The Great Cat Debate. Are Cats Really Liquid or Solid?


Are cats liquid or solid? This amusing question has been circulating online, with many people humorously debating whether cats’ behavior and anatomy means they should be classified as liquid or solid states of matter. The debate underscores how cats often seem to pour themselves into containers or spread themselves out on surfaces, defying the rigid structure we expect from solids. While settled science categorizes cats as solid matter, the whimsical question invites a fun exploration of cat behavior, anatomy, and fluid dynamics. This article will look at the evidence behind the liquid vs. solid cat debate.

The Science of Matter

Matter exists in three common states: solid, liquid, and gas. On a molecular level, solids have a tightly packed crystalline structure where the atoms or molecules are not free to move around. Solids maintain a fixed shape and volume because of the strong intermolecular forces holding the molecules together (State of matter, 2022). Liquids have a more fluid structure than solids. The molecules have enough energy to move past one another but still interact through intermolecular attractive forces. This allows liquids to conform to the shape of a container but maintain a nearly constant volume (States of matter: Definition and phases of change, 2023). Gases have molecules with enough kinetic energy to move freely and spread out. With very weak intermolecular forces, gases expand to fill any container and take on its shape and volume (States of Matter | Earth Science, 2022).

Key properties that differentiate solids, liquids and gases include viscosity, flow, shape, and volume. Viscosity describes a fluid’s internal resistance to flow – liquids have low viscosity while solids have very high viscosity. Liquids can flow and change shape, while solids maintain their shape. Gases have very low viscosity and expand freely. The volume of liquids is nearly constant, while gases change volume to fill a container. Solids have fixed volumes determined by their crystalline structure.

Cat Behavior

Cats are known for their ability to contort themselves and fit into very small spaces. Have you ever seen a cat squeeze into a cardboard box or crawl under a bed? Their flexible spine and loose skin allows them to maneuver into the tightest spots with ease. When given an open, flat surface like a bed or couch, cats tend to spread out and relax. The typical “loaf” posture with all four legs tucked underneath is a prime example. Cats seem to enjoy flattening themselves out as much as possible when resting. Their unusual fluidity gives them the unique ability to mold to their environment and find comfort in the oddest spaces.

The Cat Loaf

The cat loaf refers to a position that cats often assume where they tuck their paws under their body and rest with their legs unseen. This compact, loaf-like shape gives the phenomenon its name. Cats loaf for a variety of reasons, often as a sign of relaxation, comfort, or feeling secure in their environment (source).

When cats loaf, their bodies take on a rounded, doughy appearance without clearly defined edges. Their legs disappear within the loaf shape as if they have become part of a cohesive, malleable mass. This demonstrates the looseness and fluidity of a cat’s body, which can condense into a solid-looking form or spread out in relaxation. Unlike the stiff, well-defined shape of a true solid, a resting cat flows into the container of whatever surface it occupies.

The ability to loaf comes from a cat’s flexible spine that allows its legs to tuck under its body (source). The loose skin and muscle structure further enable the animal to compress down in a liquid-like manner. Overall, the phenomenon of cat loafing exhibits the fundamentally soft, fluid essence of cats beneath their cute furry exterior.

Cats Lack Rigid Structure

Unlike many other animals, cats lack a fixed, stable skeletal structure. Their bones are relatively small and light compared to their body size. Cats have a loosely connected, flexible spine that allows them to arch and stretch into different positions. Their shoulder blades are not tightly attached to any other bones, enabling free range of motion. Cats’ ribs are also not joined directly to their spine, leaving space for their ribcage to compress. Overall, a cat’s skeleton is like a series of unconnected, bendable parts rather than a rigid framework. This loose structure gives cats great flexibility and compressibility compared to animals like turtles with their fused shell or deer with a stiff spinal column. Cats can contort their bodies and slip into spaces that would be impossible for animals with more solid, inflexible bones.


The Physics of Cats

Cats have a remarkable ability to land upright when falling from heights. This is due to their “righting reflex” which allows them to quickly twist their bodies mid-air to get their feet under them (Purina, 2023). Studies have examined this cat-righting reflex to understand how cats transform in falls to land upright.

