"William Morse"  wrote in message
news:cfg2si$ngn$1{at}darwin.ediacara.org...
> I think the definition of life has to encompass the use of fuel, but it
> should be something like "the ability to maintain a structure against an
> energy gradient by using an available energy source."

Agree.  I would point out that one free-energy gradient is being maintained
at the expense of a second free-energy gradient that is being discharged.  It
is this "discrimination" between thermodynamic gradients - yielding to one,
while actively resisting the other - that is the essential feature.

> This gets around
> the crystal question because their structure is the lowest energy
> solution, not a structure maintained against a gradient.

> Actually, the crystals that Tim touts as quasi-alive are not at the
global lowest energy, as they carry information.  The energy minimum
is strictly local.  Watson-Crick base pairs are also "local" energy
minima.

> Flames utilize an energy source but do not maintain a structure.

I might quibble with this.  Candle flames and Bunsen burner flames
maintain their structure quite well.  However, this is due to interaction
of flame with a steady fuel supply, rather than being due to the flame
alone.
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