Yet more crazy YouTube videos of weird, geologically relevant stuff! This time...it's non-newtonian fluids!
Newtonian fluids are the sort of everyday, hum-drum fluids we generally interact with (like coffee, or beer). If you exert some force over area on a newtonian fluid, it deforms pretty much instantly in proportion to the force applied to it. Another way of saying this is that newtonian fluids have a constant viscosity.
BUT non-newtonain fluids have a variable viscosity; generally, this viscosity varies nonlinearly as a function of either the amount of shear stress (force over an area) applied OR as a time-dependant function. Examples of non-newtonian fluids include things like ketchup (which gets stuck in the bottle until you shake it; the sudden application of force to the ketchup drastically reduces the viscosity, letting it flow out of the bottle) and whipped cream (which experiences an increase in its viscosity as a function of applied shear stress).
If you are lucky enough to be a geologist, then you actually have more opportunities than most to interact with non-newtonian fluids. Drilling muds and clays, used to lubricate drill bits, are examples of non-newtonian fluids. Even cooler, of course, are things like debris flows, which behave as viscous, non-newtonian fluids.
You can make your own shear-thickening non-newtonian fluid right at home, by mixing ~2 parts corn starch with 1 part water; get it good and gloppy, and you've got a fluid that, when you gently push against it, behaves just like water, but when you smack it hard, it behaves more like plastic. Try it out! It's insanely fun!
And, if you are really ambitious, you can fill up a whole giant tub of the stuff, and run across it, like these nuts did (the whole video is in Spanish, so that's a little tricky; still, it's fun!):
AND, just for more fun: here's a video of some of the "do-it-yourself home-made cornstarch non-newtonian fluid", put on a speaker!