Walking while holding a hot drink comes with a hazard – spilling it on the floor and yourself. But this relatively everyday activity can also teach us about a far larger natural hazard too.
Earthquakes occur when tectonic plate boundaries suddenly move, grinding against each other as huge amounts of tension stored in them is released.
The resulting shaking can vary from simply rattling a few plates and sending ornaments spilling off shelves to the floor, to bringing entire buildings crashing to the ground.
But in even the biggest earthquakes some buildings escape relatively unscathed. When Mexico City was hit by a magnitude eight earthquake in 1985, around 412 multi-storey buildings collapsed. Most of the destroyed structures were between eight and 18 storeys high while those higher and shorter remained largely intact.
When scientists looked at why this bizarre pattern of damaged occurred they discovered an explanation that can be found in the way your tea or coffee behaves as you walk.
Watch physicist Helen Czerski, a research fellow at University College London, reveal what they discovered in the video and why it might help keep you safe in an earthquake.
This video is part of BBC Reel’s Big Questions playlist.
If you liked this story, sign up for the weekly bbc.com features newsletter, called “The Essential List”. A handpicked selection of stories from BBC Future, Culture, Worklife, and Travel, delivered to your inbox every Friday.