Matt:

Is it true that a well placed nuclear bomb detonated over the central United States would erase the hard drive of every computer in the country? I guess no one would really care whether their computers worked if their skin was falling off. Please settle my mind about this.

-- Jim Stewart, La Jolla

Settle? Hmmmm. I'll stop you from puzzling over the old question, but I'll give you something new to fret about. That's a trend these days...the year of new things to fret about. May as well pile on this one, while we're at it.

Yes, a well-placed nuclear bomb could fry every hard drive in the country. It would fry not only all hard drives, but every other type of unshielded magnetic storage device, semiconductors, and most electrical wiring. Apparently the nuke geeks have known about this for 40 years, but it just hasn't come up much in conversation. The feds have to protect their Nevada facilities from wipeouts during nuke testing. I guess the rest of us are on our own.

When a nuclear device is detonated, among other stuff, it emits a spectacular pulse of energy in the range of tens of thousands of volts lasting less than a second. When this electromagnetic radiation encounters an unshielded bit of electronic or electrical gear, the voltage surge fries it or the radiation wipes out the data. And this could be a nuclear device set off 250 miles straight up, which wouldn't kill people, just electronics. That day you'll oversleep because your alarm will be fried. But so what? You can't drive to work anyway, cause your car won't start. But so what? The office computers are useless. So stay home and watch TV. Uh-oh, no TV. No radio. A big nationwide nuthin'. Chin up, Jim. The experts say it's possible for this to happen, but the odds are pretty slim that it ever will.