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From: merkle@beatnix.UUCP (Ralph Merkle)
Newsgroups: sci.misc
Subject: Re: Engines of Creation: Nanotechnology
Message-ID: <636@elxsi.UUCP>
Date: Sat, 5-Dec-87 17:04:40 EST
Article-I.D.: elxsi.636
Posted: Sat Dec  5 17:04:40 1987
Date-Received: Fri, 11-Dec-87 07:17:54 EST
References: <799@sbcs.sunysb.edu> <2698@drivax.UUCP> <1063@sugar.UUCP> <2411@watcgl.waterloo.edu> <1445@m-net.UUCP>
Sender: nobody@elxsi.UUCP
Reply-To: merkle@beatnix.UUCP (Ralph Merkle)
Organization: ELXSI Super Computers, San Jose
Lines: 49
Keywords: nanotechnology foresight drexler

>In <2411@watcgl.waterloo.edu> kdmoen@watcgl.waterloo.edu (Doug Moen) writes:
>>peter@sugar.UUCP (Peter da Silva) writes:
>>>Even Drexler is uneasy about the "Grey Goo".

>You have to find it first.  The difficulty is that, in order to decide
>if a particular bit of nanomachinery is Gray Goo (or a part thereof),
>you have to analyze its program to see if it ever quits reproducing.
>This is exactly equivalent to the halting problem, which is insoluble.

>Russ Cage, Robust Software Inc.    (313) 662-4147    {sw1a7,umix}!m-net!rsi

Nope.  Just destroy anything that is not identifiable as 'friend'.  That's
the principal the immune system uses, and it seems to work okay most of
the time.

     I should mention that Drexler has proposed more detailed designs of
nano computers than the popularizations in EOC.  The more detailed designs
look quite plausible and look like variations on Babbage's
Analytical Engine -- only with smaller gears, levers, etc.  The key trick
in simplifying the design problem is to (1) propose a few intuitively
plausible building blocks -- rods that can be slid back and forth, knobs
that stick out of the rods, etc.  Then (2) propose a specific chemical structure
for each building block, and demonstrate that -- within reasonable engineering
tolerances -- it can be treated like the intuitively simple building
block (example -- a 'rod' can be made out of a series of carbon atoms,
alternately single and triple bonded).  Finally (3) put the basic building
blocks together into some interesting structure -- such as a computer.

     The major limitation today is the manufacturing technology.  Given
an atomic machine shop even I could start making interesting nano-machines
using the 'building block' approach.   Current molecular-scale fabrication
technology is limited to the construction of arbitrary sequences of
amino acids (protein engineering).  Understanding how to build a protein
is rather difficult right now, though a great deal of funding
is being poured into research in this area.  Building a working machine
composed of hundreds or thousands of proteins is beyond current design
technology -- though NOT current MANUFACTURING technology.  If someone
(God, ET's or whoever) gave us the specific amino acid sequences of the
needed proteins, we could easily (this is the scientists 'easily', not the
engineers 'easily') produce the proper proteins in the proper amounts.
Assembly of the proteins is simple:  stir them together and watch them
self-assemble.  This is a standard assembly technique used in existing
protein-based machines (us!).

     Now it's just a small matter of programming :-) to build a molecular
level machine shop from proteins.

     Ralph C. Merkle
     ...!sun!elxsi!merkle