No Running on the Swimming Pool

Most of you, especially the younger crowd, are familiar with oobleck. The name comes from a Dr. Suess Book about a most unusual weather event, but it's applied to a mixture of two common substances: cornstarch and water. When these two are mixed together in the right ratio (I think it's about two parts water to one part starch by volume, but you can add a little more of whatever seems to be short to get it right) you get what's called a non-Newtonian fluid. In most fluids the rate of deformation in response to pressure is proportional to the amount of pressure. That is, the harder you press on the fluid, the more rapidly it flows. In non-Newtonian fluids, increasing pressure leads to a decreased rate of flow. In other words, increased pressure leads to a rapid increase in viscosity.

Oobleck is a lot of fun to play with, though the childish name that's tacked on to it is a little grating to me. Why not just call it "cornstarch and water?" Do we assume children will be be uninterested if we don't give it a silly name? But the activity is a favorite of elementary teachers (you don't need to know any science to do it, and it's safe), and the name is pretty much fixed, I think. Typically, the mix is made up, sometimes with coloring for nice effects and the kids play with it. Typically, no real science is done with either (as you can see from the first paragraph, the core concepts are not elementary- though there are descriptive and predictive aspects that could be addressed that generally aren't). And typically, only a few cups total are enough for a classroom of kids.

But what could you do if you had a whole swimming pool of the stuff?