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I was going to reply to each of the interesting posts that I missed
while I was out of town, one at a time... but this whole thread has had stuff
worth replying to, so I'll just put it all into one post for the whole thread.
My question about "Why water?" was more intended to refer to life on other
planets than here on Earth. I think David is right: Self-organizing living
systems (organisms) on Earth are prone to incorporate water into their
organization, regardless of what other elements, compounds, and minerals, etc,
are also incorporated. Therefore, if one is going to try to construct an
organism using Earth organisms as the model, it just makes sense to begin with
water.
But, in constructed organisms and especially on other planets, I'm
not convinced that water would necessarily be required. Water is present here,
in every possible arrangement of the molecule, and there seem to be functional
requirements in organisms which are served by the properties of water as a
solvent, a conductor of electricity, a fluid, etc. which have
probably led to it being universally incorporated into Earth
organisms. However, just as blood can be copper or iron based... the functional
requirements that water serves (in the organization of living
organisms) are not dependent on the water, itself. It goes the other way;
there is water in organisms because of the functional requirements of the
organization and the plentiful nature of water on this planet.
It seems logical to me that organizational
requirements ought to be able to be fulfilled by other means.
I suspect that whatever raw materials are available on any
given planet will be what is incorporated into the life forms
which self-organize on it. In that case, alien organisms are not
likely to look like we are used to seeing, either. I loved Star Trek, but I was
always a little irritated with the total reliance on "humanoid" beings as
the various series aged. The original series was far more realistic in that
sense, because it had so many more life forms which were completely
different from us.
Judith
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