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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
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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?
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