In a breakthrough published on July 28, 2025, Penn State scientists led by Professor Victor Pasko have revealed the precise mechanism behind lightning initiation—a mystery that has puzzled researchers since Benjamin Franklin’s era. Their advanced computer simulations show that cosmic rays entering Earth's atmosphere seed high-energy electrons. Within thunderclouds, strong electric fields accelerate these electrons, causing collisions with nitrogen and oxygen molecules.

This cascade produces X‑rays and gamma‑ray bursts, triggering further electron avalanches via the photoelectric effect ultimately sparking a lightning bolt in what researchers describe as a cosmic‑ray‑driven “hidden pinball game” of charged particles.

The research also provides a clear explanation for "dark lightning" events terrestrial gamma‑ray flashes that occur without visible light or radio emissions revealing how compact cloud regions can generate high‑energy bursts silently.

These findings mark the first quantitative, physics‑based model detailing how lightning begins inside storm clouds. Beyond satisfying scientific curiosity, the work has practical implications: improving storm detection, enhancing aircraft safety, and refining weather‑monitoring tools by illuminating the electromagnetic signals that precede strikes.