X-Message-Number: 15026
Date: Sun, 26 Nov 2000 00:04:50 -0500
From: Thomas Donaldson <>
Subject: answer to Mike Perry

Hi everyone!

A short reply to Mike Perry's answer to me on msg #15017:

If your proposal to make a machine which imitates (say) my brain on a
quantum level ie. the behavior of every atom which makes it up, then
it's far from obvious that anyone could make such a machine. Each atom
would need to be imitated with its own computer; given that we do not
have a small number of atoms in our brain, and a full imitation requires
not just the imitation of the our brain but also at the least the input
and output to all our peripherals (otherwise known as eyes, ears, nose,
hands ... remember what I said about input and output being constant
while we remain alive) then the possibility of getting together enough
atoms to do this imitation raises its ugly head. Moreover, we'd also
have a highly parallel machine, with every computer imitating an atom.

It's not that I think that we can't make our computers much smaller
than we have them now. But it's unlikely that we could make a computer
which used only one atom... other than a computer which behaved exactly
like the atom of which it was made. If we made each computer much larger
(even 100 atoms) then we could easily start running into problems. If 
we are simply taking atoms and putting them together to make a human
being, we are doing no more than making the organic human being.

Furthermore, such a computer would also have to show the ability to
grow and change, two features our brain shows. Doing so requires the
input of new atoms and output of others ie. it cannot just start with
a fixed common set of atoms. Since the original idea of a Turing 
computer was also a SEQUENTIAL computer, such a system would only
be able to work in its own computer world --- which fails completely 
as a real system in the real world. (Given that we are imitating ech
atom, it fails even more radically than other ways to make a human

On the good side, this IS one attempt to realize a human being as
a Turing machine. We may find that we should look more closely at these
issues, particularly the issue of TIME. Yes, I know that time was
not a variable in Turing machines, but in any practical machine we
will need it ... and that may render meaningless for some questions of
its ability to deal with time.

		Best wishes and long long life, for all,

			Thomas Donaldson

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