ὄζειν

In 1840, German-Swiss chemist Christian Friedrich Schönbein noticed a peculiar sharp odor near his electrolysis equipment. He recognized it as the same smell that lingers after a lightning strike. He named the substance ozone, from Ancient Greek ὄζειν (ózein), to smell, because the odor was the molecule's most immediately obvious property. The name was a sensory description, nothing more.

Ozone is O₃—three oxygen atoms bonded together instead of the usual two. It forms when ultraviolet radiation or electrical discharge splits O₂ molecules, and the freed oxygen atoms bond with intact O₂ to create O₃. The molecule is unstable, reactive, and toxic at ground level. But fifteen to thirty-five kilometers above the earth, in the stratosphere, ozone performs an essential function: absorbing the sun's ultraviolet-B and ultraviolet-C radiation.

In 1985, Joseph Farman, Brian Gardiner, and Jonathan Shanklin published a paper documenting a massive seasonal depletion of ozone over Antarctica—the ozone hole. Chlorofluorocarbons (CFCs), used in refrigerators and aerosol sprays, were destroying stratospheric ozone at an alarming rate. The discovery triggered the Montreal Protocol of 1987, the most successful international environmental treaty in history.

The ozone layer is now slowly recovering, projected to return to 1980 levels by approximately 2066. The word ozone, coined simply because the molecule smells, became one of the most important words in environmental science. Schönbein could not have imagined that the sharp odor from his laboratory equipment would name the shield that protects all life on earth from radiation.