During the Dust Bowl, people living in northern Texas and Oklahoma had to contend with storms of flour-fine dust that could last for days. The dust blasted through the cracks in window frames and under doors, blinded people, and smothered cattle to death. But it also made people into walking tasers.


Children would run up to their mothers for a hug, and both mother and child would wake up on the ground, knocked unconscious by a massive static shock. Two men shaking hands could knock each other out. Any person who had been out in a dust storm for any length of time could be a danger.


Physicists know that sand storms can provoke lightning, but no one knew how static charge could build up during a "duster." Troy Shinbrot at Rutgers University recently came up with a model that showed how particles of dust could build up large static charges. He didn't believe in his idea, until he calculated that it would only work when the particles reached a certain density in the air. When testing the theory out with glass beads, he saw that once they reached a certain density the level of charge shot up.

Here's how it works. Think of dust particles as little globes, each with two hemispheres. When the particles become polarized, one hemisphere becomes positive and the other hemisphere becomes negative. Since positive charges attract negative charges, a negatively charged hemisphere on one dust particle can attract a positively charged hemisphere on another dust particle. When they meet, they neutralize by transferring the electron from the negatively charged hemisphere to the positively charged hemisphere.

Remember, the hemispheres are part of larger particles. The larger particles already were neutral, with a positive and a negative charge. So when its positively charged hemisphere acquired an electron, the entire particle acquired an overall negative charge. This process could be repeated until the particle built up a major charge.

People could build up major charges as well. As could cars and buildings. As dust storms came through, they could short out the electrical systems on people's cars. They'd blank out radio stations. And, yes, they would occasionally directly strike people with lightning.


Image: Library of Congress.

[Via The Worst Hard Time, Swirling Dust Shocks Physicist.]