From: hal@finney.org
Date: Tue Sep 25 2001 - 17:43:18 MDT
Andrew Clough, <aclough@mit.edu>, writes:
> I've run into this idea before, in Vinge's novel A Deepness in the
> Sky. Was it inspired by this list, or vice versa? Anyway, assuming a
> straight path, you won't feel any free fall. In fact, you'll always feel
> at least some gravity, always perpendicular to the tunnel floor! Of course
> you'd need a vacum in there, and some means of propulsion to overcome the
> inevitable friction loss...or maybe just have the recieving station a
> little lower...
The practical problem is that for short distances, the slope of the
tunnel is too small to overcome friction. Theoretically you could go
from one side of New York City to the other in 40 minutes using this,
but the forces involved are miniscule, thousandths of a "g". You'd never
get going.
And for long distances, the problem is the necessary tunneling depth.
A train from NY to LA would be over 250 miles deep at the center.
The deepest hole which has ever been dug was less than 10 miles deep,
and that was a massive effort drilling straight down.
The idea is simply not of practical use today.
Hal
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