Not A Friend to ID: John Gribbin and the ‘Unique Earth’ Argument: a book review of ‘Alone in the Universe: Why Our Planet is Unique’ by John Gribbin


Guillermo Gonzalez

Article ID:



Jan 31, 2024


Jan 31, 2012

This review first appeared in the Christian Research Journal, volume 35, number 5 (2012). For further information about the Christian Research Journal click here.

a book review of

Alone in the Universe:
Why Our Planet is Unique

by John Gribbin

(Wiley, 2011)

John Gribbin is an astrophysicist and a prolific popular science writer. His latest book is a timely one, coming when the public’s interest in life beyond Earth has been heightened by discoveries of hundreds of exoplanets by NASA’s Kepler mission. In Alone in the Universe, Gribbin reviews this and other recent developments in astrobiology. The book’s subtitle, Why Our Planet Is Unique, gives away the punch line (sort of—restricting his focus to the Milky Way galaxy, he leaves open the question of civilizations in the broader universe). This delightfully contrarian book will not set well with the average astrobiology enthusiast, but it should be popular among Intelligent Design (ID) proponents. Does this make Gribbin a friend of ID? Not necessarily.

At times, reading Alone in the Universe is like reading a condensed version of Rare Earth or The Privileged Planet. Gribbin does mention Rare Earth, but he is silent on the latter. He covers much of the same ground as these books, including exoplanets, the Drake Equation, the Fermi Paradox, the history of life on Earth, the life-friendly properties of carbon and water, and planetary habitability. This last topic is the central theme of the book. Gribbin takes us on a journey through time and space, starting at the scale of the Milky Way galaxy and gradually narrowing his focus until he reaches his final topic—us. With each step Gribbin reinforces just how uncommon we are, even to the point of having a repetitious chapter title structure beginning with chapter 2, “What’s So Special about…?”

As he notes in the acknowledgements, Gribbin consulted with a number of prominent scientists while writing this book. These include Douglas Lin, Bernard Pagel, James Lovelock, and Charles Lineweaver. Lin and Pagel are astrophysicists. Lovelock is the originator of the Gaia hypothesis. Lineweaver published a paper on the Galactic Habitable Zone (GHZ) concept in Science in 2004, a few years after Bon Brownlee, Peter Ward, and I introduced it. I was not surprised, then, when I found that Gribbin devoted an entire chapter to the GHZ.

The GHZ concept is a way of quantifying habitability on the scale of the Milky Way galaxy. I agree with nearly everything Gribbin writes in this chapter. He does have a good grasp of the concepts. In short, the boundaries of the GHZ (which has the shape of a flattened annulus) are determined by two factors: the abundances of heavy elements like oxygen and iron, and threats to life. Heavy elements in the disk decline as you go out from the center of the Milky Way. This has important implications for the formation of planets, since it is known that the incidence of planets detected around sun-like stars depends on the star’s heavy element abundance. So if a star is far from the galactic center, it is less likely to be accompanied by planets. The inner boundary of the GHZ is set by various sorts of threats to life on a planet. They include supernovae, Oort cloud comets, gamma ray bursts, and the giant black hole at the galactic center.

Both observations and simulations show that the kind of solar system we inhabit, with giant planets far from the host star in nearly circular low-inclination orbits, is rare. Observations of exoplanets show, instead, that Jupiter mass planets have a wide range of orbits. Some are very close to their host stars; these are called “hot Jupiters.” Most others have more eccentric orbits than the planets in our solar system. Had Jupiter formed with a significantly less circular orbit, Earth’s orbit would be less circular (causing larger climate shifts) and less stable. Gribbin justifiably devotes several pages to discussing the important roles Jupiter has actively played in Earth’s history including its formation, the delivery of water, and protection from comets.

Next, Gribbin focuses his attention on the sun. He rightly notes that the sun is not an average star. About 95 percent of nearby stars are less massive than the sun. The sun is among the 20 percent of stars that lack a stellar companion. A recent finding is that only about 10 percent of sun-like stars have a chemical abundance pattern similar to the sun’s. There is also some evidence that the sun’s brightness is more stable than most other stars with similar mass and chemical composition.

