By Melissa Pandika
WHY YOU SHOULD CARE
Because learning how this trippy, drippy fluid works will help you de-stress and feel smart.
By Melissa Pandika
Need a few minutes to zone out? Forget yesterday’s fish tank screensaver; instead be mesmerized by the wild undulations of a weird green slime known as oobleck, set to a trippy soundtrack and bizarrely entrancing.
No, it’s not a radioactivity experiment gone wrong. Anyone with a few minutes can make the cornstarch-and-water mixture, but where it gets interesting is that the simple slime, while technically a liquid, can also behave as a solid.
Oobleck gets its name from the green globs in Dr. Seuss’s Bartholomew and the Oobleck.
Most substances shift physical states — solid to liquid to gas — in response to changes in temperature. Freezing water transforms it into ice; boiling it turns it into steam, for example. But oobleck is a non-Newtonian fluid, meaning it changes state with variations in pressure.
To investigate how this happens, Derek Muller performs a simple experiment on his YouTube channel, Veritasium: pouring oobleck onto a speaker and gradually adjusting the speed of vibration, or the frequency.
As Muller cranks up the amplitude, or volume, the green puddle starts to ripple. When he sets the speaker to about 20 Hz — the frequency recommended by physicists who study oobleck — the shapeless slime transforms into a writhing, eerily lifelike mass. “That is incredible!” Muller exclaims.
Oobleck is a non-Newtonian fluid, meaning it changes state with variations in pressure, kind of like L.A. traffic.
He then discovers that higher frequencies — faster vibrations, or higher pressure — make the slime look like a smooth, solid orb. At even higher frequencies, it actually appears to levitate.
But how does changing the frequency alter oobleck’s physical state? Muller explains that low frequencies — slower vibrations, or lower pressure — keep the starch particles spread out, allowing them to move effortlessly past each other. As a result, the oobleck flows like a liquid. But increasing the frequency causes the starch particles to crowd together, forming a more solid substance.
In fact, L.A. traffic is a little like a non-Newtonian fluid, Muller explains. At midday, when very few people are on the road, traffic flows smoothly. But come rush hour, “suddenly everything gets clogged, and you’re basically in what is a solid,” he says.
That might not take the edge off your workday commute, but a few minutes staring at some trippy, drippy oobleck should do the trick. Watch the complete video from Veritasium:
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