[ExI] Tunnels

[John Clark]

On Sat, Jul 19, 2014  David Lubkin <lubkin at unreasonable.com> wrote:

> Are there any credible technologies, either current or plausible future,
> that can stymie tunneling


To stop the tunneling you just need to detect it, and you can do that with
a gravity detector if it's sensitive enough. Einstein's General Theory of
Relativity says that time moves more slowly in a strong gravity field than
in a weaker one, and the gravity is weaker if there is a tunnel under your
feet because there is less mass there. So to find tunnels and other
interesting things in the earth you just need a good clock.

If you set a atomic fountain clock 3.1 billion years ago today it would be
off by less than a second; it works by measuring the microwaves given off
by cesium atoms. If you move such a clock upward by one foot it's in a
weaker gravitational field because it's one foot more distant from the
earths center, you can detect that weakening by noting that the clock is
running measurably faster. Such a clock could also function as a super
accurate accelerometer allowing a submarine to know exactly where it was
without surfacing to take a GPS reading. In a decade clocks should be at
least 100 times as accurate by switching from microwave frequencies to
optical ones or by using entirely new techniques such as cold atom
interferometry.

Such clocks contain no moving parts and so may be ripe for miniaturization,
perhaps a good idea for a start up company.

  John K Clark
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