from  the  book  by  the  same  name

The Evidence of Astronomy

The Privileged Planet

As we survey all the evidence, the thought insistently arises that some supernatural agency-—-or, rather, Agency-—-must be involved. Is it possible that suddenly, without intending to, we have stumbled upon scientific proof of the existence of a Supreme Being? Was it God who stepped in and so providentially crafted the cosmos for our benefit?

Astronomer George Greenstein 1

Astronomy leads us to a unique event, a universe which was created out of nothing, one with the very delicate balance needed to provide exactly the conditions required to permit life, and one which has an underlying (one might say "supernatural") plan.

Nobel laureate Arno Penzias 2

There's nothing unusual about Earth. It's an average, unassuming rock that's spinning mindlessly around an unremarkable star in a run-of-the-mill galaxy—"a lonely speck in the great enveloping cosmic dark," as the late Carl Sagan put it.3

The fact that life flourishes on our planet isn't exceptional. Creatures of all kinds undoubtedly abound, we're told, in countless locations among the ten trillion billion stars in the universe. Some scientists have estimated there are up to ten trillion advanced civilizations.4 Sagan put the number at one million for our Milky Way galaxy alone.5

After all, the forces of nature are so automatic that life is sure to have evolved wherever water exists. That's why whenever scientists raise new speculation about liquid water being present on another celestial body-—the underground worlds of Jupiter's frozen moons Europa and Ganymede are currently the most fashionable examples—then the automatic assumption is that living organisms must necessarily and inexorably follow.

If life can emerge from non-life so quickly and efficiently on a planet as undistinguished as ours, they reason, then why not throughout the universe's hundreds of billions of galaxies? To them, life is like a soup mix: just add water!

The very title of astrobiologist David Darling's recent book nicely encapsulates this optimistic philosophy: Life Everywhere. He's enthusiastic about claims that "life may arise inevitably whenever a suitable energy source, a concentrated supply of organic (carbon-based) material and water occur together." These ingredients, he said, "are starting to look ubiquitous in space."7 Consequently, he believes microbial life, at least, "is widespread."8

In short, Earth has no privileged status. Polish scientist Nicholas Copernicus deflated our oversized ego by putting us in our place long ago—the universe doesn't revolve around us; instead, we're just living in a humdrum hamlet off the beaten path in a nondescript suburb of the vast Milky Way. We have no grand role, no meaning, no significance, no reason for being other than ... well, just being.

"The universe that we observe," said Oxford's Richard Dawkins, "has precisely the properties we should expect if there is, at bottom, no design, no purpose, no evil and no good, nothing but blind, pitiless indifference."9

This is the essence of what I was taught as I studied science. Of course, these conclusions neatly bolstered my atheistic values. Somehow I managed to avoid getting too depressed by the personal implications of all of this, strangely finding hope and inspiration in the belief that we are not alone in the universe. Even if God didn't exist, at least there were millions of advanced civilizations out there.

Beaming Messages to Hercules

Ever since I first watched the classic movie The Day the Earth Stood Still as a child, I've been enthralled by the fanciful images of teeming inter-galactic life portrayed in science fiction. Sure, Star Trek and Star Wars are silly—but still, the idea of other exotic creatures living in the strange nooks and crannies of the universe was always intriguing and even comforting to me.

Later I became fascinated by the Drake Equation, an attempt by astronomer Frank Drake to quantify the number of civilizations that might exist in our galaxy. The equation factors in such variables as how many of the two hundred to three hundred billion stars in our Milky Way might resemble our own sun, the percentage of stars that may have planets in habitable zones, and so forth.

Though the specific numbers that scientists then plugged into Drakes equation mostly amounted to rank conjecture fuelled by their own biases— one scientist admitted it was "a way of compressing a large amount of ignorance into a small space"10—this did lend an air of scientific certainty to a highly speculative issue.

Then I cheered from afar in the mid-1970s as Drake and Sagan beamed a message of greeting to the great globular cluster M13, which is a concentration of a quarter million stars in the constellation Hercules. "While I knew there wasn't much practical science involved with this intragalactic phone call—it would take more than twenty-two thousand years for the message to reach its destination—nevertheless there was something romantic and adventurous about trying to communicate with the civilizations that most assuredly populated those distant stars.

All of this helped form my perspective as I would gaze over the years at the twinkling stars in the dark heavens. But now my attitude was changing. After studying the latest evidence from various scientific disciplines—-from astronomy to cosmology to geology to oceanography to microbiology-—my conclusions were being tugged in the opposite direction.

It's turning out that the Earth is anything but ordinary, that our sun is far from average, and that even the position of our planet in the galaxy is eerily fortuitous. The idea that the universe is a flourishing hothouse of advanced civilizations is now being undermined by surprising new scientific discoveries and fresh thinking.

