X-Message-Number: 12756
From: Thomas Donaldson <>
Subject: some comments on nanotechnology
Date: Wed, 10 Nov 1999 23:38:38 +1100 (EST)

About nanotech devices:

The very first point I want to make is that we'll need much more than 
nanotechnology to do anything significant in the world. Nanotechnology is
a way of acting on the world, but before we go out and act on the world
we must first figure out what it is that we want to do. That alone is
a big job, even if once we do so we can then do what we want instantly
with no expenditure of time or energy.

The second point concerns a problem with nanotechnology (which holds with
biotechnology too, though some features of biotechnology may specifically
exist to deal with it). I've read Drexler's book NANOSYSTEMS. It seems to
me that it omits two problems, which when we come to use nanotech devices
are likely to turn out to be quite significant.

1. We want to put together our nanomachines out of smaller, basic 
   machines. It may well be that each basic machine will fail only in the
   most extreme situations, but a nanomachine made out of many basic
   machines becomes much more subject to failure: only one of its
   parts may fail, but by failing make it impossible for any other
   part to work. (To say that failure is impossible ignores such things
   as the possibility that a radioactive component slipped into its
   manufacture, and after decay disrupts it... and lots of other ways
   manufacture might sometimes go wrong, even if only rarely).

   This problem occurs also if we use MANY nanomachines. Even if the
   probability of failure is very small, it will increase the more
   nanomachines we use. Depending on how we use them, that failure
   may be minor or catastrophic ... just like any other devices,
   actually.

2. To be useful for ANY purpose, our nanomachines cannot act totally
   separate from everything else. They must act on something else in the
   world, something which is NOT a nanomachine. And just as happens in
   biological creatures, that opens things up to lots of EXTERNAL
   disruptive influences. That's why our cells make various antioxidant
   biochemicals to protect themselves from the disruptive effects of
   oxygen, to give a simple common example. If they could come into 
   contact with oxygen only when they "needed to", all that apparatus
   wouldn't be needed.

   And yes, certainly, we might do many things to protect them from
   disruption. But no method is likely to protect against ALL POSSIBLE
   disruption. Moreover, all the extra machinery to protect against
   disruption makes the devices bigger... in some cases, probably big
   enough that they are no longer nano at all.

3. Nanotech devices do consist of about 90 different kinds of parts. 
   HOWEVER so does everything else. We call those parts ATOMS, and however
   we make our device we must use some form of chemistry to do so. One
   feature of chemistry is that our atoms don't necessarily stay where
   we put them. Sure, with nanodevices we might make stable chemicals
   which would not have been easy to make otherwise (though chemists even
   now work on ways to synthesize the wildest chemicals). Even so, that
   chemistry provides one way in which external influences can break 
   a nanotech device ... perhaps, when we actually have them, the most
   common way. Not every atom happily combines with every other, and
   keeping a chemically active molecule from doing what it wants can
   be certainly be done, but once more requires extra atoms solely for
   that purpose. Protecting our device from other active chemicals
   nearby isn't easy either, and adds more to the device when we do
   it. Among other problems, not every chemical is stable at the 
   temperatures, light levels, and vibrations we might want to use it. 

These 3 points should be thought about whenever we try to build a real,
working nanotech device. I personally suspect (but no, I cannot now 
PROVE) that our biotechnology has the form it has (lots of very small
nanotech devices working in a fluid, rather than put together into 
larger machines) comes exactly from means to avoid these problems.
(And please note that I'm not saying these machines must be the same
as enzymes, or that the fluid is water).

So these are some points for those who think nanotechnology alone will
solve all our problems.

			Best wishes and long long life,

				Thomas Donaldson

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