🚀 go-pugleaf

In article <1346@tdat.teradata.COM> swf@teradata.com (Stanley Friesen) writes:

   In article <1992Oct28.130939.9964@cs.rochester.edu> dietz@cs.rochester.edu (Paul Dietz) writes:

   [... conditions for life ...]

							For example,
   |perhaps deposition of organic material from space is required.

   This last is an extremely unlikely requirement.  The basic upshot of the
   Urey experiment and its follow-ups is that organics form spontaneously
   under most non-oxidizing 'medium-energy' conditions.  The presence of
   organics in interstellar dust clouds just confirms this basic ubiquity.

OK, organics are everywhere, Paul Dietz's example is flawed.

   [...]

   Now, it is true that we do *not* know the exact range of
   temperatures and pressures under which the ubiquitous organics are
   able to generate life forms, but this is a much smaller level of
   uncertainty than you suggest.

But what we do know is that simply putting lots of organic chemicals,
amino acids, what-have-you together, even in planetary quantities for
billions of years, is not likely to `generate life forms'.  That was
my original point that started this discussion: that organic chemicals
do not seem to be prone to generating self-reproducing systems,
largely because in order to reproduce they must have very carefully
controlled conditions, and such conditions will not evolve when there
is no evolutionary pressure (it's a chicken-and-egg syndrome). The
current idea is that one starts with a self-reproducing system that
does not _need_ such a finely-controlled environment (such as a clay
mineral), that such a system can, over time, select to control more of
its environment (a `cell') and that this environment may be suitable
for the development of nucleic acids (or something similar). But it's
a very long and precarious chain to get from clays to algae (or even
to viroids). And clay minerals aren't going to be sending us any radio
signals.

Lest you misunderstand me, I fully support spending money on SETI:
it's not expensive, and it attempts to answer one of the really big
questions about the universe. But none of us really expect to find
high-tech civilizations everywhere (for the simple reason that we
haven't seen them yet) and I think the reason lies in that term of the
Drake equation. When we get out there, I don't expect to find
universal dumb life, I expect to find no life at all.

Nick Haines nickh@cmu.edu