They collide with the positive ones a little above the ground, zapping a bolt of lightning upward.
Lightning appears to be a bit sexist.
For reasons no one yet understands, men account for about 84 percent of lightning fatalities and 82 percent of the injuries, according to scientists with the National Severe Storms Laboratory and the National Weather Service. About 20 percent of the victims are killed outright, with most survivors losing some hearing or vision. The study of lightning has been a neglected child in meteorology ever since Ben Franklin flew his famous kite, proving that lightning is electrical. But it's getting more attention now because lightning might be more useful in predicting severe storms than had been thought. NASA, which hosted a recent symposium on lightning at its Global Hydrology and Climate Center in Alabama, has placed a high priority on adding sensors to weather satellites that could map lightning on a continual basis.