RE: Understanding nanotech

Billy Brown (
Wed, 1 Sep 1999 23:37:47 -0500

Robert J. Bradbury wrote:
> > On Mon, 30 Aug 1999 23:15:56 -0500 "Billy Brown"
> > <> writes:
> > > Multiply that out, divide by 3 billion people, and you
> > > get an approximate natural energy budget of 5.6x10^4 KW per person.
> > > We should be able to use whatever fraction of that we care to actually
> > > harvest without fear of creating a global heat problem.
> Not without distorting the weather or killing plants and animals
> (and whatever humans choose to live "off of" them).

Why? Right now almost all of that energy is ultimately converted to heat and radiated back into space. If we intercept some of it for industrial uses first, that has no effect at all on the total generation of heat.

OK, sure, if we put all of the factories in one big pile we'll probably create some nasty side effects, but we don't particularly want to do that anyway. Spreading out our radiation of waste heat to approximate natural conditions is a much smaller problem than building all those solar power collectors in the first place.

I think you can reasonably conclude that nanotech makes the global climate a resource that must be actively managed and protected, just like deep sea fisheries are today. However, that does not mean that the problems involved are insoluble (or even particularly difficult, given the technology you are already assuming).

> > Those numbers work out to 5.7x10^4 KW per person, modeling the earth as
> > disk of the given radius, facing the sun. But the earth's population is
> > now reported to be 6 billion rather than 3 billion.
> We must be using different calculators because when I take
> Insolation*Pi*R_earth^2 / 6*10^9
> I get 2.93*10^7.

Well, let's see:

1) Total area of a disk with radius 6.37*10^9 m:  1.3x10^14 m^2
2) Total solar energy striking said disk at 1374 W/m^2: 1.7x10^17
3) Divide by 6 billion people: 2.9x10^7 W per capita
4) Convert to KW: 2.5x10^4 KW per capita

So our only disagreement was how many people have to split the pie.

Now, the claim I was disputing was that energy expenditures greater than 10^4 W per capita would significantly affect the Earth's heat balance. Even if it were all new energy (from nuclear fusion, for instance), this amount seems too low (only 0.1% of the current energy flow) to have such drastic effects. I'm sure it would have significant climatological effects if it is released indiscriminately, but cooking the planet is another story altogether.

> I would generally agree with Hal, in that I think we can get almost
> an order of magnitude more power without too much trouble.
> More than that and it is going to start creating problems
> until we have a lot of computer power to simulate the potential
> effects.

Which, of course, is one of the very first things that nanotech would give us. For that matter, we'll probably have the horsepower to tackle the global climate well before molecular manufacturing becomes practical.

> But I suspect you can get probably 2-4 orders of magnitude
> better by doing more efficient assembly (i.e. chemical reactions
> that utilize/reuse the free energy effectively), reusing building
> blocks (so once you have invested in building them, you don't rebuild
> them) and going to more efficient nanodesigns. So we are probably
> wasting mental energy on the wrong side of the problem.

Yes. Besides, in this kind of slow-AI/fast-nanotech scenario I see very little chance of Earth having a large active population of humans for long enough to make these issues significant. Those who want to do big things in physical space will migrate out into the solar system, where the resources and breathing room they need are plentiful. Those who are happy with VR will tend to live in it, which leaves them with very modest needs in the physical world. The number of humans who need to divide Earth's physical resources is likely to be quite modest - maybe a few tens of millions - and I'd expect a large percentage of them to be back-to-nature types, which furt her reduces their energy needs.

Billy Brown, MCSE+I