Rare Earth: Why Complex Life Is Uncommon in the Universe (Hardcover)

This is a work filled with broad, sweeping suppositions, yet it seems that as always the devil is in the details and I was left unconvinced that the authors really had the details right to support their "Rare Earth" theory. It is an interesting, if ultimately unconvincing book. Interesting theory, lots of conjecture, and lots of "What if..." in every chapter.

To me it seems that in many places sweeping statements are made, but never supported. Take for instance the statement on page 110 "Changes in ocean chemistry caused by increased tectonic activity beginning a billion years ago facilitated the evolution of skeletons." But the section does not, to me, provide adequate support or explanation for this supposition.

Also take for example the Drake Equations which - while properly explained - is misstated in the details.

The equation is usually written: N = R* x fp x ne x fl x fi x fc x L where:

N = The number of civilizations in The Milky Way Galaxy whose electromagnetic emissions are detectable.
R* =The rate of formation of stars suitable for the development of intelligent life.
fp = The fraction of those stars with planetary systems.
Ne = The number of planets, per solar system, with an environment suitable for life.
fl = The fraction of suitable planets on which life actually appears.
fi = The fraction of life bearing planets on which intelligent life emerges
fc = The fraction of civilizations that develop a technology that releases detectable signs of their existence into space.
L = The length of time such civilizations release detectable signals into space.
(Source: Seti Institute, http://www.seti-inst.edu/science/drake-bg.html)

However, as given in the text of "Rare Earth" the formula is:

N* x fs x fp x ne x fi x fc x fl = N

This does not appear to be a big difference, however, the terms fi, fl, and fc are each mis-defined in the book. fi is defined as planets where life does arise, not intelligent life; fc as planets on which intelligent life emerges, not civilizations that develop a technology; and fl as percentage of lifetime of a planet that civilizations release detectable signals into space, not planets with life. This may seem nothing more then nit picking over details, but to me this is symptomatic of the entire work. If you can't even get a few simple 40 plus year old definitions right how accurate is the rest of the work? The belief that earth is the rarest of planets and then the selection of information to support that idea appears to be the main thrust here.

Good science uses data to take you to a logical, fact supported conclusion, you get the reverse when to select facts to support a preconceived conclusion.

Overall an unsatisfactory book.

As an example of the latter, the authors seem to imply that the Sun has little or no interaction with the Galaxy's spiral arms and that the inter-arm regions of a spiral galaxy have a lower stellar density than inside the spiral arms. Neither is correct. It is true that the Sun is not now located in a spiral arm. However, the Sun orbits the Galactic center, taking about 250 million years to do so. The Galaxy's spiral arms do not rotate with the stars. The Sun therefore probably passes through at least one spiral arm every orbit. Over its lifetime the Sun has made approximately 20 orbits, plenty of time to pass through multiple spiral arms. Indeed the authors seem to be unaware of a proposal that massive extinctions in the Earth's past were caused by passage of the Sun through a spiral arm.

In many places the presentation also seems muddled. If we are told that Jupiter is more than 300 times the mass of the Earth (p. 235), do we really need to be told less than three pages later that Jupiter's mass is 318 Earth masses (p. 238)?

While reading it, I kept finding myself saying, That's not right, or, But what about ....? It's truly disappointing because the title is so provocative and because we are learning so much about the formation of planets and the origin of life on the Earth. However, having read the book, I certainly would not have purchased it initially.

The book does have some nice summaries of astrobiology, evolution, plate tectonics, snowball earth events, etc. If you are in the simple sciences (physics, astronomy, biology etc.), this book may provide a good read because there is a lot of theory but little real information. If you are looking for analysis and solid conclusions, this book will be a clear disappointment.