[extropy-chat] Dark matter and ET

[Damien Sullivan]

On Mon, Jul 18, 2005 at 01:49:01AM -0700, The Avantguardian wrote:

> DNA based wetware does this. It maximizes the metric of copy number by
> replication and does so by assimilating matter/energy from surrounding
> space-time.

Maybe, but saying that DNA itself is computronium is I think a bit much.  It's
a nicely dense storage medium, and yeah a few problems have been tackled in
the lab with naked DNA, but we're a ways yet from a general system.

> Not yet. But we are closing in on it. The Human Genome project showed us the
> blue-prints that will allow us to reverse-engineer and then modify ourselves
> in ways that are truly astounding.

True, though I think a 'real' AI would outstrip that.  Biology has been weak
on spare parts, or on backups.  Being able to tinker with the DNA which forms
brains isn't as appealing as being able to copy and tinker whole minds.

> reason for gratitude. Inefficient? Show me an artificial solar power device
> more efficient than chlorophyll and photosystems I & II. 

Well, depends on the purposes.  For generating electricity from sunlight you
want photovoltaics, at 15-30% efficiency, or a solar-driven turbine at perhaps
higher efficiency.  Photosynthetic efficiency in full sunlight is I think
between 2% (maintenance) and 8% (rapid growth phase) efficiency, and that's
for making sugars or oils which would then have to be turned into
electricity...

But I've read that photosynthesis is limited by CO2 availability (and
efficiency can be 20% in dim light) which may explain a lot about why plants
and leaves are shaped and distributed the way they are.  If we wanted to build
stuff out of sunlight and water and atmospheric CO2 we might not do any better
better; I don't know the energy costs of extracting CO2, or of breaking it up
chemically (how?) to do stuff with the carbon.

But for running a modern computer I'll take the solar panels.

> to feed humans. We could eat a larger percentage of the biomass but people
> don't generally find insects and slime-molds palatable. 

Insects or slime-molds would just be eating the plants.  If you want biomass
efficiency, be vegetarian.

> > improvements. I think the logical extrapolation is to a system that has
> > converted its mass into efficient computronium.

Now, what *is* biological computronium is neural matter.  I used to take for
granted that it was crappy, what with using neurons instead of wires, even if
they were self-repairing, and having unbelievably slow signals.

But I figure a brain has 1e6 to 1e8 times the raw computing power of a desktop
CPU (or more accurately, would take that many CPUs to be emulated), while
using about as much power.  I'd thought CPUs massed a few grams, so the brain
would be only 1000x as mass efficient, but on checking with friends I'm being
given the idea that modern CPUs are in the hundreds of grams.  And brains are
more resistant to EMPs, and have their memory built in (which is probably part
of the efficiency).

I'd wondered why a brain should be more power efficient, given that it's using
whole ions as charge carriers, instead of light electrons.  And why neurons
didn't lay down conducting polymer to use fast electrons instead.  But then I
remembered KE = mv^2/2.  Ions are 10,000x more massive than electrons... and
being moved about 1e6 times more slowly.  I don't know how many ions are used,
vs. how many electrons, but it's at least a sign that moving small things very
quickly is in fact not the route to energy efficiency.

Pit about the lack of backups.

-xx- Damien X-)