From: Anders Sandberg (asa@nada.kth.se)
Date: Wed Aug 27 1997 - 07:07:12 MDT
"Nicholas Bostrom" <bostrom@mail.ndirect.co.uk> writes:
> The Low Golden Willow:
> > What the hell are these nanites living on?!
>
> Sun or chemical binding energy, for example.
>
> >Their very life requires
> > energy, not to mention, as Anders noted, the cost of trying to
> > concentrate extremely diffuse and oxygen-bonded uranium.
>
> Use dynamite then. But energy wouldn't be a problem.
Yes it is! You are simply assuming energy will not be a problem,
in which case high-energy nano could of course easily wipe out
anything. But in the real world energy *is* a problem; even
building a solar collector system for nanites is non-trivial
and doesn't give that much power. And in the uranium-extraction
scenario discussed here, chemical binding energy is not available
since the materials are already at a very low energy state.
I have noticed that many people overestimate the power of
nanotech because they forget the energy needs. A good example
is Williams' _Aristoi_.
> > And they're not living off of rock. It's hard to get lower energy
> > states than found in a lot of rock without using nuclear processes.
> > That's why aluminum mining is so expensive.
>
> With nanotech, we might be able to catalyse arbitrary prosesses and
> gain energy, as long as there is a net increase in chemical binding
> energy.
Yes, but rock is mainly oxides and silicates. You can't use it as a
fuel.
I think there is some confusion here about binding energy etc (no
wonder, I'm not 100% sure about the terminology myself). Just to
get things straight: each molecule has an enthalpy, which is
roughly its "chemical potential". If chemical A and B are transformed
into chemicals C and D, the difference in total enthalpy tells
us how much energy is needed to cause the reaction (if the
difference is negative), or how much energy is released (if the
difference is positive). These are absolute thermodynamic constraints,
in addition energy might be needed to start the reaction, although
this can be lowered using catalysts.
So the problem here is that the enthalpy of pure uranium or TNT
is high, while the raw materials have a low enthalpy. So you need
a lot of energy to make them, even if your nanotech is good.
> > And is the energy state of diamondoid material higher than that of
> > organic material? Probably, in which case this gray goo plague needs
> > constant input or can only grow by processing lots of material -- which
> > means that it grows very slowly.
Could we get some numbers here? What is the average enthalpy of
organic stuff compared to diamond?
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