Pour water into a glass or a jug, and the water takes the shape of the object immediately. Pour honey into a bottle, and it’ll likely take minutes before the slow-moving stuff fully conforms to its new container.
Both are liquid, but they’re not the same.
To differentiate levels of liquidity, rheologists — scientists who study the “deformation and flow” of liquids — use something called the Deborah number. The quicker the liquid takes the shape of its container, the lower its Deborah number, the “more liquid” it is.
On the extreme end are liquids like glass and tar pitch. It took an astounding 69 years for a single drop of the latter substance to fall at Trinity College, which set up a tar pitch experiment in 1944 and finally recorded its first drop on camera in 2013.
So what about cats? Are they really liquid?
If you’re a cat lover and you haven’t been living under a rock for the last 10 or 15 years, you’ve almost certainly seen memes showing photos of felines and their uncanny ability to conform their bodies to containers, as well as their tendency to “pour” themselves.
My Buddy is an expert in the latter, often electing to drop down from the couch in the laziest possible way, by shifting his weight and letting his body follow the path of least resistance until he slides off the side and onto the floor.
Marc-Antoine Fardin, a physicist with the French National Center for Scientific Research and Paris City University, won an Ignoble Prize for taking the memes seriously and studying the fluid properties of felines. Cats, Fardin wrote in an article about feline liquidity, “are proving to be a rich model system for rheological research.”
Cats, he concluded, are a “non-Newtonian liquid” with the ability to “alter their shapes to fill out the container without changing their volume,” putting them in the same general category as ketchup.
So the next time my cat gets all imperious with me, I’m going to remind him he’s a glorified condiment.
via Pain In The Bud