Twins are something of a natural phenomenon. While scientists understand the egg-splitting process that creates twins, researchers aren’t so sure why it happens. That fascination has been with humans for thousands of years — if you need proof, just look to the night sky, where the constellation Gemini (Latin for “twins”) shows how our interest in these duos has become part of both the astronomical and astrological world. Regardless of your own twin status or horoscope sign, you can celebrate these dynamic duos with the five facts about twins below.
The World Currently Has the Most Twins It’s Ever Had
Many humans know the joy (and occasional annoyance) of having siblings. But some of us have a particularly unique relationship thanks to being half of a twin set. Being born a twin is relatively rare; in the United States, just 3.2% of new deliveries are twin births. But while that number may seem low, the world is actually experiencing the largest number of twins in known human history, largely influenced by advances in assisted reproductive technology. Researchers believe the number of twins born each year has increased over the last five decades, particularly when it comes to fraternal twins. A 2021 survey of 165 countries — about 99% of the world’s population — found that 1 in 42 babies born today is a twin, a statistic that equates to 12 twin births for every 1,000 pregnancies. That number is up from the 1980s, when just nine sets of twins were born for every 1,000 pregnancies. And it adds up — scientists believe some 1.6 million twins are born each year.
Only 1 in 3 sets of twins are identical; the remaining two-thirds are considered fraternal, essentially siblings born at the same time who may or may not look alike. But even if identical twins seemingly appear as carbon copies, they do have some differences — such as their fingerprints. The patterns on our fingertips develop in utero, and how they look for the rest of our lives is heavily affected by our environment before birth. Blood pressure, umbilical cord length, and how fast a fetus grows all impact the final print design. Because identical twins share the same DNA, it’s likely their prints will be similar, though they’ll never be duplicates. In the history of fingerprint studies, no two people have ever had matching marks, including twins.
The city of Twinsburg lives up to its name each summer, beckoning thousands of twins to northwestern Ohio to celebrate their distinctive sibling relationships. Since 1976, the Twins Days Festival has been the world’s largest gathering place for twins. Event organizers believe more than 2,145 twins (and other multiples, like triplets and quadruplets) attended the three-day fest in 2022, participating in events like the twin talent show, parade, and award ceremony. The event has also come to serve another purpose — by gathering so many multiples in one place, scientists have a chance to collect data on twins’ genetic and behavioral similarities (and differences), giving researchers more insight into how our DNA and environment may play roles in our health and well-being.
Where You’re Born Increases Your Odds of Being a Twin
While the global number of twins is higher than ever before, there’s one part of the globe that holds the record for having the highest concentration of twins. Scientists believe the west coast of Africa, which includes countries such as Benin and Nigeria, beat the odds by a landslide on twin births. Studies from the 1970s on have pointed to both countries as the twin capitals, having anywhere from 27 to 40 sets of twins per every 1,000 births. It’s unclear to researchers why twins are more abundant in that region of the world, though doctors and citizens point to possible cultural factors, like the regional diet that includes okra leaves and yams (which may have plant compounds that play a role in maternal fertility).
Similarities and differences can be an endless topic of conversation for twins, though some research suggests that twins become less alike the older they get — at least, genetically. As they grow older, twins often make contrasting life choices and have different environmental exposures (aka interactions with chemical or biological substances, like cigarette smoke or UV radiation from the sun). This can cause differences in appearance or behavior as they age, or lead one twin to develop a medical condition the other does not have. A 2005 study from the Spanish National Cancer Center analyzed blood samples from twins and found that younger twins had more identical genes than older twins, especially those who lived apart — meaning that despite being born a duo, all twins eventually blaze their own paths in the world.
Nicole Garner Meeker
Writer
Nicole Garner Meeker is a writer and editor based in St. Louis. Her history, nature, and food stories have also appeared at Mental Floss and Better Report.
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There’s something magical about train travel for just about everybody, whether you’re an engineering nerd, a hopeless romantic, a world traveler, or an easily excitable 8-year-old. Trains have gone through a lot of changes in the last few centuries, but they remain one of the most common modes of transportation throughout the world.
How did trains work before steam power? Who managed to crash more than 140 trains in his lifetime? Which trains are creating homes for marine life off the coast of Delaware? All aboard for these nine facts about trains.
Before 1833, local time was all over the place; communities set their clocks to noon when the sun was highest in the sky, which led to at least 144 different local times in North America. This wasn’t a huge deal when people were traveling slowly by foot and horseback, but with trains, people could suddenly travel across wider distances more quickly — and train operators needed consistent schedules to coordinate. Even small miscommunications about time could lead to missed connections and accidents. Railroads established a four-time-zone system in 1833, and used it for decades before the U.S. government officially established time zones in 1918.
Japan’s bullet trains are known for their lightning speed, but a handful of trains have eclipsed them — one of them being Shanghai’s maglev train, which uses magnetic levitation instead of wheels on conventional tracks. Its entire 19-mile run takes just seven and a half minutes, reaching top speeds of 286 miles per hour.
That’s just the tip of the iceberg for maglev trains. The fastest recorded train speed is nearly 375 miles per hour, clocked during a test run of a maglev train in Japan.
The earliest railroad tracks were for horse-drawn trains, not locomotives. The tracks provided extra support and guidance, which meant that horses could carry greater loads. After the Liverpool and Manchester Railway opened with a steam-powered locomotive in 1830, jokes and cartoons about unemployed horses abounded, although horses were still used for shunting — moving trains from one line to another. Horses continued to haul streetcars into the 20th century.
Credit: George Rinhart/ Corbis Historical via Getty Images
America’s First Locomotive Reportedly Lost a Race to a Horse
When the Baltimore & Ohio Railroad — you might know it as the B&O Railroad — began operations in May 1830, it used only horse-drawn carriages. Steam locomotives were in use in Britain already, but because the planned system in America had steep hills and sharp curves, some engineers doubted that the machines could handle the route. This concerned B&O directors, so they turned to an inventor named Peter Cooper to see if he could create an engine that was up to the task. He cobbled one together out of scraps, including an old brass engine, discarded wheels, and musket barrels. Later dubbed “Tom Thumb,” it performed beautifully along a 7-mile test run, then again on a 13-mile test, reaching a then-impressive 18 miles per hour.
According to an 1868 lecture at the Maryland Institute by B&O lawyer John H.B. Latrobe, who was present on the 13-mile test, Tom Thumb also took part in a bit of a race. The owners of a stagecoach company saw the engine running along the track and challenged Cooper to a race along double tracks. The engine got an early lead, but a part slipped off, causing it to come to a halt. It was a quick fix, but by the time Cooper got going again, the horse was too far ahead. Losing the race didn’t have any effect on Tom Thumb’s future, though — he’d already impressed the B&O directors, who were determined to make the locomotive the way of the future.
In Victorian Times, Trains Were Considered Hazardous to Your Health
As train travel was starting to get popular in the mid-19th century, rumors spread — among doctors and nondoctors alike — that trains were dangerous, and not because of crash risks. All sorts of woes were attributed to the speed and roughness of locomotive travel. Some believed it could trigger insanity and create “railway madmen.” Others claimed it could cause miscarriages or upset women’s delicate constitutions. One doctor said that a train trip made a patient’s “brain congestion” worse, even though he’d been feeling better after treatment with leeches.
Credit: Mario Tama/ Getty Images News via Getty Images
New York’s MTA Turned Decommissioned Trains Into Artificial Reefs
When trains in New York City’s subway system get decommissioned, they can be sold, scrapped, or repurposed. Many of them can then be found on the ocean floor, providing homes for marine life as artificial reefs. Some car models work better than others; the Redbird cars, made of carbon steel, worked so well that states started competing for them. Redbird Reef in Delaware is home to around 700 such decommissioned cars, and they created a thriving ecosystem in an area that used to be barren. The stainless steel Brightliner cars, on the other hand, disintegrated almost immediately underwater — the material was vulnerable to corrosion, and their corrugated texture made it easy for currents to rip them apart.
It’s no fun getting caught at a railroad crossing and waiting for a long freight train to pass. But next time it happens, you can thank your lucky stars it’s not 4.57 miles long, like one train that ran in Western Australia in 2001. It was both the longest and heaviest train recorded. Pulled by eight locomotives, the 682 ore cars made a 171-mile journey transporting iron ore from a couple of mines run by mining company BHP to Port Hedlund.
