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Mary Ann Evans, later known by her pen name, George Eliot, was born in 1819 on the grounds of the Arbury Hall Estate in Warwickshire, England, where her father worked. She had a good education in a staunchly religious environment, learning French, Italian, and Latin and studying the Bible. Her path began to change when she met a ribbon manufacturer named Charles Bray who was a self-taught freethinker and radical. She began to question everything, including her religious beliefs, which greatly annoyed her father. But her course had been set, and soon she began to write — and what a writer she was.

In 1859, her first complete novel, Adam Bede, was published to instant critical success — and much speculation as to who this George Eliot fellow could be. The novel also introduced a new form of realism and psychological analysis into modern fiction, something that would be further developed in her later novels, such as The Mill on the Floss, Silas Marner, Middlemarch, and Daniel Deronda. Her novel Middlemarch, A Study of Provincial Life initially received mixed reviews, but literary critics of the 20th century reevaluated the novel, hailing Eliot’s use of realism in historical events, her examination of rural society, and the themes of political reform, education, and the status of women. Middlemarch is now widely considered her greatest work and one of the greatest novels in the English language.

Today, George Eliot is viewed as one of the most important Western writers of all time. But there are aspects of her life and work that are not so well known, ranging from her literary accomplishments beyond fiction to what was seen at the time as a scandalous love life.

George Eliot (1819-1880) pen name of Mary Ann Evans.
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She Had More Than One Reason to Use a Pen Name

Eliot decided to write under a pseudonym in 1857. She wanted to avoid the stereotype of women’s writing at the time, which was considered lighthearted and frivolous. She also wanted to shield herself from scandal, as she was an unmarried woman living with a married man. She told her publisher that the pen name would serve as “a tub to throw to the whale in case of curious enquiries.” It is likely that she chose the name George in tribute to her lover, George Henry Lewes. She chose Eliot because she found it to be “a good, mouth-filling, easily pronounced word.”

British novelist Charles Dickens.
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Charles Dickens Had His Suspicions About George Eliot’s True Gender

Charles Dickens wrote a letter to Eliot in 1858 in praise of her first published work, Scenes of Clerical Life. Dickens began with “My Dear Sir,” but soon respectfully explained his doubts regarding her gender: “I have observed what seem to me to be such womanly touches, in those moving fictions, that the assurance on the title-page is insufficient to satisfy me, even now.” In 1859, after the publication of her first complete novel, Adam Bede, Eliot revealed her true identity — partly in response to a number of imposters who were claiming authorship. This prompted Dickens to write her another letter in praise of her work, this time addressed to “My Dear Madam.” Despite revealing her true identity, Eliot continued to publish under her pen name.

George Eliot, pen name of Mary Ann Evans.
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She Didn’t Only Write Novels

Eliot’s greatest literary achievements were her novels, but she wrote more than fiction. Her first prominent literary work was an English translation of David Strauss’ The Life of Jesus, Critically Examined — a controversial work that questioned the literal truth of biblical texts. The Earl of Shaftesbury called Eliot’s translation “the most pestilential book ever vomited out of the jaws of hell.” Along with her various translations, Eliot wrote for and edited the left-wing journal The Westminster Review. She also published two volumes of poetry, but her poems never achieved the same success as her novels.

George Eliot - handwritten dedication to her husband on an edition of the English writer's novel.
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Her Romantic Life Was Scandalous in Its Day

Eliot’s lover, George Henry Lewes, was a man of many talents: dramatist, novelist, biographer, literary critic, philosopher, scientist, and editor. But today he is remembered primarily for his decades-long relationship with the famous author. Lewes was a married man and couldn’t obtain an official divorce, but he and Eliot lived openly together until his death in 1878. It was a scandal at the time, and Eliot became estranged from many family members and friends, but it never tore the couple apart. After moving to Germany with Lewes in 1854, Evans wrote to a friend explaining her views on the relationship: “Light and easily broken ties are what I neither desire theoretically nor could live for practically. Women who are satisfied with such ties do not act as I have done — they obtain what they desire and are still invited to dinner.”

Statue of George Eliot in Nuneaton town centre.
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She Was a Harsh Critic of Other Women Authors

Eliot used a pen name partly to avoid being pigeonholed among what she saw as the “less serious” female authors of her day. She was not afraid of criticizing these authors, and did so very publicly in her essay “Silly Novels by Lady Novelists.” She described these works as having a “particular quality of silliness that predominates in them — the frothy, the prosy, the pious, or the pedantic.” She made it very clear, however, that “fiction is a department of literature in which women can, after their kind, fully equal men.”

Title page of The Mill on the Floss by George Eliot.
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She Gave Us a Few Modern Words and Phrases

Eliot coined, or at least popularized, a number of words and phrases that we use today. Among them are the words “chintzy” (meaning gaudy or trashy), “floppy,” “lampshade,” and “lunchtime.” She was also the earliest person to have used “pop,” short for “popular,” in relation to “pop music.” She wrote in a letter, “There is too much ‘Pop.’ for the thorough enjoyment of chamber music they give.”

