُقدِّم معلومات تقنية صعبة الفهم، ولكنَّه في أغلب مادته سهل ويسير، بل مُبهر ورائع، والكتاب بشكل عام يستحق تقدير مُمتاز لتميُّزه وتفرُّده، فهو على ما يبدو أهمّ مرجع في بعض أبوابه، وأحياناً المرجع الوحيد في أبواب أخرى، ويُنصح بقراءته، بل وأتمنى أن يُترجم إلى اللُّغة العربية!

Introduction, The Privileged Planet

· Discovery is seeing what everyone else saw and thinking what no one thought. —Albert von Szent-Györgyi [In I. Good, ed., The Scientist Speculates (New York: Basic Books, 1962), 15.] [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p ix.]

· In his book Pale Blue Dot, the late astronomer Carl Sagan typifies this view while reflecting on another image of Earth (see Plate 2.), this one taken by Voyager 1 in 1990 from some four billion miles away: Because of the reflection of sunlight . . . Earth seems to be sitting in a beam of light, as if there were some special significance to this small world. But it’s just an accident of geometry and optics. . . . Our posturings, our imagined self-importance, the delusion that we have some privileged position in the Universe, are challenged by this point of pale light. Our planet is a lonely speck in the great enveloping cosmic dark. In our obscurity, in all this vastness, there is no hint that help will come from elsewhere to save us from ourselves. [Carl Sagan, Pale Blue Dot (New York: Ballantine Books, 1994), 7.] [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p x.]

· The fact that our atmosphere is clear; that our moon is just the right size and distance from Earth, and that its gravity stabilizes Earth’s rotation; that our position in our galaxy is just so; that our sun is its precise mass and composition—all of these facts and many more not only are necessary for Earth’s habitability but also have been surprisingly crucial to the discovery and measurement of the universe by scientists. Mankind is unusually well positioned to decipher the cosmos. Were we merely lucky in this regard? [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p x.]

· To put it both more technically and more generally, “measurability” seems to correlate with “habitability.” Is this correlation simply a strange coincidence? And even if it has some explanation, is it significant? [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p xi.]

· They argue that although Earth’s complex life and the rare conditions that allow for it are highly improbable, perhaps even unique, these conditions are still nothing more than an unintended fluke. In a lecture after the publication of Rare Earth, Peter Ward remarked, “We are just incredibly lucky. Somebody had to win the big lottery, and we were it.” [Stuart Ross Taylor puts it with refreshing bluntness: The message of this book is clear and unequivocal: so many chance events have appened in the development of the Solar System that any original purpose, if it existed, has been lost. Superimposed on these chance events from the physical world are those of biological evolution, which has managed to produce one highly intelligent species out of tens of billion attempts over the past four billion years. In Destiny or Chance, 204.] [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p xiii.]

· Most scientists presuppose the measurability of the physical realm: it’s measurable because scientists have found ways to measure it. Read any book on the history of scientific discovery and you’ll find magnificent tales of human ingenuity, persistence, and dumb luck. What you probably won’t see is any discussion of the conditions necessary for such feats, conditions so improbably fine-tuned to allow scientific discoveries that they beg for a better explanation than mere chance. [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p xiii.]

· Engineer and historian Henry Petroski calls this constrained optimization in his illuminating book Invention by Design: “All design involves conflicting objectives and hence compromise, and the best designs will always be those that come up with the best compromise.” [Henry Petroski, Invention by Design (Cambridge: Harvard University Press, 1996), 30.] [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p xiv.]

Section 1: Our Local Environment

Chapter 1: Wonderful Eclipses

· Perhaps that was the necessary condition of planetary life: Your Sun must fit your Moon. —Martin Amis [Martin Amis, London Fields (New York: Vintage Books, 1991), chap. 22.] [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p1.]

· Finally, there were the amateur astronomers and eclipse chasers, people who try to see as many total solar eclipses as they can fit into a lifetime. Eclipse chaser Serge Brunier explains in his book Glorious Eclipses: Their Past, Present, and Future, what drives them: It would be an understatement to say that I immediately became passionate about celestial events, which I have followed ever since, over the course of the years and the lunations, more or less all over the planet. Each time, there is the same astonishment and, each time, the feeling has grown that eclipses are not just astronomical events, that they are more than that, and that the emotion, the real internal upheaval, that they produce—a mixture of respect and also empathy with nature—far exceeds the purely aesthetic shock to one’s system. [S. Brunier and J. P. Luminet, Glorious Eclipses: Their Past, Present, and Future (Cambridge: Cambridge University Press, 2000), 6.] [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p4.]

· First, consider a little-known fact: A large moon stabilizes the rotation axis of its host planet, yielding a more stable, life-friendly climate. Our Moon keeps Earth’s axial tilt, or obliquity—the angle between its rotation axis and an imaginary axis perpendicular to the plane in which it orbits the Sun— from varying over a large range. A larger tilt would cause larger climate fluctuations. [J. Laskar et al., “Stabilization of the Earth’s Obliquity by the Moon,” Nature 361 (1993): 615–617. The Moon stabilizes Earth’s obliquity by exerting a torque on Earth that reduces its precession period by about a factor of three, taking it far from a dangerous resonance. For a planet of a given size, certain combinations of rotation period, precession period, and orbital period produce resonances that cause the obliquity to vary chaotically over a wide range. Earth will approach such a resonance in about 1.5 billion years as its rotation period continues to slow because of the action of the tides. Thus, to have a stable obliquity, several factors relating to a planet’s physical and orbital properties must be met simultaneously. See O. Neron de Surgy and J. Laskar, “On the Long Term Evolution of the Spin of the Earth,” Astronomy & Astrophysics 318 (1997): 975–989. A rotation period of twelve hours would also produce a stable obliquity, with or without the Moon. So it would seem that a stabilizing moon is not needed if a planet has a rapid spin. The problem with this olution is that Earth’s originally high spin was probably caused by the collision event that formed the Moon (see below). The Moon has been gradually robbing the high spin it gave Earth, but as a trade, it has maintained its stable obliquity.] [D. M. Williams and D. Pollard, “Earth-Moon Interactions: Implications for Terrestrial Climate and Life,” Origin of the Earth and Moon, R. M. Canup and K. Righter, eds. (Tucson: University of Arizona Press, 2000), 513–525.] [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p4.]

· The Moon also assists life by raising Earth’s ocean tides. The tides mix nutrients from the land with the oceans, creating the fecund intertidal zone, where the land is periodically immersed in seawater. (Without the Moon, Earth’s tides would be only about one-third as strong; we would experience only the regular solar tides.) Until very recently, oceanographers thought that all the lunar tidal energy was dissipated in the shallow areas of the oceans. It turns out that about one-third of the tidal energy is spent along rugged areas of the deep ocean floor, and this may be a main driver of ocean currents. These strong ocean currents regulate the climate by circulating enormous amounts of heat. [The prediction that wind and tides are the main drivers of global ocean circulation was made by W. H. Munk and C. Wunsch, “Abyssal Recipes II: Energetics of Tidal and Wind Mixing,” Deep-Sea Research 45 (1998): 1977–2010. Their prediction was confirmed by Topex/Poseidon satellite altimeter data: G. D. Egbert and R. D. Ray, “Significant Dissipation of Tidal Energy in the Deep Ocean Inferred from Satellite Altimeter Data,” Nature 405 (2000): 775–778.] [One of the oceanographers who suggested the deep-water tidal theory notes, “It appears that the tides are, surprisingly, an intricate part of the story of climate change, as is the history of the lunar orbit.” C. Wunsch, “Moon, Tides, and Climate,” Nature 405 (2000): 744.] [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p6.]

· The Moon’s origin is also an important part of the story of life. At the present time, the most popular scenario for its formation posits a glancing blow to the proto-Earth by a body a few times more massive than Mars. That violent collision may have indirectly aided life. For example, it probably helped form Earth’s iron core by melting the planet and allowing the liquid iron to sink to the center more completely. This, in turn, may have been needed to create a strong planetary magnetic field, a protector of life that we’ll discuss later. [Calculations indicate that the Moon may have formed from a glancing impact by an object two to three times the mass of Mars when Earth was only about half-formed; A. G. W. Cameron, “Higher-Resolution Simulations of the Giant Impact,” in Origin of the Earth and Moon, R. M. Canup and K. Righter, eds. (Tucson: Univ. of Arizona Press, 2000): 133–144. Other simulations indicate that the impact more probably occurred near the end of Earth’s formation and with an impactor the mass of Mars; R. M. Canup, and E. Asphaug, “Origin of the Moon in a Giant Impact Near the End of the Earth’s Formation,” Nature 412 (2001): 708–712. This more recent set of simulations makes the formation of the Moon a more probable event than Cameron’s simulations imply, because smaller impactors are more common than bigger ones. But caution is appropriate here, since this is a rapidly developing area of research.] [Recent measurements of the isotopes of tungsten in Earth and primitive meteorites help to establish when Earth’s iron core formed, and confirm the Moon’s contribution to that event. This is possible because radioactive halfnium present early on (with a half-life of nine million years, after which it decays to tungsten) and tungsten have different affinities for iron. Thus, when the core formed, some tungsten went down with the iron while halfnium remained behind in the mantle and crust. The data indicate that the core formed about thirty million years after the beginning of the Solar System, about the same time the Moon is thought to have formed. See R. Fitzgerald, “Isotope Ratio Measurements Firm Up Knowledge of Earth’s Formation,” Physics Today (January 2003): 16–18, and references cited therein.] [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p6.]

· In addition, had more iron remained in the crust, it would have taken longer for the atmosphere to be oxygenated, since any iron exposed on the surface would consume the free oxygen in the atmosphere. The collision is also believed to have removed some of Earth’s original crust. If it hadn’t, the thick crust might have prevented plate tectonics, still another essential ingredient for a habitable planet. In short, if Earth had no Moon, we wouldn’t be here. [For an entertaining and informative, though sometimes speculative, account of the many ways the Moon is important for life on Earth, see N. F. Comins, What If the Moon Didn’t Exist?: Voyages to Earths That Might Have Been (New York: HarperCollins, 1993). See also C. R. Benn, “The Moon and the Origin of Life,” Earth, Moon, and Planets 85–86 (2001): 61–66.] [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p6.]

· Habitability varies dramatically, depending on the sizes of a planet and its host star and their separation. There are good reasons to believe that a star similar to the Sun is necessary for complex life. [Also see G. Gonzalez, “Is the Sun Anomalous?” Astronomy & Geophysics 40, no. 5 (1999): 5.25–5.29.] [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p6.]

· According to Einstein’s General Theory of Relativity, gravity should cause starlight passing near the Sun’s limb to “bend.” A perfect total solar eclipse creates the best natural experiment for testing this prediction. Sizes and separations of bodies are not drawn to scale; the amount of bending has been exaggerated for clarity. [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p16.]

· Arthur Eddington was a famous theoretical astrophysicist of the early twentieth century, but today most know him for his observations of a total solar eclipse that confirmed a prediction of Einstein’s General Theory of Relativity— namely, that gravity bends light. On May 29, 1919, two teams, one led by Eddington and Edwin Cottingham on Principle Island off the coast of West Africa and the other led by Andrew Crommelin and Charles Davidson in Brazil, used a total solar eclipse to test Einstein’s 1916 theory. Their goal was to measure the changes in the positions of stars near the Sun compared with their positions months later or before. Both teams succeeded in photographing the eclipse. Their results confirmed Einstein’s predictions and won him immediate acclaim. [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p15, 16.]

· The most carefully executed starlight deflection experiment was conducted during the June 30, 1973, solar eclipse, and the results again confirmed General Relativity. [Zirker, Total Eclipses, 175–179.] [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p16.]

· Other tests involving radio transmissions from space probes have also confirmed related aspects of General Relativity. Therefore, although more stringent tests of General Relativity have gone far beyond those requiring a solar eclipse, and although the British 1919 results were somewhat imprecise, solar eclipse experiments clearly played a crucial role in speeding the adoption of General Relativity. [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p17.]

· Perfect solar eclipses are optimal for all three of these uses— discovering the nature of the Sun’s atmosphere, testing General Relativity, and timing Earth’s rotation. If we experienced super-eclipses instead, we would be able to observe the chromosphere only over a small fraction of the solar limb. Also, we wouldn’t be able to measure the deflection of starlight as closely to the solar limb. Finally, the eclipse shadow on Earth would be larger, limiting its usefulness for studying Earth’s rotation. [For an illustration of this see M. Littmann, K. Willcox, and F. Espenak, Totality: Eclipses of the Sun (Oxford: Oxford University Press, 1999), 130–131.] [This would become important if the Moon’s apparent size were at least twice its present value, since the various twentieth-century starlight deflection experiments generally did not employ stars within about two solar radii of the Sun’s limb.] [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p17, 18.]

· There’s a final, even more bizarre twist. Because of Moon-induced tides, the Moon is gradually receding from Earth at 3.82 centimeters per year. In ten million years, the Moon will seem noticeably smaller. At the same time, the Sun’s apparent girth has been swelling by six centimeters per year for ages, as is normal in stellar evolution. These two processes, working together, should end total solar eclipses in about 250 million years, a mere 5 percent of the age of Earth. This relatively small window of opportunity

· also happens to coincide with the existence of intelligent life. Put another way, the most habitable place in the Solar System yields the best view of solar eclipses just when observers can best appreciate them. [J. O. Dickey et al., “Lunar Laser Ranging: A Continuing Legacy of the Apollo Program,” Science 265 (1994): 482–490.] [The future lifetime of the biosphere for complex life is probably no more than 500 million years. See S. Franck et al., “Reduction of Biosphere Life Span as a Consequence of Geodynamics,” Tellus 52B (2000): 94–107.] [My (GG) discovery that the observability of perfect solar eclipses correlates with habitability was a rather surprising conclusion, and its publication (“Wonderful Eclipses,” Astronomy & Geophysics 40, no. 3 (1999): 3.18–3.20) generated some interest—including articles in several newspapers [“Eclipse shows signs of Life,” The Daily Telegraph (June 23, 1999): 16; “Right Distance for a ‘Perfect’ Total Eclipse,” The Irish Times (July 12, 1999): 12; “In the Shadow of Brilliance,” Chicago Sun-Times (June 27, 1999): 32; “Leben wir unter einem einzigartigen Stern?” Spectrum (July 17, 1999): 8], a BBC radio interview, which aired on August 11, 1999 (the day of the European total solar eclipse), and a mention in “The Year in Weird Science” section of the January 2000 Discover magazine. This last item is the most revealing one—the moniker “weird” implies that the result of my study contradicted the expectations of Discover’s editorial staff.] [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p18.]

· Earth is ideal for observing perfect solar eclipses. Beyond this, perfect solar eclipses are optimal for measuring a range of important phenomena, such as the solar flash spectrum, prominences, starlight deflection, and Earth’s rotation. But even more than this, perfect solar eclipses provide great opportunity for discoveries about the Sun. Finally, besides inspiring awe and allowing us to discover the nature of the Sun’s atmosphere and the element helium—both unanticipated—perfect solar eclipses became the occasion for discovering the correlation between habitability and measurability itself, hardly an insignificant point. [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p19.]

Chapter 2: At Home on a Data Recorder

· For example, data from ancient tidalites—fossilized remains of sediments deposited during periodic coastal tidal flooding—tell us that 500 million years ago days were twenty hours long and months were 27.5 modern Earth days. [For a specific example of this type of study, see C. P. Sonett and M. A. Chan, “Neoproterozoic Earth-Moon Dynamics: Rework of the 900 Ma Big Cottonwood Canyon Tidal Laminae,” Geophysical Research Letters 25 (1998): 539–542. More general reviews of paleoastronomy as applied to tidal rhythmites are given by E. P. Kvale et al., “Calculating Lunar Retreat Rates Using Tidal Rhythmites,” Journal of Sedimentary Research 69, no. 6 (1999): 1154–1168, and G. E. Williams, “Geological Constraints on the Precambrian History of Earth’s Rotation and the Moon’s Orbit,” Reviews of Geophysics 38, no. 1 (2000): 37–59.] [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p28.]

· Since simple life is a prerequisite for complex life, and complex life is a prerequisite for technological life, technological life requires the narrowest range of conditions. Because our primary interest is complex life and ultimately technological life, we need the criterion that most clearly separates simple life from the complex life that may become technological.39 With this in mind, we can define the minimum complex organism as a macroscopic aerobic metazoan—that is, largish, oxygen-breathing, and multicellular. Without oxygen, large mobile organisms aren’t possible, especially those with large brains. This is a basic limitation resulting from simple chemistry and physiology. [We should specify that these statements are true given the physical conditions that obtain in our universe. We’re not saying that this must be true for any conceivable type of life, with any conceivable set of physical laws and parameters in any possible universe.] [We can distinguish between simple and complex life in a number of ways. We could differentiate between single-celled and multicellular (or metazoan) organisms, eukaryotes and prokaryotes (with and without a nucleus, respectively), aerobic and anaerobic organisms (oxygen-breathing or not, respectively), or microscopic and macroscopic organisms. Yet another possibility is to define simple life as that which dominated Earth over most of its history.] [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p32.]

