Roland Wittje’s informative article “Noise: From nuisance to research subject” (Physics Today, February 2020, page 42) shows how the concept of noise in physical systems has evolved and proliferated, from its origins in 19th-century studies of acoustics, to a general notion of unwanted fluctuations across a swath of disciplines extending well beyond the borders of physics. The proverb “one person’s noise may be someone else’s signal” suggests a concise, general, and likewise proverbial definition: Noise is information out of place.
That formulation, of course, paraphrases a celebrated observation by William James,1 about certain “elements of the universe” being “irrelevance and accident—so much ‘dirt,’ as it were, and matter out of place,” which was explored in depth by Mary Douglas.2
