In the Rheology Bulletin, 83(2) July, 2014, M.A. Fardin from the University of Lyon conducted a study in which he explored the rheological nature of cats concluding that cats can be either liquid or solid depending on their container . . . as described in this excerpt.
a.
b.
c.
d.
FIG.1:(a) A cat appears as a solid material with a consistent shape rotating and bouncing, like Silly Putty on short timescales. We have De >>1 because the time of observation is under a second. (b)At longer timescales, a cat flows and fills an empty wineglass. In this case we have De <<1. In both cases, even if the samples are different, we can estimate the relaxation time to be in the range τ=1s to 1min. (c-d) For older cats, we can also introduce a characteristic time of expansion and distinguish between liquid (c) and gaseous (d) feline states.[(a)Courtesy of http://cat-bounce.com, (b) http://www.dweebist.com/2009/07/kitten-in-wine-glass/, (c) http://imgur.com/gallery/UuNSR, (d) http://imgur.com/s7JtV%5D
Rheology is, of course, the study of the flow of a material (in this case, cats). The paper goes on the describe attributes such as the low affinity between cats and water surfaces, the spreading of a cat on a rough surface, and spontaneous rotation of a cat in cylindrical jar.
Fascinating.
Gunsmoke and Knitting 