· At its basic level, however, chemical life must be able to carry the instructions for the construction of its progeny from basic atomic building blocks. These instructions, or “blueprints,” require, among other important things, a complex molecule as the carrier. This molecule must be stable enough to withstand significant chemical and thermal perturbations, but not so stable that it won’t react with other molecules at low temperatures. In other words, it must be metastable. Also, to allow for diverse chemistry, it must have an affinity for many other kinds of atoms comparable with the affinity it has for itself. Carbon excels in this regard, but silicon falls far short. Other elements aren’t even in the race. [See N. R. Pace, “The Universal Nature of Biochemistry,” Publications of the National Academy of Sciences 98 (2001): 805–808.] [Biochemist A. E. Needham comments on the metastability of carbon reactions: “As in so many other respects, carbon seems to have the best of both worlds, in fact, combining stability with lability, momentum with inertia. Most organic compounds are metastable . . . that is to say they are not in complete equilibrium with their environmental conditions and are easily induced to react further.” The Uniqueness of Biological Materials (Oxford: Pergamon Press, 1965), 30.] [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p32.]

· There are other arguments in favor of carbon, such as the fact that it forms gases when combined with oxygen (to make carbon dioxide) or hydrogen (to make methane), and both gases allow free exchange with the atmosphere and oceans. And most important, when other key atoms— hydrogen, nitrogen, oxygen, and phosphorus—are added to carbon, we get the informational backbones (DNA and RNA), and the building blocks (the amino acids and proteins) of life. Carbon gives these molecules an information-storage capacity vastly exceeding that of hypothetical alternatives. [In contrast, silicon forms a mineral, silica, when oxidized. This results from the tendency of silicon to form single bonds with the oxygen atoms, rather than double bonds as carbon does. The double bonds carbon forms with each oxygen atom do not leave the oxygen atoms free to form bonds with other carbon atoms in its vicinity. However, this is what happens with the single-bonded oxygen atoms attached to silicon—they bond with other silicon atoms, forming a stable crystalline matrix of SiO2.] [Biologist Michael Denton argues that the weak chemical bonds that allow large organic molecules to form threedimensional shapes are also an essential requirement for life: Nearly all the biological activities of virtually all the large molecules in the cell are critically dependent on their possessing very precise 3-D shapes. Nature has provided no other glue to hold together the molecular superstructure of the cell. While we cannot have carbon-based life in the cosmos without covalent bonds, as there would be no molecules, just as certainly, we cannot have carbon-based life without these weak noncovalent bonds—because the molecules would not have stable, complex 3-D shapes. Nature’s Destiny: How the Laws of Biology Reveal Purpose in the Universe (New York: The Free Press, 1998), 114.] [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p33.]

· Life also needs a solvent, which provides a medium for chemical reactions. The best possible solvent should dissolve many types of molecules, transporting them to reaction sites while preserving their integrity. It should be in the liquid state, since the solid state doesn’t allow for mobility and the gaseous one doesn’t allow for sufficiently frequent reactions. Further, the solvent should be liquid over the same range of temperatures where the basic molecules of life remain largely intact and in the liquid or gaseous state. Water, the most abundant chemical compound in the universe, exquisitely meets these requirements. [By chemical compound, we mean a substance composed of molecules containing more than one type of atom. The most abundant molecule in the universe is molecular hydrogen. It is interesting that the water molecule is composed of the two most abundant reactive elements in the universe.] [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p33.]

· Harvard chemist Lawrence J. Henderson described the many ways that water and carbon are uniquely suited for life in his classic 1913 work, The Fitness of the Environment. Our increased knowledge of chemistry over the past century has only reinforced his arguments. [The Fitness of the Environment: An Inquiry into the Biological Significance of the Properties of Matter (New York: The Macmillan Company, 1913). Henderson’s work was a quantitative extension of the nineteenth-century work by William Whewell, Astronomy and General Physics, Considered with Reference to Natural Theology (London: William Pickering, 1833), ninth edition published in 1864.] [See Nature’s Destiny; J. D. Barrow and F. J. Tipler, The Anthropic Cosmological Principle (Oxford: Oxford University Press, 1986), 524–541; The Uniqueness of Biological Materials; and P. Ball, Life’s Matrix: A Biography of Water (New York: Farrar, Straus and Giroux, 1999). Unlike the “Face on Mars,” which disappeared after images with greater resolution were obtained with newer orbiters, the apparently high fitness of water for chemical life has only become more impressive as our “resolution” in chemistry has increased since the nineteenth century.] [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p33.]

· First, water is virtually unique in being denser as a liquid than as a solid (the element bismuth is another substance with this property). As a result, ice floats on water, insulating the water underneath from further loss of heat. This simple fact also prevents lakes and oceans from freezing from the bottom up. It’s very difficult, if not impossible, to alter such a situation once attained. If ice were to sink to the bottom, it would remain there, unable to melt, separated from the Sun’s warmth. [Ice actually has higher heat conductivity than liquid water. But, ice forming on water still acts to slow heat loss from the water below. First, considerable heat is given off as ice forms at the base of the ice sheet, slowing the formation of new ice. Second, the ice does not convect, so heat must flow through it only by conduction; as its thickness grows, the insulation increases. Third, snow forming on the surface of the ice provides extra insulation, since snow is a better insulator than ice.] [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p33.]

· Second, water has very high latent heats when changing from a solid to a liquid to a gas. So more heat is needed to vaporize one gram of water than the same amount of any other known substance at ambient surface temperature (and higher than most others at any temperature). This means that it takes an unusually large amount of heat to convert liquid water to vapor. Similarly, vapor releases the same amount of heat when it condenses back to liquid water. As a result, water helps moderate Earth’s climate and helps larger organisms regulate their body temperatures. This characteristic also permits smallish bodies of water to exist on land; otherwise, ponds and lakes would evaporate more easily. [The amounts of heat given off by a gram of water as it condenses from gas to liquid and also from liquid to solid are called latent heats. As heat is applied to a body of water, it both raises the temperature of the water (specific heat) and evaporates some of it (latent heat). But the heat energy that goes into evaporating water does not raise its temperature. The very high latent and specific heats of water work together to reduce temperature changes in an environment that is subject to varying input from energy.] [Needham, The Uniqueness of Biological Materials, 13.] [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p34.]

· Third, liquid water’s surface tension, which is higher than that of almost all other liquids, gives it better capillary action in soils, trees, and circulatory systems, a greater ability to form discrete structures with membranes, and the power to speed up chemical reactions at its surface. Finally, water is probably essential for starting and maintaining Earth’s plate tectonics, an important part of the climate regulation system. [K. Regenauer-Lieb, D. A. Yuen, and J. Branlund, “The Initiation of Subduction: Criticality by Addition of Water?” Science 294 (2001): 578–580.] [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p34.]

· Frank H. Stillinger, an expert on water, observed, “It is striking that so many eccentricities should occur together in one substance.” [Stillinger, ”Water Revisited,” Science 209 (1980): 451.] [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p34.]

· Michael Denton describes one of these ends, the weathering of rock: Take, for example, the weathering of rocks and its end result, the distribution of vital minerals upon which life depends via rivers to the oceans and ultimately throughout the hydrosphere. It is the high surface tension of water which draws it into the crevices of the rock; it is its highly anomalous expansion on freezing which cracks the rock, producing additional crevices for further weathering and increasing the surface area available for the solvation action of water in leaching out the elements. On top of all this, ice possesses the appropriate viscosity and strength to form hard, grinding rivers or glaciers which reduce the rocks broken and fractured by repeated cycles of freezing and thawing to tiny particles of glacial silt. The low viscosity of water confers on it the ability to flow rapidly in rivers and mountain streams and to carry at high speed those tiny particles of rock and glacial silt which contribute further to the weathering process and the breaking down of the mountains. The chemical reactivity of water and its great solvation power also contribute to the weathering process, dissolving out the minerals and elements from the rocks and eventually distributing them throughout the hydrosphere. [Denton, Nature’s Destiny, 40–41.] [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p34, 35.]

· John Lewis, a planetary scientist at the University of Arizona, agrees that carbon and water have no equals. After considering possible alternatives, he concludes: Despite our best efforts to step aside from terrestrial chauvinism and to seek out other solvents and structural chemistries for life, we are forced to conclude that water is the best of all possible solvents, and carbon compounds are apparently the best of all possible carriers of complex information. [J. S. Lewis, Worlds Without End: The Exploration of Planets Known and Unknown (Reading: Helix Books, 1998), 199.] [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p35.]

· Henderson was also struck by the overall fitness of carbon and water for life: “From the materialistic and the energetic standpoint alike, carbon, hydrogen, and oxygen, each by itself, and all taken together, possess unique and preeminent chemical fitness for the organic mechanism.” [Henderson, The Fitness of the Environment, 248.] [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p35.]

· Water appears to be an ideal match for carbon-based chemistry. For starters, organic reactions are optimal over the same range of temperatures that water is liquid at Earth’s surface. At low temperatures, reactions become too slow, while at high temperatures, organic compounds become unstable. [Denton, Nature’s Destiny, 115–116.] [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p35.]

· Earth’s ability to regulate its climate hinges on both water and carbon, not least because carbon dioxide and water vapor—and to a lesser extent, methane—are important atmospheric greenhouse gases. These life-essential vapors are freely exchanged among our planet’s living creatures, atmosphere, oceans, and solid interior. Moreover, carbon dioxide is highly soluble in water. Together, they create a unified climate feedback system, and have kept Earth a lush planet for the past 500 million years. Indeed, it’s hard to ignore the need for the planetary environment to be so closely linked to the chemistry of life. [There is as much carbon dioxide in a liter of water as there is in a liter of air. Without the high solubility of carbon dioxide in water, creatures such as ourselves could not rid our cells of this product of oxidative metabolism. While doing so, the dissolved carbon dioxide forms a weak acid in the blood, which helps buffer and regulate acidity in organisms (Denton, 132–137). This synergy between carbon and water is also important on the planetary scale. The carbon dioxide dissolved in rainwater forms a weak acid important in the chemical weathering of exposed rocks.] [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p35, 36.]

· Life needs a habitable planet to exist, but simple organisms seem to be necessary ingredients for making a habitable planet. [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p36.]

· Of course, even simple life requires far more chemical elements than carbon, hydrogen, and oxygen. A tiny bacterium needs seventeen elements, and humans need twenty-seven. In general, the larger and more complex the organism, the more diverse the proteins and enzymes it requires. [R. E. Davies and R. H. Koch, “All the Observed Universe Has Contributed to Life,” Philosophical Transactions of the Royal Society of London B 334 (1991): 391–403; V. Trimble, “Origin of the Biologically Important Elements,” Origins of Life and Evolution of the Biosphere 27 (1997): 3–21.] [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p36.]

· While most of the essential elements are concentrated enough in seawater for life, the oceans aren’t an adequate source of all elements. For example, the atmosphere is the primary source of nitrogen, and the continents are the primary source of several mineral nutrients, including molybdenum. This suggests that planetary environments lacking a nitrogen-rich atmosphere and continents may not be able to support a robust biosphere. [The case of molybdenum is interesting. It is key to the operation of two enzymes, nitrogenase and nitrate reductase, which are involved in nitrogen fixation. Nitrogen in gaseous form is not useful to life, and so its conversion to a chemical form that life can use is essential. The fact that no other transition metal is used by life for nitrogen fixation, even though molybdenum is rare in some parts of the land, implies that there is no substitute for it. Francis H. C. Crick and Leslie E. Orgel cited the scarcity of molybdenum in Earth’s crust as possible evidence that Earth was “seeded” by an extraterrestrial civilization (called directed panspermia, or what a skeptic might call the Little-Green-Man-in-the-Gap theory); “Directed Panspermia,” Icarus 19 (1973): 341–346.] [Note also that many chemical elements are found in Earth’s oceans only because they have been washed away from the continents. On a planetary body with oceans but without continents, many of the life-essential elements might not be available in sufficient concentration.] [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p36.]

· Complex life also requires a certain minimum biological support system through the activity of autotrophs, organisms that synthesize organic molecules from simple inorganic matter. For example, photosynthetic algae and some bacteria synthesize food from such inorganic materials as carbon dioxide, nitrogen, methane, hydrogen, and various minerals. These algae and bacteria, and their organic products, then become food for other organisms that require organic food—heterotrophs like us. [B. M. Jakosky and E. L. Shock, “The Biological Potential of Mars, the Early Earth, and Europa,” Journal of Geophysical Research 103 (1998): 19359–19364.] [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p37.]

· Life relies on chemical energy for its immediate metabolic needs, and chemical energy is all about the exchange of electrons. The most energy is released when elements located on opposite ends of the periodic table exchange electrons. Oxygen is second only to fluorine in the amount of chemical energy released when it combines with other elements. Hydrogen, and carbon combined with hydrogen, or hydrocarbons, are the best substances to combine with oxygen. All complex life forms use such oxidation reactions (other common reactions yield far less chemical energy). And not incidentally, the products of oxidation are water and carbon dioxide, the nontoxic and essential components of the climate regulation system. [Denton notes that chemical reactions with fluorine are too energetic for the stability of organic reactions, and the product of hydrogen and fluorine is a very reactive acid.] [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p37.]

· So hydrogen, carbon, and oxygen, together, offer the best source of chemical energy. This remarkable fact was not lost on Henderson: “This is the last argument which I have to present, but it is one of the most potent. The very chemical changes, which for so many other reasons seem to be best fitted to become the process of physiology, turn out to be the very ones which can divert the greatest flood of energy into the stream of life.” [Henderson, The Fitness of the Environment, 247–248.] [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p37.]

· Recent studies of the organisms called extremophiles have made many astrobiologists more optimistic about the prospects for finding life of this sort on other planets. [”Extremophiles” are microorganisms that can live in extreme environmental conditions, far from the average in temperature, pressure, moisture, salinity, and acidity. See Michael Gross, Life on the Edge: Amazing Creatures Thriving in Extreme Environments (Cambridge: Perseus, 2001); L. J. Rothschild and R. L. Mancinelli, “Life in Extreme Environments,” Nature 409 (2001): 1092–1101.] [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p37.]

· There’s increasing evidence that deep subsurface microbial communities feed off dissolved organic matter, either from fossil soils or from fresher organic material brought down from the surface. As a result, thermal vent and deep subsurface communities may not be able to exist on a world that has never had abundant surface life or is far from a source of light energy. [For more information on the dependence of subsurface life on surface life, see R. A. Kerr, “Deep Life in the Slow, Slow Lane,” Science 296 (2002): 1056–1058.] [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p38.]

· Research by Abel Méndez, an astrobiologist at the University of Puerto Rico at Arecibo, suggests that most prokaryotes—“simple” organisms without a nucleus—grow best between 70 to 126 degrees Fahrenheit, with optimum growth at 96.8 degrees. This is important because the biodiversity in the tropical regions depends mostly on the growth rate of such organisms. Complex life is even less tolerant to changes in temperature. Temperatures quite different from this optimum would provide much less support for a complex biosphere. [We put the word simple in quotes because even the simplest organisms on Earth are quite complex, requiring lengthy DNA molecules, numerous proteins and diverse chemicals.] [That’s between 294 and 325 degrees Kelvin (21 to 52 degrees Centigrade), with optimum growth at 309 degrees Kelvin (36 degrees Centigrade). Méndez develops an equation of state of life for prokaryotes, in which he relates the growth rate of prokaryotes to the temperature, pressure, and water concentration of their local environment. See “Planetary Habitable Zones: The Spatial Distribution of Life on Planetary Bodies,” paper presented at the 32nd Lunar and Planetary Science Conference, March 12–16, 2001.] [The diversity of vascular plants correlates with the productivity of an ecosystem. See S. M. Schneider and J. M. Rey-Benayas, “Global Patterns of Plant Diversity,” Evolution and Ecology 8 (1994): 331–347. More recent studies confirm that biodiversity generally correlates with productivity; see R. B. Waide, et al., “The Relationship Between Productivity and Species Richness,” Annual Review of Ecology and Systematics 30 (2000): 257–300. Productivity, in turn, depends on such factors as temperature and nutrient availability; see A. P. Allen, J. H. Brown, and J. F. Gillooly, “Global Biodiversity, Biochemical Kinetics, and the Energetic-Equivalence Rule,” Science 297 (2002): 1545–1548.] [Denton notes that the solubility of oxygen in water drops rapidly as temperature increases, and the metabolic demand for oxygen doubles with every eighteen-degree rise in temperature; these factors alone limit complex life to temperatures below 115 F. Denton, Nature’s Destiny, 124.] [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p39.]