In short, new findings are suggesting that we are special. More and more scientists are studying the mind-boggling convergence of scores of extraordinary "coincidences" that make intelligent life possible on Earth and concluding that this can't possibly be an accident. They're seeing signs of design, a kind of unlikely fine-tuning for life similar to the fine-tuning of physics that we explored in the previous chapter.

In fact, said one noted researcher, "new evidence which could potentially have refuted the [design] hypothesis has only ended up confirming it."11 Once again, we find the evidence of science pointing in the direction of a Creator.

And rather than our lives being purposeless, scientists for the first time are uncovering concrete evidence that suggests at least one surprising purpose for which we were created—that is, to discover and learn about the surroundings in which we have been placed.

In other words, as we'll see in this chapter, one purpose for which we were designed is to do science itself.

Right Place, Right Time

As the new millennium dawned, geologist Peter D. Ward and astronomer Donald Brownlee, both professors at the University of Washington in Seattle, published a provocative and highly successful book that raised this disquieting question about Earth: "What if it is utterly unique: the only planet with animals in this galaxy or even in the visible universe ...?"12

Their book, Rare Earth, marshals evidence from a wide range of scientific disciplines to build its case that "not only intelligent life, but even the simplest of animal life, is exceedingly rare in our galaxy and in the universe."13 They called the conclusion "inescapable" that "Earth is a rare place indeed." 

Although Ward and Brownlee uncritically buy into the idea that microbial life may very well be more prevalent, a view they draw from the way life seemed to have effortlessly developed on Earth "about as soon as environmental conditions allowed its survival,"15 their conviction that the existence of complex life is "extraordinarily rare" is bolstered by convincing data divorced from any theological framework.

Calling their book "carefully reasoned and scientifically astute," Don Johanson, director of the Institute of Human Origins at Arizona State University, remarked: "In spite of our wishful thinking, there just may not be other Mozarts or Monets."16 David Levy, of comet Shoemaker-Levy fame, added, "As we know it on Earth, complex life might be very rare, and very precious."17 Said the Times of London: "If they are right it could be time to reverse a process that has been going on since Copernicus."18

More and more scientists are observing the stunning ways in which our planet—against all odds—-manages to fulfill a large number of finely balanced criteria that are absolutely crucial to supporting a habitat suitable for humankind.

"Rather than being one planet among billions, Earth now appears to be the uncommon Earth," said science educators Jimmy H. Davis and Harry L. Poe. "The data imply that Earth may be the only planet 'in the right place at the right time. '"19

A Bold and Audacious Claim

Earth's location, its size, its composition, its structure, its atmosphere, its temperature, its internal dynamics, and its many intricate cycles that are essential to life-—the carbon cycle, the oxygen cycle, the nitrogen cycle, the phosphorous cycle, the sulfur cycle, the calcium cycle, the sodium cycle, and so on—testify to the degree to which our planet is exquisitely and precariously balanced.20

As they begin their influential textbook Earth, Frank Press of the National Academy of Sciences and Raymond Siever of Harvard University write about what they call "the uniqueness of planet Earth."21

They note how its atmosphere filters out harmful ultraviolet radiation while working with the oceans to moderate the climate through the storing and redistributing of solar energy, and how the Earth is just large enough so that its gravity retains the atmosphere and yet just small enough not to keep too many harmful gases. Then they describe the Earths interior as ... a gigantic but delicately balanced heat engine fuelled by radioactivity. ... Were it running more slowly... the continents might not have evolved to their present form; Iron may never have melted and sunk to the liquid core, and the magnetic field would never have developed. If there had been more radioactive fuel, and therefore a faster running engine, volcanic dust would have blotted out the sun, the atmosphere would have been oppressively dense, and the surface would have been racked by daily earthquakes and volcanic explosions.22

These kind of highly choreographed geological processes-—-and there are lots of them-—-leave me shaking my head at the astounding ways in which our biosphere is precisely tuned for life. Even more interesting, though, is the "why" question behind them. What accounts for all of these astounding "coincidences?"

Press and Siever, while marvelling that Earth "is a very special place," don't broach the possibility of design.23 Ward and Brownlee skirt the issue in Rare Earth, preferring instead to occasionally pepper in words like "sheer luck" and "a rare chance happening."24 At a conference, Ward remarked: "We are just incredibly lucky. Somebody had to win the big lottery, and we were it."

But does luck really explain why Earth enjoys this incredible convergence of extremely unlikely circumstances that have allowed human beings to flourish? Going far back into time, Christians have reached a far different conclusion: Earth was created by God as the stage upon which the human drama would be played out. What's amazing about modern science, including new discoveries just within the last few years, is that this view of the universe seems to be far better supported today than in ancient times.