Before there was demolition derby, there were staged, head-on train collisions. From the 1890s through the 1930s, train crashes were a popular attraction at fairs and festivals, drawing tens of thousands of spectators. One of the biggest wrecks was an 1896 publicity stunt in Waco, Texas, for a struggling railroad line known as the Katy Railroad. The company offered rides to the crash site for $2 from anywhere in Texas, and built a temporary town around the viewing area, complete with a restaurant and jail. The crash itself created a massive explosion, which sadly killed two people in the crowd.
This is just one of the most famous out of hundreds of on-purpose train collisions. The most prolific train-wrecker was Joe Connolly, otherwise known as “head-on Joe.” Between 1896 and 1932, Connolly staged 70 wrecks and destroyed 146 locomotives — at least. He became an engineer of chaos, coming up with extra stunts such as strapping dynamite to the trains. The practice, which came to be viewed as wasteful, fell out of favor during the Great Depression.
It Takes Almost a Week To Ride the Full Trans-Siberian Railroad
The longest single-train ride in the world is the Trans-Siberian Railroad. The main track starts in Moscow and travels 5,772 miles through diverse Russian landscapes before arriving in Vladivostok, a large port city on the sea of Japan. The full journey takes more than six days.
Other routes on the network are the Trans-Mongolian Railroad, which heads through Mongolia to Beijing, China, and the Trans-Manchurian Railroad, which dips down into northeastern China before meeting the main line back in Vladivostok.
Sarah Anne Lloyd
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Sarah Anne Lloyd is a freelance writer whose work covers a bit of everything, including politics, design, the environment, and yoga. Her work has appeared in Curbed, the Seattle Times, the Stranger, the Verge, and others.
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You may think your upstairs neighbor’s 1 a.m. vacuuming session is noisy, but it’s nothing compared to what nature (and the occasional human-made marvel) can throw at us. Sounds can injure your ear immediately once they reach 120 decibels, the typical volume of a police siren if you’re right beside it, but the loudest sound ever recorded was more than 300, loud enough to increase atmospheric pressure to a point that causes damage to far more than just human ears.
Decibels are logarithmic measures of sound intensity — so keep in mind that the scale gets exponentially bigger as the number goes up. Doubling the volume on your stereo does not even come close to doubling the decibel output. So when an undersea creature produces a noise around 30 decibels higher than the loudest rocket launched by NASA (true story), you know you have a seriously big sound on your hands.
Which natural phenomenon produced the loudest known sound? What widely misunderstood sea giant generates an ear-shattering kind of Morse code? Just how loud is an asteroid impact? These six giant sounds will put that garage band next door in some serious context.
The loudest sound ever recorded was an 1883 volcanic eruption on the Indonesian island of Krakatoa, clocking in at an estimated 310 decibels. Not that anybody who heard the explosion at full blast lived to tell the tale; it was estimated to have a force equivalent to 10,000 times that of the atomic bomb dropped on Hiroshima, Japan, in 1945, and destroyed most of the island while shooting unstable clouds of hot gas to the surrounding area.
However, plenty of witnesses farther away did survive — and there were a lot of them. Some 100 miles away in North Jakarta, the noise still reached around 172 decibels. Violent tsunamis shook the Indian Ocean, and the waves even rocked boats in South Africa. Atmospheric pressure spikes reached as far as England, and a cloud of ash bathed an area of 300,000 square miles around the volcano in darkness. The global temperature even dropped, and didn’t return to normal until five years later.
The closest we’ve come to a repeat of Krakatoa was likely the Hunga Tonga-Hunga Ha’apai eruption near the Polynesian island of Tonga in January 2022. Sonic booms were felt as far north as Alaska, and researchers more than 6,000 miles away at Boise State University in Idaho recorded subterranean frequencies equivalent to about 100 decibels. The force, which was about half that of Krakatoa, sent a wave of pressure around the globe.
Fortunately, this blast wasn’t nearly as deadly, with three fatalities recorded compared to Krakatoa’s estimated 36,000. Still, it wreaked a lot of havoc. Tonga was largely cut off from the rest of the world for days, ash blanketed large swaths of the surrounding area, and tsunamis caused major damage along the coastlines. On one of the closer outlying islands, all the homes were destroyed. The volcano had created its own new island several years before; that was entirely obliterated, along with large chunks of two nearby islands.
Planet Earth is full of loud animals. Howler monkey cries can be as loud as gunshots, for example, and some species of bats emit high frequencies that could be harmful to us if they were low enough to hear. But nobody holds a candle to the sperm whale, whose clicks and calls have been measured as high as 230 decibels. That number drops significantly if the sound is traveling through air, but at 170 decibels, it’s still ear-shattering.
Scientists had thought for a long time that sperm whales were silent, but whalers had long told stories of what sounded like knocking on ships’ hulls when sperm whales were present. Once scientists listened to sperm whales with an underwater receiver, they thought the “muffled, smashing noise” was coming from inside the ship at first, before realizing they were picking up the atypical sounds of sperm whales, which don’t have the song-like quality of other species.
These Morse code-like clicks, used by sperm whales to communicate with one another, form an elaborate language, including phrases of clicks called codas. Different groups of whales even have different dialects within their codas. In addition to their communicative clicks, sperm whales also send out waves of sound at multiple frequencies as a form of echolocation while hunting their favorite food: giant squid.
You’ll often see explosions compared to the force of a nuclear blast — but no blast was bigger than Tsar Bomba, aka Big Ivan, a Soviet thermonuclear bomb detonated as a test on a small island in the Arctic Ocean in 1961. It was at least 3,300 times more powerful than the United States bomb dropped on Hiroshima in 1945, although its potential capacity was twice that. The flash was seen more than 600 miles away, and monitors as far away as New Zealand recorded three rounds of pressure waves.
As for the sound itself: A cameraman recording the event described it as “a remote, indistinct and heavy blow, as if the Earth has been killed.” The blast is typically referred to in terms of its force rather than its decibel level, but 224 decibels is a common estimate.
It’s no secret that rocket launches are really, really loud, but the Saturn V rocket, launched in the 1960s and 1970s during the Apollo program, was notoriously noisy. In testing, it measured as high as 204 decibels, although NASA notes that it typically maxed out at 195 — still plenty noisy enough to be dangerous.
Legends have circulated about this noise, some of them myths. It didn’t melt the concrete underneath it or start grass fires a mile away. Still, launch viewers had to stand around 3.5 miles away from the pad for their own safety.
NASA’s new Space Launch System (SLS) rockets will be even louder and more powerful, but the launch pads will have built-in sound dampening capabilities, using around 450,000 gallons of water that will rush onto the pad at launch to protect both eardrums and the equipment itself.
Asteroid impacts, like the 2013 Chelyabinsk Event, have created some of Earth’s biggest sounds, but the 1908 Tunguska Event in Siberia is perhaps the most legendary. Scientists believe that a space rock around 120 feet in diameter entered Earth’s atmosphere at about 33,500 miles per hour. After the resulting heat and pressure destroyed the rock itself, it became a fireball, releasing a destructive level of energy with no impact crater. Researchers were able to track ground zero from the pattern of the trees in the decimated forest around it; they fanned out radially away from the crash site until the very center, where trees stood upright, but entirely stripped of bark and branches.
One witness describes the impact’s sound as “a mighty crash… followed by a noise like stones falling from the sky, or of guns firing.” He had been working at a trading post 40 miles from the impact, and had been knocked out of his chair by a heat blast that made him feel as if his shirt was on fire. Later, scientists would estimate the sound of the blast at around 197 decibels.
Sarah Anne Lloyd
Writer
Sarah Anne Lloyd is a freelance writer whose work covers a bit of everything, including politics, design, the environment, and yoga. Her work has appeared in Curbed, the Seattle Times, the Stranger, the Verge, and others.
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The human body holds a host of extremes. The smallest muscles and bones stretch only a few millimeters, while other structures could wind around the Earth twice. Some organs in the body are completely vestigial, their use rendered obsolete by evolution, while others are largely responsible for what makes us human. These six facts explore those biological extremes, and illuminate the importance of the tiniest bones as well as the most vital organs.
