From: Damien Broderick (thespike@satx.rr.com)
Date: Fri Mar 26 2004 - 16:42:48 MST
>
>Did Seth Lloyd mention which analysis of his supports this theory? It
>doesn't seem consistent with my understanding of what he has written, in
>particular his paper "Computational capacity of the universe" available at
>http://xxx.lanl.gov/abs/quant-ph/0110141. Quoting from page 3:
>
> > For most of its history, the universe has been matter-dominated -- most
> > of the energy is in the form of matter. As will be seen below, most of
> > the computation that can have taken place in the universe occurred
> > during the matter-dominated phase.
More to the point, he states:
< At first, this fact might seem to imply that the total number of
operations performed in the radiation-dominated universe is formally
infinite. However, as will now be seen, this is not the case. >
Of course nobody needs *infinite* computation to generate life (on a
suitable substrate) and for that life to bootstrap itself through a Spike.
However, he adds:
<In the radiation-dominated universe, by contrast, most of the energy is in
the form of effectively massless particles at thermal equilibrium so that
there is little free energy available and structural stability is hard to
maintain. In other words, the matter-dominated universe is a much more
friendly environment for conventional digital computation, not to mention
for life as we know it. >
I'm far from home base right now and don't have access to old e-files. I
believe our exchange was around 1996 or 1997, so presumably Lloyd did some
more thinking about the topic prior to this 2001 paper. Oh well. But I
recall his argument that an optimal computer will be very, very hot (by our
standards). see for example:
http://xxx.lanl.gov/abs/quant-ph/9908043
<it must have an energy throughput (free energy in and thermal energy out)
of 4.04×10^26 watts —
turning over its own rest mass energy of mc^2 ~ 10^17 joules in a nanosecond! >
Damien Broderick
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