Consider the conclusion of Michael J. Denton, a senior research fellow in human molecular genetics at the University of Otago in New Zealand, in his 1998 book Natures Destiny:

No other theory or concept ever imagined by man can equal in boldness and audacity this great claim... that all the starry heavens, that every species of life, that every characteristic of reality exists [to create a livable habitat] for mankind. But most remarkably, given its audacity, it is a claim which is very far from a discredited pre-scientific myth. In fact, no observation has ever laid the presumption to rest. And today, four centuries after the scientific revolution, the doctrine is again re-emerging. In these last decades of the twentieth century, its credibility is being enhanced by discoveries in several branches of fundamental science.25

How true are those words? Do the special conditions that allow for life on Earth demand a designer? To pursue reliable answers, I arranged a rendezvous at O'Hare International Airport in Chicago with two experts who had just collaborated on a ground-breaking book concerning this very topic. This would be a perfect opportunity to explore the stunning uniqueness of our planet.

INTERVIEW #5-. Guillermo Gonzalez, PhD, and Jay Wesley Richards, PhD

Tall, blond Jay Wesley Richards, dressed in a navy blazer, is an Ivy League philosopher who speaks in rapid-fire bursts with unflagging enthusiasm. Guillermo Gonzalez, clad in a short-sleeve shirt, his thinning hair cropped short, is a nuts-and-bolts astronomer who talks in professorial tones on such topics as "Chemical Abundance Trends among RV-Tauri Stars."

Together, they authored The Privileged Planet, which documents astonishing evidence pointing toward a designer for Earth—and toward at least one apparent purpose for humankind.

Gonzalez is informally known as a 'star guy." After graduating summa cum laude with degrees in astronomy and physics from the University of Arizona, he later earned his masters degree and doctorate in astronomy from the University of Washington at Seattle. Now an assistant professor at Iowa State University, his research centers on low and intermediate mass stars and theories about stellar and planetary evolution.

He's a hands-on and yet conceptually sophisticated scientist, having logged countless hours doing research through telescopes at Cerro Tololo International Observatory, located at an altitude of 6,600 feet in Chile, and four other locations. He is adept at analyzing photometric and spectroscopic data. A member of the International Astronomical Union and the American Scientific Affiliation, the low-key but engaging Gonzalez has seen dozens of his articles published in technical journals and featured on the covers of such popular magazines as Scientific American.

An academic overachiever with a sincere, self-effacing personality, Richards holds three advanced degrees in philosophy and theology, including a doctorate from Princeton Theological Seminary. He authored The Untamed God and has edited or contributed to such books as Unapologetic Apologetics, Signs of Intelligence, and Are We Spiritual Machines? His articles have appeared in publications ranging from Perspectives on Science and Christian Faith to the Washington Post to the Princeton Theological Review. As vice president of the Discovery Institute, Richards is considered a bright star in the burgeoning Intelligent Design movement.

Each of us clutching a soft drink, we met in an airlines hospitality suite, with Richards and Gonzalez sitting across from me at a granite conference table under florescent lights in a simple room devoid of character. Anxious to proceed, I barely let them settle into their chairs before unleashing my first question.

The Copernican Principle

I turned toward Richards. "I was taught in school that our planet is unexceptional, that we revolve around a typical star in an average, mundane part of the universe, and that there's nothing particularly unusual or special about Earth," I began. "Isn't that the view of most scientists today?"

"Yes, that's the so-called Principle of Mediocrity or the Copernican Principle," Richards replied. "Open any introductory astronomy textbook and you'll see it stated over and over that we should assume there's nothing special about our situation, our location in the universe, or the particular features of the Earth, the solar system, or humans themselves."

"But," I interjected, "isn't that appropriate in some sense?" "Yes, of course," he said. "We shouldn't assume that the Earth, our solar system, or our sun is unique in every possible way. We wouldn't be able to do science if every place in the universe had a different law of gravity or atoms had a different mass. That's fine."

"Then where does the problem come in?" I asked.

"The problem is that the Copernican Principle has taken a metaphysically bloated form, which essentially says our metaphysical status is as insignificant as our astronomical location. In other words, we're not here for a purpose, we're not special in any way, and we don't occupy a privileged place in the cosmos."

I interrupted again. "Yet isn't it true that Copernicus's discovery —-that the sun doesn't revolve around the Earth, but that the Earth revolves around the sun—quite naturally demoted humankind?"

Richards nodded wearily as if he had heard that comment a lot. "Let's go back to the beginning," he said. He stood, removed his jacket, and draped it over an unoccupied chair. Sitting back down, he continued.