The Smallest Muscle Stabilizes the Body’s Smallest Bone
The smallest muscle and the smallest bone in the human body form a convenient pair. The inner ear is home to the body’s three smallest bones, known collectively as the ossicles. Taken together, these bones are about the size of an orange seed, but the stapes is the smallest of them all. The stapes, which means “stirrup” in Latin (a reference to its shape), is essential to human hearing. Sound initially vibrates the tympanic membrane, otherwise known as the eardrum, and then travels through the ossicles. The stapes is the last bone in this chain, and causes a wave of fluid to generate in the inner ear that begins a process of converting sound waves into electrical signals that can be read by the brain. This incredibly tiny bone is supported by an equally tiny muscle called the stapedius. At less than 2 millimeters long, the stapedius is the smallest muscle in the human body.
There are some surprising lengths packed inside the human body. There’s the small intestine, for example, which could stretch 22 feet end to end (though hopefully it never has to). Not to be outdone, our nerves could stretch 37 miles if laid end to end. However, none of this compares to our circulatory system. According to the British Heart Foundation, the veins in an adult human could stretch an astonishing 60,000 miles — that’s farther than it takes to circumnavigate the globe twice. Capillaries, which transport blood between arteries and veins, make up 80% of this length.
Even Ancient Greeks Knew About the Body’s Smallest Organ
The smallest organ in the human body is located in a place you’d never think to look — the brain. The pineal gland, named after its pinecone-like appearance, is in charge of regulating our circadian rhythm by secreting melatonin. The Greek physician Galen originally named the pineal gland in the second century CE, and believed it regulated the flow of “psychic pneuma.” Descartes elaborated on the pineal gland’s function in the early 17th century, believing it was the point of contact where the soul met the body and was primarily where thoughts were formed. The gland’s true powers weren’t discovered until 1958.
The Heel Hosts the Most Variety of Fungus of Any Body Part
Not every bodily superlative is a happy one. In 2013, scientists analyzed the human body to discern what nook or crevice played host to the greatest variety of microscopic fungi. After conducting close inspections of palms, feet, toenails, groins, nostrils, and more, the researchers determined that the human heel is the body part most ripe with fungi. The heel of the foot contains 80 different types of fungi, and that number only increases when you include the rest of the foot, as toenails were found to provide refuge for 60 types of fungi (the space between toes adds another 40). While not all fungi are necessarily harmful, about half of them can be, and these numbers may help explain why feet are prone to fungal infection such as athlete’s foot.
There are 206 bones in the average adult human body, and our hands take up the lion’s share. Each hand is home to 27 bones, along with 34 muscles and 123 ligaments. Some experts estimate that a quarter of the motor cortex, the part of the brain responsible for voluntary movement, is devoted to the manipulation of our hands alone.
Although hands are impressive structures, they only just beat our feet by one measly bone. Because Homo sapiens’ primate ancestors walked on all fours, human hands and feet developed in similar ways. In fact, almost every bone in the palm is arranged in a pattern similar to the metatarsals in the foot. The only exception is a bone located at the edge of the wrist called the pisiform, which attaches various ligaments and tendons.
The Largest Lobe in the Brain Is What Makes Us Human
The frontal lobe is the largest lobe in the human brain, with studies placing its size between 25% to 40% of the cerebral cortex. Although all parts of the human brain work together, the frontal lobe is the region most associated with distinctively human characteristics such as language, creativity, and abstract thought. That’s why common systems of illnesses or injuries affecting the frontal lobe can affect someone’s personality, behavior, and in some cases, memory.
A famous medical case representing early investigations into the importance of the frontal lobe happened when a 19th-century railroad worker named Phineas Gage was severely injured after a premature explosion drove an iron bar through his skull. Though he survived the experience, Gage’s personality was irreparably altered to an almost childlike state, and his friends and family declared he was “no longer Gage.” His condition upended long-standing theories regarding the relation of the human mind and the brain, and today the case remains one of the greatest medical curiosities in history.
Interesting Facts
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Interesting Facts writers have been seen in Popular Mechanics, Mental Floss, A+E Networks, and more. They’re fascinated by history, science, food, culture, and the world around them.
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Is your stove keeping secrets from you? It’s quite possible. Manufacturers of modern appliances have packed their products with new and useful “hidden” features that may not be apparent unless you pore through the entire manual. Here are some secret hacks you may not know about your everyday appliances.
If you throw everything but the kitchen sink into your dishwasher, you may appreciate this. Many dishwashers now come with dedicated bottle jets that make cleaning bottles with long narrow necks an absolute breeze. (This feature is especially beloved by homebrewers who bottle their own beers.)
Curious children and appliances are a bad mix. As of March 2023, UL (formerly known as Underwriters Laboratories, which certifies products as safe) has a new standard that requires microwaves to have “a two-step process for opening microwave doors to help mitigate the risk of children being burned or scalded by cooked food.” (UL standards aren’t legally required, but manufacturers who want their certification must comply.) Some regular (i.e., nonmicrowave) ovens also have lock settings.
From sundown on Friday until sundown on Saturday, observant Jews are prohibited from doing any “work” on the holy day of rest (Shabbat). Manipulating electricity (by, say, switching a light off or on) is defined as work. Enter, appliances that can be set to “Sabbath mode.” In this setting, refrigerator lights will not come on when the door is opened, water and ice dispensers are disabled, ovens remain at a constant temperature, appliances do not beep or display temperature, and elevators stop at every floor.
Many (but not all) modern front-loading dryers and some washing machines offer flexibility and convenience by having reversible doors. If your laundry room setup doesn’t work with your current appliances and you’d like to reverse the direction the door opens, simply consult your manual and move the hinges to the other side.
Cleaning an oven is enough of a pain without contorting yourself around the oven door. Fortunately, most ovens and ranges have doors that are designed to lift off easily for better access, so you can clean and make minor repairs without awkward bending. Look for the latches attached to the hinges at the bottom of your door, disengage them, close the door about three-quarters of the way, and then simply lift up and out!
Many modern electric and induction cooktops now boast “melt and hold” functions. Melt allows for slow, gentle warming of things like chocolate, bringing them slowly to the desired temperature without the fuss of a double boiler or constant stirring. The “keep warm” function — often a small, separate burner toward the back of the cooktop — then keeps things nice and toasty … perfect for nacho cheese sauce while watching the big game.
Everyday spills and build-up disappear quickly and easily when using the steam clean feature on your oven. Operating at a lower temperature and for less time than a regular self-cleaning cycle, this function simply requires putting a cup or so of water in the bottom of a cold oven, selecting the setting, and then walking away. An hour or so later, oven grime is loosened, softened, and ready for wiping easily away.
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Interesting Facts writers have been seen in Popular Mechanics, Mental Floss, A+E Networks, and more. They’re fascinated by history, science, food, culture, and the world around them.
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From the shimmering green of leaves on a forest tree to the deep azure of the oceans, vibrant color fills our world — but it’s more than just pretty to look at. Often there are fascinating stories behind the colors that exist both in nature and in human artifacts, whether they’re school bus yellow, Golden Gate Bridge orange, or the blue-green of surgical scrubs. Below, we’ve rounded up some of our most dazzling stories about color from around the rainbow (and beyond).
The word “orange” refers to both a citrus fruit and the color of said fruit, so which usage came first? The color isn’t exclusive to the fruit, of course, but the term did come from it. The first use of “orange” as a color in English dates back to the 15th century, and was derived from pomme d’orenge, the French word for the citrus.
“Orange” started appearing in written English works as a color around the 16th century. Before that, English speakers just described it as “yellow-red.” Renowned 14th-century author Geoffrey Chaucer didn’t even have a singular word to describe a fox in his famous work The Canterbury Tales: “His colour was bitwixe yelow and reed [sic].”
Hollywood Uses Green Screens Because of Human Skin Tones
If you’ve seen any big-budget Hollywood film, it probably used some variety of green screen-enabled special effects. In fact, some version of green screen technology, also known as “chroma keying,” has been around since the early days of film. The reason why screens are green is actually pretty simple — human skin is not green. When a camera analyzes chrominance, or color information, it can easily separate green (or blue) from the rest of the shot so that a video backdrop can be inserted.
