25 Everyday Mysteries, Solved

Why Are Movie Previews Called “Trailers”?

Movie previews are called “trailers” because they were originally shown after the movie. In the early days of moviegoing, you didn’t just buy a ticket for one feature-length film and leave once the credits started rolling. You were instead treated to a mix of shorts, newsreels, cartoons, and, eventually, trailers — which, per their name, played after the movie rather than before — with people coming and going throughout the day. The idea for trailers came from Nils Granlund, who in addition to being a business manager for movie theaters worked as a producer on Broadway, which explains why the first trailer was actually for a play: 1913’s The Pleasure Seekers. Today there are production houses that exclusively make trailers and are handsomely rewarded for their efforts, sometimes to the tune of millions of dollars.

Why Does Catnip Make Cats High?

About 70% of cats are susceptible to the intoxicating effects of nepetalactone, the active compound in catnip. One whiff and these kitties are temporarily reduced to drooling, meowing messes, often rolling around in or rubbing their faces on the catnip source. That’s because nepetalactone is a volatile organic molecule that binds to receptors in a cat’s nose, stimulating neurons that activate the olfactory bulb, amygdala, hypothalamus, and other areas of the brain, causing a euphoric effect. The buzz seems to wear off after 10 to 15 minutes, leaving cats extremely chill thereafter.

Why Do We Say “the Best Thing Since Sliced Bread”?

In 1928, when inventor Otto Frederick Rohwedder of Davenport, Iowa, first released his bread loaf-slicing invention, the advertisement claimed it was “the greatest forward step in the baking industry since bread was wrapped.” Riffing on the theme, customers began to compare all later inventions to his, and the modern idiom evolved from there.  

Why Do Brides Wear White?

Walk through any bridal shop and it’s obvious that white wedding dresses are the norm, but that wasn’t always the case. Historically, brides often repurposed their best dress as their wedding gown, and most were not white — specifically because white was exceptionally difficult to keep clean prior to modern washing machines and stain removers. Queen Victoria, who wore a lacy white gown at her 1840 wedding in place of the then-popular red, is often credited for popularizing bridal white (though Mary, Queen of Scots wore white during her 1558 Notre Dame wedding, and many lesser-known royals did before Victoria’s reign). Within a decade of Victoria’s wedding, dressmakers and etiquette books had run with the idea that white was virginal and pure, with the popular Godey’s Lady’s Book writing that a white dress was “an emblem of the innocence and purity of girlhood, and the unsullied heart which she now yields to the keeping of the chosen one.”

Why Is a Week Seven Days?

The seven-day week is a timekeeping oddity. Unlike days, months, and years, the week doesn’t align with any celestial reality, and it doesn’t divide elegantly into existing periods of time. For example, there aren’t 52 weeks in an average year — there are 52.1428571429. So how did this happen? Babylonians, the ancient superpower of Mesopotamia, put a lot of stock in the number seven thanks to the seven observable celestial bodies in the night sky — the sun, moon, Mercury, Venus, Mars, Jupiter, and Saturn. This formed the seven-day week, which was adopted by the Jewish people, who were captives of the Babylonians in the sixth century BCE. Eventually, it spread to ancient Greece and elsewhere thanks to the battle-happy Macedonian Alexander the Great. Efforts have been made throughout history to reform the seven-day week, but this oddball unit of time has become ingrained in many religions, including Judaism, Christianity, and Islam, rendering any sort of tweak pretty unlikely.

Why Is the Sky Blue?

Think about the atmosphere as a prism. In a prism, white light refracts through its polished surfaces and separates into the colors of the rainbow. The sun produces white light, so when its light travels through the atmosphere, it refracts a rainbow of colors. Each color comes from an electromagnetic wave. While red has the longest, slowest wavelength, blue and violet move in quick, short waves. As these colors pass through the atmosphere, they oscillate charged particles in air molecules like oxygen and nitrogen. Blue and violet are scattered in all directions at around 10 times the efficiency of red light, so they get the highest coverage area in our sky. Our eyes are more sensitive to blue than violet, which is why we see the sky as blue.

