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no, seriously: http://www.boingboing.net/2009/03/03/britains-vast-cement.html
Superseded by radar, and apparently doesn't help much with faster planes, but one wonders whether this might be an effective technique for detecting stealthed aircraft.
Superseded by radar, and apparently doesn't help much with faster planes, but one wonders whether this might be an effective technique for detecting stealthed aircraft.
