BH:===
>"IOW, the results you present from Mason would also be 'opinion' in the way
>Miller is using the term."
>
KO:==
>I would disagree. Mason is reporting on what we could claim to know based
>on actual physical evidence; he wasn't speculating based on the evidence.
>
And the people that Miller refers to as "considerable opinion",
do you think they were just making stuff up out of thin air?
BH:===
>"I'm going to omit the Mason quote for sake of space. Let's see what we can
>agree on. Can we agree that hard evidence ends 3.8 billion years ago with
>the Isua rocks of Greenland?
>
KO:===
>No. As Mason points out, we have hard evidence in the form of meteorites
>that, when heated, give off the right gases in the right proportions to make
>a reducing atmosphere.
>
Fine, but this is indirect evidence. Enough evidence to allow
you to speculate that maybe the earth's early atmosphere was
reducing.
BH:===
>"Can we agree that at this latest point of hard evidence that the earth's
>atmosphere was most likely neutral or mildly reducing?"
>
KO:===
>Yes, that evidence seems rather clear.
>
BH:===
>"The rest seems to me to be speculation."
>
KO:==
>The rest of what? Mason? He supports everything with evidence. My
>summary? I base it on Mason. I don't see any speculation here.
>
Apparently we disagree on what constitutes evidence and
what is speculation. Let's take a look at an extensive
review put out by the space studies board:
<The search for Life's Origins> Space Studies Board,
National Academy Press, Washington D.C. 1990.
Chapter 3 of this report deals with early planetary environments
and contains a section on earth. Here they review a lot of
results which I'm not going to try to summarize. Instead I'll
jump to the closing paragraph of this section, which begins
as follows:
====================
"These speculations on chemical evolution, multiple
origins of life, and models of early environmental
conditions in the atmosphere and oceans can only
be substantiated by the geological record. Ancient
rocks of all types--especially samples of sedimentary
environments--are critical, and efforts to find them
are of high priority."
=====================
Brian Harper
Associate Professor
Applied Mechanics
The Ohio State University
"He who establishes his arguments
by noise and command shows that
reason is weak" -- Montaigne