Why Is It Considered Rude to Point at Another Person?

When assisting theme park guests, Disney employees are trained to point with two conjoined fingers, index and middle. While the act reportedly doubles as a nod to Walt Disney’s smoking, the larger explanation is that standard pointing is considered rude in numerous cultures — especially if aimed at another person. A perception that dates back to Shakespeare’s time suggests pointing brings unwanted attention to the recipient, implying that they’ve committed a wrong. Repeated pointing in Japan can even instigate hostility. And figurative “finger-pointing” is defined as “making explicit and often unfair accusations of blame.” In situations where you feel compelled to point, it is kinder to use an open palm, flight attendant-style.      

Is the “Five-Second Rule” Real?

Most people know the “five-second rule”: the idea that if food that’s fallen on the floor has been there less than five seconds, it’s still acceptable to eat. No one knows the origins of this questionable rule — and plenty of people think it’s kind of gross — but that hasn’t stopped anyone from picking up a dropped Oreo and shouting “five-second rule!” before.

Actual scientists have devoted time and resources to testing the five-second rule. And surprisingly, it’s not an entirely bogus theory — depending on the cleanliness of the floor. To be clear, no scientist has gone on record recommending that you eat dropped food. However, a science experiment conducted at the University of Illinois Urbana-Champaign proved that as long as the food was picked up within the five-second time limit, the presence of microorganisms on the dropped food was minimal. However, the experiment was conducted after first sanitizing the flooring, and it only applied to hard flooring like tile and wood, which are less likely to serve as an incubator for pathogens. No testing was conducted on carpeting and other soft surfaces, which can hold moisture and become breeding grounds for bacteria. In any case, it’s definitely not recommended to blindly follow the five-second rule. You have no way of knowing which pathogens are on your floor, so unless you regularly disinfect, it’s best to play it safe and follow another rule: When in doubt, toss it out.

Why Is It So Cold on Airplanes?

Passengers often complain about the cold temperature in airplane cabins. Flight staff will provide passengers with a blanket, but they don’t ever increase the heat. That’s because the temperature on an aircraft has been set in a very intentional way — and it’s for your safety.

A study by ATSM International found that people were more likely to faint on an aircraft than on the ground due to a condition called hypoxia. The pressurized environment of an airplane cabin can prevent our body from getting enough oxygen, which causes fainting. The warmer the temperature onboard the aircraft, the more likely this is to happen. To prevent passengers from passing out, airlines intentionally lower the cabin temperature. While this might be slightly uncomfortable, it’s much safer for your body.

Why Is New York Called “the Big Apple”?

Before it was used to refer to the city that never sleeps, “big apple” was an idiom used to mean a very big deal, an object of great desire or big dreams. The first time New York City was referred to as a “big apple” in print may have been in 1909, when American journalist Edward S. Martin wrote in his book The Wayfarer in New York that those in the Midwest are “apt to see in New York a greedy city … it inclines to think that the big apple gets a disproportionate share of the national sap.” The phrase doesn’t seem to have been intended as a nickname, however.

It was actually a horse-racing column published by the New York Morning Telegraph that popularized the term. “The dream of every lad that ever threw a leg over a thoroughbred and the goal of all horsemen. There’s only one Big Apple. That’s New York,” racing journalist John J. Fitz Gerald wrote in a 1924 column eventually called “Around the Big Apple.” However, Fitz Gerald apparently first heard the term from two Black stable hands in New Orleans. As etymologist Michael Quinion explains, “the Big Apple was the New York racetracks … the goal of every aspiring jockey and trainer … for those New Orleans stable hands the New York racing scene was a supreme opportunity, like an attractive big red apple.” The expression was later further popularized by jazz musicians in the 1920s and 1930s, then picked up in the 1970s by Charles Gillett, president of the New York Convention and Visitors Bureau, who began a tourism campaign around the slogan.

