Cats Are Liquid — A Scientific Investigation

Every cat owner has seen it: a cat folds itself into a bowl three sizes too small, drapes over the narrow arm of a chair, or pours itself into a cardboard box that seems physically impossible for its body to fit inside. Turns out, this isn’t just internet meme material — it’s a legitimate area of physics research.

The rheology of cats

In 2017, French physicist Marc-Antoine Fardin was awarded the Ig Nobel Prize in Physics for tackling exactly this question: can a cat be classified as a liquid? His field is rheology — the study of how materials flow and deform under stress. Fardin’s key insight was borrowing a concept called the Deborah number, which physicists use to decide whether a material behaves like a solid or a liquid.

The idea is simple: it depends on time. If the time it takes an object to conform to its container’s shape is short compared to how long you’re observing it, it behaves like a liquid. If that “relaxation time” is long compared to your observation window, it behaves like a solid.

A cat squeezing into a sink over a few seconds, observed over a minute? That’s liquid behavior. A cat in a bathtub full of water, actively resisting and holding its shape? That’s decidedly solid.

So… are cats liquid?

According to Fardin’s research, the answer is: it depends on the cat, the container, and how stressed the cat is. Cats are, in a sense, both — shape-shifting between solid and fluid states depending on the situation, which is a pretty perfect description of every cat I’ve ever met.

Why this actually matters

Beyond the fun headline, Fardin’s work is a great example of the Ig Nobel Prize’s motto: research that first makes you laugh, then makes you think. Studying something as mundane as a cat squeezing into a box turns out to be a genuinely useful way to explore real concepts in fluid dynamics and material science — just with a much cuter test subject than most rheology papers get.

Next time your cat pours itself into an impossibly small box, you can tell them, with full scientific backing: you’re being a liquid right now.