Do we live on a "privileged" planet?
By: Amy Combs
Astronomy
December 1, 2004


The Privileged Planet
Guillermo Gonzalez and Jay W. Richards, 444 pages, Regnery Publishing, Washington, D.C., 2004; ISBN 0-89526-065-4; hardcover, $27.95.

Is there life elsewhere in the universe? The Privileged Planet gives a new spin to the argument that conditions on Earth are essentially unique.

Authors Guillermo Gonzalez and Jay W. Richards suggest Earth was designed for scientific discovery. They introduce the “measurability” concept—-the idea that Earth is ideal for scientific observation. For example, the authors argue that if the Moon were slightly larger or smaller, scientists couldn’t study eclipses. Or if atmospheric conditions were different, astronomers wouldn’t be able to observe stars from Earth’s surface. The authors then ask what the chances are that another planet could have the same specifications necessary for conducting scientific research.

The book critiques the Copernican principle, which holds that Earth is not special in its ability to support life. The authors argue that Earth’s measurability demonstrates the flaws in the Copernican principle and marks the theory’s limitations as astrobiology dogma.

Yet instead of analyzing research, the book focuses on debates about the search for extraterrestrial intelligence (SETI), specifically the Drake equation. The book also dwells on numerous philosophical statements by Carl Sagan. But because SETI now extends to planetary evolution and prebiotic molecular chemistry, the authors’ criticisms paint a misleading view of the subject. More analyses of peer-reviewed studies and less criticism of philosophical statements would be better.

The book’s second limitation is its circular-reasoning tendency. The authors repeatedly argue that a system’s components would not be as measurable if the system itself were entirely different.

For example, one chapter explains that, since earthquakes exist, scientists can measure and learn more about them. However, planets without similar quakes wouldn’t provide scientists with as much information about plate tectonics, the structure of planetary mantles, or related geological phenomena; and so on.

But while we’ve learned much about the solar system, we know very little about planets outside the solar system. Thus it’s reckless speculation to claim natural systems on other planets would pose insurmountable barriers to any inhabitants making scientific discoveries.

Despite these criticisms, the authors’ argument does move forward one side of the origin-of-life debate. Because the topic of extraterrestrial life elicits extreme responses across the board, the authors’ general skepticism is useful.

The authors’ ability to juggle research perspectives from many different fields is also impressive. Each chapter presents thought-provoking examples of astronomical, geological, and biological systems, and then demonstrates how scientific observation is possible due to the conditions that make Earth habitable.

This ambitious, multidisciplinary approach paints an inspiring portrait of the delicate balance needed to sustain life. At the very least, the book’s poetic praise of Earth’s pristine measurability will leave readers much to ponder.

Amy Coombs is a research technician in a biophysics lab; her science features have aired on National Public Radio.