Re: Computability in principle

From: Erann Gat (gat_at_jpl.nasa.gov)
Date: 11/07/03 

Date: Thu, 06 Nov 2003 18:19:44 -0800

In article <ZIudnZjnT7cuZzeiRVn-hg@io.com>, ix@io.com (Lupo LeBoucher) wrote:

> Posted and CC:ed
>
> In article <gat-0411031328270001@k-137-79-50-101.jpl.nasa.gov>,
> Erann Gat <gat@jpl.nasa.gov> wrote:
> >
> >There are about 10^80 particles in the known Universe.
> >The universe is about 10^18 seconds old.
> >The Planck time, the time that it takes light to travel the diameter of a
> >proton, believed to be the smallest possible time scale on which physical
> >processes can occur, is 10^-43 seconds.
> >
> >So if you turned the entire universe into a computer and had it do nothing
> >but count it could enumerate about 10^141 = 2^468 states.
>
> In fact, it is a little smaller than this, at least according to Seth
> Lloyd. I thought he lost his marbles or was making a joke when I first
> read this in Physical Review Letters, but it is sort of important for the
> reasons you mention:
> http://focus.aps.org/story/v9/st27

Interesting. He uses a completely different methodology but comes up with
an answser that's within twenty orders of magnitude, which is not that
much of an error when dealing with numbers of this magnitude. (If you
really want to blow your mind with big numbers see
http://home.earthlink.net/~mrob/pub/math/largenum.html)

E.