The hurdles that animals overcame even to exist on Earth are extensive, the authors claim, and they devote the bulk of their book to describing them. For example, the massive planet Jupiter orbits in just the right way in our solar system to fling asteroids and comets away from Earth, thus protecting it from frequent impacts that otherwise might sterilize life. Our gravitational waltz with the Moon stabilizes the tilt of Earths axis, preventing wild swings of temperature. On a broader scale, we live in a peaceful part of a stable galaxy, far from damaging supernovas and other outbursts. Ward and Brownlee believe, creating dead zones where higher life cannot evolve.
Scientists often lapse into jargon and convoluted arguments when they write for the public.
Refreshingly, thats not the case here. Rare Earth reads like a breeze, with straightforward writing and dashes of clever imagery. A lovely sequence near the end of the book invokes the emotions that one might feel when gazing into a starry sky and realizing that we may have few companions. And yet its not likely that Rare Earth will change minds in the scientific community. There are too many hand-waving arguments, and much of the text relies too heavily upon controversial theories.