"The story is that the ancients-—-Aristotle, Ptolemy, medieval Christians—all thought we were at the center of the universe, sort of the throne of the cosmos, the most important place that everything revolved around. Then Copernicus and Kepler came along and said they can explain the movement of the planets better by assuming that the sun is at the center and that the planets-—including Earth-—-revolve around it. So we've been displaced from the center and removed from our position of privilege. This was the start of a long march of science that continued to demote us. Scientists later determined the sun isn't at the center of the universe; that we aren't at the center of the galaxy; and that the universe ultimately had no center, because scientists came to believe in the nineteenth century that it was infinite and eternal. You can see how this trend helped us to see ourselves as less and less significant, less and less at the center of things. So the Copernican Revolution came to represent the conflict between science and religion. Religious superstition maintained the Earth and humankind are the center of the universe, both physically and metaphysically, but modern science has disproved that. Humans have been stripped of their false sense of uniqueness and importance. While religious folk continued to insist there is something unique, special, intentional, and purposeful about our existence, scientists maintain that the material world is all there is, and that chance and impersonal natural law alone explain its existence."

I was following along in full agreement. Richards's assessment was entirely consistent with what I had been taught in school. But then he added the clincher.

"The problem," he said, a slight smile playing at the corner of his mouth, "is that this historical description is simply false."

Setting the Record Straight

Richards's claim startled me. "False?" I declared. "What do you mean? In what way?"

"Read Ptolemy, Galileo, Copernicus, Kepler. Read Dante," he said. "In Dante's Divine Comedy, the surface of the Earth is an intermediate place. This was true in Aristotelian cosmology, which was Christianized in the Middle Ages. For Aristotle, the world was made of air, earth, fire, and water. Earth is heaviest, so it naturally falls to the bottom. So the Earth was not so much at the center as it was at the bottom of the universe. It was sort of the cosmic sump. It was the place where things decay and die. Everything above the moon was made of a different type of matter—quintessence—and God dwelled in the heavenly sphere outside the celestial sphere of the stars. Man was in an intermediate place."

Gonzalez spoke up. "Dante then inverted these levels as you go the other way, down to hell," he said.

"Exactly," continued Richards. "You had nine levels going up toward God and getting closer to perfection, and then there were nine levels getting closer to absolute depravity, down to hell. Thus, in medieval cosmology, what we would call the center of the universe is Satan's throne. That's a very important point. If you imagine the center of the universe is Satan's throne and that the Earth itself is the cosmic sump, then clearly this is not the stereotype that we've been given that the center of the universe prior to Copernicus was the preeminent spot." 

Gonzalez added: "The Enlightenment later retold the story by saying the church, because of its arrogance, put humans in the center."

Richards nodded. "That's the irony," he said. "It was the Enlightenment that made man the measure of all things. When you really think about it, Christian theology never actually put man literally in the center. We have a very important role to play in this cosmic drama, so much so that God even becomes incarnate. But it was never the case that everything was literally created solely for us. Many centuries ago, Augustine said God didn't create the world 'for man' or because of some sort of compulsion, but 'because he wanted to.'26 In The Divine Comedy, the reader learns that the actual sense of us being in the center was merely a bias. We discover, in fact, that everything was arranged so that God is at the metaphysical center-—that is, the place of supreme importance. Instead of denigrating Earth, actually Copernicus, Galileo, and Kepler saw their new scheme as exalting it. For instance, Galileo waxes poetic about how the Earth, like the other planets, reflects the glory of the sun and is no longer just a cosmic sump.27 So in the transformation from medieval cosmology to the Renaissance view, this new perspective elevated man in some ways."

Other historical researchers have come to the same conclusion. Said one: "The Copernican system, far from demoting man, destroyed Aristode's vision of the earth as a kind of cosmic sink, and if it did anything, it elevated humanity. In making the earth a planet, a heavenly body, Copernicus infinitely ennobled its status."28

But something didn't add up to me. "Didn't the church persecute Copernicus, Galileo, and Giordano Bruno for their view that the Earth revolved around the sun?" I asked.

"First of all," Richards said, "some claim Copernicus was persecuted, but history shows he wasn't; in fact, he died of natural causes the same year his ideas were published. As for Galileo, his case can't be reduced to a simple conflict between scientific truth and religious superstition. He insisted the church immediately endorse his views rather than allow them to gradually gain acceptance, he mocked the Pope, and so forth. Yes, he was censured, but the church kept giving him his pension for the rest of his life."

Indeed, historian William R. Shea said, "Galileo's condemnation was the result of the complex interplay of untoward political circumstances, political ambitions, and wounded prides."29 Historical researcher Philip J. Sampson noted that Galileo himself was convinced that the "major cause" of his troubles was that he had made "fun of his Holiness" — that is, Pope Urban VIII—in a 1632 treatise.30 As for his punishment, Alfred North Whitehead put it this way: "Galileo suffered an honorable detention and a mild reproof, before dying peacefully in his bed."31

"Bruno's case was very sad," Richards continued. "He was executed in Rome in 1600. Certainly this is a stain on church history. But again, this was a complicated case. His Copernican views were incidental. He defended pantheism and was actually executed for his heretical views on the Trinity, the Incarnation, and other doctrines that had nothing to do with Copernicanism. Now, here's the point I want to make: it's very important if you're going to advance the Copernican Principle that you make it look like it's grounded in the historical march of science. But when you actually look at the data, it's just not true. Writers of astronomy textbooks just keep recycling the myth, sort of like the flat-Earth myth, which was the idea that Columbus was told the Earth was flat and he thought it was round. That's just wrong too." 

