Better living through fluid dynamics
Don't ever say that scientists aren't tackling the pertinent issues in life. A South Korean scientist has discovered how to hold a coffee cup without spilling it everywhere, a problem that seemingly every coffee-swilling human being can relate with. Jiwon Han, a student at the Korean Minjok Leadership Academy, studied why coffee spills so easily by testing different types of glassware, ranging from a wine glass to a regular, standard-issue cylindrical mug. And to really make the whole affair more scientific, Han investigated how each cup's motion, as well the oscillation of the coffee in the cup, affected the likelihood of sloshing. And it turns out that one has a big impact on the other—with the shape of each vessel creating different oscillations that alter the risk of spilling.
But the real difference-maker is all about finding the best way to hold a coffee cup, rather than the container itself. As Han found in his study, the "second harmonic mode of the hand motion corresponds to the resonance frequency of the first antisymmetric mode of coffee oscillation, resulting in maximum spillage." In other words, your grip can have an add-on effect that either increases or decreases your chance of getting coffee all over your sleeve.
But as the study sought to uncover how to hold a coffee cup without spilling, it came up with a few impractical solutions, like walking backwards in order to mitigate hand motion. By walking backwards while holding coffee, Han determined that the frequency of hand motion ends up being more conducive for keeping your mug still. He cautioned, however, that doing so could might pose logistical challenges.
"By walking backwards, we are able to significantly change the frequency characteristics of our hand motion... leading to a subsequent decrease in the probability of coffee spilling. Of course, walking backwards may be less practical," Han wrote.
So the next best way to a hold coffee mug is with a claw-like overhead grip. By doing so, your hand acts as a pendulum, allowing the liquid in your mug to swing more freely without crashing into contrasting frequencies (i.e. the motion of your walking gait). This lets the coffee do its thing without banging up against a host of other motions. So it turns out that Toy Story was right all along when its three-eyed aliens revered The Claw.
The years humankind spent spilling coffee were in vain, as there's not much to keeping your coffee from spilling after all. Next time you're speeding back to your cubicle, think back to Toy Story, and make use of the claw. The Claw is love. The Claw is life. Treat your coffee like a small green alien.