October 2001's _Scientific American_ has an article that consolidates on a
popular level some of the explanations for the Fermi Paradox. See "Refuges
for Life in a Hostile Universe" by Guillermo Gonzalez, Donald Brownlee and
Peter D. Ward. (It's not online, but the issue contents are at
http://www.sciam.com/2001/1001issue/1001quicksummary.html)
There are few points they make, including that only certain conditions are
right for forming earthlike planets, particle and electromagnetic radiation
is too high in many of the places where they could be formed, and other
factors in the galactic environment might make complex life less likely.
Only a narrow region of the galaxy has these conditions. They call this the
Galactic Habitable Zone (GHZ).
An underlying assumption here seems to be that earthlike worlds are needed
for life to arise -- at least for complex life to arise. This does not seem
an unreasonable one.
There are several other assumptions in the article, though the authors note
and answer many of them.
Any comments?
Daniel Ust
http://uweb.superlink.net/neptune/
"Macroeconomics for the Real World" is now online at:
http://uweb.superlink.net/neptune/Macro.html
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