"Scholars at the time knew it was a sphere," added Gonzalez. 

"Even the ancient Greeks knew it was a sphere. They'd known it for a thousand years or more," said Richards.

I knew they were right about that. David Lindberg, former professor of the history of science and currently director of the Institute for Research in the Humanities at the University of Wisconsin, said in a recent interview:

One obvious [myth] is that before Columbus, Europeans believed nearly unanimously in a fiat Earth—a belief allegedly drawn from certain biblical statements and enforced by the medieval church. This myth seems to have had an eighteenth century origin, elaborated and popularized by Washington Irving, who flagrantly fabricated evidence for it in his four-volume history of Columbus. The truth is that it's almost impossible to find an educated person after Aristotle who doubts that the Earth is a sphere. In the Middle Ages, you couldn't emerge from any kind of education, cathedral school or university, without being perfectly clear about the Earths sphericity and even its approximate circumference.32

Now in addition to the flat-Earth myth being exploded, here were Richards and Gonzalez asserting that the Copernican Principle was based on faulty history as well.

"So," continued Richards, "Guillermo and I embarked on a project to document whether there are important ways in which Earth is special or exceptional. To do this we had to show that there's not this long historical march of science showing how unimportant we are. We had to point out that the history is wrong and that what we're doing stands in the good tradition of science, which says, 'Let's find out what the world is like to the best of our ability'"

"And," I said, "what did you find?"

Richards and Gonzalez exchanged glances. "Well, scientists have generally followed the Copernican Principle by saying that our planet is ordinary and that therefore life undoubtedly abounds in the universe," Richards began. "We believe, however, the evidence is quite to the contrary." He gestured toward his colleague to continue.

"We've found that our location in the universe, in our galaxy, in our solar system, as well as such things as the size and rotation of the Earth, the mass of the moon and sun and so forth—a whole range of factors— conspire together in an amazing way to make Earth a habitable planet," Gonzalez said. "And even beyond that, we've found that the very same conditions that allow for intelligent life on Earth also make it strangely well-suited for viewing and analyzing the universe."

"And we suspect this is not an accident," Richards added. "In fact, we raise the question of whether the universe has been literally designed for discovery."

The Ingredients for Life

With that framework set, I moved ahead to discuss one of the main attitudes of scientists who embrace the Copernican Principle. "They believe if you can just find a place anywhere in the universe where water stays liquid for a long enough period of time, then life will develop, just as it did on Earth," I said. "I assume you don't agree with that."

"No, I don't," Gonzalez said. "It's true that in order to have life you need water—which is the universal solvent-—-for reactions to take place, as well as carbon, which serves as the core atom of the information-carrying structural molecules of life. But you also need a lot more. Humans require twenty-six essential elements; a bacterium about sixteen. Intermediate life forms are between those two numbers. The problem is that not just any planetary body will be the source of all those chemical ingredients in the necessary forms and amounts."

I interrupted to point out that science fiction writers have managed to speculate about extra-terrestrial life that's built in a radically different form-—-for instance, creatures based on silicon instead of carbon. Gonzalez was shaking his head before I had even finished my question. "That just wont work," he insisted. "Chemistry is one of the better understood areas of science. We know that you just can't get certain atoms to stick together in sufficient number and complexity to give you large molecules like carbon can. You can't get around it. And you just can't get other types of liquids to dissolve as many different kinds of chemicals as you can with water. There's something like half a dozen different properties of both water and carbon that are optimal for life. Nothing else comes close. Silicon falls far short of carbon. Unfortunately, people see life as being easy to create. They think it's enough merely to have liquid water, because they see life as an epi-phenomenon—just a piece of slime mold growing on an inert piece of granite. Actually, the Earth's geology and biology interact very tightly with each other. You can't think of life as being independent of the geophysical and meteorological processes of the planet. They interact in a very intimate way. So you need not only the right chemicals for life but also a planetary environment that's tuned to life."

That sparked a related issue. Scientists have dreamed of terra-forming a planet like Mars, essentially making over its environment to create a planet that's more conducive to settlement by humans. "Would that be very difficult?" I asked.

"Absolutely. From the magnetic field to plate tectonics to the carbon dioxide cycle-—-ongoing life depends on a variety of very complicated interactions with the planet," he said.

