Path: utzoo!mnetor!uunet!lll-winken!lll-lcc!lll-tis!elxsi!beatnix!merkle
From: merkle@beatnix.UUCP (Ralph Merkle)
Newsgroups: sci.misc
Subject: Re: Engines of Creation: Nanotechnology
Message-ID: <657@elxsi.UUCP>
Date: 5 Jan 88 06:02:30 GMT
References: <1315@sugar.UUCP> <827@hubcap.UUCP>
Sender: nobody@elxsi.UUCP
Reply-To: merkle@beatnix.UUCP (Ralph Merkle)
Organization: ELXSI Super Computers, San Jose
Lines: 49

in article <1315@sugar.UUCP>, peter@sugar.UUCP (Peter da Silva) says:
} 
} In article <636@elxsi.UUCP>, merkle@beatnix.UUCP (Ralph Merkle) writes:
}> peter@sugar.UUCP (Peter da Silva) writes:
}> >Even Drexler is uneasy about the "Grey Goo".
}> 
}> 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.
} 
} Great job. Your grey goo detector sounds just like the sort of thing to run
} wild and turn you into grey goo. These tiny little machines are going to be
} real susceptible to radiation... so what happens when a carbon-14 in your
} little sliding rod state machine decays and your nanomachine "immune system"
} suddenly forgets that your red blood cells are "friends".

    The suggestion that you 'destroy any non-friend' was made in response to
the erroneous statement that identifying grey goo was as hard as the halting
problem.  This is clearly not the case.  It is not essential that you
infallibly determine whether or not a particular nano-machine running a
particular nano-program will or will not destroy the world before you
destroy it.  'Beyond reasonable doubt' might be a better criteria.

     The simplest way of insuring that 'counter goo' doesn't get out of hand
is to make counter goo NON replicating.  A factory manufactures counter goo,
the counter goo is shipped to the area under attack, and the counter goo does
its thing.  If the counter goo is equipped with 'tiny time pills' that
make it disintegrate after some reasonable period of time, then it's even
more rigidly limited.

     The suggestion that nano machines are subject to radiation damage is
true, the inference that this implies it is impossible (or even difficult,
once you are capable of manufacturing a nano-machine in the first place -))
to manufacture a nano machine that will self-destruct rather than run wild
is not true.  If each 'counter goo' machine had several self-destruct
circuits, and each self destruct circuit would fire in the event of a
detected fault, then the probability that the overall machine would
continue to function following any fault can be made arbitrarily low.

     The detailed design is left as an exercise to the reader.....-)

     I am not overly concerned about accidental destruction of the planet --
I AM concerned about PLANNED destruction of large parts of the planet --
past history suggests several groups will make vigorous efforts to develop
systems capable of this, and they might well USE them.....  My concern
becomes acute when said systems are pointed at ME -- so far, it hasn't
happened -- and I'd like it to stay that way.

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