Dear Prime Minister Taro Aso, I'm writing to urge you to initiate measures that would protect Japan in the event of an EMP attack.

EMP is an acronym for electromagnetic pulse. This phenomenon was first discovered in 1962 when the U.S. detonated a nuclear bomb high above the Pacific Ocean that had the surprising effect of disabling most electronic circuitry within range of the explosion. (The Russians found the same effect during their nuclear tests.)

Nuclear explosions emit gamma rays and an enormous pulsed current of high-energy electrons, creating a massive electrical field and sending voltage spikes and current surges through power lines and communications cables. The energy of this pulse reaches everything in line of sight of the detonation. The higher the altitude of detonation, the wider the area affected.