Why Do They Mist Produce at the Grocery Store?

Many grocery stores display produce in open cases fitted with tiny jets to periodically bathe the veggies in a cool mist. (Some supermarkets even pipe in the sound of thundering rain to add to the rainy vibe.) The purpose behind misting is not to keep produce clean or extend its shelf life — it’s a clever way for grocers to make the fruits and vegetables look fresher and healthier so consumers purchase more. Water clinging to leafy greens also adds weight, which increases revenue for the store when vegetables are sold by the pound.

Ironically, misting actually shortens produce’s shelf life because water allows bacteria and mold to take hold. Misted veggies will likely not last as long in your fridge as those that weren’t misted in the produce aisle — which is another, perhaps sneakier, way to get you to buy produce more often.

What’s the Difference Between a Couch and a Sofa?

Though usually used interchangeably, these are technically two different pieces of furniture — and the distinction lies in the words themselves. “Couch” comes to us from French, namely coucher — “to lie down” — whereas we have the Arabic word suffah to thank for “sofa.” In the most traditional sense, a sofa would be a wooden bench that comes complete with blankets and cushions and is intended for sitting. eBay’s selling guide used to distinguish between the two by defining a couch as “a piece of furniture with no arms used for lying.” Though it may be a distinction without a difference these days, purists tend to think of sofas as a bit more formal and couches as something you’d take a nap on and let your pets hang out on.

Why Is Pink Considered a Color for Girls, and Blue for Boys?

Originally, it was actually the other way around. For much of the 19th century, most infants and toddlers wore white dresses. Dresses facilitated diaper-changing, and white cotton could easily be cleaned with bleach. But around 1900, childcare experts began to push for a greater distinction between little girls and boys, amid fears that boys were growing up “weaker” and “lazier” than their fathers had. Many U.S. publications and stores responded in part by recommending pink clothing for boys and blue clothing for girls, although some also recommended the opposite color scheme. According to Dressmaker magazine, “Blue is reserved for girls as it is considered paler, and the more dainty of the two colors, and pink is thought to be stronger (akin to red).”

But around World War II, everything changed. Soon pink was heavily marketed as the preferred color for girls, and blue for boys. It’s not entirely clear what led to the switch, and the colors chosen were somewhat arbitrary — the focus was primarily on creating clothes specific for each child in an attempt to curb hand-me-downs, and thus sell more product. Once the 1950s began, hospitals wrapped newborns in pink or blue blankets, based on their sex (today’s standard blankets contain pink and blue stripes).

What Does the “QR” in “QR Code” Mean?

QR codes are those pixelated-looking black-and-white squares that you can scan with your phone for more information about something, whether it’s an advertisement or a piece of art. They’ve become ubiquitous, especially after the COVID-19 pandemic popularized contactless menus and payment. However, they’re very rarely called by their full name. “QR” actually stands for “quick response,” and the codes can be used to share far more than a link. If you wanted to, you could share an entire book with one code. The technology was first developed by a Toyota subsidiary in the mid-’90s as a way to track auto parts, but QR codes found new life as a way to direct smartphone users from a physical space to a digital one. They used to require a special reader, but nowadays, most smartphone camera apps will read QR codes on their own.

Why Are You Supposed to Keep Your Elbows Off the Table?

In the Old Testament, the Book of Ecclesiastes includes the line, “Be ashamed of breaking an oath or a covenant, and of stretching your elbow at dinner.” Many have translated this directive as a warning to keep elbows off the table at all times. Table manners were originally introduced to prevent mealtime fights, with the knife and fork establishing each eater’s boundary lines. Today, the elbow rule stops people from slouching or accidentally leaning their arms into food dishes. Moreover, when breaking bread with a group, placing your elbows on the table blocks those on either side of you from making eye contact.

Why Do You Cry When You Cut Onions?

