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 mice to elephants. Using high-speed fluid dynamics videos and flow-rate measurement at Zoo Atlanta, we discover the "Law of Urination", which states animals empty their bladders over nearly constant duration of average 21 seconds (standard deviation 13 seconds), despite a difference in bladder volume from 100 mL to 100 L. This feat is made possible by the increasing urethra length of large animals which amplifies gravitational force and flow rate. We also demonstrate the challenges faced by the urinary system for rodents and other small mammals for which urine flow is limited to single drops. Our findings reveal the urethra evolved as a flow-enhancing device, enabling the urinary system to be scaled up without compromising its function. This study may help in the diagnosis of urinary problems in animals and in inspiring the design of scalable hydrodynamic systems based on those in nature.
Or coffee - with or without beer. :rofl:SteamKing said:I don't think this study is complete. They didn't control urination duration for beer consumption.
The "Law of Urination" states that the average time it takes for a mammal to urinate is approximately 21 seconds. This has been observed in a variety of mammals, including humans, elephants, and dogs.
The size of the bladder, the length of the urethra, and the force of the urine stream are all factors that can affect the time it takes for a mammal to urinate. Additionally, the level of hydration and the individual's physical health can also play a role.
While the "Law of Urination" has been observed in many mammals, it is not a universal phenomenon. Some exceptions have been found, such as in cats and rabbits, whose urination times are significantly shorter than 21 seconds.
The "Law of Urination" was first proposed by a team of researchers who measured the urination times of various mammals, including humans, dogs, and elephants. They found that the average urination time across these species was approximately 21 seconds.
Understanding the "Law of Urination" can help us better understand and diagnose urinary problems in humans, such as urinary retention and bladder dysfunction. It can also aid in the development of more efficient and effective methods for urinary catheterization.