In the new Fox television series Dark Angel, America in 2019 is in a decade-long collapse because terrorists exploded a nuclear weapon high in our atmosphere, unleashing an electromagnetic pulse (EMP) that annihilated our communications systems. Could such an explosion destroy modern life?
The disruptive abilities of an EMP were unintentionally demonstrated in 1962 when the United States conducted a high-altitude nuclear weapons test in the South Pacific. About 1,000 miles away, in Hawaii, radio transmissions were interrupted, telephones didn't work, and streetlights went out. With the end of the Cold War, concern about a direct nuclear attack has faded, making way for worry about more esoteric threats like EMP. The House Armed Services Committee is sufficiently alarmed by the prospect of an EMP attack that they just ordered creation of a commission to investigate the United States' vulnerability.
To produce an EMP, a nuclear device must be detonated in the upper atmosphere (about 30 to 300 miles up). The gamma rays that are produced interact with molecules found lower in the atmosphere, causing a cascade of reactions that result in an extraordinarily intense, microsecond burst of energy delivered to earth. When this pulse hits any device with electrical wiring--from broadcast systems to power grids to your car's ignition--the energy can be conducted through it, either temporarily or permanently disabling it. For a nuclear event, an EMP is people-friendly. Humans aren't directly injured by the blast because it's so distant and because there is no radioactive fallout.
To defend against EMP, the military "hardens" or insulates its weapons, surveillance, and communications systems primarily by shielding their electrical innards in relatively inexpensive metal casings. But the big question would be the effect on civilian systems. Power grids, for example, are supposed to be able to compensate if one or several points fail. And financial institutions have duplicate information-storing systems. But no one, except perhaps James Cameron, creator of Dark Angel and the Terminator, knows how bad it could get. But if he's right, one thing's certain: In a post-EMP world, there will be no hit television series.
Explainer thanks John Pike and Steven Aftergood of the Federation of American Scientists, retired Rear Adm. Eugene Carroll of the Center for Defense Information, Andrew Drozd of Andro Consulting Services, andSlatereader Alan Allport for posing the question.