After only a few weeks of life, babies begin to distinguish their first color (after white and black) — red. Humans perceive color thanks to three types of cones found in our eyes, each tuned to short (blue), medium (green), and long (red) wavelengths. Although cones perceive color from birth, it takes time for the human brain to make sense of those inputs. Because an infant’s vision is blurry during the first few weeks of life, red is the only color capable of being captured by the retina when viewed around 12 inches from a baby’s face. At around 2 months old, babies can begin to distinguish between reds and greens, followed closely by yellows and blues a few weeks later.
Researchers estimate that some 300 million people around the world are colorblind, most of them male. On the opposite end of the spectrum are those with an exceedingly rare genetic condition that allows them to see nearly 100 million colors — or 100 times as many as the rest of us. It’s called tetrachromacy, or “super vision,” and it’s the result of having four types of cone cells in the retina rather than the usual three. Because of the way the condition is passed down via the X chromosome, the mutation occurs exclusively in women.
One tetrachromat describes her ability this way: “If you and I look at a leaf, I may see magenta running around the outside of the leaf or turquoise in certain parts where you would just see dark green. Where the light is making shadows on the walls, I’m seeing violets and lavenders and turquoise. You’re just seeing gray.” In short, tetrachromats see colors within colors, and even the tiniest change in the color balance of a particular hue will be apparent to them. It’s estimated that 12% of women have a fourth retina cone, but only a fraction of them experience tetrachromacy. In total, only about 1% of humans have the condition.
Picture a rainbow, which comprises the visible spectrum of light, and you’ll notice that black isn’t in it. Scientifically speaking, black is the absence of light, and because light is required for color, black contains no color. (Black’s opposite, white, is the total of all colors of the visible spectrum.)
However, people usually think of black as a color in an artistic sense: as a pigment that absorbs visible light and reflects almost none, approximating the absence of light. Thus, the “black” we see is really a reflection of a mix of very dark colors. Here’s another mind-bending fact: Nothing in nature can be pure, absence-of-light black except the inner reaches of a black hole (although researchers have come close with Vantablack and other materials).
Between 6,000 and 10,000 years ago, all humans had brown eyes, until a single genetic mutation caused one human to be born without the usual brown-black melanin pigment that colors irises brown. Irises without this pigment experience what’s known as the Tyndall effect. Because of blue’s short wavelength, that spectrum of light is reflected most by the fibers in the iris, causing eyes to take on a bluish color even though there is no blue pigment present. Today about 10% of the world’s population has blue eyes, though that number is skewed heavily by northern Europeans. In Finland and Estonia, for example, 89% of people have blue eyes — the highest percentage in the world. The U.S. comes in much lower, at around 27%.
Human Eyes Are Most Sensitive to the Green Wavelength of Light
Electromagnetic radiation comes in a variety of types, including radio waves, gamma rays, and visible light. The human eye can perceive wavelengths around 380 to 740 nanometers (nm), also known as the visual light range. The size of the wavelength determines the color we see: For example, at 400 nm our eyes perceive the color violet (hence the name “ultraviolet” for wavelengths directly under 400 nm), whereas at 700 nm our eyes glimpse red (but can’t see the “infrared” wavelengths just beyond it).
In the middle of this spectrum of visible light is the color green, which occupies the range from 520 to 565 nm and peaks at 555 nm. Because this is right in the middle of our visual range, our eyes are particularly sensitive to the color under normal lighting conditions, which means we can more readily differentiate among different shades of green. Scientists have also found that the color green positively affects our mood in part because our visual system doesn’t strain to perceive the color — which allows our nervous system to relax.
Glimpse a fleet of buses parked at any U.S. public school, and you’ll notice they’re all the same deep yellow — and it’s been that way for nearly a century. In an effort to standardize school bus construction around the country, thus ideally making them both safer and cheaper to mass-produce, school transportation officials met at Columbia University in 1939 to discuss a universal color for these vehicles. Fifty shades were hung up on the walls, ranging from lemon to deep orange. The color that was finally selected — known today as National School Bus Glossy Yellow, or Color 13432 — was chosen because of its ability to stand out from the background. Education officials didn’t know it at the time, but Color 13432 is wired to capture our attention, as the shade stimulates two of the three types of cones in the human eye — sending double the transmission to the brain compared to many other colors. That’s one reason a big yellow school bus is just so hard to miss.
Look at your arm, and you’ll see blue veins crisscrossing just beneath the skin. That’s an optical illusion. Human veins are not blue, and are actually transparent. While deoxygenated blood is a darker hue of red (which you’ve likely seen if you’ve ever donated blood or had blood drawn), the blue color comes from your skin scattering light, so that we perceive the veins beneath the skin as blue. The color perception of veins can also change depending on skin tone, as darker skin will turn veins more of a greenish color. While blue blood doesn’t occur naturally in humans, it is found in animals such as the horseshoe crab (whose blue blood has saved countless human lives). This family of crab sports blue blood because it contains copper pigments instead of iron.
The Golden Gate Bridge’s Orange Color Wasn’t Planned
San Francisco’s Golden Gate Bridge, completed in 1937, has a bright earthy tone dubbed “international orange” — but when construction began in 1933, it was on track to be a boring, standard bridge color like black or silver (although the Navy also suggested yellow and black stripes so that it would be highly visible for ships). Consulting architect Irving Morrow noticed that some of the beams were primed in a reddish-orange color, and made it his personal mission to bring a similar shade to the finished product.
The warm color, he argued, was uniquely suited to San Francisco. It would stand out even on foggy days, and when the sun was out, the hue would pop against the blue sky and water. Such a distinct look would highlight the massive scale and stunning architecture of the bridge.
Morrow made his case to the Department of War, the permitting agency for the bridge, in 1935, and successfully convinced them. Today, the color gets touched up in small segments, since repainting the whole bridge would be a massive undertaking.
Want to replicate the bridge’s tone in your own home? The exact mix is on the bridge’s website.
According to Astronomers at Johns Hopkins, the Color of the Universe Is “Cosmic Latte”
We tend to think of space as cold and dark, but that’s only because most stars are light-years away from the pale blue dot we call home. The universe is actually quite bright on the whole, and its color has been given an appropriately celestial name: “cosmic latte.” In 2002, astronomers at Johns Hopkins University determined the shade after studying the light emitted by 200,000 different galaxies. They held a contest to give the result — a kind of creamy beige — its evocative moniker. (Other entries in the contest included “univeige” and “skyvory.”)
As with just about everything in the universe, however, the color isn’t fixed: It’s become less blue and more red over the last 10 billion years, likely as a result of redder stars becoming more prevalent. In another 10 billion years, we may even need to rename the color entirely.
The sun sends its rays to Earth as white light, meaning they contain everything in the color spectrum (red, orange, yellow, green, blue, indigo, violet). But blue is unlike the other colors, because its specific wavelength (between 450 and 495 nm) is more frequently scattered by particles in the atmosphere in a process known as Rayleigh scattering. At midday, the sky is pale blue as the sun’s light travels through less of the atmosphere, but as the sun heads toward the horizon, the sky becomes a richer blue because light travels through more of the atmosphere (thus scattering more blue light).
However, this is only half of the answer, because indigo and violet have even shorter wavelengths than blue, which raises the question: Why isn’t the sky violet? Figuring out this conundrum means taking a closer look at the human eye. The cones inside the eye are coded to perceive red, green, and blue, and it’s the combinations of these inputs that determine variations of color. Because of the eye’s sensitivity to the color blue, the sky takes on that particular hue instead of violet. Other animals likely perceive the sky (and the rest of the world) in a different hue because most mammals have only two different types of cones.
Yellow Pages Were Created Because a Printer Ran Out of White Paper
One day in 1883, Cheyenne, Wyoming-based printer Reuben H. Donnelley was busy printing the latest edition of the phone directory when he unexpectedly ran out of white paper. Unwilling to put off production until he could restock, he instead resorted to finishing the job with yellow paper, unknowingly creating an icon of the then-nascent information age. After subscribers commented on how these yellow pages were easy to find amid piles of white-hued publications, Donnelley produced the first official Yellow Pages phone book three years later. Using the color yellow for telephone business directories then became the norm around the world.