Richards jumped in. "People generally think that because they plant a seed and it grows that it's easy to create the right environment for life, but that's misleading," he said. "A good example is the hermetically sealed biosphere that some people constructed in Arizona several years ago. They thought it would be relatively easy to create a self-contained environment conducive to life, but they had a devil of a time trying to make it work."

"But life can also exist in some terribly harsh conditions," I pointed out. "For instance, there are life forms that live off of deep-sea thermal vents. They don't seem to need oxygen or any particular support from the broader environment." 

"On the contrary," Gonzalez said, "the only things down there that don't need oxygen are some microorganisms that breathe methane. But larger organisms, which need to regulate their metabolism, are invariably oxygen-breathers. The oxygen comes from surface life and marine algae. The oxygen gets mixed in with the ocean and transported into deep waters. So those organisms are very directly tied to the surface and the overall ecosystem of the planet."

Astounded by the Earth's fine-tuned physical, chemical, and biological interrelationships, some writers have gone so far as to liken our biosphere to a "super-organism" that is quite literally alive. In fact, James Lovelock's pantheistic Gaia Hypothesis even seeks to deify our planet. However, Gonzalez and Richards said it's unnecessary to go that far.

"Despite these admittedly incredible interrelationships, there's nothing that requires anyone to see the Earth itself as being an organism, especially a god or goddess," Richards said.

Then he turned to an image quite familiar to those who see the earmarks of design in Earth's complex and interconnected machinery. "That's sort of like deifying a watch because of its amazing properties," he said, "rather than looking beyond the watch to the one who made it."

The Hostile World of M13

I granted the point that only certain kinds of planetary environments can play host to life. On the other hand, the universe is salted with trillions of stars, with countless terrestrial bodies undoubtedly revolving around them. Surely the mathematical odds favor many stars spawning Earth-like habitats—a point that argues against the idea that Earth is special and therefore designed. But while my untrained eyes see each star as having equal potential to preside over a civilization-bearing solar system, I was soon to learn differently as I pursued questions concerning the conditions that are necessary for life to flourish. I turned toward Gonzalez. "As we look out at the billions of stars that constitute our Milky Way galaxy," I said, "can't we logically assume that planets teeming with life are strewn all over the place?"

"No," he said unequivocally, "that's not a logical assumption based on the evidence. Along with Don Brownlee and Peter Ward of the University of Washington, I developed a concept called the Galactic Habitable Zone—that is, a zone in the galaxy where habitable planets might be possible. You see, you just can't form a habitable planet anywhere; there's a large number of threats to life as you go from place to place."

My mind flashed back to when Drake and Sagan beamed their message to the large concentration of stars called globular cluster M13. Their theory was that by transmitting their greeting toward a place packed with stars, there would be a higher chance of detection by an intelligent civilization. When I asked Gonzalez what he thought of that experiment, his reply was immediately dismissive.

"The problem is that if the probability of life at any one star is zero, then the probability for all the stars remains zero," he said.

"Zero?" I replied. "There are more than a quarter million stars in that globular cluster. Don't you think any of them harbor planets with life?"

Gonzalez stood his ground. "A globular cluster is one of the worst places in the entire galaxy to expect any life," he replied.


"Two reasons," he said. "First, globular clusters are among the most ancient things in our galaxy. Since they're extremely old, their stars have a very low abundance of heavy elements—carbon, nitrogen, oxygen, phosphorous, calcium, and so on. Instead, they're made up almost entirely of hydrogen and helium. In contrast, Earth is composed of iron, oxygen, magnesium, and silicone. Next comes sulfur.

"You see, the Big Bang produced basically hydrogen and helium. That's what the earliest stars were made of. The heavier elements were synthesized-—-cooked, if you will-—-in the interior of stars. Eventually, when these stars exploded as supernovae, these elements got expelled into the interstellar medium. They coalesced into other stars, where more heavy elements were cooked. Then they were expelled again and again, with stars subsequently containing ever-greater amounts of these metals, or heavier elements. Now, you need these elements to eventually build terrestrial planets like Earth. Because the very old stars in globular clusters formed so early that they're composed virtually exclusively of hydrogen and helium, they're not going to have planets accompanying them. Maybe there will be dust, or grains, or boulders, but that's about it. You're not going to have Earth-size planets.

"The second problem is that globular clusters are so densely packed with stars that they wouldn't allow for stable, circular orbits to exist around them. The gravitational pull of the stars would create elliptical orbits that would take a hypothetical planet into extremes of cold and heat, which would create a life-prohibitive situation."

His assessment made sense, but it caused me to wonder why Sagan and Drake, both knowledgeable astronomers, would waste their time trying to communicate with the stars of M13- Gonzalez shook his head when I asked him about it.

