>>>     Of course for the water to be any good, it has to be in liquid form.
>
>> You're aware that (on Earth) there are organisms that live in solid ice,
>> right?
>
>    They did not originate in ice. The simply adapted to it afterwards.

That's true. It's also true that planets that are far from the Sun right 
now might have been nearer at some point. Or the Sun's output may have 
changed.

But ultimately, yes, it seems more plausible that life would originate 
and thrive in a liquid or possibly vapour environment, rather than a 
solid one. (I have no idea whether it's feasible in plasma.)

>> What makes you think that chemicals which are "rare" on Earth would
>> necessarily be rare elsewhere?
>
>    There would have to be a significantly different process that formed
> those rare elements than here on Earth. What would that process be?

A cursory glance at the chemical composition of the surface or 
atmosphere of various planets around us indicates wildly differing 
chemistry. I don't know enough about planet formation to speculate as to 
why. (Presumably different elements get transported to different places 
or something...)

>>> (Also, most liquids other than water get denser when they
>>> solidify, which is a big problem.)
>
>> Care to explain why?
>
>    If water had a higher density when it freezes (as happens with the vast
> majority of other chemical compounds), life on Earth wouldn't exist because
> all bodies of water would freeze from the bottom up, killing all living
> organisms.

OK. But presumably that's only "a big problem" if the chemical we're 
talking about has a solid phase that can potentially exist on the planet 

your hypothetical planet never gets that cold, the fact that solid 
ammonia is more dense than liquid ammonia shouldn't be a problem.

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> On planets or moons much further away where another liquid
> is in plentiful supply (eg methane) couldn't some kind of life develop
> that uses that instead?

I would say it's plausible.

Water's chemistry is somewhat unusual in a number of ways (particularly 
the fact that it can dissolve such a wide range of solutes), but it 
seems plausible to me that you could use some other solvent.

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>    It might be that if the weather system on Earth (over periods of millions
> of years) was such that water never froze at large portions of it, it might
> be hostile for life for other reasons. Perhaps a changing climate is somehow
> necessary for life. As said, I don't know.

I don't know either, which is why I wouldn't dismiss the possibility 
that life could start in other liquids.

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On 11/01/2011 02:03 PM, Warp wrote:

>    Actually the definition of "species" is a hard one.

Yes, actually.

I suppose back when everybody thought that all life was fixed and 
unvarying forever, it seemed less problematic. But now that we know that 
one species gradually changes into another... it's a bit like trying to 
classify whether a specific colour is "red" or "orange". The distinction 
is almost arbitrary.

>    By definition two animals are of different species if they cannot produce
> fertile offspring. However, this definition is lacking.
>
>    It's lacking because the definition implies transitivity:

There's a much bigger problem: Some species reproduce asexually. (!)

> However, there are eg. so-called ring species (look it up)

Another of the interesting items from The Ancestor's Tale which my 
initial post skipped over. A continuum of organisms, distinct at the 
ends, but continuous and unbroken across the middle.

>    A ring species is actually an excellent demonstration of how speciation
> can happen gradually, unlike the straw man that some creationists present
> of "a species suddenly transforming into another".

It also neatly demonstrates that geographic separation is not a 
necessary condition for speciation.

>    The difficulty of classifying B in the example also demonstrates the
> completely fuzzy line between when a species becomes another species.
> If you trace the ancestry of a modern species back to an ancestral species
> which spawned one or more other modern species, it's hard to define when
> exactly the modern species became to exist exactly.

Ring species show fuzziness in the spatial domain, ancestor trees show 
it in the temporal domain. Either way, the problem remains the same: how 
to map discrete names to continuous phenomena?

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Warp wrote:
>   I don't think it would be physically possible for any kind of life to
> form that far from the Sun.

There's the Vernor Vinge story "A deepness in the sky", wherein the 
protagonists evolved around a sun that was hot only a few decades out of 
each several centuries and managed to hibernate through the cold times. I 
imagine something like that with a comet could work out. Hard to see how it 
would *evolve*, mind, unless the body started out in a close orbit that got 
more and more eccentric over time somehow.

>   Chemicals need to react with each other, which means that there must be
> some kind of solution where they can freely float or otherwise move.

Weightlessness?

> (Also, most liquids other than water get denser when they
> solidify, which is a big problem.)

I'm not sure that's as much of a problem as you think it is for anything 
other than fish.  Why do you think the fact that it floats is important?

Also, it floats in part because it's a polar molecule (i.e., electrically 
asymmetrical), which may very well be more important than the result of 
floating.

-- 
Darren New, San Diego CA, USA (PST)
   Serving Suggestion:
     "Don't serve this any more. It's awful."

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Warp wrote:
> life on Earth wouldn't exist because
> all bodies of water would freeze from the bottom up, killing all living
> organisms.

Well, unless they evolved in San Diego. ;-)

-- 
Darren New, San Diego CA, USA (PST)
   Serving Suggestion:
     "Don't serve this any more. It's awful."

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Invisible wrote:
> But ultimately, yes, it seems more plausible that life would originate 
> and thrive in a liquid or possibly vapour environment, rather than a 
> solid one. 

There is much hard sci-fi about life in jupiter's clouds, never landing on 
solid ground, taking energy from both the planet and the sun.  It doesn't 
seem too unreasonable.

-- 
Darren New, San Diego CA, USA (PST)
   Serving Suggestion:
     "Don't serve this any more. It's awful."

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Invisible wrote:
> ID is not testable. It's so vague that any time someone falsifies it, 
> the proponents can just claim that the theory says something slightly 
> different, and hence is not falsified.

That's a different problem. Denying the evidence of the failed tests doesn't 
mean that it passed the tests. It only means the proponents are pushing the 
concept regardless of whether it has failed the tests.

ID is certainly testable: We've found no irreducibly complex substructures, 
we have overwhelming evidence of evolution, etc.

-- 
Darren New, San Diego CA, USA (PST)
   Serving Suggestion:
     "Don't serve this any more. It's awful."

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scott wrote:
> but maybe that's just because we haven't figured out yet what is driving 
> those events, so they just *appear* random to us.

FWIW, the answer to this speculation is "no, we have proven that's not the 
case."  :-)

-- 
Darren New, San Diego CA, USA (PST)
   Serving Suggestion:
     "Don't serve this any more. It's awful."

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Warp wrote:
> "Observances of the National Day of Prayer took place throughout the
> U.S. in 2009 and again in 2010.

OK. But it has been around longer than either of us have been alive; it's 
not something Obama ass-pulled. I'm not sure what "The Obama administration" 
refers to there, but I'm pretty sure it encompasses far more than "Obama".

-- 
Darren New, San Diego CA, USA (PST)
   Serving Suggestion:
     "Don't serve this any more. It's awful."

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