Rouslan Krechetnikov is a mechanical engineer at the University of California at Santa Barbara, and he spends most of his time working on fluid dynamics, the flow of air on a plane’s wings, the stability of a rocket, and other weighty problems. None of that has brought him as much attention as his newest paper in the journal Physical Review E: “Walking with coffee: Why does it spill?”
Krechetnikov and a graduate student, Hans Mayer, decided to divert
from weightier subjects last year after a scientific conference,
where they had watched fellow researchers stumble to their tables,
trying not to get coffee all over themselves and the floor.
“The project was certainly fun. We just wanted to satisfy our
curiosity and, given the results, to share what we learned with the
scientific community through peer-reviewed literature,” Krechetnikov
They set up a simple
experiment, watching a person walk in a straight line, mug in hand.
They had their test subject look at the coffee cup. They had their
test subject look at the floor ahead. They shot video of it all,
recording how the coffee oscillated and how long it took to spill.
The results. Don’t rush. You may think the coffee will spill less if you get
it to the table more quickly, but the opposite is true. Slow down
and the sloshing will too. Watch the cup, not the floor. You will spill less.
The abstract concludes: “The studied problem
represents an example of the interplay between the complex motion of
a cup, due to the biomechanics of a walking individual, and the
low-viscosity-liquid dynamics in it.” Isn't science wonderful?