Why does coffee spill more often than beer? (w/ Video)

Watch even the most careful waiter bring a cup of coffee to your table, and you'll realize that carrying liquid is not easy. When set in motion, the coffee starts sloshing, little waves appear, and spilling may ensue, leaving you with a half-empty cup. Beer, on the other hand, does not slosh as readily. Emilie Dressaire, an Assistant Professor of Mechanical and Aerospace Engineering, speculated that the difference was due to the foam on the beer and she and her colleagues from Princeton Universi...