The word dates back to the 1920s, constructed from rather obvious Greek roots, translating literally as “study of flow.” The classic quote every rheological society eventually pulls for its motto is from Heraclitus of Ephesus:
Everything flows and nothing abides; everything gives way and nothing stays fixed.
Etymologically, rheology is quite dull.
The reason I absolutely adore rheology is because it’s an exact inverse of orbital mechanics. While orbital mechanics features absolutely gorgeous, elegant mathematics for relatively straightforward, dull-to-observe outcomes, fluid dynamics has horrible, incomplete, ugly mathematics to describe amazingly beautiful outcomes. Rheology is the “is this really necessary?” complication that encompasses fluid dynamics and expands to embrace all those strange borderline-fluid-like deforming, sliding, flowing materials that purists ban from fluids for not technically being liquids.
Rheology is perfect for cocktail physics demonstrations (along with typical density, non-Newtonian fluids, and other food-based demos) for science outreach. The best part? A well-stocked bar can provide all the necessary components for interesting rheological experiments without needing to tuck extra equipment into my purse in advance, allowing for impromptu guerrilla science education whenever the mood strikes.