· Méndez also notes that life cannot survive at arbitrarily high pressures; the maximum limit is nearly one thousand times the pressure at Earth’s surface. Several environments in the Solar System where liquid water may exist exceed this limit. Moreover, while various species of extremophiles can tolerate extremes in temperature, salt content, moisture, and pH, few can tolerate a very broad range of environmental conditions. In fact, they’re somewhat challenging to maintain in the laboratory. So while we can certainly learn something of the extreme range of conditions in which life can exist by studying extremophiles, we shouldn’t assume we will find them on planets with environments significantly different from ours. [Research on thermophiles indicates that these organisms resist high temperature by incorporating certain key amino acids in their protein structure. These alterations (relative to their mesophilic cousins) make the amino acid sequences much more restrictive; they also make the proteins more rigid at lower temperatures. See C. Vielle and G. J. Zeikus, “Hyperthermophilic Enzymes: Sources, Uses, and Molecular Mechanisms for Thermostability,” Microbiology and Molecular Biology Reviews 65 (2001): 1–43.] [ James Lovelock concurs: There are salt-tolerant bacteria, the halophiles, that live precariously in the saline regions of Earth. These bacteria have solved the problem directly by evolving a special membrane structure that is not disrupted by salt. It works, but at a price; for these organisms cannot compete with mainstream bacteria when the salinity is normal. They are limited to their remote and rare niche, and depend upon the rest of life to keep Earth comfortable for them. They are like those eccentrics of our own society whose survival depends upon the sustenance that we can spare but who could barely survive alone. The Ages of Gaia (New York: W. W. Norton & Company, 1988), 108.] [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p39.]

· Earth has probably contaminated most of the other planetary bodies in the Solar System with its microbes. On most bodies—such as Mercury, the Moon, Jupiter, and asteroids—Earthly life can’t flourish. Mars, however, was probably wet for some time in its early history, and might have supported life. But today we find no evidence of life on its surface. Even with an early helping of our microbes, the harsh conditions on the other planetary bodies in the Solar System prevented them from surviving or transforming their host planets into more habitable environments. [The inability of Earth’s microbes to transform Mars into a lush planet weighs against panspermia as an effective way of “seeding” a planet that is not just like Earth; Venus, too, was not maintained in a habitable state by Earth’s life. These two natural experiments give us clues as to the close connection between life and the geology of a planet. How much more difficult to expect, then, that a single microbe could seed a distant planet orbiting another star?] [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p39.]

· In taking basic mineral elements and energy sources to produce organic compounds, autotrophs make their environment more habitable for all life. For example, marine organisms deposit carbonates—an important part of the carbon cycle—on the ocean floor (we’ll discuss this cycle in Chapter Three). In addition, marine phytoplankton produce most of the oxygen in the atmosphere. We and our animal cohabitants also depend on simple life directly: as food sources, digestive aids, and decomposers. And simple life makes Earth a more measurable place—through tree rings, stomata on leaves, mites in cave stalagmites, foram skeletons in deep ocean sediments, and pollen in lake sediments, to name a few. [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p40.]

· Isn’t it surprising that processes on Earth would encode such high-grade, accessible information as a mere accidental byproduct of cosmic evolution? It’s equally surprising from the perspective of biological evolution, since this information conferred no survival advantage on living things throughout Earth’s long past. After all, we’ve only recently noticed it and are still perfecting the technology required to recover and read it. [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p40, 41.]

· At the same time, Earth’s capacity for recording data, especially in highresolution ice cores, could confer survival advantages on an advanced civilization. In particular, it could help us maintain Earth’s present level of habitability long into the future by teaching us the proper relationship between temperature and atmospheric carbon dioxide. [Another example of ancient records that may enhance future survival is the field of paleotempestology—the study of ancient severe storms from their effects on lake sediments and coastal areas. While it is still a very young field of study, there is hope that enough historical hurricanes and severe storms will be found in the sediment record to discern correlations with the global climate. From this, it may be possible to prepare long-term forecasts of hurricane threats. Two recent studies are J. P. Donnelly et al., “Sedimentary Evidence of Intense Hurricane Strikes from New Jersey,” Geology 29, no. 7 (2001): 615–618; K. B. Liu and M. L. Fearn, “Reconstruction of Prehistoric Landfall Frequencies of Catastrophic Hurricanes in Northwestern Florida from Lake Sediment Records,” Quaternary Research 54 (2000): 238–245; A. J. Noren et al., “Millennial-Scale Storminess Variability in the Northeastern United States During the Holocene Epoch,” Nature 419 (2002): 821–824.] [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p41.]

Chapter 3: Peering Down

· Plate tectonics plays at least three crucial roles in maintaining animal life: It promotes biological productivity; it promotes diversity (the hedge against mass extinction); and it helps maintain equable temperatures, a necessary requirement for animal life. It may be that plate tectonics is the central requirement for life on a planet and that it is necessary for keeping a world supplied with water. —Peter D. Ward and Donald Brownlee [Brownlee and Ward, Rare Earth (New York: Copernicus, 2000), 220.] [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p45.]

· Earthquakes destroy property and kill many people every year; nevertheless, they benefit both our planet’s habitability and scientific discovery. Without earthquakes, we probably wouldn’t even be here and, if somehow we were, we would know far less about Earth’s interior structure. [The complete lack of earthquakes would not prevent us from learning something of Earth’s deep interior. Seismic waves generated by underground nuclear tests have been used to measure the depth of the inner core, for instance. Of course, the severe limitations imposed on the placement and number of underground uclear detonations prevent them from competing with natural earthquakes as probes of Earth’s interior.] [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p45.]

· About two hundred million years ago, only one supercontinent, called Pangaea, pierced the ocean surface of a watery, lopsided planet. Pangaea has since divided like a puzzle, with its pieces well distributed over Earth’s face. [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p47.]

· Heat flowing through Earth’s outer liquid core causes it to convect, like the heat-transferring convection on a hot afternoon that produces cumulus clouds. Because it conducts electricity, the outer core sets up a dynamo generator. But Earth’s magnetic dynamo is even more demanding than the man-made variety. In an electrical dynamo, the magnets have permanent fields, but the geodynamo must regenerate its magnetic field. Otherwise, it would decay after only a few hundred years. Such a self-sustained planetary dynamo requires, among other things, the circulation provided by a planet rotating fast enough to produce eddies in the outer core. [Moreover, an original magnetic field was needed to get it started, probably from the Sun. Theoretical models suggest that Earth’s solid inner core began forming about a billion years ago, making it at least two billion years younger than the geomagnetic field itself. So a solid inner core doesn’t appear to be essential, but it probably yields a stronger, more stable field; see P. H. Roberts and G. A. Glatzmaier, “Geodynamo Theory and Simulations,” Reviews of Modern Physics 72, no. 4 (2000): 1081–1123. A sharp increase in the magnetic field strength 2.7 billion years ago, as evidenced by paleomagnetic evidence, has been interpreted as the onset of the nucleation of the solid inner core, but more data are needed to know for sure; see C. J. Hale, “Paleomagnetic Data Suggest Link Between the Archean-Proterozoic Boundary and Inner-Core Nucleation,” Nature 329 (1987): 233–237. Just when the inner core forms in a terrestrial planet depends on the concentration of radioactive elements there. The higher their concentration, the earlier it can form; see S. Labrosse, et al., “The Age of the Inner Core,” Earth and Planetary Science Letters 190 (2001): 111–123.] [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p48.]

· We now know from studies of dated lava flows on land that the planetary magnetic field has changed polarity many times in the past. Magnetic reversals aren’t strictly periodic, but occur roughly every million years. The last one occurred 780,000 years ago. Because they are global events, magnetic reversals serve as universal markers for geologists to match widely separated seams of rock. [However, some polarity reversal “events” last less than fifty thousand years. See Lowrie, Fundamentals of Geophysics, 295–306.] [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p49.]

· As geophysicist David Sandwell notes, “Indeed, the ability to observe magnetic reversals from a magnetometer towed behind a ship relies on some rather incredible coincidences related to reversal rate, spreading rate, ocean depth, and Earth temperatures.” Sandwell goes on to describe how these four scales conspire to produce measurable fields at the ocean surface: Most of this magnetic field is recorded in the upper mile or two of the oceanic crust. If the thickness of this layer were too great, then as the plate cooled as it moved off the spreading ridge axis, the positive and negative reversals would be juxtaposed in dipping layers; this superposition would smear the pattern observed by a ship. On Earth, the temperatures are just right for creating a thin magnetized layer. [David Sandwell, ”Plate Tectonics: A Martian View,” in Plate Tectonics: An Insider’s History of the Modern Theory of the Earth, N. Oreskes, ed. (Westview Press: Boulder, 2001), 342.] [Sandwell, Plate Tectonics, 343.] [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p50.]

· The German meteorologist Alfred Wegener first proposed one of the main elements of plate tectonics theory, continental drift, in the 1920s. His theory of moving continents nicely accounted for the jigsaw-puzzle fit of the outlines of some continents and the similar rocks found on now widely separated lands. [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p53.]

· In the 1960s, however, land and sea floor magnetic measurements provided convincing evidence for continental drift and sea floor spreading and for plate tectonics theory more generally. The rejection of the old geosynclinal theory in favor of plate tectonics ranks as one of the great paradigm shifts in science, and Earth’s measurability was vital in the breakthrough. [An introduction to this subject as applied to the Atlantic is J. G. Sclater and C. Tapscott, “The History of the Atlantic,” Scientific American (June 1979): 156–174.] [As late as 1960, geology textbooks were still confident of the geosyncline theory. For example, Clark and Stearn write in their textbook, “The geosynclinal theory is one of the great unifying principles in geology. In many ways its role in geology is similar to that of the theory of evolution, which serves to integrate the many branches of the biological sciences. . . . Just as the doctrine of evolution is universally accepted among biologists, so also the geosynclinal origin of the major mountain systems is an established principle in geology.” T. H. Clark and C. W. Stearn, The Geological Evolution of North America (New York: Ronald Press, 1960), 43.] [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p54.]

· Most of us associate earthquakes with death and destruction, but ironically, earthquakes are an inevitable outgrowth of geological forces that are highly advantageous to life. [We say “ironically” because earthquakes can cause death and destruction, which might seem to count against the correlation. Here we should note that the ability to detect and measure earthquakes allows advanced civilizations the freedom to prevent such deaths. Many large population centers are located near plate boundaries, where earthquakes are most frequent, but it doesn’t have to be that way. We now know where strong earthquakes are likely to happen with a fairly high degree of confidence. They don’t just happen haphazardly, though we still cannot predict their timing. Also, better building codes have greatly improved earthquake survivability of buildings in threatened regions, for those people who choose to remain there. We could virtually eliminate deaths from earthquakes if we chose to do so.] [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p55.]

· A tectonically active crust builds mountains, subducts old sea floor, and recycles the carbon dioxide in the atmosphere, all of which make Earth more habitable. But it’s not obvious that a cold, rigid, floating chunk of crust should be subducted deep into Earth. The continuous presence of liquid water on Earth’s surface may explain why it has maintained long-lasting plate tectonics. Apparently, the chemical reactions of water with the minerals in the crust weaken it, providing lubrication that allows the crust to bend without breaking. [See Z. Mian, “Understanding Why Earth Is a Planet with Plate Tectonics,” Quarterly Journal of the Royal Astronomical Society 34 (1993): 441–448; K. Regenauer-Lieb, D. A. Yuen, and J. Branlund, “The Initiation of Subduction: Criticality by Addition of Water?” Science 294 (2001): 578–580.] [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p55.]

· Plate tectonics makes possible the carbon cycle, which is essential to our planet’s habitability. This cycle is actually composed of a number of organic and inorganic subcycles, all occurring on different timescales. These cycles regulate the exchange of carbon-containing molecules among the atmosphere, ocean, and land. Photosynthesis, both by land plants and by phytoplankton near the ocean surface, is especially important, since its net effects are to draw carbon dioxide from the atmosphere and make organic matter. [The carbon cycle is too complex for us to cover in detail here. For a general review of the carbon cycle and its interaction with the climate, see L. R. Kump, J. F. Kasting, and R. G. Crane, The Earth System (New Jersey: Prentice Hall, 1999), 128–151. For a recent summary of the state of the art in modeling carbon dioxide’s role in Earth’s ancient climate, see T. J. Thomas and R. A. Berner, “CO2 and Climate Change,” Science 292 (2001): 870–872.] [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p55.]

· Plate tectonics plays another life-essential role: it maintains dry land in the face of constant erosion. A large rocky planet like Earth wants to be perfectly round, with erosion eventually wearing down the mountains and even the continents, creating a true “waterworld.” Its interior must continuously supply energy to keep it from getting bowling-ball smooth. Without geological recycling, such a place would probably become lifeless, since it would lack a way to mix all the life-essential nutrients in its sunlight-drenched surface waters. [Biological productivity in Earth’s oceans is limited primarily by the availability of certain key nutrients, especially phosphorous and iron. Most of the needed nutrients flow into the oceans from the rivers. But it seems that even this is not sufficient for all regions of the oceans. A simple oceanographic experiment conducted in 1995 caught many by surprise. (See K. H. Coale et al., “A Massive Phytoplankton Bloom Induced by an Ecosystem-Scale Iron Fertilization Experiment in the Equatorial Pacific Ocean,” Nature 383 (1996): 495–501.) Small amounts of water-soluble iron were spread in a small patch of the eastern Pacific Ocean known to have a low biological productivity. Quickly, the populations of phytoplankton and zooplankton skyrocketed. Apparently, iron was the key limiting nutrient in these waters. Because of global wind patterns, some regions of the oceans receive very little dust from the continents, and the eastern equatorial Pacific is one of them. The iron in the dust is in a form that the biota can use. A planet without continents would lack both rivers and dust as sources of iron.] [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p57.]

· And a strong magnetic field contributes mightily to a planet’s habitability by creating a cavity called the magnetosphere, which shields a planet’s atmosphere from direct interaction with the solar wind. If solar wind particles— consisting of protons and electrons—were to interact more directly with Earth’s upper atmosphere, they would be much more effective at “sputtering” or stripping it away (especially the atoms of hydrogen and oxygen from water). For life, that would be bad news, since the water would be lost more quickly to space. [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p58.]

· Also vitally important is a planet’s mass. A planet’s habitability depends on its mass in many ways; terrestrial planets significantly smaller or larger than Earth are probably less habitable. Because its surface gravity is weaker, a less massive Earth twin would lose its atmosphere more quickly, and because of its larger surface-area-to-volume ratio, its interior might cool too much to generate a strong magnetic field. [M. H. Hart, “The Effect of a Planet’s Size on the Evolution of Its Atmosphere,” Southwest Regional Conference on Astronomy & Astrophysics 7 (1982): 111–126; G. Gonzalez, D. Brownlee, and P. D. Ward, “The Galactic Habitable Zone: Galactic Chemical Evolution,” Icarus 152 (2001): 185–200.] [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p59.]

· In contrast, without getting more habitable, a more massive Earth-twin would have a larger initial inventory of water and other volatiles, such as methane and carbon dioxide, and would lose less of them over time. Such a planet might resemble the gas giant Jupiter rather than our terrestrial Earth. In fact, Earth may be almost as big as a terrestrial planet can get. While life needs an atmosphere, too much atmosphere can be bad. For example, high surface pressure would slow the evaporation of water and dry the interiors of continents. It would also increase the viscosity of the air at the surface, making it more difficult for big-brained, mobile creatures like us to breathe. [Even though we do not yet know when or from where Earth received most of its water, there are several reasons a larger Earth-twin would probably start out with deeper oceans. First, it would collect a larger fraction of the water from asteroid and comet impacts, because a smaller fraction of the ejecta would be lost to space. Second, the greater gravitational focusing factor would cause more asteroids and comets to impact than a simple geometrical calculation would indicate. Third, as noted in the text, a larger terrestrial planet will have less surface relief.] [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p59.]

· To add insult to injury, the surface gravity of a terrestrial planet increases with mass more rapidly than you might guess. Intense pressures compress the material deep inside, so that a planet just twice the size of Earth would have about fourteen times its mass and 3.5 times its surface gravity. This higher compression would probably result in a more differentiated planet; gases like water vapor, methane, and carbon dioxide would tend to end up in the atmosphere. [Here, the relevant scaling relation is the fact that the mass of a sphere of uncompressed matter increases with diameter raised to the third power.] [Smaller terrestrial planets follow the uncompressed scaling relations fairly closely but begin to deviate significantly before they get as big as Earth. Earth’s mean density is 5.52 grams per cubic centimeter. Mars, about half the size of Earth, has a mean density of 3.93 grams per cubic centimeter.] [J. S. Lewis, Worlds Without End: the Exploration of Planets Known and Unknown (Reading: Helix Books, 1998), 64–66. If we had ignored compression, we would expect such a planet to be only about eight times more massive, with twice the surface gravity.] [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p59.]

· Maybe you’re still pining away for some adventure on a sci-fi–inspired giant terrestrial planet, but there’s another problem with larger planets— impact threats. To put it simply, they’re bigger targets. Asteroids and comets have a really hard time avoiding larger planets, so these planets suffer more frequent, high-speed collisions. While their bigger surfaces distribute the greater impact energy over more area, this doesn’t compensate for the larger destructive energy, since surface area increases slowly with mass for terrestrial planets more massive than Earth. [A larger terrestrial planet will have a larger impact cross section for asteroids and comets. The impact cross section increases with increasing planet mass for two reasons. First, the physical size of the planet is greater. Second, gravitational focusing is greater for more massive planets, irrespective of their sizes.] [This is due to self-compression effects. We should add that systems that can form giant Earth siblings will also be likely to form other smaller terrestrial planets (G. W. Wetherill, “The Formation and Habitability of Extra-Solar Planets,” Icarus 119 (1996): 219–238). Therefore, the problems noted above for a very large terrestrial planet in a given system would still not prevent it from having a terrestrial planet in the required mass range (but there are other problems associated with a system that forms massive planets—more on this in Chapter Five). Of course, the same cannot be said of a system that forms only small terrestrial planets.] [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p60.]

