If you’ve ever wiggled a balloon against your hair, you know that rubbing together two different materials can generate static electricity. But rubbing bits of the same material can create static, too. Now, researchers have shot down a decades-old idea of how that same-stuff static comes about.

The same-material phenomenon produces important real-world effects, such as generating lightening in volcanic eruptions, gumming up the processing of powders in manufacturing, and causing explosions in grain elevators. Physicists thought they understood what was going on, but suddenly "the dominant theory appears to be dead," says Troy Shinbrot, an applied physicist at Rutgers University, New Brunswick, in New Jersey who was not involved in the new work.

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