Purple is the least common color found on national flags (gracing only the banner of the Caribbean country Dominica), while red is the opposite, and can be found on a whopping 74% of flags, according to Guinness World Records. Around 50% of these flags use red to represent the blood of those who fought for the country, extolling the virtues of bravery and valor. This includes the U.S. flag, with the red standing for “hardiness and valor.” Meanwhile, when red is considered alongside vexillology’s second-favorite color, blue, only nine countries in the world (out of 196 total) have flags without red and/or blue in them.
No One Is Sure Why the Backstage Room Is Called a “Green Room”
One early reference to a “green room” in the sense of a waiting room appears in TheDiary of Samuel Pepys, the famed journal kept by a civil servant in 1660s London. Pepys mentions a “green room” when going to meet the royal family — likely a reference to the color of the walls. A “green room” was then tied to the theater in English playwright Thomas Shadwell’s 1678 comedy A True Widow, which includes the line: “Selfish, this Evening, in a green Room, behind the Scenes.” However, Shadwell doesn’t mention why it was called a green room. One notable London theater did have a dressing room covered in green fabric, but other theories behind the term reference actors going “green” because of nervousness, amateur or young (aka “green”) actors, or a place where early actors literally waited “on the green” lawns of outdoor theaters — among many other ideas. It’s possible we’ll never know the origin of the phrase for sure.
Pink Was Once Considered a Color for Baby Boys, While Blue Was for Baby Girls
Before pink and blue, there was white. For much of the 19th century, most infants and toddlers wore white dresses regardless of their biological sex. Dresses facilitated diaper-changing, after all, 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). All of this likely didn’t matter much to the babies themselves: Research has shown that children generally do not become conscious of their gender until age 3 or 4.
Our eyes perceive color in the visible spectrum due to particular wavelengths, and violet is the shortest, at 380 nm. This is why the invisible wavelengths just below this threshold are known as ultraviolet, or UV rays (and why wavelengths directly above 700 nm are known as “infrared”).
The color purple, however, is what physicists call a “nonspectral color,” meaning it isn’t represented by a particular wavelength of light, but is instead a mixture of them as perceived by our brain. While some people use violet and purple interchangeably, the two colors are distinct; violet (which is part of the visible spectrum) has a more bluish hue, whereas purple is more red. The cones in our eyes receive inputs, and our brain uses ratios of these inputs to represent subtleties of color. Purple is therefore a complete construction of our brain, as no wavelength represents the color naturally. But purple isn’t alone — the same can be said for other colors such as black and white, as well as particular hues mixed with gray scale, such as pink and brown.
Although the sky is blue throughout the year, it’s often a richer blue in the fall and winter, especially in latitudes farther from the equator. Why? Well, the answer has to do with both electromagnetism and the biology of the human eye. As a refresher: When sunlight enters Earth’s atmosphere, gas and dust particles reflect the shorter wavelengths of visible light (such as blue) more than longer wavelengths (such as red). That — and the sensitivity of the human eye to the color blue — is why the sky appears as a cool sapphire.
However, as the seasons progress, one part of this equation changes: the sun’s position. As the sun gets lower and lower in the sky during its annual journey back toward the equator (and eventually the Tropic of Capricorn), the angle of the sun’s light hitting the atmosphere causes even more blue light to scatter, while red and green light decrease. That causes the sky to turn an even richer blue. These blue skies are especially easy to see in much of North America as cooler temperatures mean less moisture (and therefore fewer clouds), giving you an uninterrupted view of that deep azure atmosphere.
Walk into any hospital (or watch any medical drama), and surgeons are almost always wearing bluish-green scrubs. Because blue and green are far removed on the color spectrum compared to red, these cooler colors help refresh a surgeon’s eyes when operating on a patient (whose insides are essentially various shades of red). Because surgeons are visually focused on red-hued environments, glancing at a white background (the chosen hospital color of times past) can leave a ghostly green after-image, much like what your eyes experience after a camera flash. However, if the surrounding environment is green, then those after-images simply blend into the background.
In Elizabethan England, It Could Be Illegal To Wear Purple
From ancient times until as recently as the 19th century, the color purple was closely associated with royalty — often because they were the only class that could afford such luxury, which was extremely expensive to produce in the days when the color was still made from sea snails. Persian kings and Egyptian rulers wore the illustrious hue, and Julius Caesar similarly donned a purple toga, setting a 1,500-year-long trend for subsequent emperors in Rome and Byzantium.
The color was so intimately tied with the ruling class that the children of kings, queens, and emperors were said to be “born to the purple.” By the 16th century, however, things slowly began to change, as a wealthy merchant class began snatching purple-dyed garments of their own. In 1577, fearing that such lavish spending on “unnecessary foreign wares” could bankrupt the kingdom, Queen Elizabeth I passed sumptuary laws that essentially outlined a strict dress code based on class. Of course, the color purple (and crimson) was reserved for her majesty and her extended royal family, “upon payne to forfett the seid apparel.”
Scientists Recently Created the World’s Whitest Paint
In April 2021, scientists from Purdue University revealed a new shade of white paint. At first glance, it may look like any other plain white hue found at the local paint store. But unlike those other pigments, Purdue’s white paint reflects 98.1% of the sun’s rays. (Most white paints, by contrast, reflect only about 80% to 90%.)
According to Guinness World Records, that reflective ability makes the paint the whitest white that’s ever been created. And what Purdue’s hue lacks in chromatic sophistication, it more than makes up for in utility. According to The New York Times, if 1% to 2% of the world’s surface (about half the size of the Sahara) could be coated with this ultra-white paint, “the planet would no longer absorb more heat than it was emitting.” Although painting half the Sahara is not in the cards, painting the many, many rooftops that dot the world could help fight our current planetary fever while also cutting A/C costs. At midday, for example, the new paint makes surfaces 8 degrees Fahrenheit cooler than the surrounding ambient air temperature.
Colorblindness is relative. Just as we can perceive hues that dogs can’t, hummingbirds can see colors that humans can’t. Whereas the three types of color-sensitive cone cells in our eyes allow us to see red, green, and blue light, hummingbirds (and most other birds) have a fourth type of cone attuned to ultraviolet light. In addition to UV light, birds may even be able to see combination colors like ultraviolet+green and ultraviolet+red — something we mere humans can only imagine. Having four types of cones cells, known as tetrachromacy, is also common in fish and reptiles, and researchers believe that dinosaurs possessed it as well.
Being able to see this way is especially useful for hummingbirds, whose endless quest for sugar is aided by their ability to discern different-colored flowers — including “nonspectral” colors that combine hues from widely different parts of the color spectrum. Purple is the only nonspectral color we humans can perceive (it involves both blue and red, or both short and long wavelengths of light), but some birds might see as many as five: purple, ultraviolet+red, ultraviolet+green, ultraviolet+yellow, and ultraviolet+purple.
If the very idea of bullfights makes you see red, you’re not alone — even though bulls themselves 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.
Whether they’re about showing up to school in your underwear or having your teeth fall out, most dreams have one thing in common: They’re in color. Not for everyone, though. Roughly 12% of people dream entirely in black and white, making their nightly visions much like watching an old movie. That comparison isn’t a coincidence, either. The number used to be much higher: In the 1940s, 75% of Americans reported seeing color in their dreams only rarely or never, and some researchers believe that black-and-white television is part of the reason why. Color TV didn’t become common until the 1950s and ’60s, so for many years, most people’s most common experiences with visual stories were in gray scale.
In addition to their spots and long necks, giraffes have another distinguishing feature: Their tongues are often dark purple. Whereas most animals have pink tongues, a giraffe’s is infused with melanin that makes it darker — sometimes it’s even blue or black rather than purple — although the base and back are pink. And while it hasn’t been proved definitively, the most widely accepted theory is that the melanin provides ultraviolet protection, preventing giraffe tongues from getting sunburned while the animals feed on tall trees. Giraffe tongues are also long (up to 21 inches) and covered in thick bumps known as papillae, which help protect them from the spiky defensive thorns of the animal’s favorite snack: acacia trees.
Giraffes aren’t the only creatures with darker tongues, of course; okapis, polar bears, impalas, and chow chow dogs have them as well, among other animals. However, giraffes are distinguished from their purple-tongued friends not only by their status as the world’s tallest mammal, but also because they give birth standing up. Newborn giraffes fall to the ground from a height of more than 5 feet, not that they mind — they can stand within half an hour and run within 10 hours, usually alongside their doting (and similarly dark-tongued) mother.
