It did to Dr. Hans C. Mayer(also from California Polytechnic State University, San Luis Obispo) and Dr. Rouslan Krechetnikov, two scientists from the Department of Mechanical Engineering at the University of California (Santa Barbara).
Their article “Walking with coffee: Why does it spill?” was published in the journal Physical Review Letters E (Volume 85, Issue 4; Phys. Rev. E 85, 046117 (2012)). It explains the biomechanics of walking with coffee, and the invariable spills.
They explain, “In our busy lives, almost all of us have to walk with a cup of coffee. While often we spill the drink, this familiar phenomenon has never been explored systematically. Here we report on the results of an experimental study of the conditions under which coffee spills for various walking speeds and initial liquid levels in the cup.” [Paper]
These two professors found that the normal human stride (our walking gait) moves at almost the same frequency as the motion (or, oscillations) of coffee within a mug.
The movement of liquid, such as coffee, in a cylindrical container, like a mug, is very similar to the back-and-forth motion of a pendulum. Further, the frequencies of the oscillations of the liquid inside depends of the height and diameter of the container.
They measured the average coffee mug and found the typical height and diameter is about 3.9 inches (10 centimeters) and 2.8 inches (7 centimeters), respectively.
Now, carefully grab another cup of Joe and settle back for page two.