Alone In The Universe

Why Our Planet is Unique

John Gribbin, 2011, Beaverton 525 GRI

I "believe" intelligent life is rare in the Galaxy; we are the result of a long string of low probability events. However, other forms of intelligence may result from other event strings; we don't know everything yet.

Gribbin describes events on the string, and assigns probabilities to them (for example, the surprising circularity of solar-planetary orbits), but his clincher is that "they" aren't here when they have had plenty of time to get here, so they aren't "out there" either. The implication is that the Solar system is a desirable place for star-spanning civilizations to travel to and remain.

Well, maybe not. Star-spanning civilizations may seek specific characteristics that our Solar System lacks; it may be a cradle of life, but the grownups don't live in cradles. The elemental composition optimum for spacefaring may be as different from our life-originating system as a space station is from a baby crib.

For example, very little of the solar system's water is easily accessible in shallow gravity wells; almost all of it is locked up in the gas giants. Jupiter's core is about 20 times as massive as the Earth, the while water is a tiny fraction of the atmosphere, at -100C and below, almost all of the water is frozen and the vapor pressure is miniscule. Any water is highly compressed ice on and in the core. Uranus and Neptune may contain 10 to 20 Earth masses of water and ice, but it would be hard to extract.

Other star systems may be arranged with far more accessable water, or more easily-used sunlight, or farther from supernovae, or closer to other sources of essential materials.

The book is too number-deprived to hold my technical interest. I managed 75 out of 205 pages, but I need to focus my limited time on other books.