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  •  Since you're here, let me ask something (8+ / 0-)

    about SETI

    (oh, by the way, I've read a lot of your books! They're cool)

    I'm a statistician.

    I've seen various equations for the likelihood of life elsewhere.  Different ones have different estimates of different things (often varying by orders of magnitude).

    But, aren't all these formulas arguing from an N of 1?

    I mean, there's only one planet with life that we know of....so, how can we even take wild guesses?

    Does life need water? Well, life on Earth seems to....elsewhere?

    Must a life form be solid?  Why?  Why not gaseous life, or liquid?  

    Any thoughts on this?

    thanks!

    •  I'm a biologist... (6+ / 0-)

      ...and while I agree with you that we're arguing from a single datum, it's all the information we really have on life, so it's what we have to use for now.  As for your questions, I'll see what I can do to answer them, even though I'm not David Brin. :-)

      First, while I think it's possible for life to exist without water, as I can imagine that machines can be created that satisfy all the characteristics of life (organization, energy use, homeostasis (responsiveness to the environment), growth, reproduction, and even evolution), I have difficulty imagining life spontaneously arising without water or some similar solvent.  The chemicals required for life have to be in solution so they are readily available for the kinds of reactions and structures that will lead to life.  As for that chemical being something other than water, well, there are other chemicals that are polar solvents, but they have their problems.  I'm not optimistic about other chemicals being ubiquitous universals solvents in the same class as water.

      Second, life is mostly liquid anyway.  You and I are mostly water and the material dissolved in it.  We happen to think we're solid because of bones (salt, not organic matter), skin, muscles, and connective tissue (solid proteins), but we're not.  Look at a jellyfish as an extreme example.  They're mostly gelatin, which is more liquid than solid.  Protozoans and algae are even more liquid than the jellyfish.  All that's "solid" about them is the cell membrane, and even that is described as a "fluid mosaic" in structure.  It just happens to be insoluble in water.

      BTW, I noticed that you didn't even question carbon as the central element in living things.  Good choice not to.  The only other possibility is silicon, and that isn't as flexible as carbon.  I'd have to do some digging to see if it's even possible to have aromatic rings of silicon, but I doubt it.

      "Iraq: the bravest 1% fighting for the richest 1%." ~ An Unknown Kossack.

      by Neon Vincent on Sun Dec 16, 2007 at 03:04:46 PM PST

      [ Parent ]

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