· To have advanced technology, you need life forms complex enough to develop it. That’s technological life. Now, technological life requires a narrow set of conditions, narrower than the conditions for complex life, and much narrower than the conditions for simple life. [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p60.]

· We could say a species is technological if, at the very least, it can plan several years ahead, control and shape the basic elements with fire as a central energy source, and alter its environment enough to enhance its survival and prosperity. [Fire is not a typical exothermic reaction. It releases great heat in a slow, nonexplosive manner. This makes it very useful for a wide variety of technological applications. See Michael Denton, Nature’s Destiny (New York: The Free Press, 1998), 122–123.] [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p60.]

· Controlling fire may be the single most important requirement for technology. Early on, fire was used to make pottery and smelt metal ores. More recently, fire has allowed our species to sustain the large population needed to develop high technology, which requires that plenty of individuals be free to focus their attention on matters not directly related to survival. A species that shapes metal to form tools to build large dams, bridges, and skyscrapers would therefore be technological, while one that spends all its time hunting wild animals, gathering wild fruits, and picking lice would not. [Certainly, some building materials can be shaped without metal tools. For example, wood can be shaped with stone axes, but many more construction options are available with bronze- and iron-age tools. Fire is also required to run a steam engine and prepare ceramics and durable bricks. The steam engine and the dynamo generator were arguably the most important prerequisites for the transition from basic to high technology. Both require the ability to shape iron.] [In retrospect, it seems surprising that human beings learned how to purify metals from ores. About seven thousand years ago, people in the Middle East learned how to smelt copper from colorful azurite and malachite ore. Early potters probably discovered copper smelting by accident when they experimented with powdered malachite and azurite for use as pigments in their carbon-fueled and oxygen-starved kilns. This turned out to be just the environment needed for removing oxygen atoms from the copper oxides in the ore to produce pure copper metal. Soon afterward, the early smelters improved their skills at eliminating impurities by adding a “flux”—another mineral that chemically combined with impurities and formed easily removed slag. Hematite, an iron oxide, was the most popular flux used in the Middle East for copper smelting. The very same conditions that allowed humans to purify the copper ore allowed them to produce iron metal from the hematite flux. This is probably how iron smelting was discovered. See Stephen Sass, The Substance of Civilization: Material and Human History from the Stone Age to the Age of Silicon (New York: Arcane Publishing, 1998). Are these just curious historical accidents on the way to high technology? Was this just an unusually fortuitous path to metalworking?] [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p60, 61.]

· Technological life needs simple and complex life directly as food sources and as beasts of burden, but it also needs them indirectly to regulate the climate and provide energy. Through glorious acts of creative imagination, the wood from trees and the vast accumulated deposits of ancient life were transformed into the fuels that drive the engines of modern research—coal, gas, and oil. [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p61.]

· The early modern Industrial Revolution—with its fuel-hungry steam engines, electric generators, and iron smelters—would not have happened without wood or coal. If you doubt this, just visit a part of the world where people use dried dung as fuel because wood is scarce; they can typically do little more than boil a small pot of water. [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p61.]

· Interestingly, each new energy source has been abundant and long-lasting enough to hold us over while we developed the technology needed to reach the next level of energy generation. Burning wood kept us going for thousands of years. Without wood, inhabitants of, say, a rocky, lichen – covered world would be hard-pressed to find an abundant, concentrated source of long-lasting heat. On Earth, all the forests would have been cut down decades ago had we not learned to use coal. In fact, England lost its forests before coal became widely available as a substitute for wood. [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p62.]

· Berkeley geologist George Brimhall writes: The creation of ores and their placement close to the Earth’s surface are the result of much more than simple geologic chance. Only an exact series of physical and chemical events, occurring in the right environment and sequence and followed by certain climatic conditions, can give rise to a high concentration of these compounds so crucial to the development of civilization and technology. [George Brimhall, ”The Genesis of Ores,” Scientific American (May 1991): 84.] [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p62.]

· So Michael Denton writes, “Another fascinating coincidence is that only atmospheres with between ten and twenty percent oxygen can support oxidative metabolism in a higher organism, and it is only within this range that fire—and hence metallurgy and technology— is possible.” [Denton, Nature’s Destiny, 117.] [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p64.]

· Although much more could be said, it should be clear that Earth’s magnetic field and plate tectonics—as well as the associated carbon cycle, nutrient mixing, and continent building—are crucial for both life and scientific discoveries in fields as diverse as geophysics and astronomy. The development of technology, which is essential for decoding mysteries in many corners of the cosmos, also hinges on a number of key planetary processes, including the right kind of atmosphere. Luckily for us, we have just the right atmosphere. [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p64.]

Chapter 4: Peering Up

· The combined circumstance that we live on Earth and are able to see stars— that the conditions necessary for life do not exclude those necessary for vision, and vice versa—is a remarkably improbable one. This is because the medium in which we live is, on the one hand, just thick enough to enable us to breathe and to prevent us from being burned up by cosmic rays, while, on the other hand, it is not so opaque as to absorb entirely the light of the stars and block any view of the universe. What a fragile balance between the indispensable and the sublime. —Hans Blumenberg [Well into writing this book, we discovered that Hans Blumenberg came very close to reflecting on the correlation between habitability and measurability in this introductory sentence to his monumental volume The Genesis of the Copernican Revolution, translated by Robert M. Wallace (Cambridge: MIT Press, 1987), 3, originally published as Die Genesis der kopernikanischen Welt in 1975. Regrettably for the progress of natural philosophy and happily for the progress of our personal publishing ambitions, it serves only to introduce his case for the importance of historical contingencies in scientific progress, and he does not develop the idea in detail.] [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p65.]

· Consider the atmosphere’s transparency, which is actually just part of the story. Our atmosphere participates in one of the most extraordinary coincidences known to science: an eerie harmony among the range of wavelengths of light emitted by the Sun, transmitted by Earth’s atmosphere, converted by plants into chemical energy, and detected by the human eye. [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p66.]

· Earth’s atmosphere is transparent to radiation between 3,100 to 9,500 Å and to the much longer radio wavelengths. The radiation we see is near the middle of that range, between 4,000 and 7,000 Å, the range in which the Sun emits 40 percent of its energy. Its spectrum peaks smack in the middle of this visible spectrum, at 5,500 Å. This is but a tiny sample of the entire range. The near-ultraviolet, visible, and near-infrared spectra— the light most useful to life and sight—are a razor-thin sliver of the universe’s natural, electromagnetic emissions: about one part in 1025. That is much smaller than one star out of all the stars in the entire visible universe: about 1022. [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p66.]

· As it happens, our atmosphere strikes a nearly perfect balance, transmitting most of the radiation that is useful for life while blocking most of the lethal energy. Water vapor in the atmosphere is likewise accommodating, a fact that even the fifteenth edition of the staid Encyclopaedia Britannica picks up on: “Considering the importance of visible sunlight for all aspects of terrestrial life, one cannot help being awed by the dramatically narrow window in the atmospheric absorption . . . and in the absorption spectrum of water.” [Encyclopaedia Britannica, fifteenth ed. 18 (1994): 203.] [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p66, 67.]

· It seems plausible that this is merely an artifact of our eyes having evolved through natural selection to decipher just the spectrum of light that happens to get through the atmosphere. But this fact isn’t so easily dismissed. As George Greenstein notes: One might think that a certain adaptation has been at work here: the adaptation of plant life to the properties of sunlight. After all, if the Sun were a different temperature could not some other molecule, tuned to absorb light of a different color, take the place of chlorophyll? Remarkably enough the answer is no, for within broad limits all molecules absorb light of similar colors. The absorption of light is accomplished by the excitation of electrons in molecules to higher energy states, and the general scale of energy required to do this is the same no matter what molecule you are discussing. Furthermore, light is composed of photons, packets of energy, and photons of the wrong energy simply cannot be absorbed. [For a more detailed discussion on this point, see Denton, 47–70, and references cited therein. For a technical discussion, see W. H. Freeman and A. P. Lightman, “Dependence of Microphysical Phenomena on the Values of the Fundamental Constants,” Philosophical Transactions of the Royal Society of London A 310 (1983): 323–336; J. D. Barrow and F. J. Tipler, The Anthropic Cosmological Principle (Oxford: Oxford University Press, 1986), 338. They derive the typical surface temperature of a star (and thus the typical photon energy) and the typical energy of biological reactions from first principles and confirm that the two are surprisingly close. They consider it a genuine coincidence.] [George Greenstein, The Symbiotic Universe (New York: William Morrow, 1988), 96–97.] [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p67.]

· In other words, because of the basic properties of matter, the typical energy involved in chemical reactions corresponds to the typical energy of optical light photons. Otherwise, photosynthetic life wouldn’t be possible. Photons with too much energy would tear molecules apart, while those with too little energy could not trigger chemical reactions. Similar arguments hold for the wavelength range over which the atmosphere is transparent. So stars that don’t emit the right sort of radiation in the right amounts won’t qualify as useful energy sources for life. [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p67.]

· A rainbow is in effect a natural spectroscope as big as the sky. Once scientists learned how to use a prism to replicate a rainbow, it was only a matter of time before someone scrutinized the solar spectrum. But rainbows won’t appear on just any planet. A good rainbow needs a partially cloudy atmosphere, the golden mean between the uniformly cloudy and uniformly dry. [The best rainbows are produced when raindrops between 0.5 and 1.0 millimeters are abundant. Such conditions are best realized in thunderstorms (with rain falling at a rate near one inch per hour). The high surface tension of liquid water maintains the spherical shape of raindrops less than two millimeters in size as they fall to the ground; larger drops become significantly distorted. A spherical shape is necessary to produce the brilliant colors in a rainbow. A liquid substance with a smaller surface tension could not produce such large spherical drops and therefore could not produce colorful rainbows. Of course, one can also see a rainbow at the bottom of a waterfall, but not without direct sunlight.] [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p69.]

· The idea that Earth has feedback processes in which its biota interact with its nonliving parts to regulate the global climate is known as the Gaia hypothesis. James Lovelock and Lynn Margulis first proposed this in the 1970s, arguing that such interactions tend to make the environment more fit for life, mostly by taking the edge off climate change. Lovelock has compared Earth’s regulation system, which he calls geophysiology, to the metabolism of a mammal or a redwood. [See J. Lovelock, The Ages of Gaia: A Biography of Our Living Earth (New York: W. W. Norton & Company, 1988), and J. Lovelock, Gaia: The Practical Science of Planetary Medicine (Oxford: Oxford University Press, 2000).] [While we find much to laud in the Gaia hypothesis, we do not agree with all the extrapolations that Lovelock and his supporters draw from it. We would not agree to call the Earth system a “superorganism,” or elevate it to a metaphysical status, or consider people to be infectious “disease agents.” We also disagree with Lovelock’s characterization that the present is in a “fever” state, while the ice ages are “healthy”; the evidence we presented in Chapter Two strongly disconfirms such a view.] [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p70.]

· Earth’s present-day atmosphere, then, gives us exceptional access not only to the past but also to the wider universe, while maintaining a life-nurturing environment. And like the layering processes discussed previously, there’s no reason to suppose that we are specially adapted to decode this information, since doing so gave us no survival advantage—that is, not until very recently. [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p73.]

· Curiously, Earth’s transparent atmosphere does provide survival advantages to a civilization advanced enough to use the stored information, but much too late in the process to be explained in Darwinian terms. [One could argue that explorers of years past benefited from star navigation, but it is unlikely the survival of the human race depended on it.] [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p73.]

· For example, the transparency of the atmosphere, especially with respect to high-precision astrometry (measuring position on the sky) of faint objects, allows astronomers to catalog the population of near earth objects, or NEOs, which include both near Earth asteroids and comets. NEOs have Earthcrossing

· orbits, which means they can hit us. Currently, about 1,250 NEOs are known, most discovered in the past few years. [NASA, in collaboration with the U.S. Air Force, is the main supporter of NEO research at the present time (http:/neo.jpl.nasa.gov). The LINEAR project is currently the most productive program (http:/www.ll.mit.edu/LINEAR/). NASA is committed to discovering 90 percent of NEAs greater than one km in diameter by 2008. See also “Sources of the Asteroid Threat,” Sky & Telescope 100 (December 2000): 32–33.] [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p73.]

· Had our atmosphere been completely cloud-covered or translucent, we would not know about impact threats until it was too late. Nor would we have developed a space program, which is a prerequisite for deflecting NEOs. Had our atmosphere been thicker but still partly transparent, the additional distortions of telescopic images would have severely limited our ability to catalog these faint objects. So once again we see life and discovery walking hand-in-hand. [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p74.]

· On January 18, 2000, a fiery ball streaked across the sky, its explosions breaking the early-morning silence of the frigid Yukon and waking its sleepy residents. Defense satellites had tracked it from space and confirmed its extraterrestrial origin. Its smoke trail lingered in the sky for a full day like the Cheshire cat’s grin. This had been the largest bright meteor, called a bolide, detected over land in ten years. A few days later, a resident near Whitehorse, Yukon, searched the ice-covered Tagish Lake and found several fragments of the space visitor. Today, the few Tagish Lake fragments on the market fetch a handsome sum. Scientists called meteoriticists are willing to pay top dollar for meteorite fragments, not only because they are rare and hard to locate, but also because they contain unique and important information. [News item, “Yukon Meteorite Bonanza,” Sky & Telescope 99 (June 2000): 22. This was a fortunate landing, since it’s much easier to see dark meteorites against the white backdrop of ice and snow. Deserts and the ice fields of Antarctica have yielded many good-quality specimens. Meteorite hunters prefer ice fields, though, since they can easily pick out the dark space rocks against the blue-white background. What’s more, ice flows against mountain ranges concentrate meteorites on the surface, while the cold temperatures and isolation from the atmosphere help to minimize their erosion. For a firsthand account of meteorite collecting in Antarctica, see B. Livermore, “Meteorites on Ice,” Astronomy 27 (July 1999): 54–58. See also the readable personal account of Guy Consolmagno, Brother Astronomer: Adventures of a Vatican Scientist (New York: McGraw-Hill, 2000).] [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p75.]

· So why are meteorites so important? For starters, they contain samples of the early Solar System. Such material is not available from the homogenized and processed planetary bodies. [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p76.]

· But some of the scattered asteroidal debris ended up on Earth, blessing it with almost all of its life-essential volatile elements and simple organics. [Carbon is only a trace element in the bulk Earth. Had it not been delivered to Earth’s surface near the end of its formation by asteroids and comets, there may not have been enough carbon near the surface for life to flourish. Water was also brought to Earth’s surface by asteroids. Some asteroids contain large amounts of water chemically bonded in the minerals (called hydration). Once hydrated, the minerals in asteroids can better retain their water than if the water had not been present in hydrated form. The hydration of the minerals with water requires special conditions. One possibility is that the short-lived radioactive isotopes present in the very early history of the solar nebula heated the asteroid building blocks enough for hydration to occur. Another possibility is that shock waves in the gas provided enough heating and water vapor pressure to hydrate the minerals in the dust. Jupiter may have been the source of the shock wave. See F. J. Ciesla et al., “A Nebular Origin for the Chondritic Fine-Grained Phyllosilicates,” Science 299 (2003): 549–552.] [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p78.]

· As we learn more about the seemingly accidental features of our atmosphere and Solar System, we begin to recognize a trend: The Earth system offers not only a habitat but also a great viewing platform for its inhabitants. Because the processes that produce such a happy planetary state are intricate and interdependent, Earth is likely to be a very rare kind of place. [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p79.]

Chapter 5: The Pale Blue Dot in Relief

· There has been considerable speculation about the possibility of life in Europa’s ocean, much of it driven by the naïve assumption that the presence of liquid water virtually guarantees life, regardless of other environmental conditions. [For a review of this topic, see C. F. Chyba and C. B. Phillips, “Europa as an Abode of Life,” Origins of Life and Evolution of the Biosphere 32 (2002): 47–68.] [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p88.]

· Earth’s long-lasting hydrological cycle, plate tectonics, oscillating magnetic field, continents, stable orbit, and transparent atmosphere together provide the best overall “laboratory bench” in the Solar System. Earth’s surface strikes a balance between the permanence required to preserve patterns written on it and the dynamic yet gentle circulation that subtly sways these “recorder pens” without tearing up its paper-thin crust. The crust records and stores information while maintaining the most habitable environment for complex life in the Solar System. Continents amid oceans of water, enabled by plate tectonics—as Earth enjoys exclusively—seem to be the best overall habitat for observers. No other locations yet discovered hold a candle to this one blue dot, however pale it may appear to some. [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p101.]

