04 Aug 2012

New Discoveries in Oobleck Science

Category: ScienceAdmin @ 9:51 am

If you have not ever seen anyone jog on a mixture of corn starch and water – “oobleck” – check out the video from the Spanish TV show, "El Hormiguero," included in Wired Magazine’s July 11, 2012 online article, "Defying Gravity: When Strange Liquids Act Like Solids."

Water and cornstarch combine to form what in scientific circles is called a non-Newtonian fluid – a viscous fluid (sticky, slow-flowing) that doesn’t always act like we usually expect liquids to behave. When you apply sudden pressure to oobleck, the stuff forms semi-solid columns strong enough to support the weight of an adult but only for a very short time.

What I find even more interesting than the fluid itself is the previous lack of research on it. It seems that most scientists simply cataloged it with similar fluids and assumed that changes in viscosity under pressure (typical of non-Newtonian fluids in general) accounted for the observed phenomena. Scientists are people, too, and as such they are prone to making unquestioned assumptions, although the practice of science ought to discourage at least some of that.

It turns out that the increased viscosity caused by the force of running upon a corn-starch-and-water mixture is insufficient to stop a human body from sinking down into the muck. Recently a graduate student, Scott Waitukaitis of the University of Chicago, along with his physics advisor, Heinrich Jaeger, researched this behavior of oobleck when subjected to sudden impact. They published their findings in the July 2012 issue of Nature.

Such research will undoubtedly lead to safer and/or more exciting travel across human-made corn-starch-and-water swamps. Seriously, a related possibility is liquid body armor using other non-Newtonian fluids.

If something as common as corn starch and water bears further research, how much more is all around us, still waiting for the day when some inquiring mind will ask a question no one thought to ask before? I have long been of the opinion that education should encourage children to think for themselves much more than it should worry about children memorizing information already known to others. New discoveries require interest. Acting upon an interest requires faith in oneself.

By the way, if your children want to try running on oobleck at home, you have a great opportunity for generating and solving real-world science and math problems, such as:

  1. What is the best proportion of corn starch to water? (Try some experiments in a container big enough to punch your fist into or stomp with one foot.)
  2. Does temperature affect the ideal proportion for No. 1 above?
  3. How much corn starch and water will be needed to fill a child’s swimming pool? (Getting the answer to this question requires asking and answering additional questions, like, "What is the volume of the swimming pool?")
  4. What will it cost to buy all that corn starch?
  5. What is an environmentally-friendly use for the oobleck when we are done experimenting with it?
  6. About how much corn was needed to make all that corn starch?

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