[ExI] underground (was: Trying for a minimum technical comment)

[Mike Dougherty]

I thought I hit send; this has been sitting in Drafts for 2 days.  I
assumed it was changing the subject line that ensured it got no
response.

On Tue, Dec 18, 2012 at 9:08 PM, Adrian Tymes <atymes at gmail.com> wrote:
> One major thing you missed: water tables.  Underground spaces
> would get flooded easily (and irregularly), in many places people
> currently choose to live (and thus where you'd have to dig to get
> people to move in, since most people won't move away from
> establish supply infrastructure, and are correct to refuse to).

I was imagining huge projects rather than individual homes.  I did
consider the air handling issue, but figured it would be pretty
obvious and solvable.  Edmonton Mall, Mall of America come to mind as
examples of huge common airspace over heterogeneous usage (unlike an
office building).  Of course this is a nontrivial engineering problem.
 Is it bigger than lifting thousands of tons of counterweight+cable
for a space elevator?  Or lifting thousands of tons of materials to
GEO for solar energy stations?  My intuition says that it shouldn't be
as difficult as that.  I have no idea, though, how many orders of
magnitude in error my intuition might be.  I don't think the
fascination with burrowing drives the imagination in the same way as
the fascination with flight.  I see much evidence in cultural
references to under-earth or in-earth being a bad thing compared to
all the "up there" and "out there" references to getting off/away from
this rock.  Oh sure, Dwarves and Drow Elves like the underearth, but
beyond that you're left with underworld creatures and evil stuff that
was cast down from the heavens.  I think there's an important
psychological problem to be solved to make underground cities viable.

You are correct, I had not considered underground water.  Too little
water when you need it can be a big problem.  Too much water when you
don't need it can also be a big problem.  I assumed there would be
some economy of scale putting whole towns underground rather than
individual homes with individual liabilities.  If 20,000 of your
neighbors have a common problem to solve, it will get resources that
no single person is likely to afford.

While in Mexico I was told by a tour guide that the Mayans/Aztecs
lived in cenotes to the tune of 5,000 person cities.  Cliff Dwellers
built pretty sophisticated living spaces using available "tech" in CE
1270.  We build subways.  We build cities full of skyscrapers.  We
seem to be able to build damn-near anything.  It may be years from
now, but I imagine there will be a time when we need the space and the
idea to burrow into this planet will make sense.