"It's really surprising that they would think there would be any chance of a civilization receiving their message in a globular cluster," Gonzalez said. "They should have known better! Frankly, I think they were so deluded by their complete belief in the metaphysical Copernican Principle—that life was just going to be everywhere in the galaxy —-that they overlooked the facts."

Living in the Safe Zone

Gonzalez's explanation made me wonder about the suitability of other places to harbor intelligent life. I knew that there are three basic types of galaxies in our universe. First, there are spiral galaxies like our own Milky Way. These are dominated by a central spherical bulge and a disk with "spiral arms" extending outward from the nucleus in a spiral pattern, resembling a celestial pinwheel. Second, there are elliptical galaxies, which are sort of egg-shaped. And, third, there are irregular galaxies, which appear disorganized and distorted. I asked Gonzalez to assess the life-bearing potential of each one.

"Certainly, our type of galaxy optimizes habitability, because it provides safe zones," he said, his tone professorial. "And Earth happens to be located in a safe area, which is why life has been able to flourish here. You see, galaxies have varying degrees of star formation, where interstellar gases coalesce to form stars, star clusters, and massive stars that blow up as supernovae. Places with active star formation are very dangerous, because that's where you have supernovae exploding at a fairly high rate. In our galaxy, those dangerous places are primarily in the spiral arms, where there are also hazardous giant molecular clouds. Fortunately, though, we happen to be situated safely between the Sagittarius and Perseus spiral arms. Also, we're very far from the nucleus of the galaxy, which is also a dangerous place. We now know that there's a massive black hole at the center of our galaxy. In fact, the Hubble space telescope has found that nearly every large nearby galaxy has a giant black hole at its nucleus. And believe me-—-these are dangerous things! Most black holes, at any given time, are inactive. But whenever anything gets near or falls into one, it gets torn up by the strong tidal forces. Lots of high energy is released—-gamma rays, X-rays, particle radiation—and anything in the inner region of the galaxy would be subjected to high radiation levels. That's very dangerous for life forms. The center of the galaxy is also dangerous because there are more supernovae exploding in that region. One more thing: the composition of a spiral galaxy changes as you go out from the center. The abundance of heavy elements is greater towards the center, because that's where star formation has been more vigorous over the history of the galaxy. So it has been able to cook the hydrogen and helium into heavy elements more quickly, whereas in the outer disk of the galaxy, star formation has been going on more slowly over the years and so the abundance of heavy elements isn't quite as high. Consequently, the outer regions of the disk are less likely to have Earth-type planets. Now, put all of this together-—-the inner region of the galaxy is much more dangerous from radiation and other threats, the outer part of the galaxy isn't going to be able to form Earth-like planets because the heavy elements are not abundant enough; and I haven't even mentioned how the thin disk of our galaxy helps our sun stay in its desirable circular orbit. A very eccentric orbit could cause it to cross spiral arms and visit the dangerous inner regions of the galaxy, but being circular it remains in the safe zone. All of this" he said, his voice sounding a bit triumphant, "works together to create a narrow safe zone where life-sustaining planets are possible."

Scanning the Stars for Life

Suddenly, the Earth was sounding pretty special, nestled as it is in a sliver of space that gives it safe haven from the otherwise menacing conditions of the Milky Way. But what about other types of galaxies? Might they also provide threat-free neighborhoods for life-populated planets?

"What about elliptical galaxies?" I asked Gonzalez. "Do they have the potential to harbor life?"

"Elliptical galaxies look amorphous and are sort of egg-shaped, with stars having very random orbits, like bees swarming a beehive," he explained. "The problem for life in these galaxies is that the stars visit every region, which means they'll occasionally visit the dangerous, dense inner regions, where a black hole may be active. In any event, you're less likely to find Earth-like planets in elliptical galaxies because most of them lack the heavy elements needed to form them."

This was an important point, because I knew that most galaxies fall into the elliptical category.

"Most elliptical galaxies are less massive and luminous than our galaxy," Gonzalez continued. "Our galaxy is on the top one or two percent of the most massive and luminous. The bigger the galaxy, the more heavy elements it can have, because its stronger gravity can attract more hydrogen and helium and cycle them to build heavy elements. In the low-mass galaxies, which make up the vast majority, you can have whole galaxies without a single Earth-like planet. They just don't have enough of the heavy elements to construct Earths. Just like a globular cluster-—you can have a whole globular cluster with hundreds of thousands of stars, and yet there won't be a single Earth. If you look at the deepest pictures ever taken by the Hubble Space Telescope, they show literally thousands of galaxies when the universe was really young. People have commented, 'Wow, look at all those galaxies! I wonder how many civilizations there are looking back at us?' In that picture, I'd say zero. Thousands and thousands and thousands of galaxies—-but zero Earths, because the heavier elements haven't built up enough yet."

