Oxford maths PhD student Sophie Abrahams explicates the Ig Nobel Prize-winning research on what happens when one walks backwards while (or whilst) holding a cup of coffee.

The 2017 Ig Nobel Prize for fluid dynamics was awarded to Jiwon (Jessie) Han, for studying the dynamics of liquid-sloshing, to learn what happens when a person walks backwards while carrying a cup of coffee.

He documented that research, in the study “A Study on the Coffee Spilling Phenomena in the Low Impulse Regime,” Jiwon Han, Achievements in the Life Sciences, vol. 10, no. 1, 2016, pp. 87-101. Here you see him demonstrate that the basic physics of walking with a cup of coffee, back in 2015 while he was a high school student:

All of this was inspired by an earlier Ig Nobel Prize.

The 2021 Ig Nobel Prize for fluid dynamics was awarded to Rouslan Krechetnikov and Hans Mayer for studying the dynamics of liquid-sloshing, to learn what happens when a person walks while carrying a cup of coffee.

REFERENCE: “Walking With Coffee: Why Does It Spill?” Hans C. Mayer and Rouslan Krechetnikov, Physical Review E, vol. 85, 2012.