The physics of poop: Why it takes you and an elephant same amount of time to defecate

The physics of poop: Why it takes you and an elephant same amount of time to defecate
(Image: Shutterstock, Anna Efimova)

The ancient Chinese practiced copromancy, the diagnosis of health based on the shape, size and texture of feces. So did the Egyptians, the Greeks and nearly every ancient culture. Even today, your doctor may ask when you last had a bowel movement and to describe it in exquisite detail.

Sure, it’s uncomfortable to talk about. But that’s where science comes in, because what we don’t like to discuss can still cause harm. Irritable bowel syndromeinflammatory bowel diseasegastrointestinal infections and other poop-related ailments cost Americans billions of dollars annually.

But trying to stem these problems was not our main motivation for trying to figure out some of the physics of defecation. It was something else, much more sinister.

When parenthood hits, it hits hard. One of us is a working dad who survived by learning a new set of skills, one of which was fecal analysis. Years of diaper changes and then potty training turned me from a poo-analysis novice to a wizened connoisseur. My life passes by in a series of images: hard feces pellets like peas to long feces like a smooth snake to a puddle of brown water.

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