Vincent van Gogh (French, 1853–1890) Self-Portrait.
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Virginia Woolf and Vincent van Gogh Were Both Fans

Virginia Woolf greatly admired Eliot, both for her writing and the way she lived her life. She called Middlemarch a “magnificent book which with all its imperfections is one of the few English novels written for grown-up people.” Vincent van Gogh was also inspired by Eliot, who, alongside Charles Dickens, was one of his favorite authors, in part due to her vibrant depictions of provincial life. In a letter to his brother, van Gogh explained how Eliot’s novel Felix Holt, the Radical, was “a book that touched me deeply, and it will no doubt have the same effect on you.” He sent his brother a copy of the book along with the letter.

Tony Dunnell
Writer

Tony is an English writer of nonfiction and fiction living on the edge of the Amazon jungle.

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What’s your favorite way to puzzle? Maybe you like assembling giant jigsaws with your family, filling out the daily crossword in pen, or playing brain-teaser apps on your phone. Between real-life escape rooms and video game dungeons, today’s puzzle options are nearly infinite. But how much do you really know about them? From the origins of Sudoku to the distracting power of Minesweeper, these seven facts about puzzles will make you think about your favorite pastimes in a whole new way.

Holding a white blank final piece of the jigsaw.
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An “Enigmatologist” Is Someone Who Studies Puzzles

You probably already know the word “enigma,” meaning something that’s mysterious, hard to understand, or, well, puzzling. Combine that with “ology,” indicating a field of study, and it makes sense that “enigmatologist” would mean one who studies puzzles. The word is a relative newcomer to the lexicon, and is typically attributed to New York Times puzzle editor Will Shortz, who graduated from Indiana University with a self-designed Enigmatology degree in 1974.

While the term hasn’t made it into all the major dictionaries, Merriam Webster does list “enigmatology” alongside the more generic definition of “the investigation or analysis of enigmas.”

Crossword enthusiasts get their own word, “cruciverbalist,” coined in the early 1980s. Speaking of which…

Close-up of a crossword puzzle and pencil.
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The First Modern Crossword Puzzle Was Published in 1913

The first modern crossword puzzle was published in the New York World’s “Fun” section on December 21, 1913, although simpler ancestors appeared in kids’ puzzle books in 19th-century Britain. Unlike the format we’re used to in today’s papers, the puzzle’s clues weren’t organized into “across” and “down”; instead, two numbers indicated a start and end point within the diamond-shaped grid.

Just a decade later, crossword puzzles were a standard offering in major U.S. papers, and serious cruciverbalists still observe December 21 as Crossword Puzzle Day. But while the New York Times puzzle is among the most iconic crosswords today, the Gray Lady was notoriously slow to adopt the practice. The paper finally relented soon after the bombing of Pearl Harbor: “We ought to proceed with the puzzle, especially in view of the fact it is possible there will now be bleak blackout hours,” wrote the Sunday editor at the time in a memo to the publisher, “or if not that then certainly a need for relaxation of some kind or other.” Their first puzzle finally appeared on February 15, 1942 and, despite its stated goal of helping to calm nerves during wartime, includes several clues about the then-current events of World War II.

Close-up of someone playing with a Rubik's Cube.
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There Are 43 Quintillion Possible Rubik’s Cube Arrangements

Each Rubik’s Cube shows nine different colorful squares on each face; to solve it, you need to twist rows of smaller cubes both horizontally and vertically until each face of the cube is the same color. Some people are really, really good at solving it, regularly finishing expertly-scrambled cubes in less than five seconds.

This is a pretty incredible feat, considering that there are 43,252,003,274,489,856,000 different configurations, but solving it is less complicated than it might appear. A team of scientists borrowed Google’s computers to find the quickest solution to each configuration, and it turns out each can be solved in 20 moves or less. Since people are not computers, this knowledge doesn’t exactly spell out each solution for a human being, but “speedcubers,” as they’re called, memorize hundreds of algorithms to help them attack each new configuration.

Hands of diverse people assembling a jigsaw puzzle.
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The First Jigsaw Puzzles Were Geography-Learning Tools

The first commercial jigsaw puzzles originated in 18th-century England, when cartographer John Spilsbury started pasting maps to thin wood and slicing out individual countries with a scroll saw. He called them “dissected maps,” and while they were originally teaching aids, their popularity spread throughout Britain in the mid-1700s. By the mid-1800s, these puzzles featured other popular images from things like zoology and fairy tales.

Interlocking puzzles — the kind you’re likely used to today — started with Parker Brothers in the early 20th century. Homemade versions took off during the Great Depression as both a low-cost way to entertain yourself and, for anybody with a jigsaw, a way to make some extra cash by selling them or renting them out.

Geometric shapes on a wooden background.
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“Tetris” Is a Blend of “Tetra” and “Tennis”

“Tetris” is so ubiquitous now that it’s entered everyday speech outside of the game. (Maybe you used it the last time you packed a moving truck!) But the game has only been around for 40 years or so, and the etymology of its name is a little surprising.

One part is obvious: “Tetra” is a Greek numeral prefix, meaning “four.” Each Tetris piece is made up of four smaller squares. The “is” on the end isn’t just for style, but it’s not particularly relevant to the gameplay, either: Creator Alexey Pajitnov just really, really liked tennis, and included the suffix in the name.

Close-up of Bill Gates.
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Bill Gates Himself Was Addicted to Minesweeper

Those who were around to experience the early years of Windows probably know two games a little too well: Solitaire and the much more stressful Minesweeper.

