Expert: Steve Nelson - 1/18/2008

Question
Would it be possible to slowly lower a very long cable down to earth from the Thermosphere? Would it be theoretically possible (possible dynamics of needing it 'weighted' in space and possible forces from the earth, including want of slow entry speed to reduce/negate any thermal issues)?

Answer
Short answer:  you're talking about a space elevator, which is technically possible, but the practical issues are absolutely staggering.  

Then again, many things that humans have constructed over the centuries have faced staggering technical challenges and overcome them.  The Panama canal.  The pyramids.  Gravity Probe B.  The list goes on.  

For an in-depth look at space elevator technology and the history of the continued effort to develop one, see these references.  For information on the active community of space enthusiasts trying to develop the technology and the latest developments, see here:
http://www.spaceelevator.com/
Also, for a pretty thorough (I read it, most of it I've seen before, but it is thorough) breakdown of the technology and history of their development, see the wikipedia entry:
http://en.wikipedia.org/wiki/Space_elevator