Tuesday, April 17, 2012

Lewis Darnell: "Life in the Universe": primitive bacteria may be common, advanced life not

Author:  Lewis Darnell

Title: “Life in the Universe

Publication: London: Oxford University Press, 2007/2009, 202 pages, paper, ISBN 978-1-85168-505-9, Introduction, 8 chapters, conclusion.  From “Beginners ‘ Guides” series

Amazon link

This book, by a British physicist,  really lays out very clearly “what life is” and the circumstances that lead self-replicating organic systems to get started and survive.  Much of his discussion goes back to basic Chemistry 101, how atoms attract electrons and form bonds and compounds. 

The most “primitive” life, the prokaryotes, don’t have a cell nucleus to store their genetic information, a strategy left for eukaryotes.  Darnell makes a case for the idea that prokaryotes may be quite common on many planets in the universe, and may be able to travel in meteorites.  For a habitat to nurture advanced life is much more improbable.

Darnell’s book was written before many of the more interesting “exoplanets”, such as those in the Gliese system, 20 light years away, were discovered.  Nevertheless, Darnell pretty much lays out how “terms of service” for advanced life comport with circumstances all over the universe.

It’s likely, for example, that only a relatively narrow sliver round the center the Milky Way, about 27000 light years from the Center, is stable enough.  But that still means a circle about 60000 light years in circumference to find other stars with solar systems with planets as “perfect” as Earth turned out to be – itself by chance.  The risks of supernova, maybe 30-40 light years away, affecting planets over hundreds of millions of years is more than we had thought, and may be more an issue during periods when the solar system revolves through a denser part of the spiral arm (right now, we're in a less dense portion and are safer; in a hundred million years or so, that can change).

Many smaller galaxies may not have habitable regions at all.

In the solar system, the best chance for interesting life may actually reside on Titan.  The largest moon of Saturn has an interesting, if frigid, reducing chemistry on its surface, and possibly a subterranean ocean (like Europa).  Imagine the possible “political problems” if both environments on Titan produced sentient life. Europa may not be quite as promising, in Darnell's view. Dartnell gives detailed discussion of the history of Mars probes, and even of the theory that a meteorite found in Antarctica in 1996 represents “panspermia” from Mars.  What’s even more “disturbing” is the idea that Venus might have developed life, even advanced life, before a catastrophe and runaway greenhouse effect destroyed it all.   If so, it is a colossal tragedy.  Is that a warning for us?

Darnell feels that it could be a long shot to build earth-like life on planets around stars not like our Sun.  But because small red dwarfs, or M stars, are so plentiful (even within 20 or so light years of the Sun), they deserve attention. Planets in the "goldilox" zone around these stars are likely to be tidally locked, always facing one side to their suns.  That could mean extremely windy and stormy conditions from violent temperatures swings.  Maybe a larger planet could be stable enough and have enough real estate in the "twilight zone" for an interesting (if politically volatile) civilization. But M stars also have problems with extremely variable output, although they last hundreds of billions of years, maybe long enough for life to learn to adapt.  Their planets also may be less likely to have stable magnetic fields, but maybe a larger planet still would. 

Life may be the way The Universe resists inevitable entropy, as required by the laws of physics.  But intelligence seems rare, but perhaps we’re early in the time scale of the universe.  We’ve almost wiped ourselves out with nuclear war.  Maybe it would take hundreds of millions of years for another civilization in the “sliver” around the Milky Way to arise, but one probably would eventually.  Another good question concerns the nature of sentience, self-awareness, and free will, up to the point that the individual ego experiences the consequences of its own actions, and sometimes of the actions of others.  By the “anthropic” principle, we can understand only our own style of consciousness.  Consider social insects.  Do individual ants have self-awareness, or is that facility reserved for the colony as a whole?  Is consciousness a basic component of physics that cannot be destroyed (because it is essentially information) once it exists?

Wikipedia attribution link for Titan picture. 

(I still have to give the Amazon link manually. I get database errors on the automated version. Still looking into why.) 

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