Chapter 6: Our Helpful Neighbors

· We can . . . be thankful that the Solar System in which we live has been unreasonably kind throughout the long history of human efforts to understand its dynamics and to extend that knowledge to the rest of the universe. At each step along the way, it has served as a perspicacious teacher, posing questions just difficult enough to prompt new observations and calculations that have led to fresh insights, but not so difficult that any further study becomes mired in a morass of confusing detail. —Ivars Peterson [Ivars Peterson, Newton’s Clock: Chaos in the Solar System (New York: W. H. Freeman, 1993), 286.] [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p103.]

· The mere presence of the Moon and other planets in the Solar System fostered the development of celestial mechanics and modern cosmology. Danish astronomer Tycho Brahe’s (1546–1601) observations of the paths of the planets against the background stars allowed Johannes Kepler (1571–1630) to formulate his three famous laws of planetary motion. [We owe this insight to philosopher of science Robin Collins. Stanley Jaki makes a similar point about the Earth-Moon system in Maybe Alone in the Universe After All (Pinckney, MI: Real View Books, 2000), as does Peterson, 286, 293, with regard to the Solar System.] [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p104.]

· Kepler’s three empirical laws served as the foundation of Isaac Newton’s more general physical laws of motion and gravity, which became the foundation for Einstein’s General Theory of Relativity two centuries later. The planets may have inspired Kepler, but the Moon inspired Newton to apply his Earthly laws to the broader universe. Without the Earth-centered motion of the Moon, the conceptual leap from falling bodies on Earth’s surface to the motions of the Sun-centered planets would have been much more difficult. [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p104.]

· Ivars Peterson, at the conclusion to his work Newton’s Clock: Chaos in the Solar System, also notices this remarkable coincidence (while discussing dynamical chaos): A deep-seated puzzle lies at the heart of this newly discovered uncertainty in our knowledge of the Solar System. Was it an accident of celestial mechanics that the Solar System happens to be simple enough to have permitted the formulation of Kepler’s laws and to ensure predictability on a human time scale? Or could we have evolved and pondered the skies only in a Solar System afflicted with a mild case of chaos? Are we special, or were we specially fortunate? [Peterson, Newton’s Clock, 293.] [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p105.]

· The relationship between Earth and its Moon is so intimate that it’s probably best not to think of Earth as a lone planet, but as the habitable member of the Earth-Moon system. This partnership not only makes our existence possible, it also provides us with scientific knowledge we might otherwise lack. [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p108.]

· Jupiter and Saturn are probably the most significant planetary protectors, since they shield the inner Solar System from excessive comet bombardment. [See J. I. Lunine, “The Occurrence of Jovian Planets and the Habitability of Planetary Systems,” Publications of the National Academy of Sciences 98, no. 3 (2001): 809–814. The classic study on the relation between Jupiter and Earth’s habitability is G. W. Wetherill, “Possible Consequences of Absence of Jupiters in Planetary Systems,” Astrophysics and Space Science 212 (1994): 23–32.] [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p114.]

· Early in the Solar System’s history, Earth probably experienced several collisions with enormous asteroids. Some may have vaporized its oceans and sterilized the entire planet. These impacts would have hurled many fragments from Earth’s surface into space. It’s possible that some of these Earthly fragments could have seeded Mars with living organisms. Thus, Mars, or even Venus, if it was hospitable to life early on, could have served as a temporary life storage surface while Earth recovered from a sterilizing impact; a subsequent impact on Mars would have reseeded Earth. An isolated planet would lack such temporary refuges for life. [N. Sleep et al., “Annihilation of Ecosystems by Large Asteroid Impacts on the Early Earth,” Nature 342 (1989): 139–142.] [C. Mileikowski et al., “Natural Transfer of Viable Microbes in Space: 1. From Mars to Earth and Earth to Mars,” Icarus 145 (2000): 391–427.] [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p115.]

Section 2: The Broader Universe

Chapter 7: Star Probes

· Within this unraveled starlight exists a strange cryptography. Some of the rays may be blotted out, others may be enhanced in brilliancy. Their differences, countless in variety, form a code of signals, in which is conveyed to us, when once we have made out the cipher in which it is written, information of the chemical nature of the celestial gases. . . . It was the discovery of this code of signals, and of its interpretation, which made possible the rise of the new astronomy. —William Huggins [Cited in The Book of the Cosmos: Imagining the Universe from Heraclitus to Hawking, ed. D. R. Danielson (Cambridge: Helix Books, 2000), 319.] [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p119.]

· If the laws of physics had been such that stars were much larger or did not produce so many sharp absorption lines in their spectra, or if pulsars and white dwarfs were impossible, the universe would have been a far less measurable place. [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p127.]

· In the late 1950s, astronomers introduced the concept of the Circumstellar Habitable Zone (CHZ). While its definition has varied somewhat since then, they’ve generally defined it as that region around a star where liquid water can exist continually on the surface of a terrestrial planet for at least a few billion years. This definition is based on the assumption that life will flourish if this minimum requirement is met. [S.-S. Huang, “Occurrence of Life in the Universe,” American Scientist 47 (1959): 397–402; J. S. Shklovsky and C. Sagan, Intelligent Life in the Universe (Holden-Day: San Francisco, 1966); M. H. Hart, “Habitable Zones About Main Sequence Stars,” Icarus 37 (1979): 351–357; J. Kasting, D. P. Whitmire, and R. T. Reynolds, “Habitable Zones Around Main Sequence Stars,” Icarus 101 (1993): 108–128; S. Franck et al., “Habitable Zone for Earthlike Planets in the Solar System,” Planetary and Space Science 48 (2000): 1099–1105.] [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p]

· They usually mark the inner boundary of the Circumstellar Habitable Zone as the point where a planet loses its oceans to space through a runaway greenhouse effect, and define its outer boundary as the point where oceans freeze or carbon dioxide clouds form, both of which increase a planet’s albedo and trigger a vicious cycle of increasing coldness until the oceans freeze over completely. [The oceans do not literally boil away. Rather, water gets into the stratosphere, where it is photo-dissociated by solar UV light and its hydrogen is lost to space.] [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p128.]

· Stars play two essential life-support roles: as sources of most chemical elements and as steady suppliers of energy. [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p132.]

· This is a practical application of what is often called the Weak Anthropic Principle (WAP), or just the Anthropic Principle, which states that we should expect to observe conditions, however unusual, compatible with or even necessary for our existence as observers. [Here we are making use of the WAP as applied to the observable and quantifiable universe. Other, much more speculative, versions of the Anthropic Principle assume the existence of some “multiverse.” We will revisit this topic again in Chapter Thirteen.] [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p136.]

· Textbooks and science writers often assert that the Sun is an average or typical star. As Jay Pasachoff wrote in one of his popular introductory astronomy texts, “The Sun is an average star, because there are stars that are smaller than the Sun and stars that are larger.” But when we actually compare the Sun’s properties with those of other stars in detail, we find that this is not the case. [Jay Pasachoff, Contemporary Astronomy (Philadelphia: Saunders College Publishing, 1989), 129. To be fair, we should note that more recently some textbook writers have begun to note that the Sun is not an average star. For example, Michael Zeilik writes in the caption to one of his figures showing the relative numbers of stars of each type in a pyramid drawing, “This pyramid, which shows the relative numbers of common stars, illustrates that the sun is not an ‘average’ or ‘typical’ star” (Astronomy: The Evolving Universe, Eighth Edition (New York: John Wiley & Sons, 1997), 315, Figure 14.18.)] [See G. Gonzalez, “Is the Sun Anomalous?” Astronomy & Geophysics 40, no. 5 (1999): 5.25–5.29, and G. Gonzalez, “Are Stars with Planets Anomalous?” Monthly Notices of the Royal Astronomical Society 308 (1999): 447–458; B. Gustafsson, “Is the Sun a Sun-like Star?” Space Science Reviews 85 (1998): 419–428.] [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p136.]

· So the Sun’s local environment seems to offer the best type of habitat for complex life. At the same time, its particular properties disclose vital scientific information more abundantly than many more common types of stars, while also providing us with an excellent example of stars in general. [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p142.]

Chapter 8: Our Galactic Habitat

· Ironically, our relatively peripheral position on the spiral arm of a rather ordinary galaxy is indeed rather fortunate. If we had been stationed in a more central position—say, near the galactic hub—it is likely that our knowledge of the universe of other galaxies, for example, might not have been as extensive. Perhaps in such a position the light from surrounding stars could well have blocked our view of intergalactic space. Perhaps astronomy and cosmology as we know these subjects would never have developed. —Michael J. Denton [Michael Denton, Nature’s Destiny (New York: The Free Press, 1998), 372.] [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p143.]

· Look at the sky on a clear night far from city lights and you’ll see a fuzzy band of white light that looks like a wispy, luminous string of clouds. The ancient Chinese saw it as a river in the sky. The Greeks and Romans explained it with the myth of Heracles, the son of Zeus, who bit the breast of Zeus’s wife Hera, spilling her white milk across the black firmament. The Romans called this part of the sky the Via Lactea, the Milky Way, and at least in the West, the name stuck. (The word galaxy, by the way, derives from the Greek words for Milky Way.) [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p143.]

· Astronomers usually subdivide the Milky Way galaxy into four regions, or “populations”: halo, bulge, thick disk, and thin disk. Each region is characterized by the ages, compositions, and movements of the objects within it. The halo contains only old metal-poor stars in highly elliptical orbits (recall that astronomers call all elements heavier than hydrogen and helium “metals”). The bulge, as fat as the disk is thin, contains stars spanning a large range in metal content, from about one-tenth to three times the Sun’s. It is unlike the halo in that some stars still form there today. The orbits of its stars are also elliptical, but less so than those in the halo. The flattened thick and thin disks overlap. The thin disk contains the greater diversity of objects, including most of the stars in the Milky Way, while the thick disk is more puffed up with older, more metal-poor stars. [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p146.]

· Observers could not sample such diverse delights from every place in the Milky Way galaxy. The Sun, you see, is very near the mid-plane, having crossed it a mere three to five million years ago. The gas and dust in our neck of the woods is quite diffuse compared with other local regions in the local mid-plane. This gives us a fairly clear view of objects in the nearby disk and halo, as well as distant galaxies. [P. C. Frisch, “The Galactic Environment of the Sun,” American Scientist 88 (2000): 53–54.] [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p146, 147.]

· Second, we know we are living in a spiral galaxy because we can map its structure from the inside. This might seem impossible, like a tapeworm trying to describe the exterior of its host. But astronomers have learned to take advantage of the peculiar properties of the flattened rotating disk of gas and stars. So-called differential rotation allows radio astronomers to translate the measured radial velocities of interstellar gas clouds into distances from the Sun. [Specifically, astronomers have used radio frequencies of carbon monoxide and neutral hydrogen to map a large fraction of our galaxy’s spiral structure. At radio frequencies the galaxy is largely transparent.] [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p150.]

· We occupy the best overall place for observation in the Milky Way galaxy, which is itself the best type of galaxy to learn about stars, galactic structure, and the distant universe simultaneously; these are the three major branches of astrophysics. [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p151.]

· Like the Circumstellar Habitable Zone in our Solar System, there is also a Galactic Habitable Zone (GHZ). And its first requirement is to maintain liquid water on the surface of an Earth-like planet. But it’s also about forming Earth-like planets and the long-term survival of animal-like aerobic life. The boundaries of the Galactic Habitable Zone are set by the needed planetary building blocks and threats to complex life in the galactic setting. [The material in this section is based on the following paper: G. Gonzalez, D. Brownlee, and P. D. Ward, “The Galactic Habitable Zone: Galactic Chemical Evolution,” Icarus 152 (2001): 185–200; a less technical summary is given in G. Gonzalez, D. Brownlee, and P. D. Ward, “The Galactic Habitable Zone,” Scientific American (October 2001): 60–67.] [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p152.]

· The Big Bang produced hydrogen and helium and little else. Over the next 13 billion years, this mix was cooked within many generations of stars and recycled. Beginning with the fusion of hydrogen atoms, massive stars make ever-heavier nuclei deep in their hot interiors, building on the ashes of the previous stage and forming an onion shell–like structure. Exploding as supernovae, the massive stars eventually return atoms to the galaxy. But they return them with interest, by producing heavy elements that didn’t exist before. [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p152, 153.]

· Because different processes produced gas giants and terrestrial planets, differences in the initial metal content probably led to different ends. And since it now looks as if you need both gas giants and terrestrial planets to form a habitable system, the optimum metal content for building a habitable planetary system might be quite narrow. [At present astronomers do not have any observational evidence for terrestrial planets around other stars, so they cannot say for certain how their formation depends on initial metallicity. But if the core instability accretion model is the correct description of the formation of giant planets, then this implies that terrestrial planet formation, too, will depend strongly on metallicity. A rock-ice core must form before a giant planet can grow by accreting hydrogen and helium.] [Theoretically, an Earth-mass planet could form in a system with a smaller initial metallicity than the Sun. However, it would have to form where water can condense, beyond the so-called “frost line.” In our Solar System that place is in the outer region of the asteroid belt. Such a planet would have a much higher abundance of volatiles, resembling in some ways the gas giants. Needless to say, such a planet would not be habitable, even if it were to migrate into the Circumstellar Habitable Zone.] [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p156.]

· Several large extinction events are evident in the geological record. After many years of debate, today most paleontologists are convinced that one of them, the Cretaceous/Tertiary (K/T) extinction sixty-five million years ago, was the result of an impact by a large extraterrestrial body. [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p159, 160.]

· Black holes are fearsome objects, distorting space, time, and common sense, so densely packed that not even light can escape their horizons. [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p162.]

· As if our galaxy’s habitable zone weren’t exclusive enough, the broader universe looks even less inviting. About 98 percent of galaxies in the local universe are less luminous—and thus, in general, more metal-poor—than the Milky Way. So entire galaxies could be devoid of Earth-size terrestrial planets. [This is because the average metallicity of a galaxy correlates with its luminosity. Since luminous galaxies contain

· more stars, galaxies at least as luminous as the Milky Way galaxy contain about 23 percent of the stars. When we compare our Galactic setting with other galaxies, it is not clear which is the more appropriate statistic. If the total luminosity (or mass) of a galaxy is also relevant (and not just the metallicity of a given star), then the smaller statistic is more appropriate. For observational evidence of the correlation between galaxy luminosity and metallicity, see D. R. Garnett, “The Luminosity-Metallicity Relation, Effective Yields, and Metal Loss in Spiral and Irregular Galaxies,” Astrophysical Journal 581 (2002), 1019–1031.] [Of course, since a given galaxy will have its own bell curve of stellar metallicities, a galaxy moderately less luminous than the Milky Way galaxy will contain some solar metallicity stars. They will tend to be closer to the dangerous nucleus, however. Thus, there’s no sharp dividing line between galaxies with Earth-mass planets and those without. Nevertheless, a galaxy with a mean metallicity less than one-tenth solar is not likely to have any Earth-mass terrestrial planets.] [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p167.]

Chapter 9: Our Place in Cosmic Time

· In the 1920s, American astronomer Edwin Hubble began a careful study that led to a rediscovery of the reality of cosmic time. It began as a fairly mundane research project. Using the one hundred–inch Hooker telescope at Mt. Wilson in California—then the world’s largest— he was studying the Andromeda nebula, and later extended his work to other so-called spiral nebulae. At least since the time of Immanuel Kant scientists had wondered whether these football- and cigar-shaped objects were nearby and smallish, or distant and enormous. Kant had conjectured that they might be “island universes” in their own right. [For a very readable historical account of Hubble’s discoveries and the events leading up to them, see R. Berendzen, R. Hart, and D. Seeley, Man Discovers the Galaxies (New York: Columbia University Press, 1984). See also A. Sandage, “Edwin Hubble 1889–1953,” The Journal of the Royal Astronomical Society of Canada 83, no. 6 (1989): 351–362. In later decades Hubble moved to the newer, and larger, 200-inch telescope at Mt. Palomar, also in California.] [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p169.]

· With further study, Hubble noticed that the spectra of many nebulae tended to be “shifted” toward the longer-wavelength, red end of the electromagnetic spectrum compared with our Sun and nearby stars. By combining these redshift data with distance measurements, he eventually discovered that the more distant a nebula, the greater its redshift. [Astronomer Vesto Slipher had earlier noticed various redshifts and blueshifts of astronomical objects, but it was left to Hubble to discover the connection between distance and redshift. Also, in 1917 astronomer Willem de Sitter found static solutions to Einstein’s equations that exhibited redshifts. But the de Sitter models predicted a quadratic redshift dependence on distance, whereas a simple expanding universe model predicts linear redshift increase with distance. (His solutions also required a universe without matter, suggesting it might not apply to the actual universe, which contains a bit of matter.) The first published observations of Hubble in the 1920s were insufficient to exclude these models. It was not until 1931 that Hubble’s observations of galaxies reached sufficient distance to exclude the de Sitter static models. For more on this interesting historical note, see L. M. Lubin and A. Sandage, “The Tolman Surface Brightness Test for the Reality of the Expansion. IV. A Measurement of the Tolman Signal and the Luminosity Evolution of Early-Type Galaxies,” Astronomical Journal 122 (2001): 1084–1103.] [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p169, 170.]

