X-Message-Number: 15164
Date: Sat, 23 Dec 2000 00:44:49 -0700
From: Mike Perry <>
Subject: Reply to Thomas Donaldson

As it happens, I have something to say on both of the "2 more comments" of
Thomas Donaldson's #15149

First he writes:
...
>
>The piece by Mark Plus is a very interesting antidote to people going
>on about how the rate of progress has increased. I am not so sure
>that it really represents what is going on, but I'd also say that 
>whatever may be the rate of progress, and how it is to be measured,
>it's far from clear that we're going much faster than before.
>
Basically I concur with this, despite sympathies with the "spike" idea, that
in certain ways things are going off the charts, heading upward very fast.
We know that progress in many areas can't go on forever unless some
fundamental-looking physics can be circumvented. Mainly, I'm hoping, not for
arbitrary, across-the-board progress, but for certain basic things, the most
basic of all being the end of involuntary death. I also think a software
revolution is coming soon--so you should be able to talk to your computer,
and have it play a lot more intelligent role in addressing the problems
you'd like to be solved--but of course this won't be the be all and end all..

Going to the second comment,

>Finally, I got to read Mike Perry's answer to my short reply to
>him. This was back towards the end of November (27th, I think). Basically
>he argues that speed does not matter ie. if we make a machine which
>imitates me, or Bob Ettinger, or anyone reading this, it won't matter
>at all that it works far more slowly that I, Bob Ettinger, or the 
>readers work.
>
 
As far as I can tell, the message you refer to is #15030. Of course I never
said "it won't matter at all that it works far more slowly ...". On the
other hand, with suitable slowed-down surroundings, I see no reason why the
entities inside would notice anything unusual. 

>This should be clearly fallacious.

Not if you understand what I'm trying to say.

> First, if we put such a machine
>in the real world, it simply won't survive very long.

No argument. Not relevant however. I'm talking about thought experiments
only. Note that three times in my posting (#15030 again) I state that I'm
not claiming the machine would operate or could operate in realtime. (If you
don't want to consider systems that do not operate in realtime, why not just
say so and be done with it?)

> If, on the other
>hand, we take such a slow version of us and have it live in a universe
>which is similarly slowed down, we escape one problem only by putting
>ourselves in the midst of another: where does this ENTIRE SLOWED 
>UNIVERSE come from, and how do we create it?

Well, the present universe is said to have 10^122 bits, a finite number. The
bit transitions over time obey the laws of quantum mechanics, and seem to be
effectively computable, at least (and as a last resort) by a Turing machine
with infinitely inscribed tape. So, as a thought experiment, we could
envision simulating/emulating the whole universe on a Turing machine. The
tape would contain a description of things down to the quantum level--a
finite string of bits, which would be updated repeatedly to trace out what
was happening in the universe. (It could contain much other information
too.) In a remote future our expanding universe may have much more
information storage capacity, and maybe then you actually could imitate an
earlier version of the universe which had fewer bits. 

> For that matter, just what is the point of doing so?

I've tried to address this before, here goes again. The point is not
(necessarily) that you'd ever want to do this, it is that it could,
apparently, be done *in principle.* This says something profound about the
nature of reality. Practical issues are another matter.

>In what way is the entire universe imitatable by a Turing machine? 

See my comments above. To add to that, the universe, and things inside it,
behave over finite stretches of time as finite state machines, with the
quantum state (suitably understood) corresponding to the "state" of the
thing in quesion. This point is discussed at some length in Tipler's
*Physics of Immortality*.

>For that matter, even if it were, does it
>follow that parts of it are also?

It sure does--how else could the whole be so? As a last resort, you imitate
the whole to imitate one of the parts. 

Mike Perry

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