One of the few things I recall from college Probability Theory class is that
if something happened once, no matter how unlikly, it can happen again. For
example, since the Chicago Cubs won back to back World Series championships
in 1907 and 1908, theoretically, they could do it again.
Meteorites containing peptides, amino acids, nucleobase isomers and other
building blocks bombard a planet that already more than likely contains the
same stuff, since it is composed of accreted asteroids, comets and
meteorites. So we have these compounds in an oxidizing atmosphere with lots
of lightning storms. Add in the hundreds of known constraints on the
parameters for carbon-based life forms, (distance from the nearest star,
perfect magneto-field, etc., etc.) What is the logical probability that
these compounds will randomly assemble themselves into DNA and RNA molecules
that will self-replicate and start using proteins to build living cells. The
cells will then assemble into tissues and organs until a complex
multi-cellular organism results. These organisms then sexually reproduce
(Yaaaay!) and diversify until they evolve into humans. The humans randomly
develop consciousness, self-awareness and intelligence.
Sure, this could happen again. And Ernie Banks could come out of retirement,
suit up, and hit the game-winning home run as the Cubs cruise to a
consecutive World Series victory!
Phil Whitmer
Joshua Tree Earth & Space Museum
------------------------------------
Hello
It is of course OK to be skeptical of claims of life elsewhere in the
Universe. Carolus Linnaeus, the founder of biology, to avoid considering
sailor tales (and later Bigfoot, Yeti, and Loch Ness claims) insisted on a
type specimen. The controversy over ALH 84001 boils down to whether the
truncated hexaoctahedral magnetite crystals found constitute a type
specimen, or were they produced abiotically on Mars (they are not produced
abiotically on Earth). It is always possible to posit by some Rube
Goldberg-like mechanism am abiotic origin to almost any trace biological
evidence. Insisting that evidence absolutely not have any abiotic orgin
possible under any circumstances is a hurdle too high and in my view, too
illogical. That is the difficulty.
Of possible use in this brouhaha is Rudolf Carnap's theory of logical
probability assigned to theories. An accepted type specimen is of course,
proof positive; the probability of extraterrestrial life then is 100%. But
the probability is still nonzero that microscopic life indeed does exist
under the frozen lake of Elysium. Assigning probability to a theory is a
difficult task, and the popular media folks are totally clueless on the
concept. IMVHO, the evidence is such that it is more probable microscopic
life exists/existed on Mars that not.
But Carnap's ideas, endorsed by Martin Gardner, will be helpful in this
situation. An outline of them is found in Carnap, R. Philosophical
Foundations of Physics, Basic Books, London 1966. edited by Martin Gardner.
Francis Graham
Kent State University
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