· Finally and most significantly, the combined discoveries implied that the universe itself was expanding. In an historical instance of the left hand not knowing what the right hand is doing, Albert Einstein’s General Theory of Relativity had already predicted that the universe was either expanding or contracting. Unfortunately, Einstein found the notion so distasteful that he had introduced a “fudge factor,” a variable called a cosmological constant, theoretically retrofitted to keep the universe in steady, eternal equilibrium. But upon learning of Hubble’s discovery, Einstein made a widely publicized trip to California to see Hubble’s data for himself. As a result of Hubble’s discoveries, and the works of Georges Édouard Lemaître, a Belgian Roman Catholic priest and physicist who had studied under Arthur Eddington, and Soviet Aleksandr Friedmann—whose solutions to Einstein’s theory implied an expanding universe—he repented of his cosmological constant, famously calling it the “greatest blunder” of his career. [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p170, 171.]

· For example, consider the account C. F. von Weizsäcker gives of a discussion he had with the physical chemist Walther Nernst in 1938: He said, the view that there might be an age of the universe was not science. At first I did not understand him. He explained that the infinite duration of time was a basic element of all scientific thought, and to deny this would mean to betray the very foundations of science. I was quite surprised by this idea and I ventured the objection that it was scientific to form hypotheses according to the hints given by experience, and that the idea of an age of the universe was such a hypothesis. He retorted that we could not form a scientific hypothesis which contradicted the very foundations of science. He was just angry, and thus the discussion, which was continued in his private library, could not lead to any result. [C. F. von Weizsäcker, The Relevance of Science (New York: Harper & Row, 1964), 151. Weizsäcker was at one time an assistant to the famous German physicist Werner Heisenberg. Quoted in the introduction to God and Design: The Teleological Argument and Modern Science, Neil A. Manson, ed. (London: Routledge, 2003), 3.] [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p171.]

· It also marked a striking convergence of theory and discovery. In the 1920s, Lemaître and Friedmann had first proposed expanding models of the universe derived from Einstein’s equations. Friedmann saw that General Relativity implied that “at some time in the past (between ten and twenty thousand million years ago) the distance between neighboring galaxies must have been zero.” Lemaître was the first to describe an early version of the Hot Big Bang model (although he didn’t give it that name). As he put it, “The evolution of the world can be compared to a display of fireworks that has just ended: some few red wisps, ashes and smoke. Standing on a well-chilled cinder, we see the slow fading of the suns, and we try to recall the vanished brilliance of the origin of the worlds.” [Originally published as “Über die Krummung des Raumes,” Zeitschrift für Physik 10 (1922): 377–386.] [Georges Édouard LeMaître, La Revue des Questions Scientifiques, 4e serie 20 (1931): 391.] [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p172.]

· In 1965, however, two engineers at Bell Telephone Lab, Arno Penzias and Robert Wilson, noticed excess noise in a radio antenna at seven centimeters wavelength. They found it coming from all directions of the sky with equal strength, and couldn’t attribute it to any known sources of radiation. Cosmologists quickly interpreted this finding as the long-sought relic radiation from the Big Bang, which, unbeknownst to Penzias and Wilson, some physicists had already predicted. (Because it was detected in the microwave part of the electromagnetic spectrum, it’s called the cosmic microwave background radiation, or CMBR. Although we tend to associate “microwave” with boiling water and burnt popcorn, the backgroundradiation spectrum corresponds to a blackbody emitter 2.7 degrees above absolute zero.) Because it was a prediction of the Hot Big Bang model and not of the Steady State model, Penzias and Wilson’s discovery effectively sounded the death knell for the latter. [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p174.]

· John Barrow and Frank Tipler describe the significance of this: The background radiation has turned out to be a sort of cosmic “Rosetta stone” on which is inscribed the record of the Universe’s past history in space and time. By interpreting the spectral structure of the radiation we can learn of violent events in the Universe’s distant past. [J. D. Barrow and F. J. Tipler, The Anthropic Cosmological Principle (Oxford: Oxford University Press, 1986), 380.] [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p176.]

· In the 1940s, no one knew the origin of the chemical elements. As Big Bang cosmology took hold, theorists soon recognized that the universe had cooled too quickly to form anything beyond lithium. Hydrogen and helium predominate in the universe at large. But whence came all the other elements? Astrophysicists eventually concluded that the elements heavier than lithium were produced inside stars well after the Big Bang. By the late 1950s they had worked out many of the details of this theory, called stellar nucleosynthesis. [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p178.]

· The last two tests involve the cosmic microwave background radiation: one confirmed the change in its temperature with redshift, and the other the shape of its spectrum. [The following studies report on measurements of the temperature of the microwave background at large redshift values: P. Molaro, S. A. Levshakov, M. Dessauges-Zavadsky, and S. D’Odorico, “The Cosmic Microwave Background Radiation Temperature at zabs = 3.025 toward QSO 0347-3819,” Astronomy & Astrophysics 381 (2002): L64–L67 and R. Srianand, P. Petitjean, and C. Ledoux, “The Cosmic Microwave Background Radiation Temperature at a Redshift of 2.34,” Nature 408 (2000), 931–935. Both studies used “fine-structure transition” absorption lines of neutral and ionized carbon seen against the light of background quasars. Commenting on the work of Srianand et al., John Bahcall remarked, “It is almost as if nature planted an abundance of clues in this anonymous cloud in order to allow some lucky researchers to infer the temperature of the CMB when the Universe was young.” (“The Big Bang Is Bang On,” Nature 408 (2000), 916.) Bahcall was impressed that the properties of the cloud studied by Srianand et al. would conspire to permit them to measure the temperature of the background and to eliminate other possible explanations of the observations.] [See Lubin and Sandage, “The Tolman Surface Brightness Test,” 1086.] [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p179.]

· According to the best current measurements of Type Ia supernovae light curves, dark energy is now overwhelming gravity’s tug at cosmic scales, and accelerating the universe’s expansion. Until about six billion years ago, gravity still ruled the roost, and the cosmic expansion was decelerating. Although this is new evidence, if the prevailing interpretation of the Type Ia supernovae observations is correct, the universe should continue to expand and even accelerate indefinitely. [E. H. Gudmundsson and G. Björnsson, “Dark Energy and the Observable Universe,” Astrophysical Journal 565 (2002): 1–16. In 1999, astronomers Fred Adams and Greg Laughlin speculated about the state of the universe 10150 years into the future! The recent discovery of the cosmological dark energy quickly made their scenario obsolete. See F. Adams and G. Laughlin, The Five Ages of the Universe: Inside the Physics of Eternity (New York: The Free Press, 1999).] [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p]

· Moreover, right now we have an advantage: The various independent radiation emissions—cosmic rays, the microwave background, the galaxy’s starlight, synchrotron emission from its magnetic fields, and warm dust—happen to be enough alike to allow us to do both galactic and cosmic astronomy. About this striking fact, mathematician and cosmologist Michael Rowan-Robinson says, “Possibly we just have to accept this as a coincidence, as we have to accept the similar apparent sizes of sun and moon.” But this “coincidence” is an outcome of the particular age of the cosmos, the age that is also the most habitable. [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p187.]

· Michael Rowan Robinson’s entire quote is as follows: It was pointed out by Hoyle that the energy densities of the microwave background, of cosmic rays, of the magnetic field in our Galaxy, and of starlight in our Galaxy are all of the same order, ~10-13 W m-3. . . . But the coincidence of these three Galactic energy densities with the energy density of the microwave background, whose spectral shape and isotropy point to a cosmological origin, remains a mystery. Possibly we just have to accept this as a coincidence, as we have to accept the similar apparent sizes of sun and moon. [In Cosmology (Oxford: Clarendon Press, 1977), 144–145.] Here energy density is simply the amount of energy per unit volume, averaged over a large volume of space. [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p410.]

· We also benefit from the fact that the Milky Way’s nucleus is currently inactive. An active galactic nucleus would emit lots of obtrusive chargedparticle radiation. Similarly, studying the background radiation is much easier between spiral arms, where there is less interstellar dust, than inside a spiral arm. In general, then, those very places in the galaxy most threatening to complex life are also the poorest places to measure this echo of the Big Bang (and any other cosmological source). [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p188.]

· In 1826, the German astronomer Heinrich Wilhelm Mathäus Olbers gazed at the heavens and asked a deceptively modest question, “Why is the night sky dark?” Generations of astronomers learned to call his question Olbers’ Paradox.The dark sky seemed to be a paradox because a static and eternal universe uniformly filled with an infinite number of stars—just the universe assumed by many scientists—should produce a uniform and intensely bright sky, day and night. Many proposed solutions to the paradox failed. For instance, some claimed that intervening gas and dust would block much of the starlight. But it became clear that given enough time, even such inert matter would begin to glow hot and bright with the energy absorbed from an infinite swarm of stars. [Olbers was actually reframing a similar question asked by Jean Philippe Leys de Cheseaux of Lausanne in 1744, “Why is the sky dark?” Astronomers have been asking this question in some form at least since Kepler.] [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p191; 193.]

· Simply put, there’s no paradox if the universe is neither eternal nor infinite in the requisite sense. In fact, a dark night sky is itself evidence for a beginning. [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p193.]

· Besides answering a popular scientific riddle, however, this fact is obviously important for both life and discovery. Just imagine the obstacles to observation posed by a sky as bright as the surface of the Sun. It is precisely because the universe is not infinite and eternal that we can discover so much about it, despite its enormous size. We can distinguish and separate the variety of information that is transmitted to us from the heavens. And lest we forget the obvious, life in a static and eternal universe bathed in intense radiation would be unlikely to prosper. [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p193.]

Chapter 10: A Universe Fine-Tuned for Life and Discovery

· There is for me powerful evidence that there is something going on behind it all. . . . It seems as though somebody has fine-tuned nature’s numbers to make the Universe. . . . The impression of design is overwhelming. —Paul Davies [Paul Davies, The Cosmic Blueprint: New Discoveries in Nature’s Creative Ability to Order the Universe (New York: Touchstone Books, 1989), 203.] [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p195.]

· One way of understanding fine-tuning is to imagine a Universe Creating Machine with numerous dials, each of which sets the value of a fundamental law, constant, or initial condition. Only if each of the dials is set to the right combination will the machine produce a habitable universe. Most of the settings produce uninhabitable universes. [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p196.]

· But what are they referring to? When physicists say, for example, that gravity is “fine-tuned” for life, what they usually mean is that if the gravitational force had even a slightly different value, life would not have been possible. If gravity were slightly weaker, the expansion after the Big Bang would have dispersed matter too rapidly, preventing the formation of galaxies, planets, and astronomers. If it were slightly stronger, the universe would have collapsed in on itself, retreating into oblivion like the groundhog returning to his hole on a wintry day. In either case, the universe would not be compatible with the sort of stable, ordered complexity required by living organisms. [There is some ambiguity as to what exactly “fine-tuned” means for observations of one universe. Moreover, although the word “fine-tuned” seems to imply a fine-tuner—that is, an intelligent agent to do the finetuning— many physicists use the word without that intended connotation. We will address some of these concerns in later chapters.] [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p197.]

· Although some scientists had suspected that the universe is fine-tuned for life, it was not until the nineteenth century that they began to gather specific examples. In his 1913 work The Fitness of the Environment, Lawrence Henderson reviewed the known properties of the environment particularly relevant to life, focusing on carbon and water. By drawing on a wealth of  data from chemistry and comparing properties of carbon and water with those of other substances, he demonstrated how remarkably well these two chemicals suit living organisms, actual or theoretical. Slight changes in their chemical properties would have a profound effect on the fitness of the environment for life. Certain other elements also seem to be uniquely suited for their biological roles. [Arguably the most important discussions in the nineteenth century of the fine-tuning of the environment for life were the Bridgewater Treatises. The one that had the greatest influence on Henderson was W. Whewell, Astronomy and General Physics, Considered with Reference to Natural Theology (London, 1833); the ninth edition was published in 1864.] [See Michael Denton’s discussion in Nature’s Destiny (New York: The Free Press, 1998) of the unique fitness for life of magnesium, calcium, iron, copper, and molybdenum: 195–208. See also J. J. R. Frauso da Silva and R. J. P. Williams, The Biological Chemistry of the Elements (Oxford: Oxford University Press, 1991).] [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p197, 198.]

· If water could not dissolve such a broad range of substances, chemistry would have developed at a snail’s pace, perhaps never reaching the status of a science. [We would also have to look for another metaphor, because snails would not exist.] [Water was one of the four basic elements of Earth, according to the ancient Greeks. Even until the eighteenth century, scientists still thought water was a basic substance, an element. Water was the most important substance in the chemist’s laboratory, serving as the universal medium for studying reactions. Motivated by their new fascination with electricity, Henry Cavendish, James Watt, and other scientists of the late eighteenth century passed an electric current through water (a process called electrolysis). From this they obtained two gases, one of them flammable, as the water disappeared. They also produced water by combining these two gases in a spark chamber. The French scientist Antoine Lavoisier later named these two gases hydrogen and oxygen. As a result, water lost its status as an element and chemists learned the difference between an element and a compound. Popular nature writer Rutherford Platt commented on the significance of this discovery: “As a milestone in the progress of probing nature’s secrets, the splitting of a molecule of water into two H’s and one O is comparable to the splitting of the atom in our time. Prior to this, scientists had no clues to the composition of water. . . and H2O led to the recognition of the elements and modern chemistry.” In Water: The Wonder of Life (Engle wood Cliffs, N.J.: Prentice-Hall, 1971), 16.] [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p198.]

· In 1952–1953 Fred Hoyle discovered one of the most celebrated examples of fine-tuning in physics. In

· contemplating the required pathway for the production of carbon and oxygen in nuclear reactions in the hot interiors of red giant stars, Hoyle correctly predicted that carbon-12 must have a very specific nuclear energy resonance not known at the time. [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p198.]

· A nuclear resonance is a range of energies that greatly increases the chances of interaction between a nucleus and another particle—for example, the capture of a proton or a neutron. An energy resonance in a nucleus will accelerate reactions if the colliding particles have just the right kinetic energy. Resonances tend to be very narrow, so even very slight changes in their location would lead to enormous changes in the reaction rates. This may seem obscure, but think of a wineglass shattering when just the right acoustic note is played. That’s a resonance. [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p198.]

· It was the lack of a known resonance at the energy level required to produce carbon that led Hoyle to make his famous prediction. Since the universe contains plenty of carbon, Hoyle deduced that such a resonance must exist. Had the resonance been slightly lower, the universe would have far less carbon. In fact, the observed abundance of carbon and oxygen depends on a few other coincidences. It turns out that the lack of a resonance in oxygen at the typical alpha particle energy in a star prevents all the carbon from being used up to make oxygen (thankfully, the closest resonance is just a little bit too low). But if the fine-tuning stopped there, the universe would have squandered most of its oxygen well before any star system had time even to think about hosting life. [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p199.]

· As a result of these four astounding “coincidences,” stars produce carbon and oxygen in comparable amounts. Astrophysicists have recently confirmed the sensitivity of carbon and oxygen production to the

· carbon-energy resonance; a change in the (strong) nuclear force strength (the force that binds particles in an atomic nucleus) by more than about half a percent, or by 4 percent in the electromagnetic force (the force between charged particles), would yield a universe with either too much carbon compared with oxygen or vice versa, and thus little if any chance for life. Including the other three required fine-tunings further narrows this range. [This confirmation consisted in self-consistent numerical calculations. See H. Oberhummer, A. Csoto, and H. Schlattl, “Stellar Production Rates of Carbon and Is Abundance in the Universe,” Science 289 (2000): 88–90; A. Csoto, H. Oberhummer, and H. Schlattl, “Fine-Tuning the Basic Forces of Nature Through the Triple-Alpha Process in Red Giant Stars,” Nuclear Physics A 688 (2001): 560–562; H. Oberhummer, A. Csoto, and H. Schlattl, “Bridging the Mass Gaps at A = 5 and A = 8 in Nucleosynthesis,” Nuclear Physics A 689 (2001): 269–279. Their most recent study is H. Schlattl et al., “Sensitivity of the C and O Production on the 3Rate,” Astrophysics and Space Science, in press. In it they include additional stages of stars’ evolution, which they did not include in their Science paper. As a result, they find less sensitivity of the carbon and oxygen abundances to changes in the energy of the carbon resonance. Interestingly, they also find some sensitivity in the minimum initial stellar mass needed to produce a supernova. This is a rich area for additional research. Although the ratio of carbon to oxygen in the bulk Earth is much smaller than the ratio produced by stars, what counts is the value in the crust. Carbon is much closer in abundance to oxygen in the crust. Their abundance ratio in the crust was probably set by the carbon and oxygen abundance ratio in comets and asteroids, which are closer to the solar ratio.] [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p199.]

· The strengths of the “fundamental forces”—the gravitational, strong nuclear, weak nuclear, and electromagnetic (these last two now often combined into one force called electroweak)—are perhaps the most popular examples of fine-tuning. These forces affect virtually everything in the cosmos. And like those individual dials on the Universe-Creating Machine, each one must take a narrow value to render a life-friendly universe. [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p200, 201.]