Solitaire was standard on Windows 3.0 as a friendly, familiar feature to help users feel less intimidated by the operating system, and as a handy exercise in using a computer mouse. Minesweeper, which used to be an add-on with the Microsoft Entertainment Pack, came standard in 3.1.

The reasoning? It was the staff favorite, and many in the Microsoft offices — especially founder Bill Gates — couldn’t keep their hands off it.

In 1994, the Washington Post reported that Gates had become so distracted that he took it off his personal machine. This did not prevent him from playing it, however: He’d just hop over to then-Microsoft-president Mike Hallman’s office to play instead. (Supposedly, his solving record was five seconds.)

Senior man doing a sudoku puzzle.
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Sudoku Dates Back at Least to 1700s Switzerland

Contrary to popular belief, Sudoku did not originate in Japan, although it did come of age there. One of its earliest forms — although it’s possible that its origins go back even earlier, to 8th or 9th century China — was a variation on magic squares developed by Swiss mathematician Leonhard Euler, who called it “Latin Squares.” It was a slightly simpler version of the game we know today: In modern Sudoku, solvers need to place a series of numbers so they only appear once in their corresponding row, column, and sub-grid, while Latin Squares used only rows and columns. A more complicated version popped up in French newspapers in the late 19th century, with both the smaller grids and a couple of diagonals thrown in.

The modern Sudoku puzzle emerged in the 1970s as “Number Place,” published in Dell Puzzle Magazines and sometimes credited to a retired architect in Indiana. A Japanese puzzle enthusiast named Maki Kaji “fell in love” with the game, renamed it Sudoku, and started printing puzzles through his game publishing company Nikoli. (The name is short for sūji wa dokushin ni kagiru, which means “the numerals must remain single” — that is, the digits must occur only once.) The idea spread quickly in Japan; unlike a crossword, you don’t need an alphabet to solve it, which is ideal when your written language doesn’t have an equivalent to the ABCs. Sudoku started spreading back out to Hong Kong, Britain, and eventually the United States in the late 1990s through the mid-2000s.

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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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Many famous moments in history — whether they involve inspiring troops before a battle or inspiring a nation against injustice — involve equally inspiring speeches. Spoken by presidents, activists, wartime leaders, and abolitionists, these famous speeches live on decades after they were delivered. Here are seven amazing facts about them that will make them seem even more remarkable.

Gettysburg Address speech at the dedication of the Gettysburg National Cemetery.
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The Gettysburg Address Is Only Two Minutes Long

Abraham Lincoln’s famous Gettysburg Address looms large in American history, but the speech itself is very short. On November 19, 1863, only four and a half months removed from the bloody Battle of Gettysburg, a crowd gathered to hear the President’s remarks at the official dedication of the Soldiers’ National Cemetery (now Gettysburg National Cemetery). The speaker before Lincoln, a famous orator named Edward Everett, had delivered a two-hour-long speech, which means the crowd might have been ready for something shorter. At only 272 words (about two minutes long when spoken), Lincoln’s Gettysburg Address masterfully encapsulates the unimaginable anguish of a nation at war with itself, but also that same nation’s hope to persevere through the bloodshed. After the speech, Everett admitted to Lincoln, “I should be glad, if I could flatter myself, that I came as near to the central idea of the occasion in two hours, as you did in two minutes.”

MLK & crowds during the March On Washington at the Lincoln Memorial.
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Martin Luther King Jr.’s “I Have a Dream” Refrain Was Improvised

Around 4 a.m. on August 28, 1963, civil rights leader Martin Luther King Jr. finished the final draft of his famous “I Have a Dream” speech. There’s just one problem with that title: Those words appeared nowhere in his prepared remarks. Hours later, King stood before the Lincoln Memorial — a century removed from Lincoln’s Emancipation Proclamation — and addressed a crowd of more than 200,000 people. In previous speeches from Birmingham, Alabama, to Detroit, Michigan, King had evoked the imagery of a dream of racial equality, but had no intention of revisiting that dream on that hot day in August. That is, until Mahalia Jackson, one of the world’s greatest gospel singers, who had performed earlier in the day, urged him on, yelling from offstage: “Tell ’em about the dream, Martin.” Then, according to one MLK speechwriter, King pushed aside his prepared text, grabbed the podium, and launched into those famous words that echo through history.

President Franklin D. Roosevelt making his First Inaugural Address in 1933.
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FDR’s “Fear Itself” Line Was Likely Inspired by Henry David Thoreau

On March 4, 1933, with the country in the grips of the Great Depression, newly elected President Franklin Delano Roosevelt delivered his first inaugural address, uttering the famous phrase that served as a bulwark against the dark days ahead: “The only thing we have to fear is fear itself.” Although the words perfectly fit the times, they were likely first written more than 80 years before by transcendentalist writer Henry David Thoreau. In a journal entry dated September 7, 1851, Thoreau wrote: “Nothing is so much to be feared as fear.” Historians haven’t made a direct connection between Thoreau and Roosevelt’s famous line, but when First Lady Eleanor Roosevelt was asked about the phrase’s possible origin, she guessed he had discovered it in a collection of Thoreau’s writings that he had with him in Washington.

