Shaking Up the Classic Oobleck Trick

By Kevin Ritchart

An update to the classic oobleck science experiment could give runners a sinking feeling.

The mixture of cornstarch and water, known as oobleck, solidifies when subjected to a forceful impact. This means oobleck, which gets its name from a sticky green substance in the 1949 Dr. Seuss book Bartholomew and the Oobleck, has the ability to hold up the weight of a person when they run across it.

But a new technique published earlier this year in an issue of Science Advances could cause runners to sink rather than make their way across a container filled with oobleck.

Thick and Thin

Oobleck is a non-Newtonian fluid, meaning that its viscosity changes depending upon the forces exerted on it. Other non-Newtonian fluids include ketchup and frog saliva, both of which get thinner when force is applied. This is the opposite of what happens when force is applied to oobleck, which becomes a solid.

Laboratory experiments showed that a cylinder dropped onto the surface of oobleck sank more quickly when the container holding the mixture was rapidly rotated back and forth.

Under normal conditions, the impact of the cylinder hitting the surface would cause the particles of cornstarch to collide with each other and bind into a solid. But by oscillating the container, the particles are moving back and forth at such a rate where they are no longer in contact with each other.

Someone attempting to run across the oobleck while it’s in motion would find their foot in the same situation as the cylinder in the lab experiments — sinking through the oobleck to the bottom of the container.

Real-World Applications

Researchers think this approach could be useful in other applications that employ non-Newtonian liquids or other things that possess similar properties. For example, this approach might be useful in industrial settings to keep cement from clogging as it runs through tubes.

But before they can expand the potential uses, researchers need to scale up the oobleck experiment and try to sink some runners.