· The strong nuclear force (often called just the nuclear force) is responsible for holding protons and neutrons together in the nuclei of atoms. In such close quarters, it is strong enough to overcome the electromagnetic force and bind the otherwise repulsive, positively charged protons together. It is as short-range as it is strong, extending no farther than atomic nuclei. But despite its short range, changing the strong nuclear force would have many wide-ranging consequences, most of them detrimental to life. [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p201.]

· The most abundant elements in Earthly life are hydrogen, carbon, nitrogen, and oxygen. If any of their main isotopes were even slightly unstable (with half-lives measured in billions or tens of billions of years), the radiation produced from their decay would pose a serious threat to organisms. [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p201.]

· Gravity is the least important force at small scales but the most important at large scales. It is only because the minuscule gravitational forces of individual particles add up in large bodies that gravity can overwhelm the other forces. Gravity, like the other forces, must also be fine-tuned for life. [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p203.]

· Think of its role in stars. A star is in a state of temporary balance between gravity and pressure provided by hot gas (which, in turn, depends on the electromagnetic force). A star forms from a parcel of gas when gravity overcomes the pressure forces and turbulence and causes the gas to coalesce and contract. As the gas becomes more concentrated, it eventually becomes so hot that its nuclei begin to fuse, releasing radiation, which itself heats the gas. [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p203.]

· What would happen to stars if the force of gravity were a million times stronger? Martin Rees, Britain’s Astronomer Royale, surmises, “The number of atoms needed to make a star (a gravitationally bound fusion reactor) would be a billion times less . . . in this hypothetical strong-gravity world, stellar lifetimes would be a million times shorter. Instead of living for ten billion years, a typical star would live for about ten thousand years. A mini-Sun would burn faster, and would have exhausted its energy before even the first steps in organic evolution had got under way.” Such a star would be about one-thousandth the luminosity, three times the surface temperature, and one-twentieth the density of the Sun. For life, such a mini-Sun is a mere “shooting star,” burning too hot and too quickly. A universe in which gravity was weaker would have the opposite problem. [Martin Rees, Just Six Numbers: The Deep Forces That Shape the Universe (New York: Basic Books, 2001), 30–31.] [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p203.]

· Cosmologist Brandon Carter first noticed the interesting coincidence that mid-range mass stars are near the dividing line between convective and radiative energy transport. This dividing line is another razor’s edge, a teetering balance between gravity and electromagnetism. If it were shifted one way or the other, main-sequence stars would be either all blue or all red (convection resulting in red stars). Either way, stars in the main sequence with the Sun’s surface temperature and luminosity would be rare or nonexistent. [This dividing line depends on the ratio of the electromagnetic to gravitational fine-structure constants raised to the 20th power. See B. Carter, “Large Number Coincidences and the Anthropic Principle in Cosmology,” in Confrontation of Cosmological Theories with Observation, M. S. Longair, ed. (Reidel, Dordrecht, 1974), 291–298. See also B. J. Carr and M. J. Rees, “The Anthropic Principle and the Structure of the Physical World,” Nature 278 (1979): 611.] [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p204.]

· Martin Rees notes that a strong-gravity terrestrial planet would prevent organisms from growing very large. Such a planet would also suffer more frequent and higher-velocity impacts from comets and asteroids. Perhaps such a planet also would retain more heat, possibly leading to too much volcanic activity. Of course, these problems could be avoided by having a smaller planet with a surface gravity comparable to Earth’s. But a smaller planet would lose its internal heat much faster,24 preventing long-lived plate tectonics. [Rees, Just Six Numbers, 30.] [This is because of its larger surface-area-to-volume ratio. A planet half the size of Earth would have about one-eighth its mass and one-quarter its surface area, resulting in twice its ratio of surface area to volume.] [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p204.]

· Astronomer Virginia Trimble observed early in the debate on fine-tuning: The changes in these properties required to produce the dire consequences are often several orders of magnitude, but the constraints are still nontrivial, given the very wide range of numbers involved. 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. [Virginia Trimble, ”Cosmology: Man’s Place in the Universe,” American Scientist 65 (1977): 85.] [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p206.]

· John Gribbon and Martin Rees reach a similar conclusion: 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. [J. Gribbon and M. Rees, Cosmic Coincidences (New York: Bantam Books, 1989), 269.] [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p206, 207.]

· A bit more abstractly, it appears that a habitable universe must have exactly three space dimensions. This insight was actually one of the earliest examples of anthropic reasoning applied to physics. In 1955 G. J. Whitrow asked whether the dimensionality of our universe is related to our existence, though P. Ehrenfest had already asked in 1917 how the laws of physics depend on the dimensionality of space. A surprisingly diverse array of phenomena hinges on this fact: the inverse square law of gravity, the stability of atoms, and wave equations, among others. [J. D. Barrow, “Dimensionality,” Philosophical Transactions of the Royal Society of London A 310 (1983): 337–346. See also Barrow and Tipler, The Anthropic Cosmological Principle, 258–276.] [P. Ehrenfest, “In What Way Does It Become Manifest in the Fundamental Laws of Physics That Space Has Three Dimensions?” Proceedings of the American Academy of Science 20 (1917): 683; G. J. Whitrow, “Why Physical Space Has Three Dimensions,” British Journal for the Philosophy of Science 6 (1955): 13–31.] [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p209.]

· John Barrow writes, “Only three-dimensional worlds appear to possess the ‘nice’ properties necessary for the transmission of high fidelity signals because of the simultaneous realization of reverberationless and distortionless propagation.” [Barrow, “Dimensionality” 341. In The Anthropic Cosmological Principle, Barrow and Tipler describe another value of a low-dimensional world like our own that helps theoretical physicists, which they call “the unreasonable effectiveness of dimensional analysis.” Dimensional analysis is a mathematical technique that allows physicists to estimate the magnitude of physical quantities without knowing the precise formula. Such a procedure would not be feasible in a universe with a large number of dimensions. See Barrow and Tipler, The Anthropic Cosmological Principle, 270–272.] [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p209.]

· Kepler’s formulation of his laws required that macroscopic bodies in our universe be well described by “classical” laws—that is, laws with distinct and measurable positions and motions. Davies argues that one should not just assume that any universe appearing from a quantum initial state would later exhibit classical properties. [Davies, The Mind of God, 159.] [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p210.]

· Harlow Shapley once marveled, “It is amazing what grand thoughts and great speculations we can logically develop on this planet—thoughts about the chemistry of the whole universe—when we have such a tiny sample here at hand.” [Harlow Shapley, Of Stars and Men: Human Response to an Expanding Universe (Boston: Beacon Press, 1958), 94.] [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p210.]

· Concerning locality, Davies writes: It is often said that nature is a unity, that the world is an interconnected whole. In one sense this is true. But it is also the case that we can frame a very detailed understanding of individual parts of the whole without needing to know everything. Indeed, science would not be possible at all if we couldn’t proceed in bite-sized stages. [Davies, The Mind of God, 156–157.] [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p210, 211.]

· Linearity and locality are closely related to nature’s long-term stability— another prerequisite for life and discovery. Our very ability to establish the laws of nature depends on their stability. (In fact, the idea of a law of nature implies stability.) Likewise, the laws of nature must remain constant long enough to provide the kind of stability life requires through the building of nested layers of complexity. The properties of the most fundamental units of complexity we know of, quarks, must remain constant in order for them to form larger units, protons and neutrons, which then go into building even larger units, atoms, and so on, all the way to stars, planets, and in some sense, people. The lower levels of complexity provide the structure and carry the information of life. There is still a great deal of mystery about how the various levels relate, but clearly, at each level, structures must remain stable over vast stretches of space and time. [George F. R. Ellis has made this point (if only in passing), joining the half-dozen or so people who have hinted at the correlation between habitability and measurability. See “The Anthropic Principle: Laws and Environments,” in The Anthropic Principle: Proceedings of the Second Venice Conference on Cosmology and Philosophy, F. Bertola and U. Curi, eds. (Cambridge: Cambridge University Press), 31.] [Within the context of the cooling rate of the expanding universe, Hubert Reeves discusses the minimum requirements for growth of complexity. The key requirement is formation of non-equilibrium structures. Too slow, and the atomic and molecular diversity would be lacking: matter would consist entirely of the final product of equilibrium reactions, iron. Too fast, and large structures—such as planets, stars, and galaxies—could not form. Thus, fine-tuning in the cooling rate is required for complexification to be possible. But we do not agree with Reeves’s suggestion that a “Principle of Complexity” should replace the Anthropic Principle, since we are more than merely complex structures—we are human observers, who can talk about fine-tuning coincidences. See “The Growth of Complexity in an Expanding Universe,” in The Anthropic Principle: Proceedings of the Second Venice Conference on Cosmology and Philosophy, F. Bertola and U. Curi, eds. (Cambridge: Cambridge University Press), 67–84.] [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p211.]

· Consider complex carbon atoms, within still more complex sugars and nucleotides, within more complex DNA molecules, within complex nuclei, within complex neurons, within the complex human brain, all of

· which are integrated in a human body. Such “complexification” would be impossible in both a totally chaotic, unstable universe and an utterly simple, homogeneous universe of, say, hydrogen atoms or quarks. Moreover, surprisingly, our universe allows such higher-order complexity alongside quantum indeterminacy and nonlinear interactions (such as chaotic dynamics), which tend to destabilize ordered complexity. [Some would argue that life flourishes at the boundaries of stability and chaos. Of course, absolute stability of the constants of nature is not required for a habitable universe. At some small level, some non-stability can be tolerated. Indeed, recent observations of absorption lines seen against distant quasars suggest that the finestructure constant has changed slightly over the history of the universe. See J. K. Webb et al., “Further Evidence for Cosmological Evolution of the Fine Structure Constant,” Physical Review Letters 87 (2001): 091301. For an analysis of the sensitivity in the Big Bang production of the light elements to changes in the fine-structure constant, see K. M. Nollett and R. E. Lopez, “Primordial Nucleosynthesis with a Varying Fine Structure Constant: An Improved Estimate,” Physics Reviews D 66 (2002): 063507. For a review of the diverse constraints on possible changes in the fine-structure constant, see G. Fiorentini and B. Ricci, “: A Constant That Is Not a Constant?” Proceedings of ESO-CERN-ESA Symposium on Astronomy, Cosmology and Fundamental Physics, Report No. INFNFE-07-02 (astro-ph/0207390). In their search for observational tests of a changing fine-structure constant, physicists are uncovering new examples of fine-tuning.] [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p211.]

· Even within the more complicated realm of quantum mechanics, for instance, we can describe many interactions with the relatively simple Schrödinger Equation. Eugene Wigner famously spoke of the “unreasonable effectiveness of mathematics in natural science”—unreasonable only if one assumes, we might add, that the universe is not underwritten by reason. Wigner was impressed by the simplicity of the mathematics that describes the workings of the universe and our relative ease in discovering them. Philosopher Mark Steiner, in The Applicability of Mathematics as a Philosophical Problem, has updated Wigner’s musings with detailed examples of the deep connections and uncanny predictive power of pure mathematics as applied to the laws of nature. [Eugene Wigner, ”The Unreasonable Effectiveness of Mathematics in the Natural Sciences,” in Symmetries and Reflections (Bloomington: Indiana University Press, 1967), 222–237.] [Mark Steiner, The Applicability of Mathematics as a Philosophical Problem (Cambridge, MA: Harvard University Press, 1998).] [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p212.]

· In his book Just Six Numbers, Martin Rees asks, “Why does our universe have the overall uniformity that makes cosmology tractable, while nonetheless allowing the formation of galaxies, clusters and superclusters?” His point is significant. If matter were evenly distributed in the universe, as might result if the expansion rate of the universe were initially faster, then lifeessential structures like galaxies, stars, planets, and rocks could not have formed and measurability would suffer, well, immeasurably. At the other extreme, if an imbalance of the forces caused all matter to clump together into a homogeneous neutronium mass or a giant black hole, life and measurability would be impossible. [Rees, Just Six Numbers, 123.] [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p212.]

· Astronomer Stuart Clark probably spoke for many when he said, “Astronomy leads us to believe that the Universe is so vast that we, on planet Earth, are nothing more than an insignificant mote.” [Stuart Clark, Life on Other Worlds and How to Find It (Chichester, UK: Springer-Praxis, 2000), 1.] [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p215.]

· Actually, over the extreme range of size scales from quarks to the observable universe, the range from humans to Earth is smack in the middle on a logarithmic scale. But more important, our middling size actually maximizes the total range of structures we can observe, both large and small. We’re really a very nice fit in the cosmos. [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p215.]

· Size scales in the universe. Although Earth and human beings are often considered “insignificant” compared to the vastness of the cosmos, the Earth-human size range actually includes the geometric mean of extremes of sizes in the universe. We are near the middle of the size scale ranging from quarks to the observable universe, when figured on a logarithmic scale (in powers of ten). For scientific discovery of both large- and small-scale structures, this middling size is near optimum. [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p216.]

· A technologically adroit ant-sized being might easily be able to construct a telescope objective half a millimeter in diameter, giving a resolution of about eight minutes of arc, only good enough for observing the Moon, the Sun, and bright stars. [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p217.]

· In his book Nature’s Destiny, biologist Michael Denton has emphasized the ways our size seems to be well adapted for technology. In particular, he makes much of how our size allows us to control fire, a necessary step toward high technology. Sustainable fires, he argues, are impractical for organisms significantly smaller than we are. [Michael Denton, Nature’s Destiny, 243.] [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p217.]

· Denton concludes: It would appear that man, defined by Aristotle in the first line of his Metaphysics as a creature that “desires understanding,” can only accomplish an understanding and exploration of the world, which Aristotle saw as his destiny, in a body of approximately the dimensions of a modern human. [Michael Denton, Nature’s Destiny, 243.] [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p218.]

· Theoretical physics and cosmology were surely unrelated to humanity’s needs for survival for most of our history. Our ancestors got along quite well without Bell’s theorem of quantum mechanics, Big Bang cosmology, and the theory of stellar nucleosynthesis. Nevertheless, in many ways we seem to be curiously overprepared, enough so that when the opportunities availed themselves, we could discover the laws of the universe, even in their most distant and obscure manifestations. This curiosity fits hand in glove with the other surprising fact that we’ve spent a good bit of ink and paper developing. We’ve moved from the details of Earth’s geophysics and atmosphere, to the beginning of cosmic time and the forces and constants that apply throughout the universe. Over and over we’ve seen a pattern: the rare conditions required for habitability also provide excellent overall conditions for discovering the universe around us. [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p218.]

Section 3: Implications

Chapter 11: The Revisionist History of the Copernican Revolution

· As astronomer Stuart Clark puts it: “Astronomy leads us to believe that the Universe is so vast that we, on planet Earth, are nothing more than an insignificant mote.” [Stuart Clark, Life on Other Worlds and How to Find It (Chichester, UK: Springer-Praxis, 2000), 1. More generally, physicist Steven Weinberg has said, “The more the universe seems comprehensible, the more it also seems pointless.” Earlier in the epilogue to the book, he says, “It is almost irresistible for humans to believe that we have some special relation to the universe, that human life is not just a more-or-less farcical outcome of a chain of accidents reaching back to the first three minutes, but that we were somehow built in from the beginning.” Steven Weinberg, The First Three Minutes (New York: Basic Books, 1977), 150–155.] [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p224.]

· Philosopher Bertrand Russell once said, “The Copernican Revolution will not have done its work until it has taught men more modesty than is to be found among those who think Man sufficient evidence of Cosmic Purpose.” [Bertrand Russell, Religion and Science (New York: Oxford University Press, 1961), 222. Quoted in Neil Manson, “Why Cosmic Fine-Tuning Needs to Be Explained,” Dissertation at Syracuse University (December 1998), 146.] [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p224.]

· As planetary scientist Stuart Ross Taylor puts it: Copernicus was right after all. The idea that the Sun, rather than the Earth, was at the centre of the universe caused a profound change in the view of our place in the world. It created the philosophical climate in which we live. It is not clear that everyone has come to grips with the idea, for we still cherish the idea that we are special and that the entire universe was designed for us. [Stuart Ross Taylor, Destiny or Chance: Our Solar System and Its Place in the Cosmos (Cambridge: Cambridge University Press, 1998), 11.] [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p224, 225.]

· Contrary to popular impression, neither Aristotle nor Ptolemy thought that Earth was a large part of the universe. Aristotle considered it of “no great size” compared with the heavenly spheres, and in Ptolemy’s masterwork, the Almagest, he says, “The Earth has a ratio of a point to the heavens.” Both of them reached this conclusion because of observations of Earth’s relation to the stars, from which they surmised that the stellar sphere was an enormous distance from Earth. [In his Physics and On the Heavens, excerpted in Dennis Danielson, The Book of the Cosmos (Cambridge: Perseus, Helix Books, 2000), 42. Danielson’s anthology brings together many of the central Western texts on cosmology. We make generous use of the primary texts included in this volume.] [Quoted in Danielson, The Book of the Cosmos, 72. The Christian philosopher Boethius (470–525), who “mediate[d] the transition from Roman to Scholastic thinking,” made the same point. See quote and discussion in John Barrow and Frank Tipler, The Anthropic Cosmological Principle (Oxford: Oxford University Press, 1986), 45.] [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p226.]