Researchers at the University of California, Berkeley conducted experiments dropping cats from various heights to observe their falling and landing behavior. They found cats reach terminal velocity after righting themselves at about 60mph when falling from around 10 stories high. Cats’ aerial maneuvers involve arching their back to rotate their front and back halves in opposite directions, extending their legs to stabilize, and twisting the front half of their body to get their feet downward (Scientific American, 2023).

The cat-righting reflex engages when cats sense they are falling and works by using their unique muscular structure and inner ear canal anatomy. Their muscular back and leg strength combined with their loose-jointed spine allows them to contort midair. Their vestibular system and wide ear canals also give cats exceptional balance and aerial awareness (Purina, 2023).

So while cat physics is complex, felines’ remarkable righting reflexes ensure they can quickly transform their bodies in free falls to get their feet under them and stick the landing.

Cats Flow Like Liquids

Multiple scientific studies have analyzed the ways that cat bodies conform to containers and environments in a liquid-like manner. In 2017, researchers won an Ig Nobel Prize for studying the fluid dynamics of cats. Their research found that cats can contort their bodies to fit into nooks, crannies, boxes, and other tight spaces in the same way that water conforms to the shape of a container ( Further analysis of cats lapping water revealed subtle dynamics similar to fluid mechanics ( High speed photography showed cats curling and shaping their tongues to lift water, demonstrating liquid-like behaviors. Just as water flows to fill any container, cats can morph and move their bodies to fit into small, confined areas. Their ability to change shape and find comfortable positions in tight spaces is comparable to the flexibility and conformity of fluids.

The Counterargument

While many believe cats display properties of liquids, some argue that cats should be considered solids. Their reasoning often focuses on a cat’s fur texture, temperament, ability to hold a physical shape, and other physical characteristics that differ from liquids like water or honey. For example, some point out that a cat’s fur is solid, with each hair maintaining its form even when a cat changes positions. Additionally, cats often perch on high surfaces and hold themselves in place, retaining a solid shape rather than spreading out like spilled milk. Their temperament, too, is cited – cats seem to have a mind of their own, while liquids conform mechanically to their containers.

However, these arguments focus only on certain moments or physical features, rather than considering cats’ overall fluidity. Just because a cat’s fur or claws may be rigid does not mean their entire body lacks liquid-like adaptability. Their ability to dramatically change shape to fit containers, despite possessing solid parts, is key evidence of their strange liquid-solid duality.

A Matter of Perspective

When determining if cats are liquid or solid, it’s important to note that states of matter exist on a spectrum. The properties of liquids and solids blur together at the margins. For example, liquids become more viscous as temperature decreases, while solids become more malleable as temperature increases. According to the Encyclopedia Britannica, viscosity measures a fluid’s resistance to flow. Highly viscous liquids like honey or molasses resist flow and deformation, behaving more like solids.

Cats display some properties of both liquids and solids. Their ability to conform to containers and squeeze into small spaces are liquid-like behaviors. However, cats can also hold fixed shapes like loaves and spheres, resisting deformation. Their structure flows and adapts, but also maintains semi-rigid form. Given these contradictory properties, whether cats are liquid or solid becomes a matter of perspective.

Some scientists and researchers argue cats exhibit more solid-like attributes, capable of supporting their own weight and moving independently. Others contend their fluidity and ability to change shape makes them more liquid in nature. In the end, there may not be a definitive answer, as cats display characteristics of both states of matter.


Throughout this article, we’ve explored several fascinating facts that reveal cats to be more liquid-like than solid. Cats can squeeze into tight spaces and conform to containers, flowing to take the shape of whatever vessel they’re placed in. Their bodies lack rigid structure and their loose skin and soft bones allow them to be malleable. Cats can also splash, drip and ripple when moving quickly. While physics shows they resist shear stress and have a defined volume like liquids, cats don’t actually behave as true liquids that turn into vapor. So in the scientific sense, cats are indeed solids.

Yet they exhibit an uncanny fluidity and liquid-like essence all their own. Their flowing, molten movements captivate us with a hypnotizing charm. So while cats may technically be solids, they embody the spirit of liquid in so many mesmerizing ways. Of all the solids in nature, none is quite as fluid, graceful and exquisite as the familiar, friendly feline we know and love.

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