Gribbin places considerable emphasis on the importance of the moon for Earth’s habitability. This includes the effects of the moon’s formation on Earth’s core, crust, and initial rotation (and their effects on the magnetic field), the stabilization of Earth’s rotation axis, and the tides. In the midst of this discussion resides the money quote of the book:

At present it [the moon] is moving outwards at a rate of about 4 cm per year, and within 2 billion years it will no longer be able to stabilize the Earth’s tilt. This ties in with one of the most curious coincidences in astronomy—indeed, in science—which seems to have no explanation and is utterly puzzling. Just now, the Moon is about 400 times smaller than the Sun, but the Sun is about 400 times farther away than the Moon, so that they look the same size on the sky.…Nobody has been able to think of a reason why intelligent beings capable of noticing this oddity should have evolved on Earth just at the time that the coincidence was there to be noticed. It worries me, but most people seem to accept it as just one of those things. (p. 143)

I’m glad it worries him. Noticing the oddity of this coincidence is the first step in realizing that we live in a universe that displays evidence of purpose. This coincidence struck me shortly after returning in 1995 from India where I experienced my first (and still only) total solar eclipse. It was the first instance of what I call the Privileged Planet pattern and for this reason made the topic of solar eclipses the first chapter of The Privileged Planet. If Gribbin had read it, he would know that someone has indeed offered an explanation for this coincidence. It is part of a broader pattern. In short, the very same conditions that make Earth a suitable planet for advanced life also make it a great place to do science. The universe is set up so that observers are located in the best places and times to observe! This thesis makes sense of a number of similarly odd coincidences in science.

In my opinion, John Gribbin is the kind of scientist who should be open to evidence of purpose in nature, and had he been born two centuries ago, he might have written a book friendlier to ID. However, scientists today are brought up in a different culture of thought, a different zeitgeist. Throughout his book Gribbin seems to accept uncritically materialistic evolutionary theories. To him the origin of life is about getting the right chemistry going. On page 11, he states, “Everything we know about the way planets form suggests that life is an almost inevitable by-product of the formation of a wet earth.” Even Brownlee and Ward don’t go that far.

A bit later Gribbin describes the cell as “a tiny bag of watery liquid containing all of the requirements for life.” No wonder he thinks the origin of life problem is all but solved! A much more appropriate metaphor for the cell is a factory, with many inter dependent parts orchestrated to achieve a common goal. Life is more than just chemistry. He offers no hint of the intractable problems faced by naturalistic theories in accounting for the origin of complex specified information in the first life and in subsequent novel biological structures. ID theorists have been discussing these problems for decades (see Stephen Meyer’s Signature in the Cell), but Gribbin apparently has not taken notice.

To Gribbin, the main source of biological novelty is Darwinian evolution driven by environmental change. The faster the environment changes, the faster organisms evolve. Thus, he postulates, as have others, that the end of a “Snowball Earth” episode (possibly combined with the rise of oxygen) opened up niches in the environment that caused organisms to evolve rapidly during the “Cambrian explosion.” One problem with this idea is that the timing isn’t quite right: the Cambrian explosion occurred about one hundred million years after the end of a Snowball Earth episode. Second, while rapid environmental change can be a factor in the history of life, it does not generate novel biological structures such as new body plans or the bacterial flagellum. As Michael Behe shows in The Edge of Evolution, Darwinian (and any other unguided) processes are at most able to create changes at roughly the genus level. Near the end of the book, Gribbin even proposes that the ice age cycles of the past few million years account for the origin of humans!

As I noted above, Gribbin makes considerable effort to show the reader just how special we are. But, ultimately, “special” as used in this book merely means “unique accident,” with no implications for ID.

I disagree with a few of the other ideas Gribbin presents. In particular, he proposes a highly speculative theory involving the collision of a large comet with Venus to account for the coincidence in time of one of the Snowball Earth episodes and the resurfacing of Venus. Not only are we lacking independent evidence for such an event, but the timing of the resurfacing of Venus is uncertain. Another uncertain topic is the sun’s birth cluster. (The sun is thought to have been formed in a star cluster, which eventually dissolved, leaving the sun a wandering lonely star.) Just how large it was and what influence it had on the young solar system are indeterminate and controversial questions. But Gribbin treats this, like several of his other topics, as essentially settled science.

Gribbin briefly discusses the current controversy over global warming (a.k.a climate change) near the end of the book. He also treats it as settled science, taking a rather extreme position. He writes, “Lovelock calculates that other feedbacks, involving both living and non-living components of the Earth System, could make the temperature of our planet jump by 4-6 °C when a tipping point is reached by the middle of the present century.” Perhaps he should consult on this topic again with Lovelock, who has had a recent change of heart!

The lack of notes also takes away from the book’s academic rigor. Overall, I would recommend this book as a quick way to get caught up on developments in astrobiology since Rare Earth and The Privileged Planet were published, but I also urge caution.—Guillermo Gonzalez

Guillermo Gonzalez, Ph.D., is associate professor of astronomy and physics at Grove City College, Pennsylvania. He has published nearly eighty scientific papers and two books, including The Privileged Planet: How Our Place in the Cosmos Is Designed for Discovery (Regnery, 2004).

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