h a l f b a k e r yProfessional croissant on closed course. Do not attempt.
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A Faraday Cage is basically a volume of space that (some form of electromagnetic wave) can't get into. It's like being in a room that's got such well-fitting doors that all outside light is blocked.
A Faraday Cage is like that, but for something other than light. Such as, say, radio waves. Or cell-phone
signals.
I propose a special dull-gray paint that would, when painted on a surface, block all cell-phone signals that hit it. Two coats of this on the inside of a room (including the door and ceiling), and cellphones won't work in this area.
Alternately, it could be calibrated for other signals. For example, it could be used to protect the electronics of an airplane from all those high-tech gadgets the passengers have in the passenger compartment (why the airlines insist on that 15-minute shutdown on takeoff and landing).
Probably about as practical as my idea
Solar_20Panel_20in_20a_20can
[normzone, Oct 04 2007]
Dunno if it's just a concept...
http://gizmodo.com/...ng-paint-157991.php
...or actually exists yet. [neutrinos_shadow, Oct 04 2007]
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I bet magnetic paint would do this. You can pick it up at the hardware store. |
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I'm sure this has been thought of and rejected. If it were that simple, the government wouldn't use expensive copper wire mesh to protect their secret rooms. |
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This could work. A faraday cage is just a metal box; if you can get good conductivity from the walls to earth then all of the energy of the radio waves is converted to electricity and dumped. If the accepted standard is the copper cage then I'd guess it works better, but you'd get some signal blocking from this, which might or might not be enough for your purposes depending on the strength of the signal and the sensitivity of your equipment. |
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To post a counter-argument to [21Q], the steam engine has been thought of and rejected too, but that doesn't mean it doesn't work, or wouldn't be appropriate in certain niches... a biomass-based economy, perhaps. |
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Both silver and nickel-loaded paints are used for just this purpose. |
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The major problem is the required seal tighness. At the highest cell phone frequencies (~2.2 GHz) the wavelength is 13.6 cm. EM radiation can penetrate this well enough that you can't have any openings longer than 1.4 cm, and this is linear openings, not diamater. Thus that tiny little crack along the door is going to let a fair amount of RF radiation through.
There may also be skin depth issues, as some frequencies will pass through to thin a layer, even if it is properly grounded, but I am less familiar with that. |
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Cool idea, but as for the airplane thing, making passengers shut off their devices is entirely unnecessary for all modern airplanes because they are shielded well enough anyway (as proven by the Mythbusters), but they do so anyway as a precaution, just in case theres a "perfect storm", a unaccounted-for combination of plane electronics and consumer devices that causes failure. |
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