I’ve read several books by David Brin and enjoyed them all.  This is the first time, however, I’ve seen a David Brin video (albeit a YouTube version).

He talks about future technologies, Space Shuttle fuel tanks representing a lost opportunity, tethers, solar sails and, briefly, Space Elevators.  He’s a skeptic of the idea of an Earth-based Space Elevator (calling it a ‘far out what if’) but is more positive about putting one on Mars.

[youtube]http://www.youtube.com/watch?v=sG_xGzpSOfA[/youtube]

.

Some small nits;

• In his discussion of solar sails, he says that no one has tried to do this.  However, the Planetary Society has tried once – and failed – and is getting ready to try again.
• He gives the impression that the taper on a space elevator has to continue increasing from the ground all the way out to the counterweight.  If my understanding is correct, it only has to grow to GEO – from there the tether width can remain constant or even decrease.