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<div class="moz-cite-prefix">On 2013-11-22 18:19, Kelly Anderson
wrote:<br>
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cite="mid:CAPy8RwaG2=Wsup4xAmhU7awRbGEqYmv8MfS__xFPrDeciiLHeA@mail.gmail.com"
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<div class="gmail_quote">On Fri, Nov 22, 2013 at 6:38 AM,
Eugen Leitl <span dir="ltr"><<a moz-do-not-send="true"
href="mailto:eugen@leitl.org" target="_blank">eugen@leitl.org</a>></span>
wrote:<br>
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> Water is perhaps the most abundant one, but one
should not rule out<br>
<br>
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Water is not particularly abundant, but it has certainly
very<br>
interesting properties, which, if taken together, make it
unique.<br>
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<div>I tend to agree with Eugen on this one. As far as I'm
aware, water is the only liquid that becomes less dense
upon freezing. Otherwise, the oceans would fill up with
ice from the bottom up. Ices are clearly not as good for
life as liquid. <br>
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<br>
Remember the high temperature water ices of double-earth: under many
conditions water behaves "normally" too. In fact, bottom-ice-free
oceans might be unusual in the universe if most terrestrials tend to
be big waterworlds. <br>
<br>
There are other expanding liquids like beryllium difluoride, but
most are elements like silicon, bismuth, antimony, gallium and
plutonium. Even I agree that a planet with plutonium oceans is
unlikely to be habitable for life. <br>
<br>
While we all know the anomalous properties of water and cherish
them, it might be because we also live in a water-dominated
environment where every little property has big effects on us. Had
we been living in a methane or high pressure water-ammonia
environment we might have written the same number of papers about
the anomalousness of methane and water-ammonia mixtures. <br>
<br>
<br>
<pre class="moz-signature" cols="72">--
Dr Anders Sandberg
Future of Humanity Institute
Oxford Martin School
Oxford University
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