Flashback Friday: Regardless of bladder size, all mammals pee for approximately 21 seconds (with video goodness).

Photo: flickr/Flavio~We don't usually post pre-prints, but we couldn't resist this one. A group of physicists from Georgia Tech went to Zoo Atlanta to watch animals urinating. To their surprise, they discovered that regardless of size, most mammals urinate for about the same amount of time (21 seconds), despite large differences in bladder volume, a phenomenon they term the "Law of Urination". They explain this law using physics, and illustrate their explanation with an amazing video (below) that is absolutely a must-see. Law of Urination: all mammals empty their bladders over the same duration "The urinary system evolved to eject fluids from the body quickly and efficiently. Despite a long history of successful urology treatments in humans and animals, the physics of urination has received comparatively little attention. In this combined experimental and theoretical investigation, we elucidate the hydrodynamics of urination across five orders of magnitude in animal mass, from ...