Quote Originally Posted by sycld View Post
So you're saying that if we use nanotechnology we'll be able to use "really really small" amounts of metals? Haha, well... maaaybe.
Haha... more like, carbon-based nanomaterials could eventually start to replace copper in various electrical and electronic applications, and various other possibilities in the same vein.

Quote Originally Posted by sycld
But I think you lost my point in this whole debate. You said:

"Aside from fuel resources (fossil fuels, etc.), most of the important ones are plentiful enough that we can probably rely on them lasting at least until we're able to take advantage of extraterrestrial resources. I don't think there are any material resources that are both so scarce they are going to be entirely depleted before that happens, and so crucial that civilization can't get along without them."

...which seemed to imply that we wouldn't have issues with materials even if all people consumed metals at the rate that we currently do in the US.

My original point which you seemed to have contention with was that not only is energy a concern, but material is a concern as well. I didn't say that such material issues were impossible to deal with, but merely that there are going to be technological issues with materials, and not just energy (as many people seem to argue.)

When I hear about how the Western lifestyle cannot be supported by the Earth, I usually hear it in terms of energy, water supply, and perhaps land use for food. I rarely if ever hear it in terms of materials supply as well, and as we're apparently only realizing now that is a concern as well: the Earth doesn't have effectively "infinite" stores of every material we need.
You're right about that, I stand corrected on the point of material resources. I didn't realize how serious the concerns about metal shortages were; so yeah, materials usage as well as energy usage seems to be a pretty important issue. However, I would still say that energy production and food production are the two MOST important things that determine the planet's ability to support a given population at a given living standard.

Quote Originally Posted by sycld
Yes, that is many orders of magnitude smaller than geological. Of course, you made the very generous assumption that only 1 millionth of the crust's Al is accessible to us. If it's on the order of 10's of %, then I guess we can multiply that number by 100,000. Then we are talking about a 5 billion year supply, give or take a factor. That's the age of the solar system. So okay you're right: Al really was a bad example, and my intuitive feel for the order of magnitude of some of these numbers is poorer than I thought.
Obviously 50K years is orders of magnitude shorter than intervals on the geological timescale; but is it "many" orders of magnitude shorter? Totally depends on what you mean by "many"! It's maybe three orders of magnitude shorter (50M years is definitely a geologically significant interval). Is three "many"? Okay, /tangent