Death hanging in the air

The accidental electrocutions at this year's Boy Scout Jamboree of four men whose tentpole touched a power line raises an obvious question: Don't power lines have insulation?

As Daniel Engber explains at Slate:

No, they don't—at least the ones that run aboveground. Most of the hundreds of thousands of miles of high-voltage transmission lines in this country are made solely of metal—either aluminum or aluminum wrapped around a steel core. Adding a layer of insulation to every line would be pricey and has been deemed unnecessary given how high the lines are off the ground. (Underground lines are insulated, both for the safety of the walkers above and to protect the lines from shovels and the like.)