Interesting Facts
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Interesting Facts writers have been seen in Popular Mechanics, Mental Floss, A+E Networks, and more. They’re fascinated by history, science, food, culture, and the world around them.
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Cars really have one job: Getting you from point A to point B. But there are plenty of conveniences that can make your journey a little easier — some obvious, some a little more subtle. Nothing’s a replacement for driving safely and watching the road, of course, but some features are designed to give you a little backup. Others are just convenient, like special hidey-holes. Not sure what that dash light or that button on your key fob does? These seven stealthy features could make you feel like you have a brand-new car.
It can be hard to remember what side your gas cap is on, especially in a car you’re not used to driving. Fortunately, there’s usually a pretty easy way to tell: In many cars, there’s a little arrow next to the gas symbol on your fuel gauge that points to the side of the car that should be facing the pump. This tiny, easy-to-miss feature can save you a whole lot of awkwardness pulling a rental car into the gas station. Even if you’re pretty sure your car doesn’t have it, double-check — it’s sneaky!
If you’re used to driving a car from before 2008, there’s a new standard dash light that may look unfamiliar: a yellow exclamation point in the middle of what looks like two parentheses with a dotted line below. It’s supposed to look like a cross section of a tire, and that light tells you that your tire pressure is low. Some cars have more fully featured tire pressure monitors that show all four wheels.
The dash light is designed to illuminate when at least one of your tires is 25% below the recommended tire pressure. If you’re seeing it, either check your tire pressure or head to a tire store — many of them will check for free. (But remember that you should be checking your tire pressure monthly anyway; tire pressure can become dangerously low before this light comes on.)
The indicators became mandatory in American vehicles after the United States Congress passed the TREAD act; the bill was from 2000, but the requirement didn’t kick in until 2008. Some car manufacturers got a head start and started including them in 2006 or 2007 models, too.
Do you sometimes see a dash light that looks like a car with wiggly lines underneath it? That means you have an electronic stability control (ESC) system, sometimes called vehicle stability control, electronic stability program, or dynamic control system. It closely monitors your steering to determine when your car might be out of control, and softly adjusts the brakes on each wheel to compensate for over- or understeering and to prevent rollovers.
If you see the dash light flickering, chances are the system has been activated and is trying to keep your car on track, or driving conditions are just slippery. If it’s steady, it could mean the system is malfunctioning. Some cars have a button that can turn it off.
If you drive a newer car, chances are you’re not turning a key in the ignition. Key fobs have become the standard way to unlock vehicles, which is convenient until your key battery dies or you have some other kind of tech malfunction.
The good news is that you might have a lower-tech backup plan built right in. Many key fobs have little mechanical keys hidden inside that you can usually release by pressing or sliding a small button, although you may have to check the owner’s manual to figure it out. Some key slots are better hidden than others; yours could be right next to the unlock button on the door, underneath the door handle, or under some sort of cap.
Whether you have something to hide or you’re just trying to squeeze a little extra storage out of your vehicle, it’s worth looking for secret pockets of space.
The rear sides of your car are called “blind spots” for a reason — they’re really hard to see, and even if you dutifully check them before changing lanes, accidents can happen. Some newer cars (and some not-so-new luxury vehicles) come with blind spot monitors (BSMs) that let you know when a car’s occupying this sneaky spot next to you. Some of these monitors are more obvious than others. It could be lights on your side mirrors, dashboard, or the pillar between your driver’s side window and your windshield. A few cars even have audible warnings if your turn signal is on but the lane next to you is occupied.
Even lower-end cars have BSMs now, but some higher-end indicators go above and beyond and steer your car away. A couple of trucks even have BSMs that extend to the trailers they’re towing. Just make sure to keep using your eyes — the monitors aren’t foolproof, and often miss vulnerable road users like pedestrians and cyclists.
If you look at your key fob, you’re probably not going to see a button that rolls down your windows, but that doesn’t mean it can’t do it. Check your manual, because sometimes a specific key sequence can lower all your windows from outside the vehicle so you can cool it down on a hot day. It’s not just newer models, either — cars more than a decade old have this function, too.
Even if you’re not planning on using this feature, you should at least figure out how not to do it by accident.
Sarah Anne Lloyd
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Sarah Anne Lloyd is a freelance writer whose work covers a bit of everything, including politics, design, the environment, and yoga. Her work has appeared in Curbed, the Seattle Times, the Stranger, the Verge, and others.
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Imagine a world without cameras — it’s almost impossible. Film, television, history, news, and even our memories are influenced by a technology that has been around for less than two centuries. Here are 10 facts that explore the amazing history of photography, and how it grew from a quirky laboratory experiment to redefining the human experience.
The Story of Photography Begins a Century Before the First Photo
“View from the Window at Le Gras,” taken in 1826 or 1827 by the French inventor Nicéphore Niépce, is widely considered the oldest surviving photograph taken with a camera — but that’s not the beginning of the story of photography. To understand the technology’s origin story, you need to go back about a century and explore the work of German scientist and polymath Johann Heinrich Schulze. Although medieval alchemists often experimented with silver chloride, and even Leonardo da Vinci conceptualized the camera obscura, Schulze (who was actually an anatomist) conducted the first serious experiments in 1717 that established how light reacted to silver salts — the very basis of what would become photography. Schulze’s rudimentary images eventually faded to black because no method existed to prevent overexposure, but the experiments astounded those who saw them, with Schulze eventually writing, “… many who were curious about the experiment but ignorant of its nature took occasion to attribute the thing to some sort of trick.” But it was no trick — only science that had yet to be fully understood.
Credit: GraphicaArtis/ Archive Photos via Getty Images
We Don’t Know the Names of the First People Ever Photographed
One day in 1838, Louis Daguerre — physicist, photography pioneer, and inventor of the daguerreotype (the earliest form of practical photography) — stood in a window overlooking Paris’ Boulevard du Temple and snapped a photograph. Since this was one of the first photographs ever taken, the image was actually less of a “snap” and more of a slog, as the process required around 10 minutes to gather enough light to produce an image on a highly polished silver-plated copper sheet. Because of this long exposure time, Daguerre’s photo captured what appeared to be an empty street, as the hustle and bustle of passing traffic didn’t stay long enough to show up in the photo. In fact, the only thing in the image except for immobile trees, sky, and concrete is a lone shadowy figure getting his boots shined, which explains why he stood still long enough to be fixed in the photo. Upon closer inspection, viewers can just barely make out the shoeshiner hard at work. Today, of course, no one knows the name of that man getting a shoeshine, or the person giving it.
The First True Digital Camera Was Invented to Photograph the Aurora Borealis
The advent of the digital camera was made possible by the invention of a little-known piece of technology called a charged-couple device (CCD) in 1969. At its most basic, a CCD is a light sensor that sits behind a camera lens and effectively replaces the need for film. Eastman Kodak engineer Steven Sasson built the first digital camera prototype in 1975, but his creation was unwieldy, requiring 16 batteries and a special screen just to view the images. The first “true” digital camera came two years later, when the University of Calgary Canada ASI Science Team created the Fairchild All-Sky imager for snapping photos of the aurora borealis. A little more than a decade later, the technology came to consumers when Fujifilm released the FUJIX DS-1P in 1988.
The world’s first digital camera scanned the night sky, and the same can be said for the largest digital camera ever made. The Legacy Survey of Space and Time (LSST) camera lies at the heart of a new telescope at the Vera C. Rubin Observatory in the Chilean mountains, but this isn’t your average DSLR. The LSST camera weighs 3 tons, contains a 3200 megapixel sensor (by comparison, an iPhone camera has only 48 megapixels), and its lens stretches a full 5 feet across. Once installed at the end of 2024, the camera will capture 15 terabytes every single night over the course of 10 years and will observe an estimated 20 billion galaxies. It’s a big camera for an equally big job.
The Left Side of Your Face Likely Looks Better in Photos
Want to capture your “good” side in your next photo? Show off that left cheek. According to a 2012 study from Wake Forest University, the left side of a person’s face often expresses more emotion than the right, and onlookers tend to find that more aesthetically pleasing. When people were asked to rate the pleasantness of male and female profiles presenting both a left and right cheek, the participants overwhelmingly chose the left as more pleasant. One theory for this left-faced bias is that emotion and spatial awareness is largely dominated by the right hemisphere of our brain but is lateralized to the left side of our body, so emotions are expressed more intensely on the left side of our face. Interestingly, Western artists throughout the centuries have had a bias for painting portraits with subjects displaying their left cheek, especially women, with “Mona Lisa” being a prime example.