A page from an Illustrated book of Winston Churchill's famous wartime speeches.
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Winston Churchill’s “We Shall Fight on the Beaches” Speech Was Not Broadcast

The dramatic conclusion to the 2017 Oscar-winning war drama Darkest Hour, a film that follows Winston Churchill as Britain descends into World War II, places the prime minister’s famous “We Shall Fight on the Beaches” speech front and center. Although it was a rallying cry for members of the U.K. Parliament to continue the fight, the British public didn’t hear Churchill’s stirring words, originally delivered on June 4, 1940, until years after the war.

Despite not being broadcast at the time, the speech was well-received, with one member of Parliament writing in a letter that it was “the finest speech that I have ever heard.” Today Churchill’s words encapsulate Britain’s dogged determination in the face of overwhelming odds as well as Churchill’s firm belief that the U.S. needed to join the Allied cause.

President Ronald Reagan in Berlin.
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Ronald Reagan’s “Tear Down This Wall” Line Was Almost Cut From the Speech

Arguably the most famous words uttered during the four decades of the Cold War came on June 12, 1987. Standing before the Brandenburg Gate in Berlin — a city still divided by the 27-mile-long Berlin Wall — President Ronald Reagan posed a challenge to the leader of the Soviet Union: “Mr. Gorbachev, tear down this wall.”

However, those words were almost never said. Weeks earlier, Reagan speechwriter Peter Robinson flew to Berlin to interview locals about the Berlin Wall. With strong support for its removal, Robinson was determined to mention the wall’s destruction in the speech. Many officials and aides fought against the line, however, thinking it “unpresidential.” The line remained — the wall, of course, did not.

resident Kennedy makes his 'We choose to go to the Moon' speech at Rice University.
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JFK Prefaced His “We Choose to Go to the Moon” Line With a Football Joke

One of John F. Kennedy’s most famous speeches arrived on September 12, 1962, at Rice University Stadium in Houston, Texas. With the famous phrase “we choose to go to the moon in this decade and do the other things, not because they are easy, but because they are hard,” Kennedy’s words committed the U.S. to besting the Soviet Union in the ongoing space race. But an often overlooked legacy of Kennedy’s speech comes directly before that famous line. Comparing the moon mission to other human feats, Kennedy questioned why we climb Everest, fly across the Atlantic, and “why does Rice play Texas?” The joke, added by the President himself, got a rise out of the audience at the time, but according to ESPN, those five words added some serious fuel to the long-standing football rivalry.

American abolitionist and women's rights activist Sojourner Truth.
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Sojourner Truth’s “Ain’t I a Woman” Speech Likely Didn’t Contain That Phrase

On May 29, 1851, Sojourner Truth — a former enslaved woman, abolitionist, and women’s rights activist — delivered her famous “Ain’t I a Woman” speech at the Women’s Convention in Akron, Ohio. In the speech, Truth powerfully advocated for the right of Black women to be involved in the fight of American women for equality. Although history knows Truth delivered a powerful oration at the convention, the only surviving versions of the speech come from secondhand accounts. The oldest account of the speech, transcribed weeks later by a journalist who attended the convention, makes no mention of the famous “Ain’t I a Woman” line, whereas a later 1863 version repeats the phrase frequently. Whether Truth uttered the words or not, the message is one that still resonates today.

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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At its most basic, an acronym is a word formed from the letters of the words it represents, generally the first letter of each word, but sometimes syllables or other parts of the word. Some acronyms have become so ubiquitous that they are no longer thought of as acronyms, but are more commonly used as words in and of themselves. These acronyms in particular primarily grew out of World War II and the mid-20th century generation.

Military radar screen scanning air traffic.
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RADAR

While the term started out as an acronym — standing for “RAdio Detection And Ranging,” “radar” is a technology used for many things, defined as “a system for detecting the presence, direction, distance and speed of aircraft, ships and other objects, by sending out pulses of high-frequency electromagnetic waves that are reflected off the object back to the source.” While the technology was developed over years by many scientists, Scottish physicist Robert Watson-Watt discovered its use for detecting enemy aircraft during WWII. While it’s still used in these sorts of military and detection contexts, it’s also now used more casually and metaphorically, as in, “Hey, I want to put this project on your radar.”

View of a flying saucer in the air.
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UFO

“UFO” stands for “Unidentified Flying Object,” and first emerged in 1953 amid the era’s space craze. The interest in potential alien visitors began a few years earlier, when, in the summer of 1947, a private pilot named Kenneth Arnold described seeing nine objects flying in close formation at a seemingly supernatural speed in Washington state. He described them as “flat like a pie and somewhat bat-shaped,” and that they “flew like a saucer would if you skipped across water.” From there, journalists began referring to them as flying saucers, which eventually became “UFO.” One important distinction: technically, “UFO” is an initialism rather than a strict acronym, since the letters themselves are pronounced rather than a whole new word.

Soldier holding up a shipped package.
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CARE (Package)

Lucky summer campers and college students might receive a care package from mom when they are away from home for the first time. Colloquially, this is “a parcel of food, money, or luxury items sent to a loved one who is away.” However, the acronym comes from a program known as the Cooperative for American Remittances to Europe. The first CARE package arrived in Le Havre, France, in May 1946, beginning a wave of responses to millions in need of food and other supplies at the end of WWII. The CARE packages usually contained staples such as butter, dried milk, canned meat, and even chocolate or chewing gum.

