Shuffling across the carpet to zap a friend may be the oldest trick in the book, but on a deep level that prank still mystifies scientists, even after thousands of years of study.

Now Princeton researchers have sparked new life into static. Using millions of hours of computational time to run detailed simulations, the researchers found a way to describe static charge atom-by-atom with the mathematics of heat and work. Their paper, "Thermodynamic driving forces in contact electrification between polymeric materials," appears in Nature Communications.

The study looked specifically at how charge moves between materials that do not allow the free flow of electrons, called insulating materials, such as vinyl and acrylic. The researchers said there is no established view on what mechanisms drive these jolts, despite the ubiquity of static: the crackle and pop of clothes pulled from a dryer, packing peanuts that cling to a box.

"We know it's not electrons," said Mike Webb, assistant professor of chemical and biological engineering, who led the study. "What is it?"

In other words, they used math to simulate the movement of around 80,000 atoms. Those simulations matched real-life observations with a very high degree of precision. It turns out, in all likelihood, static shock is a function of water, and more specifically, the free energy of stray water ions.

With that framework, Webb and Zhang revealed the molecular underpinnings of those familiar shocks in infinitesimal detail. They blew Sundaresan's black box wide open. If only Thales could see.