There’s no need to cry over spilled milk, but what about chopped onions? You can thank a chemical combination of enzymes and sulfur for the tears that well up while you make dinner. Onions use sulfur to make a mixture of amino acids and enzymes during the growing process. The acids and enzymes are separated and stored in different regions of the onion’s cells, which are called vacuoles. While the onion remains whole, the amino acids and enzymes in the onion’s cells remain separated. Once you cut into the onion, however, everything mixes together. When the two substances are combined, they form a chemical known as syn-Propanethial-S-oxide, or lachrymatory factor (LF). LF is an irritant that’s easily vaporized when it reacts with the air.

LF isn’t strong enough to affect tougher parts of your body such as your skin, but it can irritate more sensitive regions. As the vapors waft up toward your face, your eyes will begin to sting. Your body — sensing the irritant — will release a torrent of tears in an attempt to wash the chemicals from your eyes. Luckily, LF can’t do any serious damage, even in high quantities.

Producing LF is the onion’s way of defending against anything that may want to eat it. As soon as an animal bites into the root, its eyes start to burn and it’s reminded to stay away from onions. Unfortunately for onions, humans are persistent.

Why Is February the Shortest Month of the Year?

February has fewer days because of the superstitions of ancient Rome. In the late eighth century BCE, Romans — including their king Numa Pompilius — held a superstition that even numbers were somehow unlucky. Although he created a version of a 12-month calendar, Pompilius realized there was no mathematical way for every month to have an odd number of days and for the total number of days in the year to also be odd. So while the other months were either 29 or 31 days long, February became the unlucky month to have only 28 days, making Pompilius’ calendar the apparently-less-scary number of 355.

In 45 BCE, Caesar — disregarding Pompilius’ fear of even numbers — added days to a number of other months, but not February. Some experts believe Caesar didn’t want to disrupt the important festivals that took place in that month and so he just let it be. But with the introduction of the Julian calendar, February did receive a consolation prize in the form of an additional day every four years.

What Are the Tallest Beings in the World?

With a narrow range stretching for about 450 miles, from Big Sur to southern Oregon, coast redwoods (Sequoia sempervirens) are the tallest living beings in the world — and one in particular surpasses them all. Named after a titan in Greek mythology and found in California’s Redwood National Park, Hyperion stands 380 feet tall. That’s 65 feet taller than London’s Big Ben and 10 feet taller than the previous record holder, another coast redwood.

Why Do Cats “Make Biscuits”?

A nursing kitten often presses its mom’s belly with its front paws; this kneading action stimulates the flow of milk. But many full-grown cats continue the behavior, “making biscuits” on pillows, soft blankets, towels, or their owners. Veterinarians think adult cats knead when they’re feeling safe and relaxed and to show affection to humans and other cats. The act of kneading can also calm cats, like a form of feline self-care. Making biscuits may also be a sign that a cat is marking its territory with the scent glands located between its toes.

Are Sweet Potatoes Really Potatoes?

Sweet potatoes and common potatoes share part of a name, but the two are entirely different plants — and sweet potatoes aren’t even potatoes. Sweet potatoes belong to the Convolvulaceae family, a group of flowering plants that’s also called the morning glory family. Potatoes belong to the nightshade (Solanaceae) family, and are cousins to peppers, tomatoes, and eggplants. Both species get their name from an Indigenous Caribbean term, batata, which eventually morphed into the English “potato.” By the 1740s, “sweet” was added to the orange-fleshed tuber’s name to differentiate the two root crops.

Then there are yams. Although they’re often served interchangeably with sweet potatoes, this third root crop is biologically unrelated to either sweet potatoes or common potatoes. These tubers belong to the Dioscoreacea family, a group of flowering plants usually cultivated in tropical areas. Luckily, you don’t have to know their scientific classification to distinguish between the two non-spuds at the grocery store: Sweet potatoes have tapered ends and relatively smooth skin, while true yams are generally larger with rough bark and a more cylindrical shape. At most U.S. grocery stores, what you’re seeing labeled as a yam is probably actually a sweet potato.