Scuba diving safety stop performed in the deep blue sea.
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SCUBA

You can’t get your SCUBA certification without learning what this acronym stands for. It means “Self-Contained Underwater Breathing Apparatus,” which is a pretty straightforward description of the equipment and the activity. The term originated in 1952, and “scuba-diving” came around by 1956.

A camouflage helmet with bullets, peace badge and a letter from home sealed with a kiss.
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SWAK

“SWAK” is still defined as an acronym in the dictionary, meaning “sealed with a kiss.” During the war, soldiers and their sweethearts might write SWAK on the back of an envelope, perhaps even with a lipstick imprint. But as the war continued, soldiers and civilians came up with even more acronyms to express their love. Some were romantic (“OOLAAKOEW” meant “Oceans Of Love And A Kiss On Every Wave”), and some were more risqué (“CHINA” meant “Come Home, I’m Naked Already”).

Fishing sonar on a boat.
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SONAR

Similar to “radar,” “SONAR” refers to a different type of ranging. Instead of radio detection, this one’s all about using sound to navigate — it stands for “Sound Navigation Ranging.” It entered the language in 1946.

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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The human body is a beautiful, complicated collection of nerves, blood vessels, muscles, organs, and bones, all working together in intricate processes. Though science has been able to explain many things about how our bodies work, certain anatomical quirks continue to astound us today — common bodily functions included.

A woman shivering in the cold weather.
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What Are Goosebumps?

Goosebumps, known in medical parlance as piloerection, are caused by contractions in small muscles that are connected to hair follicles. This creates a depression on the skin’s surface, resulting in the hairs standing upright. Its name comes from the resemblance of skin to that of a plucked bird.

It is believed that this is an inherited trait from our prehistoric ancestors. They had thicker coats of body hair, which created insulation and kept the body warm when stimulated. While our layer of body hair is too thin to make this insulation process effective, the muscle contraction and increased electrical activity does help to stimulate the body, which is why goosebumps that are caused by the cold go away when you warm up.

Goosebumps are also associated with a wide range of emotional situations. People talk about getting goosebumps when scared, or while listening to rousing songs or watching a high-stakes sporting event. Goosebumps can be triggered by the subconscious release of the testosterone hormone. When high levels of stress occur, whether positive or negative, testosterone is released to help in the fight-or-flight decision-making process. This cues goosebumps, and we start to feel our hair prick up.

Goosebumps may be a little mysterious, but generally speaking, when you feel them cropping up, all you need to do is take a deep breath, relax a little, and maybe put on a sweater.

Question mark block with bokeh lights shining in the background.
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What Is Déjà Vu?

Have you ever had a sneaking suspicion that you’re experiencing a scenario that’s already happened? Then you’ve dealt with déjà vu. The term is (as you may have guessed) French, and the literal translation means “already seen.” But in everyday life, déjà vu refers to the weird feeling you get when you’re in a situation that feels like you’ve already lived it, and are somehow living it again.

Research shows that there’s a direct relation between déjà vu and seizures. Specifically, the phenomenon is linked to temporal lobe epilepsy and has been described in people with a known medical history of the condition.

But plenty of people have experienced déjà vu who don’t have a history of epilepsy or seizures. In healthy people, déjà vu is believed to be caused by a memory mismatch, where a new experience is stored in long-term memory and completely bypasses the short-term memory. In this scenario, you have that weird sensation that you’ve been through an experience before when in reality, it’s just your brain’s memory system having a glitch.

There are also other causes of déjà vu that might have more to do with your daily habits than your medical history. One of the most common causes of déjà vu is being overly distracted. Sleep deprivation is another. If you’re walking through life in a perpetual sleep-deprived haze, you might feel like you’re reliving experiences when in truth, you’re just too exhausted to parse reality from dreams.

An X-ray image of a persons teeth.
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Why Do We Have Wisdom Teeth?

Wisdom teeth are just like any other molar in your mouth. For the first few years of a human’s life, they eat only soft foods and have no need for molars to crush and grind. Around the age of six, the first set of molars come in. When a person reaches 12, another set appears. The wisdom teeth are the final set of molars that appear between ages 18 and 21.

Early humans were hunter gatherers who survived on leaves, roots, meat, and nuts — things that required a lot of crushing ability. The more grinding teeth you have, the easier it is to eat tough foods. As humans evolved, they began to cook their food, making it softer and easier to chew. Having three full sets of molars became unnecessary.

Additionally, early humans had larger jaws than we do today — which could support more teeth. Over time, as the need for super-powerful jaws decreased, human jaws got smaller. But the number of teeth stayed the same. That’s why today, many people need to get their wisdom teeth removed in order to create more space.

Because wisdom teeth aren’t necessary for modern humans, they may someday cease to exist at all.

A man blowing his nose with various cold medications on the table in front of him.
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Why Do We Sneeze?

The primary purpose of a sneeze is straightforward — sneezes help to remove irritants from the nasal passage. These irritants include dust, dirt, pollen, smoke, or anything else that could possibly get stuck in there. Blowing it all out is the best way your body can clear it.

