Physicists solved a decades-old mystery about static electricity

Rub two identical pieces of glass together and something strange happens. One picks up a positive charge. The other goes negative. This much has been known for centuries. What nobody could explain was why, when the two objects are made of the same material, charge should flow in any particular direction at all. Both pieces of glass are chemically identical. Both have been sitting in the same room. By every obvious measure, the situation is perfectly symmetric.

A thin film of carbon molecules from ordinary air, has been identified as the hidden force that determines which way static electricity flows.

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