Want to see cosmic rays? You might need a lot of expensive exotic gear. Nah. [The ActionLab] shows how a cup of coffee or cocoa can show you cosmic rays — or something — with just the right lighting angle. Little bubbles on the surface of the hot liquid tend to vanish in a way that looks as though something external and fast is spreading across the surface.
This is a companion discussion topic for the original entry at https://hackaday.com/2024/03/26/cosmic-ray-detection-at-starbucks/