X-Message-Number: 20976
Date: Sun, 26 Jan 2003 09:41:05 -0500
From: Thomas Donaldson <>
Subject: CryoNet #20963 - #20971

Several people have objected to what I said about MOLECULAR
nanotechnology. I have read their objections. The fundamental
problem is not that of putting someone together again when
you know where all his/her molecules should go. The problem
is that of FINDING OUT WHERE THEY SHOULD GO. It is very
important here that is virtually no need to repair the 
molecules themselves; the damage caused by freezing is on
a much larger scale, as I have said.

I don't even doubt that nanodevices could enter a frozen
body and work out the location of all of its molecules.
The problem is that those locations will be WRONG. Not
only that, but all our clues to what those locations should
be will exist on a larger than nano scale. They could not
be readable by a single nanodevice.     

Nor am I arguing that repair is impossible. We could have
devices which gather together input from many of the 
nanodevices examining the damaged brain. That would of
course require communication between them, and in that 
sense they would cease to be INDEPENDENT devices, any
more than our white blood cells are independent. That is
what I mean when I say that you would no longer be using
a nanodevice, but instead a repair reassembler made
up of many of them.

Some more specific comments:

For Kennita Watson: the problem involves not just fitting together
simple pieces of a jigsaw puzzle but also working out just what
the pieces are. They will not have been broken so that their 
boundaries will be clear, nor will they even retain their original
shape.

For James Swaze: in a sense it does not matter how small
you can make the computer itself. There remains the 
problem of getting information to it and the calculation
problem which it must perform. Remember that I was specifically
arguing against MOLECULAR nanotechnology, not nanotechnology
itself. The nanodevices engaged in repair will have to 
share information and cooperate constantly, precisely 
because they are working with a problem which is physically
much larger than they are and larger than any individual
one can perceive. Their inputs must go into a separate
computer (or hierarchical set of them) to be worked on
and the CORRECT locations inferred for repair. And as
I said before, even if the computer itself were nanosized,
the total set of devices working on repair would be no
more a nanodevice than our hands are nanodevices. Each
nanopart would do only part of the task.

I will deal with your other problems with my comments on repair
in a separate message.

For Brian Stewart: at least you worked out that I wasn't
arguing against nanotechnology! Yes, a device of the kind
you describe would be able to repair brains. Clearly lots
of details would need to be worked out, but I'd say that
was the direction in which to go.

           Best wishes and long long life to all,

                Thomas Donaldson

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