How UV Light Actually Kills Germs: The Molecular Physics Behind Germicidal Radiation
In 1877, two British scientists named Arthur Downes and Thomas Blunt published an observation that would eventually transform medicine. They noticed that bacteria exposed to sunlight stopped growing—specifically, the shorter wavelengths of light seemed most lethal. They couldn’t have known that 145 years later, their discovery would become a frontline defense in a global pandemic, with ultraviolet lamps installed in hospitals, airplanes, and municipal water systems worldwide. What happens between a UV photon striking a microorganism and that organism becoming harmless? The answer lies in a remarkably precise molecular event: the destruction of genetic code at the atomic level. ...