From: John K Clark (firstname.lastname@example.org)
Date: Tue May 19 2009 - 10:09:23 MDT
On Sun, 17 May 2009 "Matt Mahoney"
> The question is important to us because it means that
> regardless of any life prolonging mind or body enhancement,
> we will always have some doubt about our immortality even
> if we achieve it.
Youíre treating this as if it was a question in pure mathematics and it
is not. The possibility of immortality boils down to the question: is
the universe capable of making an infinite number of calculations? A
calculation is not a mathematical abstraction, it is a physical process
that consumes energy, gives off heat, and produces entropy. Even if
calculations can go on for a infinite number of years thatís not the
same as an infinite number of calculations.
Landauer, Bennett and Merkle have shown that with reversible computing
the amount of energy needed to make a calculation can be made
arbitrarily small, but the only way to do it is by slowing down the
calculation. Fortunately even a small reduction in speed can help a lot
in energy saving, the power dissipation (per unit of time) falls as the
square of the speed. We wonít know if thatís good enough to allow
infinite computation until we know more about the basic laws of physics
and cosmology, and we wonít learn that from mathematics alone.
John K Clark
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