Over the years the physicists behind the YouTube channel Sixty Symbols have answered some big questions — like what happens if you stick your hand inside the Large Hadron Collider? Or do physicists believe in God? But now these fine scientists from The University of Nottingham have brought physics to a level that I can personally appreciate. They’ve hit the streets of Dublin to demystify what goes into the finest of Irish libations, the perfect glass of Guinness Beer. Their inquiry starts with the most obvious question: What creates that thick beige froth that sits elegantly atop the dark brown stout? It sounds like a mundane question. Until you realize it’s not. The dynamics of Guinness foam can be explained partly by work done by the Irish physicist Lord Kelvin (1824-1907) long ago. But other aspects of Guinness foam are still being hotly contested by physicists today. Take for example this paper, Waves in Guinness, published in 2008 in the journal Physics of Fluids. Now we’ll let Sixty Symbols explain the rest….