msd001 at gmail.com
Sun Jul 20 16:25:33 UTC 2014
On Jul 19, 2014 8:36 PM, "David Lubkin" <lubkin at unreasonable.com> wrote:
> Israel and the United States have an interest in preventing tunnels in.
Prisons and prison nations, like North Korea or the old East Germany, have
an interest in preventing tunnels out.
I saw a mythbusters episode showing an ancient chinese tunnel defense
system that involved a deep well and drum that essentially acted as an
amplifier for the scratching sounds of a digger. They were able to detect
would-be tunnellers with surprising accuracy. However, that was protecting
a castle, not a country border. For that, the chinese built a wall that
was pretty great. :p
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