Every new technology comes with an early adopter tax. The price of the first Macintosh in 1984 comes out to about $6,000 in today’s dollars, and the first cellphone, the Motorola Dynatac 8000x, would cost around $12,000 today (with only 30 minutes of battery life). But those costs pale in comparison to the first 1MP pro camera. Released in 1995, this Fuji X/Nikon hybrid camera had a 1.3 megapixel sensor and a 131 MB removable memory card (capable of storing 70 photos), all for the eye-popping price of $20,000, which is around $38,000 today. Only 12 years later, Apple — which also made the impressive QuickTake camera in the mid-’90s — introduced a 2 megapixel camera on its original iPhone for a fraction of the cost. Today, professional photographers use cameras with 24 megapixels (or more).
The First Color Photograph Was Taken During the U.S. Civil War
Color photography is usually associated with the 20th century, but its origins date back to the early 1860s. On May 17, 1861, Scottish physicist James Clerk Maxwell, who later that very same year began publishing his world-changing electromagnetic equations, revealed the first color photograph to the Royal Institution of Great Britain. The photo showed the multiple hues of a tartan ribbon, and Maxwell created the image by having the same ribbon photographed three times using red, yellow, and blue filters and then combining them (known today as additive color theory). Maxwell first suggested this three-color method back in 1855, but it wasn’t until his collaboration with Thomas Sutton (inventor of the single-lens reflex camera), who actually snapped the images, that Maxwell’s vision finally came to life. Because the photographic plates were far less sensitive to red and green, the color wasn’t perfectly true to life, but it’s still considered the first color photo nonetheless.
Credit: Kevin Lee/ Getty Images News via Getty Images
The Most-Viewed Photograph in History Is Probably the Windows XP Wallpaper
The most-viewed photo isn’t from the lens of legendary photographers like Ansel Adams or Jacob Riis, but a simple picture of a field in Sonoma, California — and chances are you’ve seen it, too. The photograph, originally captured by photographer Charles O’Rear and named “Bliss,” was taken in 1996. Four years later, Microsoft paid O’Rear an undisclosed (but north of $100,000) amount of money to use the image as the default desktop wallpaper for Windows XP in 2002. O’Rear says the image was so valuable that FedEx refused shipment, so he hand-delivered the photograph to Microsoft’s offices near Seattle, Washington. The brilliantly bright green rolling hill (which is now a vineyard) accompanied by a picturesque bright blue sky has likely been seen by billions of people around the world due to the software’s global ubiquity.
Sometimes when you take a photo using flash, something strange happens — the image comes back with subjects sporting demonlike red eyes. What’s going on here? Well, it all has to do with the human iris. At the back of the eye are red blood vessels embedded in the choroid (a layer of tissue that nourishes the retina) that are vital to the function of the eye’s photosensitive cells and nerves. When a camera uses a flash, it’s usually to light a dim area, and in such environments, the human pupil is naturally dilated to let in more light. The pupil doesn’t have enough time to contract, so the flash illuminates the blood vessels in the back of the eye, which is then captured on the camera’s sensor. Many modern cameras now include a dual-flash system where the first flash contracts the pupil and the second flash lights the scene for the actual photo, thus eliminating that pesky red-eye effect.
We Probably Take More Photos Every Minute Than Were Taken in the Entire 19th Century
Two centuries ago, imaging pioneers were only beginning to tinker with ways to capture the world around them using chemicals and light, and now cameras are embedded in our daily lives. We don’t know how many photos were taken in the 19th century, but it’s likely it was a few million at most. In 2014, it was estimated that humanity took a staggering 1 trillion photos that year, which means that every two minutes of 2014, we likely took more photos than were taken in the entire 19th century. Experts believe that the number of cameras in the world passed 45 billion in 2022 (that’s more than five cameras for every person). As cameras continue to get better while shrinking (sometimes to the size of a grain of sand), that number is only increasing, with estimates suggesting humans will take 2 trillion photos in 2025. When that happens, every single minute of the day will create more photos than an entire century of human history.
Darren Orf
Writer
Darren Orf lives in Portland, has a cat, and writes about all things science and climate. You can find his previous work at Popular Mechanics, Inverse, Gizmodo, and Paste, among others.
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It’s a fact of life — people grow old. While modern society tends to obsess about the negatives of aging, studies suggest that we often experience more happiness and contentment in our later years. These 12 facts investigate the phenomenon of growing old, debunk some persistent myths about aging, and explore the brighter side of those golden years.
As our bodies age, they naturally become more susceptible to a variety of illnesses and maladies — but migraines are the rare exception. Migraines often first develop in adolescence, and while both sexes are affected, women are three times more likely to develop migraines compared to men (often due to a fluctuation of estrogen levels). However, the frequency of migraines eventually peaks at the age of 40 and actually gets better as we enter our golden years. Stress and hormones are the most common triggers for migraines, and these two factors usually affect older people with less severity. That said, pain, smoking, and alcohol can still contribute to migraines in seniors, and although migraines generally subside with age, they are still the second-most-common headache disorder in older people (after tension headaches). One in 10 older adults still experience them about once a year.
One of the hallmarks of aging is that our lifelong hair color begins to turn gray, or in some cases, white. Although an entire industry is built around hiding this fact, human hair isn’t actually turning gray so much as no longer supplying the pigments necessary to produce color. This occurs when hydrogen peroxide builds up after wear-and-tear on the hair follicles. That blocks the normal synthesis of melanin, which is responsible for all shades of hair color.
Older Adults Are Happier Than People in Their 20s on Average
As people age, we also gain a certain calm. A study published in 2016 in the Journal of Clinical Psychiatry analyzed a random sample of 1,546 people ages 21 to 100 in San Diego. Although younger people in the survey responded positively in terms of physical health compared to older folks (as anticipated), older adults far outperformed younger generations in terms of mental well-being. Panic disorders are also reported as less common among older cohorts compared to younger people, and developing a panic disorder later in life is a rarity.
As we age, our skin loses collagen, gets thinner, and presses our sweat glands close to the surface of our skin. This process is a bit of a double-edged sword. On the one hand, because these glands are squeezed, it’s harder for sweat to come out of our pores, meaning older people sweat less overall. This may be a check mark in the “pro” column for personal hygiene, but it does come with a few negative side effects. With a reduced ability to sweat, older adults can have trouble regulating temperature during strenuous exercise or excessive heat. Sweat also plays an important role in healing, as it helps stimulate wound closure in skin cells. Thankfully, a lifetime of physical fitness helps slow down this process so you can sweat long into your golden years.
Older people may not feel as strong as they did in their youth, but in terms of political power, they’re as strong as ever. In 2018, 64% of people 65 and over voted in the U.S. midterm election — the highest turnout of any age group — and the 65- to 74-year-old cohort also had the highest turnout in the 2020 election. There are a couple of reasons why the older vote is particularly robust. The biggest may be that older Americans, as well as seniors in other democracies, have government programs and initiatives they rely on, such as Medicare, prescription drug pricing, and Social Security, and because these policies so directly affect them, elections tend to turn out seniors in higher numbers. (There are other factors at play, too — older folks may simply have more time on their hands.) Senior citizens also grease the wheels of democracy, as they’re the most likely age group to volunteer as poll workers on Election Day.
Noses and Ears Don’t Keep Growing, But They Do Droop
While a common myth purports that our ears and nose continue to grow as we age (while the rest of us generally shrinks), that’s not entirely true. Like most other parts of our body, our ears and nose stop growing once we’re in adulthood, but the constant tug of gravity over the decades causes these cartilage-filled features to droop over time. This constant pull actually causes the collagen and elastic fibers in our ears and nose to elongate, and this lengthening, combined with surrounding facial structures losing overall volume, often produces the illusion of growing ears and noses as we age. This elongation is a slow and steady process; studies have shown that ears can lengthen some 0.22 millimeters a year. Interestingly, the process is so precise that you can discern a person’s age just by measuring their ears.