Sometimes sneezes seem to come in pairs or more. Some people — maybe even you — have a specific number of sneezes that they produce each time. If someone sneezes three times, every time, their sneezes might not be as powerful as a single-sneezer’s is, and it requires three attempts to get rid of the irritant.

Sneezing also plays an important role in fighting the spread of bacteria when we’re sick. The body’s natural reaction to infection is to produce mucus in an effort to trap the bacteria. Once trapped, it’s time to get rid of it. Sneezing is the most efficient way to expel mucus from the body. It’s also the most efficient way to spread bacteria, so remember to cover your mouth and nose.

Even when there aren’t irritants or bacteria present, your nose produces mucus to catch potential irritants before they can get to your lungs. Sometimes, through normal production, the nasal passage gets too full and needs to be reset. Whenever you get a random sneeze that seems to be out of nowhere, it’s most likely just to reset your nasal passage.

Sneezing is still something of a mystery, however, as there are some causes that don’t seem to make much sense. About one in four people sneeze when they look into a bright light. This is called a photic sneeze reflex, and it’s an inherited genetic trait. The leading theory is that a certain stimulation of the optical nerve causes the same sensation in your brain as irritation in the nose, but the true cause still eludes researchers.

Beautiful face and eyes of a women close up.
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The average person blinks about 12 times per minute, 10,000 times per day, and 4.2 million times per year. That’s a lot of blinking.

The most obvious reason that we blink is to lubricate our eyes. Lubricating tears are constantly being produced in your body and are made up of three layers: the mucous layer so that it adheres to your eye; the aqueous layer, which is a thick layer that hydrates and keeps bacteria away; and the oily layer, which prevents the other two layers, which are predominantly water, from evaporating. Every time you blink, these tears are pulled across the surface of your eye to keep it lubricated and prevent the spread of bacteria.

Additionally, blinking helps clear dust and particles that are continuously getting into your eyes. When your eyes water, the extra fluid helps cleanse and soak up the debris, while the blinking is like a windshield wiper pushing it away.

Blinking also works as a reflex in response to external stimuli. Your eyes can close in 0.1 seconds after stimulus is detected. Sometimes the stimulus is the bright bathroom light at 3 a.m. Sometimes it’s a fistful of sand. This is called the corneal reflex, and it is designed to prevent as much debris as possible from entering and damaging your eye.

Aerial shot of an adorable little boy sleeping in bed at home.
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Why Do We Yawn?

It was long believed that yawning was a respiratory function. When your body is running low on oxygen, a yawn is triggered to force a deep inhale and exhale. This increases oxygen levels in the bloodstream, and the yawn itself raises your heartbeat to pump the oxygen-rich blood throughout the body.

While this theory is still possible, or is, perhaps, one aspect of yawning, it’s not the whole story. Instead of oxygen deprivation, researchers now believe that the primary function of yawning is regulating temperature. Your brain is the most energy-hungry organ in your body. It uses about 40% of your total metabolic energy. All that energy means that your brain tends to run hot and needs some way to cool down. Your brain uses yawning like your computer uses fans.

During a yawn, cold air is brought in through the mouth. The muscles in your jaw and around your skull contract and stretch, which increases blood circulation in the area. The air cools the blood, and the increase in heart rate pumps the cooler blood to your brain. A cooler brain is a more alert brain.

Your body knows how to be efficient. If the surrounding air is cooler, yawning will be more effective. It might sound strange, but studies have shown that people yawn more frequently in cooler temperatures. People yawned 21% more often when the outside air was 70 degrees Fahrenheit versus 98 degrees (body temperature). Similar results were also found with other species of animals.

There are dozens of other triggers associated with yawning, however. Obvious culprits like boredom and drowsiness mean your brain needs to be stimulated, but yawning can also be triggered by other events like anxiety, hunger, or even a change of activity. Any time your brain needs some extra focus, it might trigger a yawn for a refreshing cool down.

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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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What pennies lack in purchasing power, they make up for in history. Long before the U.S. was even founded, variations of the word “penny” were commonly used for European currency of various denominations, including pfennig in German and penning in Swedish. (The American use of the word “penny” came from the British term for one-twelfth of a shilling.) It was in 1793 that the U.S. Mint finally struck its first penny — though its official name is the “one-cent piece” — which means that pennies have been jangling around in the pockets of Americans since the Washington administration. From design alterations to record-shattering values, here are some remarkable facts about the history (and more) of the smallest current monetary denomination in the U.S.

A half length portrait of Benjamin Franklin.
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Benjamin Franklin Designed the First Penny

Long before Abraham Lincoln’s portrait graced the face of the one-cent piece, founding father Benjamin Franklin reportedly conceived of an early coin design now known as the “Fugio” penny. Franklin’s concept was first approved and manufactured under the watchful eye of the Congress of the Confederation in 1787, predating the U.S. Mint’s production by several years. The Fugio penny’s obverse depicts a sun and sundial accompanied by the Latin word “fugio” (translating to “I fly”), as well as the phrase “Mind Your Business.” On its other side, the reverse, the cent features the words “We Are One,” surrounded by 13 chain links to represent the original 13 colonies. All told, U.S. pennies have featured 11 different designs throughout history.

