What Makes Pop Rocks Pop?

Noshin R, Flickr // CC BY 2.0
Noshin R, Flickr // CC BY 2.0

Eating most candy isn’t complicated: You take a bite, enjoy a sugar-fueled dopamine rush, and repeat until you have a stomach ache. Chemist William A. Mitchell added another step to the process when he developed Pop Rocks. When the sweet, hard candy bits hit your mouth, they act up before breaking down, creating a crackling, hissing noise that would be alarming coming from any other food product. But when it happens to Pop Rocks, you know you’re getting what you paid for. So what exactly is it about the candy that makes it just as much of a science experiment as a sweet snack?

The answer lies in carbon dioxide. It’s the same gas that gives cola, beer, and champagne their effervescence, but it’s not a common ingredient in solid foods. In the late 1950s, Mitchell wondered if it was possible to create an instant soda tablet by baking CO2 into candy. Even though his idea didn’t take off, the experiments laid the basis for Pop Rocks.

Like other hard candies, Pop Rocks are made by mixing sugar, lactose, corn syrup, and flavorings. Once those ingredients are melted together and boiled, highly-pressurized CO2 is added. When the candy mixture hardens, it traps bubbles of gas exerting pressure at 600 pounds per square inch (psi). For reference, the pressure inside a champagne bottle measures in at 90 psi.

It’s impossible to detect the special component in Pop Rocks unless you taste them. Magical things happen when the candy meets up with your mouth: As your saliva dissolves the sugar, those powerful air pockets begin to burst like miniature firecrackers on your tongue. The 600 psi carbon dioxide collides with the 15 psi pressure of the atmosphere, resulting in a crack you can feel and hear. That’s why Pop Rocks are so noisy, whether you’re eating them or standing next to someone who is.

And if you’re worried that all that pressure will do some serious damage to your body, you can rest easy. Contrary to the hysteria from kids and parents, there’s never been a known case of death by Pop Rocks. That includes when it's mixed with Coke (sorry Mikey truthers).

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What's the Difference Between Pigeons and Doves?

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iStock

To the layman, the difference between pigeons and doves has something to with color, maybe. Or location. Or general appeal (doves usually get much better press than pigeons do). But what’s the actual, scientific difference between doves and pigeons?

As it turns out, there isn’t one. Paul Sweet, the collection manager for the department of ornithology at the American Museum of Natural History, says the difference is more linguistic than taxonomic.

“The word dove is a word that came into English from the more Nordic languages, whereas pigeon came into English from French,” Sweet tells Mental Floss.

Both dove and pigeon refer to the 308 species of birds from the Columbidae family, Sweet says. There’s no difference between a pigeon and a dove in scientific nomenclature, but colloquial English tends to categorize them by size. Something called a dove is generally smaller than something called a pigeon, but that’s not always the case. A common pigeon, for example, is called both a rock dove and a rock pigeon.

“People just have their own classification for what makes them different,” Sweet says. “So in the Pacific, for example, the big ones might get called pigeons and the smaller ones might be called doves, but they’re actually more closely related to each other than they are to other things in, say, South America, that are called pigeons and doves.”

The difference boils down to linguistic traditions, so feel free to tell people you’re releasing pigeons at your wedding or that you’re feeding doves in the park. Scientifically speaking, you’ll be correct either way.

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What Is the Wilhelm Scream?

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iStock

What do Star Wars, The Lord of the Rings, Pirates of the Caribbean, Harold and Kumar Go to White Castle, Toy Story, Reservoir Dogs, Titanic, Anchorman, 22 Jump Street, and more than 200 other films and TV shows have in common? Not much besides the one and only Wilhelm Scream.

The Wilhelm Scream is the holy grail of movie geek sound effects—a throwaway sound bite with inauspicious beginnings that was turned into the best movie in-joke ever when it was revived in the 1970s.

Just what is it? Chances are you’ve heard it before but never really noticed it. The Wilhelm Scream is a stock sound effect that has been used in both the biggest blockbusters and the lowest low-budget movies and television shows for over 60 years, and is usually heard when someone onscreen is shot or falls from a great height.

First used in the 1951 Gary Cooper western Distant Drums, the distinctive yelp began in a scene in which a group of soldiers wade through a swamp, and one of them lets out a piercing scream as an alligator drags him underwater.

As is the case with many movie sound effects, the scream was recorded later in a sound booth with the simple direction to make it sound like “a man getting bit by an alligator, and he screams.” Six screams were performed in one take, and the fifth scream on the recording became the iconic Wilhelm (the others were used for additional screams in other parts of the movie).

Following its debut in 1951, the effect became a regular part of the Warner Bros. sound library and was continually used by the studio’s filmmakers in their movies. Eventually, in the early 1970s, a group of budding sound designers at USC’s film school—including future Academy Award-winning sound designer Ben Burtt—recognized that the unique scream kept popping up in numerous films they were watching. They nicknamed it the “Wilhelm Scream” after a character in the first movie they all recognized it from, a 1963 western called The Charge at Feather River, in which a character named Private Wilhelm lets out the pained scream after being shot in the leg by an arrow.

As a joke, the students began slipping the effect into the student films they were working on at the time. After he graduated, Burtt was tapped by fellow USC alum George Lucas to do the sound design on a little film he was making called Star Wars. As a nod to his friends, Burtt put the original sound effect from the Warner Bros. library into the movie, most noticeably when a Stormtrooper is shot by Luke Skywalker and falls into a chasm on the Death Star. Burtt would go on to use the Wilhelm Scream in various scenes in every Star Wars and Indiana Jones movie, causing fans and filmmakers to take notice.

Directors like Peter Jackson and Quentin Tarantino, as well as countless other sound designers, sought out the sound and put it in their movies as a humorous nod to Burtt. They wanted to be in on the joke too, and the Wilhelm Scream began showing up everywhere, making it an unofficial badge of honor. It's become bigger than just a sound effect, and the name “Wilhelm Scream” has been used for everything from a band name, to a beer, to a song title, and more.

But whose voice does the scream itself belong to? Burtt himself did copious amounts of research, as the identity of the screamer was unknown for decades. He eventually found a Warner Bros. call sheet from Distant Drums that listed actors who were scheduled to record additional dialogue after the film was completed. One of the names, and the most likely candidate as the Wilhelm screamer, was an actor and musician named Sheb Wooley, who appeared in classics like High Noon, Giant, and the TV show Rawhide. You may also know him as the musician who sang the popular 1958 novelty song “Purple People Eater.”

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