Avoid the Noise
July 2, 2012 10:24 PM   Subscribe

How far underground would I have go to escape any man made signals?
posted by Query to Technology (18 answers total) 2 users marked this as a favorite
About 2 metres of rock should do it I think, conservatively. 1 metre probably.
posted by wilful at 10:30 PM on July 2, 2012

It's a function of the sensitivity of your receiver.
posted by phrontist at 10:43 PM on July 2, 2012 [2 favorites]

radio waves are a form of electromagnetic radiation. Unfortunately googling is really hard due to the excess of craziness around this. It all depends of course on the frequency and energy. Mobile phones are in the microwave range. This looks like a useful reference, as does this. It appears that 1 metre of soil, wet, would be heaps.
posted by wilful at 10:44 PM on July 2, 2012

If you count neutrino "signals" (as in the infamous faster-than-light business), the answer is "impossible".
posted by alexei at 10:46 PM on July 2, 2012 [1 favorite]

Depends on how the entrance is structured.
posted by rr at 10:48 PM on July 2, 2012

Neutrinos are natural, though, correct? As for the size of the opening, say both a large cave opening, and a smaller shaft
posted by Query at 10:54 PM on July 2, 2012

ELF to VLF radio can easily penetrate several hundred metres through non-metallic rock; frequencies around 50~100kHz are used for positioning & sub-surface communications in mining and the caving community.
posted by Pinback at 10:59 PM on July 2, 2012 [6 favorites]

You would be better off building yourself a Faraday cage wherever is convenient.
posted by b1tr0t at 11:01 PM on July 2, 2012 [4 favorites]

"Man-made" neutrinos are generated in particle accelerators.
posted by mr_roboto at 11:04 PM on July 2, 2012

If "signals" includes the seismic signature of man-made events, then it seems that you'd sense the vibrations from a nuclear test pretty much anywhere in the earth.
posted by Dimpy at 11:22 PM on July 2, 2012

"Man-made" neutrinos are also copiously generated in (*gasp*!) nuclear reactors or explosions. I would have expected them to fall outside a narrow definition of "signal" though, since they're just an unintended byproduct, not meant to convey information.
posted by themel at 11:27 PM on July 2, 2012

The "faster-than-light" business involved neutrinos generated at CERN and detected in Italy-- a signal which penetrated hundreds of kilometers of solid rock. Straight through the planet would not be a problem.

Of course, given the cost/difficulty of creating a detector, it's not really a practical concern.
posted by alexei at 11:37 PM on July 2, 2012

I can't find the cite at the moment, but modulation of neutrino flux to encode information was just demonstrated in a well received paper this year. The navy has a longstanding interest in the invention of a practical neutrino 'radio;' however, when I stuck my head in the door of one of the MINOS neutrino bigwigs next door during grad school, he told me he did not think it would become a practical technology in the foreseeable future.
posted by samofidelis at 11:48 PM on July 2, 2012

(a large cave opening, and a smaller shaft
I have a friend who will be so happy there's a replacement to "like chucking a sausage up an alley"...

Anyway, this depends somewhat what you mean by both "man made" and "signal".

Electromag is going to be relatively limited.

Light and sound are going to be stopped rather rapidly, but are going to flow down your access route with ease. A laser beam, for example, is going to go down a straight shaft with no problems at all.

Seismic events are going to be pretty much inescapable (with the right detectors). Sure, you're not going to get much signal in an earthquake, but you search for underground deposits by making a loud bang and listening to the echoes. You could probably manage morse type encoding across the planet if you did it right.
posted by sodium lights the horizon at 4:06 AM on July 3, 2012 [2 favorites]

You could just not bring a neutrino detector, seismograph, or radio with you. That puts you back in the 1-2 meter range.
posted by ook at 5:28 AM on July 3, 2012

Reflection Seismology is a method of exploring the Earth's crust by inducing seismic waves and measuring their reflections from the Earth's innards. It can probe >~100 km deep.
posted by no regrets, coyote at 9:02 AM on July 3, 2012

Data point: Super-Kamiokande is located 1000 meters underground.
posted by Chocolate Pickle at 9:23 AM on July 3, 2012

Regarding neutrinos, they aren't just produced by the sun. Nuclear reactors also produce them.
posted by sindark at 11:18 AM on July 3, 2012

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