renewable resources?

--- On Sat, 6/6/09, Dan Wylie-Sears wrote:
"The point as I understood it was that if we have a collapse, future civilizations will have it much harder than our ancestors did. Our ancestors had to travel if they wanted both coal from outcrops at the surface and high-grade iron ore at the surface. But for our successors trying to climb the same hill from stone age to space age, there will be no outcrops of high-grade coal and high-grade iron ore anywhere."

In that case I grant that this could be a once-in-a-planet's history thing. A species will reach a technological point of no return in which, if it fails to become space faring,ithas ruined the opportunity for itself or any future species todo so.Thismay be valid.

"I think dropping raw materials out of the sky will be easy enough that it will happen once we have a serious presence in space. It's going up the gravity well that's expensive, not dropping stuff into it."

Absolutely agree with you! Droppingraw materils may be easy.

Mythought was that once a significant civilation has a presence in space, it is unlikely that there will be much material trade between them and a planet. Once most needed machinery can be manufactured in space, there is less need for importing goods up a deep gravity well. If the planet doesn't have goods needed by the colonies, why would the colonies continue to provide raw materials to the Earth?

This skips thepossible issues of whether a planet would want hundreds of thousands of tons of raw (or lightly refined) materials to be brought into orbit each year for dropoff. Most likely we'd only want those materials that are industrially useful and somewhat rare on Earth. Probably these metalswould also be desired by the space colonies as well.

Of course energy will be cheaper in space too, so it won't be completely *raw* materials: the materials will be processed so we can drop embodied energy out of the sky along with the materials. But they will be raw materials from the perspective of terrestrial industry. "

Agreed. Energycouldbe a primary import to the planet. However, unlike the physical materials of trade, these utiliies may be owned andcontrolled by planetary entities.Some critical components might even bemanufaturedby entities on the planet as well..