Re: Opinion Poll: Water and Life?

rev.goetz wrote:
John Wilkins wrote:
rev.goetz wrote:
What is the probability of abiogenesis on any given planet or moon that
has water?

Zero, unless it also has complex hydrocarbons, and a range of other chemistry
as well. If it has all these in the right proportions and conditions, the
probability of abiogenesis is exactly one.

Or perhaps you are asking for the range of conditions under which abiogenesis
occurs? In which case we can make a better guess than we once could due to
some solid research on the topic, but not give an exact figure.

Well, I should rephrase my question to this:
What is the probability that any given planet or moon has the right
conditions so that the probability of abiogenesis is exactly 1?

Such probability assignments require a sample size of sufficient size to
generalise. There is no a priori probability when facts are the determinants.
We would nee dto have, say a few hundred sample cases with some frequency
ranging from 0 to 1 of cases of life.

This probability can either be a frequency specification (n out of M cases
have L) or a Bayesian probability (the probability relies on some background
knowledge). Since we have neither in sufficient detail to make an assignment,
we really cannot say.

But if life arises from the chemical properties of naturally occurring
molecules, then it does so deterministically (since chemical properties are
deterministic). Call these prior conditions C - then if C, L will arise. What
we are researching now is whether the possible range of conditions {C} obtain
throughout the universe (with access to only one solar system plus some
inferential work done on interstellar clouds, star composition, and observed
planted elsewhere), and what class {L} of things that we would call life can
arise.

The tried and tested way in science of raising probabilities to 1 is to
observe the phenomenon in question. So when we find another case, then we will
be able to say, a posteriori, that life arises when the conditions are right.

--
John S. Wilkins, Postdoctoral Research Fellow, Biohumanities Project
University of Queensland - Blog: evolvethought.blogspot.com
Who are you going to believe? Me, or your own eyes?

.

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