A Jiffy Is an Actual Unit of Time

While you might say you'll be back "in a jiffy" to mean a short, indefinite moment, this casual term has a surprisingly precise scientific origin. In the early 20th century, the renowned physical chemist Gilbert Newton Lewis proposed a formal definition for this fleeting moment. He needed a term for an incredibly small slice of time relevant to his work in molecular physics, and the colloquial "jiffy" was the perfect candidate for a scientific makeover.

Lewis defined a "jiffy" as the amount of time it takes for light, the universe's ultimate speedster, to travel a single centimeter in a vacuum. This works out to a mind-bogglingly brief 33.3564 picoseconds, with a picosecond being one trillionth of a second. This unit was practical for calculations in chemistry and physics, linking the constant speed of light to a common, human-scale length and providing a tangible measure for events happening at the atomic level.

Interestingly, the term has been adopted differently in other fields, each tailored to its own specific needs. In computer science, a jiffy often refers to the duration of one system timer tick, which can vary but is typically around 1/100th of a second. Electrical engineers might use it to describe the length of a single AC power cycle. So while its most fundamental definition comes from the speed of light, a "jiffy" can mean very different, though always very brief, things depending on the scientific context.