In school, we learned that solids retain their shape and liquids conform to the shape of the container they're confined to. Cats seem to challenge this idea. They're technically solids, but they also have a knack for conforming to the shape of any container they wedge themselves into.
Marc-Antoine Fardin decided to give this phenomenon some serious thought — and his investigation won him the 2017 Ig Nobel Prize in physics.
Here's a breakdown of Fardin's award-winning findings.
Are cats actually a liquid?
Before we get into defining a liquid, we need to talk about rheology, which is the study of the flow of matter. Obviously, the kind of matter that flows most freely tends to be liquid, but it can also refer to soft solids, gels — literally anything that might flow.
Fardin explains that, in order to be considered a liquid, the action of conforming to the shape of a container must also have "a characteristic duration," or relaxation time. "If we take cats as our example, the fact is that they can adapt their shape to their container if we give them enough time," he wrote on Quartz. "Cats are thus liquid if we give them the time to become liquid."
Are cats a solid?
The answer is ... it depends. Much like water can be a liquid when it's warm and solid ice when it's cold enough, cats can behave like liquids sometimes and like solids other times.
In Rheology Bulletin, Fardin explained that cats can behave like both liquids and solids, depending on the situation. When they want to smoosh themselves into a wine glass, they behave like liquid, filling up the entire allotted space.
But, if you try to put a cat into a bathtub full of water, for example, the cat will act like a solid and try to minimize contact with the water. (Empty bathtubs, on the other hand, are a cat favorite.)
There are a few reasons. First, they may feel more comfortable and secure in a small space. Cats feel less stressed when they can hide.
"Hiding is a behavioral strategy of the species to cope with environmental changes and stressors," Ethologist Claudia Vinke of Utrecht University in the Netherlands told Wired.
Cats are antisocial creatures (just ask any cat owner) and hiding from their problems is their preferred way of reducing anxiety. Finally, cats seek warmth and some of their favorite tiny spaces, like cardboard boxes, are good insulators of heat, Wired notes.