Re: Minds, Machines, and the Multiverse

From: Robert J. Bradbury (
Date: Wed May 03 2000 - 21:34:18 MDT

On Wed, 3 May 2000, Eugene Leitl wrote:

Aha, Eugene is back, or maybe this thread simply got through his filters...
Or maybe its a lurking AIbot...

> Matt Gingell writes:
> > Imagine I could simulate, in real time, a system of 100 atoms using 50
> > atoms. I can then have two groups of 50 running in real time with perfect
> Of course, you can't do that. Also, you don't mention which modelling
> paradigm you're contemplating, say QM or MD.

Ah, but what got this going was Moravec's article using Higgsinium or
Monopolium as the denser atomic "matter" for the computer (not "more"
matter, just "denser" matter) and Freidkin's construction of a cellular
automata at the Planck limits. So its a CA architecture operating at
Planck limits in a volume the size of a star. Unclear is what the darn
thing weighs (e.g. whether you violate the black hole densities, though
you probably could rotate it very rapidly).

> > fidelity. Why can't I then harness each of these groups and construct
> > 2 simulated 50 atom computers? There's an infinite regress here.

Regarding Billy's comments, I went and got some numbers.
Covalent atomic bonds are usually in the range of 0.5-1.7 aJ.
von Neuman's classical limits on computer switching are kT ln 2
ranging from 4.1x10^-3 aJ at room temps to 5.9x10^-5 aJ at lHe temp.

So, if you represent a bond by a bit in a switch that can
flip at something close to the theoretical limits, you can
simulate that bond using 3-4 orders of magnitude less energy.
This makes sense because one is probably representing the bit
as a single electron, atomic magnetic alignment, etc.
Brillouin [1962] got a similar result using photons to detect holes
in punched tape (presumably related to the probability that
the photon can reliably cause a change in the energy level of
an electron orbiting an atom. This makes sense when you
consider that only UV photons have enough energy to break
atomic bonds.

Now, if you can represent that bond by the position of a very
low energy photon in a photon "gas", you can probably drive
the cost of the simulation even lower.

Anyone know the energy required to flip the magnetic alignment
of an atom?


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