X-Message-Number: 21054
Date: Tue, 4 Feb 2003 07:08:09 -0500
From: Thomas Donaldson <>
Subject: CryoNet #21045 - #21050

and a bit more for Mr. Kluytmans:

In a sense the cost of making these objects is given in Drexler.
However I note that we have not made any at all, by your own
claim. I would wait to see the results of actually making even
one nanodevice: once more, the energy cost cannot be worked out
on theoretical grounds alone, unless we have not just a version
of the nanodevice created, but a detailed version of the system
which creates it. To say that carbon and hydrogen, for instance,
would be used to make this nanodevice, is meaningless without
a detailed specification of how both elements are obtained and
the energy involved in obtaining them. Neither element exists
for very long in nature in anything like a pure state. For carbon,
for instance, if we're getting it from CO2 then we'd need to calculate
the energy involved in gathering together the CO2 and separating the
WE CAN REASONABLY CONSTRUCT. I would say the same, of course, of water
as a source of hydrogen and oxygen. The figures I've seen assume that
energy has already been spent to produce the raw materials of which
we want to build our nanodevices.

As for the kind of bonds which hold together biochemical systems,
sorry, but you make a BIG error. It may have only been
inadvertent, but given that it obviously has affected your
thinking about biochemical systems, you should know that 
individual proteins are bound together much more tightly than
by van der Waals forces. Yes, different proteins may be bound
less tightly, for good reason. Consider enzymes: they act as 
nanomachines, and when they hold the molecules on which they're
working they MAY hold them lightly. (Even nanodevices would
hardly work if they bound to the objects on which they were
working too tightly!). This doesn't mean that the enzyme itself
is lightly bound together. When a biological molecule is floppy
it is so for a reason related to its function: it may have
several different forms which can be turned into one another
with comparatively small energy. An enzyme may well be more
complex than simply a machine to do a single task, specifically
to allow other molecules to control how often it does that
task and where it does it. Put briefly, a biological molecule isn't just
floppy for no reason. It is floppy because that floppiness allows it to
perform its function. And if we made our nanodevices rigid, they would
also become limited by their rigidity.

Indeed, given that your account of Freitas' nanodevice to replace 
red blood cells, it has several problems of this kind. Sure, it can
carry more oxygen, but does that then mean that many of the cells to
which it delivers that oxygen must get it not by diffusion over 
a short distance or actual contact with the red blood cell, but 
instead by diffusion over a relatively long distance? That hardly
sounds very efficient. Again, the walls of our capillaries (and
our other blood vessels, too) work because they compress and expand.
A rigid object would not move through our circulation as well as
a compressible one with movable, extendable walls. Our bones are
rigid, but we could not walk without our highly nonrigid muscles...
we could not even stand upright. To say that your nanodevices 
would be more rigid than living systems is a DEFECT, not an 

             Best wishes and long long life for all,

                 Thomas Donaldson

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