The following is an excerpt from And Then You’re Dead: What Really Happens If You Get Swallowed by a Whale, Are Shot from a Cannon, or Go Barreling Over Niagara, by Cody Cassidy and Paul Doherty.

If you see a banana peel on the floor, how concerned should you be? If the cartoons are to be believed, the answer is, of course, very. Cartoons might understate banana peel danger by overstating the strength of your skull, but the cartoons aren’t kidding about the slipperiness of banana peels. Rigorous scientific study has confirmed bananas as the most dangerous of all fruit peels.

Slipperiness is measured by placing a block of a given material on a ramp of another material and then slowly increasing the angle of the ramp. The tangent of the angle of the ramp when the object starts to slide gives the coefficient of friction (CoF), and it usually scales from 0 (the slipperiest) to 1 (stickiest), though in some stickier situations it can go as high as 4.* Rubber on a cement sidewalk has a near slip‐proof CoF of 1.04.

*A CoF larger than 1 means the object slips at an angle greater than 45 degrees. The highest CoF we can find is the rubber on the tires of top fuel dragsters, which when spinning have a CoF on pavement of 4 (they could climb a 75‐degree wall).

Then there’s the other end of the spectrum. Sliding on socks across a wooden floor has a CoF of only 0.23, and ice is even slipperier. A walk across an ice rink can have embarrassing consequences because rubber on ice registers a potentially painful CoF of 0.15.*

*Lubricated surfaces have even less friction. The synovial fluid that lubricates your joints, for example, is one of the slipperiest substances in the world—registering at a CoF of .0003, which is a good thing, otherwise it would give cracking your knuckles a more literal interpretation.

Banana peels put all that to shame.

We know this thanks to a few daring professors at Kitasato University in Minato, Japan, who decided to double‐check the cartoons. Dr. Kiyoshi Mabuchi and his team peeled a bunch of bananas, threw them on a wooden floor, and stepped on them with rubber‐soled shoes (hopefully they had a spotter). Then they measured the forces involved.

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It turns out Elmer Fudd might not have been as clumsy as we all thought. Banana peels on wood have a CoF of only 0. 07—twice as slippery as ice and ve times slipperier than wood. Mabuchi and his team of researchers weren’t done, though. Was the banana peel slippery merely because of its water content? Would other fruit peels result in similar slippage?

To find out they peeled apples and tangerines and ran the same rigorous experiment: They stepped on them. The apple peel came in a distant second, at 0.1, and the tangerine peel was by far the stickiest, with a CoF of 0.225 (about the same as stepping on a wooden floor without a peel).

So if you’re walking through a fruit factory and have a choice of peels to step on, remember this: It’s not just a joke, banana peels are the worst. Under pressure, a banana peel oozes a gel that turns out to be extremely slippery. Your foot and body weight provide the pressure. The gel provides the humor.

Why is slipperiness so important? Walking is really just a series of falls and catches. With each step you fall forward, and with the next one you catch yourself and begin the process over again. Banana peels mess up the catching part. If you just stand on a slippery surface, you will probably be okay. But if you take a step, you initiate a fall. To stop it, your leading foot hits the ground with forward momentum at a strike angle of 15 degrees. If you know you’re walking on a slippery substance, you will change your gait to decrease that angle, demand less friction from the floor, and lessen your chances of taking a tumble. Stray banana peels have a way of sneaking up on you, though, and research suggests that taking a normal step on a substance with a CoF of less than 0.1 results in a fall 90 percent of the time.

[What if you’re shot from a cannon? Explore the outcome of other what-if scenarios.]

Of course, the real danger with falling is injuring your brain, an essential organ that lives high o the ground. Learning to walk upright sometime 4 to 6 million years ago was a big advancement for the human species, but it did introduce the problem of a slip‐and‐fall. If you were, say, the height of a small dog and you fell, your head would not build up enough speed to do any damage when it hit the sidewalk.* You could dance on banana peels, because the difference between falling twelve inches and hitting your head and falling six feet on the same organ is the difference between a bruise and a broken skull.

*This is where bugs really have us beat. No bug in the history of bugs has ever fallen to its death.

The force generated by an unrestrained falling adult onto something solid is more than enough to crack a skull. In ballpark terms (everyone’s head is a little different) your skull would crack with as little as an unrestrained three‐foot fall onto a hard surface. The skull is stronger in the front and back, and weaker on the sides, but even if you fall onto the stronger frontal bone, a fall of six feet is enough to crack it—especially if you pitch forward.

Either way, if you cannot protect your head from a fall of six feet, your skull would fracture. Fractures are dangerous for a few reasons, but bleeding is the big one. Your brain is a blood hog, which means cracking it results in a lot of bleeding inside, putting you in immediate and deep trouble.

Bleeding inside your skull can be far more dangerous than bleeding anywhere else. And it’s not just because you can bandage a leg wound and you can’t an internal skull bleed. It’s because your skull is a solid container carrying fragile cargo. If your head starts filling with blood, your brain gets squeezed. Too much blood within your skull creates pressure that strangles the rest of your brain and chokes o and kills critical brain functions, like remembering to breathe.

Of course your brain knows how fragile it is, and if you slip it works very hard to put something in the way to break your fall—hands, elbows, knees—anything but itself. Which is why you see more bruised butts than broken heads and why banana peels are usually funny, not lethal.

But “usually” isn’t the same as “always.” And that brings us to Mr. Bobby Leach, the English daredevil of Niagara Falls.

Since 1901, roughly fifteen people have attempted to go over Niagara Falls for the fame or the thrill (see p. XXX for what happened when they did). Five of them drowned; most never went back. (“I’d rather stand in front of a cannon and be blown to death,” responded the first survivor, “than do that again.”)

But Bobby Leach was a professional stuntman, daredevil, and circus performer who cheated death for a living. In 1906 he climbed into a steel barrel and went over the falls. He survived, although he needed six months of hospitalization to recover from two wrecked knees and a broken jaw.

Afterward, he went on to a successful lecturing career, touring the world with his barrel and posing for photos. In 1926, he was in New Zealand when he slipped on an unidentied fruit peel on a sidewalk in Auckland and gashed his leg. A few days later, Bobby Leach died from the complications.

From And Then You’re Dead: What Really Happens If You Get Swallowed by a Whale, Are Shot from a Cannon, or Go Barreling Over Niagara, by Cody Cassidy and Paul Doherty, Ph.D., published by Penguin Books, an imprint of Penguin Publishing Group, a division of Penguin Random House LLC. Copyright © 2017 by Cody Cassidy and Paul Doherty