Does the Color Red Really Make Bulls Mad?

No — bulls can’t actually see the color. As is the case with other cattle and grazing animals such as sheep and horses, bulls’ eyes have two types of color receptor cells (as opposed to the three types that humans have) and are most attuned to yellows, greens, blues, and purples. This condition, a kind of colorblindness known as dichromatism, makes a bullfighter’s muleta (red cape) look yellowish-gray to the animals.

So why are bulls enraged by the sight of matadors waving their muletas? The answer is simple: motion. The muleta isn’t even brought out until the third and final stage of a bullfight. The reason it’s red is a little unsavory — it’s actually because the color masks bloodstains. In 2007, the TV show MythBusters even devoted a segment to the idea that bulls are angered by the color red, finding zero evidence that the charging animals care what color is being waved at them and ample evidence that sudden movements are what really aggravate the poor creatures.

Why Do We Say “Knock on Wood”?

In the United States, we say “knock on wood” (in the U.K., it’s “touch wood”) in a variety of situations, like after mentioning something we hope will happen. It’s a means of averting misfortune, making sure we don’t “tempt fate.” Some explanations for the practice mention a Celtic or otherwise pagan association with tree spirits, the idea being that knocking on wood (particularly once-sacred trees like oak and ash) might awaken these deities and confer their protection. Others note a Christian association with the wood of the cross.

But the origins of this practice are probably much more modern. In A Dictionary of English Folklore, scholars Jacqueline Simpson and Steve Roud note that the earliest known reference to the practice only dates to 1805. It seems linked to 19th-century children’s games like “Tiggy Touchwood” — types of tag in which children were safe from capture if they touched something wooden, like a door or tree. In his book The Lore of the Playground, Roud writes: “Given that the game was concerned with ‘protection,’ and was well known to adults as well as children, it is almost certainly the origin of our modern superstitious practice of saying, ‘Touch wood.’ The claim that the latter goes back to when we believed in tree spirits is complete nonsense.”

Why Does Toothpaste Make Orange Juice Taste Terrible?

Most of us have endured this unpleasant situation at least once. The culprit is a toothpaste ingredient called sodium lauryl sulfate (SLS), which produces the foam that builds during vigorous brushing. Unfortunately, SLS also temporarily blocks the tongue’s sweet receptors, while simultaneously destroying the compounds in saliva that suppress our bitter receptors. The result is a double-whammy for our sensitive taste buds, which leaves us to taste only the unsavory citric acid from what would otherwise be a refreshing drink.

Where Did the Phrase “Devil’s Advocate” Come From?

The term “devil’s advocate” is a familiar label for someone who argues a position they don’t agree with just to make a point, but its origins are more literal than you might expect. In 1587, Pope Sixtus V established the position of advocatus diaboli, or “devil’s advocate,” as part of the process of beatification or canonization — aka becoming a saint. The devil’s advocate was the church’s skeptic, picking apart stories of reported “miracles” and more to argue against someone’s sainthood. The advocate had to be present for any part of the sainthood process to be considered valid. However, the title was primarily a popular moniker — the position’s official designation was the “promoter of the faith,” or promotor fidei.

What’s the Most Expensive Item Ever Made by Humans?

The most expensive movie ever made is Pirates of the Caribbean: On Stranger Tides, which cost a whopping $410 million. That’s a pretty penny to be sure, but it’s less than half a percent of the most expensive human-made object in history: the International Space Station, whose price tag comes in at $100 billion. Launched in 1998 after more than a decade of careful (and often difficult) planning, the ISS is a collaboration between five space agencies: NASA (United States), Roscosmos (Russia), JAXA (Japan), ESA (Europe), and CSA (Canada). It has been continuously occupied since 2000, with a full-time international crew conducting microgravity experiments and other research.

Feature image credit: Illustration by Diana Gerstacker; Photo by Jake Hills/ Unsplash