Credit: Heritage Images/ Hulton Fine Art Collection via Getty Images
Old Age Isn’t a Modern Phenomenon
A common misconception about old age is that it’s a relatively modern phenomenon, as our predecessors lived brutish lives cut short by disease and war. While modern medicine has certainly expanded life expectancy, many people in the past lived as long as people live today. For example, some ancient Roman offices sought by politically ambitious men couldn’t even be held until someone was 30 — not exactly a great idea if people didn’t live many years beyond that. Scientists have analyzed the pelvis joints (a reliable indicator of age) in skeletons from ancient civilizations and found that many people lived long lives. One study analyzing skeletons from Cholula, Mexico, between 900 and 1531 CE found that a majority of specimens lived beyond the age of 50. Low life expectancy in ancient times is impacted more by a high infant mortality rate than by people living unusually short lives. Luckily, modern science has helped more humans survive our vulnerable childhood years and life expectancy averages have risen as a result.
Another myth about getting old is that as we age, humans need less and less sleep, somehow magically subsisting on six hours or less when we enter our senior years. The truth is that the amount of sleep a person needs is only altered during childhood and adolescence as our bodies need more energy to do the tough work of growing. Once we’re in our 20s, humans require the same amount of sleep per night for the rest of their lives (though the exact amount differs from person to person). In fact, the elderly are more likely to be sleep-deprived because they receive lower-quality sleep caused by sickness, pain, medications, or a trip or two to the bathroom. This can be why napping during the day becomes more common as we grow older.
The common perception of human biology is that our bones put on some serious inches in our youth, and then by the time we’re 20 or so, nature pumps the brakes and our skeleton stays static forever. While that’s true of a majority of our bones, some don’t quite follow this simplistic blueprint. A 2008 study for Duke University determined that the bones in the skull continue to grow, with the forehead moving forward and cheek bones moving backward. Unfortunately, this imperceptible bit of a facial movement exacerbates wrinkles, because as the skull shifts forward, the overlying skin sags.
The pelvis also keeps growing throughout your life. Scientists analyzing the pelvic width of 20-year-olds compared to 79-year-olds found a 1-inch difference in width, which adds an additional 3 inches to your waistband. That means our widening in the middle as we age isn’t just about a slower metabolism.
While our hips get bigger, our pupils get smaller. The human pupil is controlled by the circumferential sphincter and iris dilator muscles, and as we add on the years, those muscles weaken. Because of this loss of muscle function, pupils get smaller as we age, and are also less responsive to light. Smaller pupils make it harder to see at night, so people in their 60s need three times as much light to read comfortably as people in their 20s. Reading a menu in a dimly lit restaurant? Forget about it. Other eye changes include an increased likeliness of presbyopia, or farsightedness (which can often be resolved with readers), and cataracts, or a clouding of the eye’s lens. In fact, half of people over the age of 80 will have experienced a cataract of some kind.
Although the body experiences some slowing down as we age, growing old isn’t all bad news. Researchers from the University of Queensland found that older people had stronger immunities than people in their 20s, as the body keeps a repository of illnesses that can stretch back decades. This extra line of defense begins to drop off in our 70s and 80s, but until then, our bodies generally just get better and better at fighting off disease due to biological experience. Additionally, as we age we experience fewer migraines, the severity of allergies declines, and we produce less sweat. Older people also exhibit higher levels of “crystalized intelligence” (or what some might call “wisdom”) than any other age group.
The Atoms That Make Up All of Us Are Already Billions of Years Old
It’s true that age is just a number, and in the cosmic view of the universe, human age is pretty insignificant. The atoms that make up the human body are already billions of years old. For example, hydrogen — one of the key components of our bodies — formed in the Big Bang 13.7 billion years ago. Likewise, carbon, the primary component of all known life, formed in the fiery cauldron of stars at least 7 billion years ago. So when someone says we’re all made of “star stuff,” they’re very much telling the truth (we’re also made from various supernovae). And while we grow old on Earth, this is only the latest chapter of a story that stretches back to the beginning of everything — and it’s a story that’ll continue until the universe ends.
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Interesting Facts writers have been seen in Popular Mechanics, Mental Floss, A+E Networks, and more. They’re fascinated by history, science, food, culture, and the world around them.
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A little sweet, a little sour — citrus fruits brighten up any meal, from breakfast to happy hour cocktails. Evolving over the course of 25 million years from just a few citrus species, today’s selection of grapefruits, oranges, lemons, and more has been eons in the making. These eight juicy facts about citrus may just give you a deeper appreciation for these pulp-packed fruits.
Many Citrus Fruits Are Sold in Red Bags For a Reason
Citrus growers often bundle together bunches of oranges in mesh bags, which you may have noticed are made from red plastic. It’s no coincidence; red bags against orange peels create an optical illusion that makes the fruit appear more vibrantly hued and enticing. The trick works for other citrus — like mandarins, clementines, tangerines, and even some grapefruit — though not all. Yellow citrus, like lemons, are often sold in yellow or green bags to create a similar color-popping effect.
Many researchers believe that all citrus fruit can be traced back to just three species: pomelos, citrons, and mandarins. Citrus trees of different species are reproductively compatible with one another; over time, cross-breeding between these “ancestor fruits” created the hybrids known as grapefruits, oranges, lemons, limes, and other citrus varieties enjoyed today.
Oranges are a go-to food for many when battling a cold, thanks to the fact that they’re packed with vitamin C — though some research suggests that the nutrient doesn’t actually prevent colds, and may only slightly cut short how long a cold lasts. Another hitch in eating oranges to help illnesses is that much of the fruit’s vitamin C is found in its peel. Just one tablespoon of the outer rind contains 14% of the recommended daily dose of vitamin C, which is about three times more than what’s found in the inner flesh.
Regardless of the flag they were working under, nearly all sailors of the past shared a common enemy: scurvy. The disease, caused by a vitamin C deficiency, plagued sailors who were unable to regularly consume fresh fruits and vegetables while out at sea. The British Royal Navy began supplying its sailors with lemons and lime juice in 1795, though not all countries picked up on the practice. During the War of 1812, skeptical American sailors nicknamed their British counterparts “limeys” to mock the practice — though the U.S. Navy eventually started doing it too.
The Largest Citrus Fruit Can Reach Basketball Size
Pomelos are grapefruit-like citrus native to Southeast Asia, known for their yellow rinds and pink inner flesh — not to mention their size. The jumbo citrus fruits can grow up to the size of a basketball and weigh as much as 22 pounds. In comparison, kumquats are the smallest known citrus, maturing at a max length of around 2 inches. (Kumquats are also the only citrus fruit you can easily eat without peeling.)
Clementines and Mandarins Are Technically Different Fruits
What’s small, orange, and easy to peel? Both clementines and mandarins, which explains why these two nearly identical citrus fruits are often confused. However, botanists say there is a difference. Clementines are an offshoot variety of mandarins, created by crossing mandarins and sweet oranges. That means all clementines are technically a type of mandarin, though all mandarins are not clementines.
Grapefruits are packed with vitamins and fiber that support heart and gut health, though people who rely on some medications are often warned away from consuming the fruits. That’s because grapefruit juice can affect how medications work. Some drugs, like those for cholesterol and high blood pressure, are metabolized in the body by the CYP3A4 enzyme found in the small intestine. Grapefruit juice can block that enzyme, which stops the medication from breaking down and causes too much to enter the bloodstream. Other drugs, like fexofenadine (Allegra) for allergies, use proteins called transporters to enter cells in the body; grapefruit juice can block this process and cause too little of the drug to circulate, rendering it ineffective.
Oranges are relatively inexpensive today, though 19th-century Europeans who woke to find them in their stockings on Christmas morning considered the fruits a grand gift. The tradition of receiving an orange as a holiday present dates to the 1800s, when Christmas revelers widely began hanging stockings on the mantle, and is commonly linked to the tale of St. Nicholas of Myra, a fourth-century bishop who reportedly tossed bags of gold into the drying stockings of poor maidens. Oranges — which were generally a rare and expensive fruit in Victorian times — represented St. Nicholas’ gifted gold, and became linked with the holiday.
Interesting Facts
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Interesting Facts writers have been seen in Popular Mechanics, Mental Floss, A+E Networks, and more. They’re fascinated by history, science, food, culture, and the world around them.
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Interesting Facts is part of Optimism, which publishes content that uplifts, informs, and inspires.
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