· As science historian Reijer Hooykaas puts it, “Metaphorically speaking, whereas the bodily ingredients of science may have been Greek, its vitamins and hormones were biblical.” [R. Hooykaas, Religion and the Rise of Modern Science (Vancouver: Regent College Publishing, 2000; originally published, Edinburgh: Scottish Academic Press, 1972), 162.] [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p228.]

· For centuries, the “Christian” West had no single, official cosmology, in part because the biblical texts and imagery lack the sort of explicit detail to provide a model of the cosmos without other sources. [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p230.]

· Over time, however, the exposure of Western scholars to Aristotle’s thought—mostly transmitted from the Muslim world—led to an integration of the Aristotelian/Ptolemaic cosmology with Christian theology. This was not initially a happy marriage. [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p230.]

· Of course, the conviction that humanity plays a part in some cosmic purpose is not exclusively Christian or uniquely biblical. It’s not even limited to the main “religions of the book”—Christianity, Judaism, and Islam. For instance, the Roman philosopher and statesman Cicero argued, far more strongly than most Christian and Jewish theologians, that since the gods and man alone share the gift of reason, and are aware of the passing of time and seasons, “all things in this universe of ours have been created and prepared for us humans to enjoy.” Cancel the theological differences, and what remains is the common conviction that the cosmos is designed, our place in the cosmos is suffused with purpose and, whether we’re the central characters or not, we play a part in some grand cosmic drama. [From The Nature of the Gods, quoted in Danielson, 56. In Genesis, Hans Blumenberg notes that, unlike the Stoicism of Cicero, for Christian theology the world was not strictly made for man but rather subjugated to him by God (174). There is a certain irony in the fact that certain Enlightenment figures made “man the measure of all things.” In so doing, they exalted man far more than medieval Christianity ever did. Then, in a startling case of historical amnesia and projection, they began to perpetuate the myth that it was the ancient and medieval world picture that erroneously exalted man above his true status. Untangling such a complicated morass, however, would take us too far afield from our chosen topic.] [Even those who dislike this theme recognize its prevalence. Daniel Quinn identifies this as the fundamental delusion we all tell ourselves—namely, “The world was made for man, and man was made to conquer and rule it.” He contends that the biblical creation narratives simply exemplify this more general view. In Ishmael (New York: Bantam, 1992), 74. See also Daniel Quinn, The Story of B (New York: Bantam, 1996), 129.] [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p245.]

Chapter 12: The Copernican Principle

· Because of the reflection of sunlight . . . the Earth seems to be sitting in a beam of light, as if there were some special significance to this small world. But it’s just an accident of geometry and optics. . . . Our posturings, our imagined self-importance, the delusion that we have some privileged position in the Universe, are challenged by this point of pale light. Our planet is a lonely speck in the great enveloping cosmic dark. In our obscurity, in all this vastness, there is no hint that help will come from elsewhere to save us from ourselves. —Carl Sagan [Carl Sagan, Pale Blue Dot (New York: Ballantine Books, 1994), 7.] [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p247.]

· Prediction 1: Earth, while it has a number of life-permitting properties, isn’t exceptionally suited for life in our Solar System. Other planets in the Solar System probably harbor life as well. [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p251.]

· Prediction 2: Our Sun is a fairly ordinary and typical star. [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p253.]

· Prediction 3: Our Solar System is typical; we should expect other Solar Systems to mirror our own. [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p254.]

· Prediction 4: Even if our Solar System is not typical, there are lots of planetary configurations that are consistent with the presence of biological organisms. Variables like the number and types of planets and moons are mainly contingencies that have little to do with the existence of life in a planetary system. [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p256.]

· Prediction 5: Our Solar System’s location in the Milky Way is relatively unimportant. [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p257.]

· Prediction 6: Our galaxy is not particularly exceptional or important. Life could just as easily exist in old, small, elliptical, and irregular galaxies. [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p258.]

Chapter 13: The Anthropic Disclaimer

· Prediction 7: The universe is infinite in space and matter and eternal in time. [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p260.]

· Philosopher of science Stephen Meyer summarizes the two important ones: [A]s physicist Alan Guth showed, our knowledge of entropy suggests that the energy available to do the work would decrease with each successive cycle. . . . Thus, presumably the universe would have reached a nullifying equilibrium long ago if it had indeed existed for an infinite amount of time. Further, recent measurements suggest that the universe has only a fraction . . . of the mass required to create a gravitational contraction in the first place. [Stephen Meyer, “The Return of the God Hypothesis,” The Journal of Interdisciplinary Studies XI, no. 1/2 (1999): 9. The articles substantiating this claim are Alan Guth and Marc Sher, “The Impossibility of a Bouncing Universe,” Nature 302 (April 7, 1983): 505–507; J. E. Phillip Peebles, Principles of Physical Cosmology (Princeton: Princeton University Press, 1993); and Peter Coles and George Ellis, “The Case for an Open Universe,” Nature 370 (August 25, 1994): 609–613. Of course this doesn’t mean that cosmologists have given up trying to get rid of an initial singularity, or beginning, with its repugnant philosophical implications. See, for example, Charles Seife, “Eternal-Universe Idea Comes Full Circle,” Science 296 (2002): 639.] [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p261.]

· Prediction 8: The laws of physics are not specially arranged for the existence of complex or intelligent life. [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p261.]

· Fred Hoyle, one of the founders of the Steady State model and an intransigent atheist, admitted, “A commonsense interpretation of the facts suggests that a superintellect has monkeyed with physics, as well as chemistry and biology, and that there are no blind forces worth speaking about in nature.” [Fred Hoyle, “The Universe: Past and Present Reflections,” Annual Review of Astronomy and Astrophysics 20 (1982), 16.] [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p263.]

· The Strong Anthropic Principle (as some define it) applies this same reasoning to the laws, constants, and initial conditions of the universe as a whole: We can expect to find ourselves in a universe compatible with our existence. True enough. One problem, however, is that some think the Anthropic Principle in its universal application is a sufficient explanation for such fine-tuning. But by itself the Anthropic Principle is not an explanation. It simply states a necessary condition for our observing the universe. It’s no explanation for why that universe exists, or is fine-tuned. What is surprising is not that we observe a habitable universe, but that a habitable universe is, so far as we know, the only one that exists. [Brandon Carter initiated the contemporary discussion of the Anthropic Principle with a formulation similar to

· this: “What we can expect to observe must be restricted by the conditions necessary for our presence as

· observers.” In “Large Number Coincidences and the Anthropic Principle in Cosmology,” in M. S. Longair, ed., Confrontation of Cosmological Theory with Astronomical Data (Dordrect: Reidel, 1974), 291–298. Reprinted in John Leslie, ed., Physical Cosmology and Philosophy (New York: Macmillan, 1990). In addition to the Weak Anthropic Principle, Carter proposed a Strong Anthropic Principle. There is an exegetical debate surrounding the meaning of the Strong Anthropic Principle, and in particular, the meaning of the word “must” in Carter’s formulation. Leslie interprets Carter in this way: The Weak sense refers to our location in time and place. The Strong sense refers to the universe as a whole. SAP means, “Any universe with observers in it must be observer-permitting.” See Leslie’s “Introduction” in Modern Cosmology and Philosophy, John Leslie, ed., (Amherst, NY: Prometheus, 1998), 2. Whether or not this is a correct interpretation, the Strong Anthropic Principle has been taken in all sorts of ways, and often does not conform to Carter’s initial formulation. We are following this definition of Weak and Strong Anthropic Principles, without judging whether this is consistent with Carter’s initial formulation.] [As we explain in endnote 14, there is a confusing variety of different definitions of the Strong Anthropic Principle in the literature. Often it is defined as meaning that the laws and constants somehow had to be what they are, or that they are necessarily what they are. Others define WAP as a selection effect and SAP as implying that the fine-tuning is the result of intentional design. This diversity is confusing, so we’ve decided to go with the definitions that are easiest to grasp. Nothing crucial in our argument depends on this way of defining WAP and SAP.] [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p266.]

· Another analogy is the popular story of the firing squad. Imagine an American intelligence officer, captured by the Nazi SS during World War II, who is sentenced to death by a firing squad. Because of this officer’s importance, the SS assign fifty of Germany’s finest sharp shooters to his execution. After lining him up against a wall, the sharpshooters take their positions three meters away. Upon firing, however, the officer discovers that every sharpshooter has missed, and that instead, their fifty bullets have made a perfect outline of his body on the wall behind him. What would we think if the officer reflected on his situation, and then responded, “I suppose I shouldn’t be surprised to see this. If the sharpshooters hadn’t missed, I wouldn’t be here to observe it”? We would rightly wonder what he was doing in intelligence, since the more sensible explanation would be that, for some reason, the execution had been rigged. Perhaps the sharpshooters had been ordered to miss, or they had colluded with one another for some unknown reason. In short, the best explanation would be that the event was the product of intelligent design. Shrugging one’s shoulders and concluding that it’s a chance occurrence is just dense. [This is derived from the popular story told by philosophers Richard Swinburne, John Leslie, and others. See John Leslie, Universes (London: Routledge, 1989), 13–15, 108.] [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p267.]

· Astronomers Fred Adams and Greg Laughlin are quite explicit on this point: The seeming coincidence that the universe has the requisite special properties that allow for life suddenly seems much less miraculous if we adopt the point of view that our universe, the region of space-time that we are connected to, is but one of countless other universes. In other words, our universe is but one small part of a multiverse, a large ensemble of universes, each with its own variations of physical law. In this case, the entire collection of universes would fully sample the many different possible variations of the laws of physics. . . . With the concept of the multiverse in place, the next battle of the Copernican revolution is thrust upon us. Just as our planet has no special status within our Solar System, and our Solar System has no special location within the universe, our universe has no special status within the vast cosmic mélange of universes that comprise our multiverse. [F. Adams and G. Laughlin, Five Ages of the Universe: Inside the Physics of Eternity, 199, 201. Emphasis in original. Not surprisingly, Adams and Laughlin do not mention even the possibility of design. Similarly, in Our Cosmic Future: Humanity’s Fate in the Universe (Cambridge: Cambridge University Press, 2000), 239, Nikos Prantzos notes that, despite “the impossibility of any physical contact among the bubble universes,” “chaotic inflation is one of the most attractive from a philosophical point of view.” One wonders what philosophical perspective he has in mind. Martin Rees uses similar reasoning. The Prologue to his book Our Cosmic Habitat (Princeton: Princeton University Press, 2001) is entitled: “Could God Have Made the World Any Differently?” He answers “yes,” and proposes that what we call laws of nature are “no more than local bylaws—the outcome of historical accidents during the initial instants after our own particular Big Bang” (xvii). But although he answers “yes” to the question, he doesn’t really mean it. In fact, the question seems to be a red herring, since he appeals to multiple universes: “In this book I argue that the multiverse concept is already part of empirical science: we may already have intimations of other universes, and we could even draw inferences about them and about the recipes that led to them. In an infinite ensemble, the existence of some universes that are seemingly fine-tuned to harbor life would occasion no surprise; our own cosmic habitat would plainly belong to this unusual subset. Our entire universe is a fertile oasis within the multiverse.” But clearly Rees is posing a false dilemma. How exactly has he ruled out the possibility that our universe looks fine-tuned because it is fine-tuned? He hasn’t ruled it out. He’s just failed to consider it. Despite Rees’s claim that the multiverse concept has empirical consequences, it’s very difficult to see what function it serves other than to avoid the bothersome implications of the evidence of fine-tuning.] [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p268-270.]

· If there were no other galaxy clusters, Edwin Hubble could never have inferred the expansion of the universe from the ruddy hue of distant galaxies. Gravitational attraction among the galaxies within our immediate galactic neighborhood, the Local Group, overwhelms the otherwise detectable effects of the cosmic expansion. An observer living in a universe containing only the rich Virgo cluster would also fail to discover Hubble’s Law. At the level of the local supercluster, which contains the Local Group and the Virgo cluster, the cosmic expansion is detectable, although the effects of gravity remain. It is only above the level of galactic clusters that the cosmic expansion is significant enough to substantially overcome the force of gravity and the “peculiar velocity” noise of nearby galaxies. In general, the farther we can sample galaxies, the more reliably we can determine the Hubble constant. [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p273.]

Chapter 14: SETI and the Unraveling of the Copernican Principle

· On the importance of information in biology, see Hubert Yockey, Information Theory and Molecular Biology (Cambridge: Cambridge University Press, 1992); Bernd-Olaf Küppers, Information and the Origin of Life (Cambridge: MIT Press, 1990); Bernd-Olaf Küppers, Molecular Theory of Evolution (Heidelberg: Springer, 1983); W. Loewenstein, The Touchstone of Life (New York: Oxford University Press, 1998). On the difference between biological information and the chemical structures that carry that information, see Michael Polanyi, “Life’s Irreducible Structure,” Science 160 (1968): 1308, and Michael Polanyi, “Life Transcending Physics and Chemistry,” Chemical and Engineering News (Aug. 21, 1967), 54–66. [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p429.]

Chapter 15: A Universe Designed for Discovery

· As we noted in the previous chapter, if an actual event is not necessary, then it is contingent. But a contingent event can be the result of chance or of intelligent design. If you dump out a box full of Scrabble letters, the law of gravity is responsible for the letters falling to the floor. But gravity doesn’t determine that the letters be in any particular order. We would normally attribute the particular configuration of the letters to chance. [Of course, if the universe were deterministic, then nothing within it would be the result of chance. Even among those who allow chance explanations, many restrict true chance explanations to the realm of quantum indeterminacy. Protons might decay by chance, but falling Scrabble letters do not. So they might insist that if we had sufficient knowledge of the initial conditions, we could trace a determining cause for every falling Scrabble piece. We don’t intend to take a position on such controversies. Here we’re simply describing the way we normally make causal explanations in everyday life. In this example, our central point is that the law of gravity alone does not determine the specific configuration of the Scrabble letters.] [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p297.]

· One of the reasons the SETI researchers in Contact attribute the string of prime numbers to ETIs is that the sequence is improbable. We know of no natural process that generates such a sequence. And what are the odds of that sequence just happening by chance? But mere improbability is not really the issue, since any non-repetitive pattern of radio signals is improbable. So how did they tell the difference? [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p298.]

· He first developed and articulated this concept in William A. Dembski, The Design Inference (Cambridge: Cambridge University Press, 1998). He developed it for the general reader in Intelligent Design: The Bridge Between Science and Theology (Downers Grove: InterVarsity Press, 1999). He has continued to refine the concept in No Free Lunch: Why Specified Complexity Cannot Be Purchased Without Intelligence (Lanham, Md.: Rowman & Littlefield, 2001). [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p432.]

· When we correctly infer design, it is often because of the presence of these two properties, improbability (or complexity) and specification. Dembski argues that this joint property—specified complexity—is a hallmark of intelligent agency. [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p298.]

· Philosopher of science Del Ratzsch notes that, historically, arguments for the design of certain natural structures have “almost always involved value,” to which we attach meaning, and which is habitually associated with mind and intentions. Such value is difficult to define, but we usually know it when we see it. [Ratzsch, Nature, Design, and Science, 72–73.] [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p300.]

· In fact, during our work on this book we encountered the following passage from Denton: What is so striking is that our cosmos appears to be not just supremely fit for our being and for our biological adaptations, but also for our understanding. Our watery planetary home, with its oxygen-containing environment, the abundance of trees and hence wood and hence fire, is wonderfully fit to assist us in the task of opening nature’s door. Moreover, being on the surface of a planet rather than in its interior or in the ocean gives us the privilege to gaze farther into the night to distant galaxies and gain knowledge of the overall structure of the cosmos. Were we positioned in the center of a galaxy, we would never look on the beauty of a spiral galaxy nor would we have any idea of the structure of our universe. We might never have seen a supernova or understood the mysterious connection between the stars and our own existence. [Nature’s Destiny, 262.] [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p309, 310.]

· Reminiscent of our first chapter, historian of science Stanley Jaki recently argued that the Earth-Moon system contributes not only to Earth’s habitability but to scientific discovery as well. Finally, Michael Mendillo and Richard Hart of Boston University anticipated the discovery described in Chapter One. In 1974, they presented a paper called “Total Solar Eclipses, Extraterrestrial Life, and the Existence of God,” which was later reported and excerpted in Physics Today. They argued, with comic precision, the following: Theorem An exactly total solar eclipse is a unique phenomenon in the Solar System.

· Lemma There are observers on Earth to witness the remarkable event of an exactly total solar eclipse.

· 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. Therefore, there is a God. [S. L. Jaki, Maybe Alone in the Universe After All (Pinckney, Mich.: Real View Books, 2000).] [In “Resonances,” Physics Today 27, no. 2 (1974): 73.] [Guillermo Gonzalez and Jay W. Richards: The Privileged Planet (How Our Place in The Cosmos is Designed for Discovery), Regnery Publishing 2004, p310.]

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