Are Cats Both Liquid and Solid? A Vet’s 2025 Exploration of Feline Fluidity 🐱

By Dr Duncan Houston BVSc, founder of Ask A Vet — decoding the furry phenomenon of feline fluidity in 2025

🧠 Why We Think Cats Are Liquid

Whether slipping into a vase, cozying up in a tiny box, or flattening on a shelf, cats seem to do the impossible—flowing and molding to fit any space. This strange ability spurred a genuine scientific inquiry. In 2017, physicist Marc‑Antoine Fardin coined this “fluid feline” concept using rheology, the science of how materials flow, and even won an Ig Nobel Prize :contentReference[oaicite:3]{index=3}.

📚 What Makes Something a Liquid or Solid?

Liquids have fixed volume but change shape depending on their container, while solids maintain both volume and shape :contentReference[oaicite:4]{index=4}. The trick lies in timescale: if an object changes shape quickly compared to observation time, it behaves like a liquid.

📐 The Deborah Number: Feline Fluidity Math

Rheology uses a factor called the Deborah number—the ratio of an object's "relaxation time" (how long it takes to adapt) to observation duration. A small number (<1) means it behaves like a liquid :contentReference[oaicite:5]{index=5}. In cats, relaxation times (several seconds to a minute) versus observation allow them to flow—thus acting liquid in these moments.

🔬 Scientific Confirmation

Fardin’s experiments—like cats filling wine glasses over seconds—showed low Deborah numbers; meaning the cats flowed like liquids :contentReference[oaicite:6]{index=6}. Further research echoes this: cats flow through tall gaps but hesitate in short ones, indicating they recognize their own fluid properties and size in real-time :contentReference[oaicite:7]{index=7}.

🧱 Why Cats Also Act Solid

On short timescales—starting leaps, stretching—they behave like solids. They can brace, climb, or freeze in place. Physicists thus call them non‑Newtonian fluids: behaving solid or liquid depending on force and timing :contentReference[oaicite:8]{index=8}.

📏 Feline Anatomy: Built for Fluidity

• Flexible spine & loose skin: These let cats flatten, tuck, and twist into odd shapes.
• Free-floating collarbone: Helps them slide into slots once the head fits :contentReference[oaicite:9]{index=9}.
• Muscles vs fat: Lean build has flexibility—less bulk resisting change.

😂 Fun Examples from the Internet

Countless memes show cats in bottles, bowls, jars—you name it. In fact, a popular “liquid cats” post by TechnoCrazed showcased them fitting into narrow glassware :contentReference[oaicite:10]{index=10}. Reddit debates also joke that cats are non‑Newtonian fluids—both gas and liquid depending on context :contentReference[oaicite:11]{index=11}.

🔍 Why This Matters to You

• Health insight: Their flexibility comes from healthy joints and muscles—so stiffness or reluctance may signal arthritis or pain.
• Environmental enrichment: Provide snug boxes, tall beds—they love confined spaces.
• Safe spaces: A ruinous squeeze into vents or appliances can end poorly—know their fluid tendencies and act.

🧪 Dual Nature in Everyday Life

At rest, cats can fill a sink like thick cream. In motion, they spring solidly across the room. Their ability to shift between states is a testament to their evolutionary design and playful ingenuity :contentReference[oaicite:12]{index=12}.

📊 Quick Reference Table

🎯 Tips for Owners

• Offer snug cozy spots: boxes, baskets, jars—cats love to feel molded in.
• Monitor stretching and flexibility—limits or pain may need veterinary check-ups.
• Understand why your cat squeezes into tight spots—safety & stress relief.
• Celebrate their quirky fluid skills—it reveals their powerful, elegant nature.

🧡 Final Thoughts from Dr Houston

Cats truly are marvels of biology and physics, capable of being both fluid and solid creatures—balanced by adaptive modes depending on time, force and context. Beyond the memes, this fluidity reflects their health, agility, and curiosity. Embrace it—just keep an eye on whether their squeezes are fun or signaling discomfort. 💙

For personalized guidance on mobility, behavior, or furniture design, the Ask A Vet app is here whenever you need it! 📱