Overhead view of a collection of pennies.
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Abraham Lincoln Was the First Real Person to Appear on a U.S. Coin

Speaking of redesigns, it was in 1909 that the penny underwent a visual change that remains constant to this day. From 1859 to 1909, the U.S. penny depicted the silhouette of a fictitious Native American person. In 1909, President Theodore Roosevelt decided to celebrate Abraham Lincoln’s 100th birthday by changing the coin’s design to feature Lincoln’s face — making Lincoln the first real person to appear on U.S. coinage. To create the design, Roosevelt enlisted the acclaimed medalist Victor David Brenner, who designed the portrait of Lincoln that now appears on all pennies. George Washington would later appear on the quarter, beginning in 1932; Thomas Jefferson was added to the face of the nickel in 1938; and FDR showed up on dimes beginning in 1946.

Blank coins are checked before going to the money press.
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Pennies Cost More To Make Than They’re Worth

Despite their storied history, pennies may not be around for much longer, due to the fact that they’re so expensive to make. The manufacturing cost for a penny is more than double its value — in 2021, each penny cost 2.1 cents to strike. That same year, the government produced 7.6 billion pennies, equating to a financial loss of $145.8 million. Part of the reason for this financial conundrum is that pennies are composed of 97.5% zinc and 2.5% copper, two metals that have recently dramatically risen in price. Several movements have begun in support of eliminating the coin from circulation, which is something America’s neighbors to the north chose to do with their own penny all the way back in 2012.

Close-up of the heads side of a penny.
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The Most Valuable Penny Sold for $1.7 Million

Not all pennies are massive money drains. In fact, one penny sold at auction in 2010 for a whopping $1.7 million. The one-of-a-kind coin was accidentally struck in 1943, using a leftover bronze coin disc from 1942 at a time when the government was experimenting with other materials so they could preserve copper for wartime efforts in World War II. The auctioned coin is the only one known to have been mistakenly cast in bronze at the Denver Mint, making it exceedingly rare, though an additional 20 Lincoln pennies were believed to have been struck in bronze at the Philadelphia and San Francisco Mints. Throughout World War II, zinc-coated steel was ultimately used for pennies as part of the aforementioned conservation efforts.

The back side to an 1826 American half cent.
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The Penny Isn’t the Lowest-Value U.S. Coin Ever Produced

From 1793 to 1857, the penny held the distinction of being the second least-valuable American coin, since the U.S. Mint produced a half-cent coin during that time period. The first half-cent depicted Lady Liberty on its face, though subsequent redesigns would alter her appearance as well as the way she was facing. The half-cent was ultimately discontinued due to its perceived worthlessness at the time — though it would be worth 14 cents today when adjusted for inflation, making it more valuable than several modern coins still in circulation. From a collector’s standpoint, the half-cent is even more valuable, with lower-quality examples selling for $40, whereas some uncirculated half-cents are valued at up to $100,000.

Close-up of a pressed penny at Death Valley National Park.
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Pressed Penny Collectors Are Known as Exonumists

Exonumia are tokens and other items that resemble money but aren’t meant to be used in circulation. One of the more popular hobbies related to exonumia is the collection of elongated or pressed pennies, the concept of which made its stateside debut at the Chicago World’s Fair of 1893. Though the inventor of the machine remains a mystery, more than two dozen designs were presented at the fair. Pressed pennies can now be found at festivals and amusement parks around the country, including at Disneyland, where you can press over 150 collectible designs onto your penny. While pressing pennies is perfectly legal in the United States, the act is actually forbidden in Canada, because the Canadian Currency Act forbids using coins for any purpose other than currency. (Although penny-pressing machines do exist in Canada, at least some use a zinc American penny instead of a Canadian coin.)

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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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Pi (π) has intrigued scholars and mathematicians for millennia, dating all the way back to the ancient Babylonians. The mathematical constant, which is the ratio of a circle’s circumference to its diameter, is approximately equal to 3.14159 — “approximately” being the key word there. More accurately, pi is an irrational number that goes on forever without repeating itself. Its ubiquity in math, science, and beyond makes it one of the most recognizable, and most mysterious, numbers in the world. As a result, it has even garnered a holiday in its honor. Every March 14 (or 3/14, corresponding to the first three digits of pi), people in and out of the scientific establishment celebrate the beauty and practicality of pi. Here are some fun facts about this celebration and the number that inspired it.

PI day concept. Drawings of circles and formula with the number PI written on a blackboard.
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The First Pi Day Took Place in the 1980s

The first known celebration of Pi Day took place in 1988 at San Francisco’s Exploratorium. Physicist and curator Larry Shaw, aka the Prince of Pi, came up with the idea at a staff retreat and organized the museum’s inaugural event, which included fruit pies and tea served at 1:59, the three digits in pi after 3.14. Later celebrations included “pi-rades” of museum staff and visitors — each with a subsequent digit of pi — marching around the building behind Shaw, who upheld the tradition until his death in 2017. The Exploratorium still holds Pi Day events every year, with lectures, concerts, pi processions, and (of course!) dessert.

the world day of PI with the inscription 3.14 on a cup of cappuccino.
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Universities Celebrate Pi Day in Their Own Unique Ways

Since that first Pi Day in the 1980s, other institutions have adopted the holiday as their own, complete with math-themed celebrations and traditions. St. Bonaventure University, for one, has its Pi Day itinerary scheduled by the minute to correspond with the digits of pi. The festivities start on March 14 at exactly 1:59 p.m. and conclude 2 hours and 65 minutes later — symbolic of 3.14159265.

