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 being!). 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 Rate This Message: http://www.cryonet.org/cgi-bin/rate.cgi?msg=15026