A non-Newtonian fluid is one that does not follow Newton's law of viscosity, which means that it has variable viscosity depending on stress. Ketchup, Flubber, and Silly Putty are examples. Another substance that fits this description is called Oobleck (1 part water to 1.5 to 2 parts corn starch), which is a suspension of starch in water. The name Oobleck comes from the title of a work by what author?