Richards interrupted to say, "Of course, we're not looking at these galaxies as they exist now; we're looking back in time, say, nine billion years ago. It's possible that some of those galaxies are now at the state where the Milky Way is. We don't know for sure."

"But," added Gonzalez, "this was back when it was much more dangerous, because it's the era of quasars, supernovae going off, and black holes. Even if you had a few regions in the galaxy where there were sufficient heavy elements to build Earths, they would have been so irradiated that life wouldn't be possible."

With elliptical galaxies being unlikely sites for budding civilizations, I turned to the last category of galaxy, called irregulars. "What's their potential for life?" I asked.

"Like the ellipticals, they also don't provide a safe harbor. In fact, they're worse. They're distorted and ripped apart, with supernovae going off throughout their volume. There are no safe places where there are fewer supernovae exploding, like we have between our spiral arms. In fact, astronomers keep finding new threats to life. For example, we're learning more about gamma ray bursts, which are more powerful than a supernova. If one of these goes off near you, the lights go out. So the probability for there being civilizations elsewhere actually keeps declining as we learn about the new threats that we didn't know about before."

"What's your opinion, then, about where Earth is located in the universe?" I asked.

"In terms of habitability, I think we are in the best possible place," Gonzalez said. "That's because our location provides enough building blocks to yield an Earth, while providing a low level of threats to life. I really can't come up with an example of another place in the galaxy that is as friendly to life as our location. Sometimes people claim you can be in any part of any galaxy. Well, I've studied other regions—-spiral arms, galactic centers, globular clusters, edge of disks-—and no matter where it is, it's worse for life. I can't think of any better place than where we are."

"That's ironic," I said. "It's the reverse of the Copernican Principle."

Richards agreed. "The propaganda of the Copernican Principle has been that the long march of science has shown how common and ordinary our situation is. But the trend is in the opposite direction. The more you pile on the threats we're discovering in most places in the universe, and you contrast that with the many ways we're in a cocoon of safety, the more our situation appears special. 

"The most famous example is our own solar system," Gonzalez said. "At one time or another, scientists have speculated that there are civilizations on just about every body in our solar system-—-the moon, Mars, Jupiter. Percival Lowell built his own observatory in Arizona to find these civilizations on Mars. He actually quoted Copernicus to justify his belief that we can't be the only civilization. Now they've backtracked to the point of saying, well, maybe there's some very simple slime mold beneath the surface of Mars or Europa. And even that is extremely questionable. That's how far back they've had to retreat."

"Very often," observed Richards, "the Copernican Principle describes properties that don't matter. Who really cares whether we're in the physical center of the galaxy? It's irrelevant! What really matters is being in the place that's most conducive to life. And that's exactly where Earth finds itself."

Planets Circling Other Stars

Within the last few years, astronomers finally have been able to discover planets orbiting other stars-—-a major confirmation of what was once merely widespread speculation. "Doesn't this confirm that there's nothing particularly out of the ordinary about our nine-planet system?" I asked.

"I'll concede," said Gonzalez, "that it demonstrates our solar system is not unique when it comes to having planets circling a star. But prior to the detection of the first planet orbiting another sun-like star in 1995, the expectation was that astronomers would find giant gas planets in large circular orbits, much like Jupiter. Jupiter orbits the sun in twelve years in a nearly circular orbit, far out from the terrestrial planets —-Mercury, Venus, Earth, and Mars. However, we're finding that the planets circling other stars are quite different from Jupiter. They orbit over a full range of distances, from just a tiny fraction of an Astronomical Unit-—which is the distance between the Earth and the sun-—-out to several Astronomical Units. Most of their orbits are highly elliptical; very few are circular. These strongly non-circular orbits utterly surprised astronomers. Because they strongly subscribed to the Copernican Principle, they had expected that other planetary systems would be just like ours. And that expectation was basically dashed."

"What's wrong with an elliptical orbit for those kind of planets?" I asked.

"It poses a problem for the habitability of any terrestrial planets in their system, because it would make them less likely to have stable circular orbits," Gonzalez replied. "For example, Earths orbit is almost a perfect circle. A planet with the mass of the Earth would be sensitive to any of the gas giant planets if they had more eccentric orbits. The Earth-like planets own orbit would be affected, making it less circular and therefore subjecting the planet to dangerous surface temperature variations."

"So," I said, "if our own Jupiter had a more elliptical orbit, the Earth wouldn't be able to maintain as circular an orbit and have the steady temperature and predictable climate that come with that."

"That's right," he said. "In fact, even small variations in our nearly circular orbit can cause ice ages, because of temperature shifts on the surface of the planet. We have to maintain a circular orbit as much as possible to maintain a relatively steady temperature. That's only possible because Jupiter's orbit isn't very elliptical and therefore doesn't threaten to distort our round orbit."