Not to be outdone, MIT posts its undergraduate admissions decisions for prospective students every year on Pi Day, often with cleverly strategic timestamps. In 2012, for example, the decisions were released at 6:28 p.m. to represent and approximate the mathematical constant tau. Three years later, they were posted at 9:26 a.m. — 3/14/15 at 9:26, corresponding to 3.1415926. And more recently, in 2020, they were made available online at 1:59 p.m., again to match the digits of pi.

Close-up of Professor Albert Einstein smoking out of a pipe.
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Pi Day Is Also Albert Einstein’s Birthday

The town of Princeton, New Jersey, celebrates Pi Day in conjunction with the birthday of one of its most famous former residents: Albert Einstein, who was born in Germany on March 14, 1879. The festivities include walking tours of Einstein’s favorite hangouts, a pi recitation competition, pie tastings, and even an Einstein look-alike contest. (Truly a genius way to celebrate.)

March 14 also happens to mark the anniversary of the death of another esteemed physicist, Stephen Hawking, who passed away at the age of 76 on that day in 2018. It’s not the only link between two of the 20th century’s most influential scientists, but it’s certainly an interesting cosmic coincidence.

Close-up of people hands taking slices of pepperoni pizza from a wooden board.
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Pi Day Is an Excuse to Get Cheap Pizza

Pi Day doesn’t really have anything to do with the kind of pie we eat — unless you count the fact that pies are traditionally circles — but that hasn’t stopped pie shops and other businesses from cashing in on the craze. Many restaurants offer discounts on pie on March 14, as well as specials on pizza, cake, and other circular treats. In the past, brands including 7-Eleven, CiCi’s Pizza, and even the Honey Baked Ham Company have gotten in on the action. If you ask us, any holiday that offers whole pizzas for $3.14 is one worth celebrating.

The Greek letter "Pi" on a chalkboard with a globe to the right.
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Pi Day Was Recognized by Congress in 2009

In the two decades after Larry Shaw’s first pi-themed celebration at the Exploratorium, Pi Day became such a widespread observance that on March 12, 2009, the U.S. House of Representatives passed a non-binding resolution supporting “the designation of a Pi Day and its celebration around the world.” The measure was backed by various science and technology organizations, including the Association for Competitive Technology and the American Chemical Society, in a lighthearted effort to encourage students to further engage with mathematics.

Pi Day has also garnered global recognition via UNESCO, which celebrates March 14 as the International Day of Mathematics.

Woman fingers with a pen writing the reminder pf Pi Day in the calendar.
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There’s More Than One Day to Celebrate Pi

March 14 isn’t the only date on which pi is celebrated. Some people also observe Pi Approximation Day on July 22, since the fraction that approximates pi is 22/7, which is that date written in the day/month format. Others cleverly honor pi on November 10, as it’s the 314th day in a non-leap year. A few even celebrate Two Pi Day (or Tau Day, as it’s also known) on June 28. Tau is the ratio of a circle’s circumference to its radius, equal to 2π or approximately 6.28 — making June 28 the perfect occasion for double servings of pi(e).

Fiona Young-Brown
Writer

Fiona Young-Brown is a Kentucky-based writer and author. Originally from the U.K., she has written for the BBC, Fodor’s, Atlas Obscura, This England, Culture, and other outlets.

Original photo by Billion Photos/ Shutterstock

Most of us are used to our wages or salary being paid directly into a bank account. Some might still receive a check in the mail. A few might even get an envelope at the end of each week or month containing their pay. But forms of payment in the past varied enormously, and some would seem downright strange to us in the 21st century. From salt to knives, here are six unusual ways people used to be paid for their labor.

Spilled salt and saltshaker on blue background.
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Salt

The word “salary” is derived from the Latin word salarium. This translates to “allowance” or “salt money,” and literally meant the allowance given to buy salt (sal is the Latin word for “salt”). Historically, salt was of great importance because it allowed for the preservation of food. Without salt, soldiers would need to fish or hunt for their food each day. Therefore, being paid in salt or with enough money to buy salt (which was an expensive commodity) made life more convenient. The word salarium made its way into French and then English, and by the Middle Ages “salary” was being used to refer to compensation for work. This is also the root of the phrase “worth your salt.”

Close-up of young bartender pouring beer while standing at the bar counter.
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Beer

After a hard day’s work, you might sit back and relax with a beer. In ancient Egypt and Mesopotamia, it might have been your payment. Egyptians considered beer a food of the gods (the deity Osiris supposedly taught people how to brew), and used it as both medicine and a type of currency. London’s British Museum holds a 5,000-year-old Sumerian stone tablet that historians think is a pay stub, and one that indicates payment made in beer. Early beers (often brewed by women) were thick, yeasty concoctions — almost meals in themselves — that were enjoyed by adults and children.

Knife-shaped premonetary currency in bronze.
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Knives

Receiving a knife as payment for your services was a common occurrence in ancient China from about the seventh to the second century BCE. In fact, money knives were often carried on a belt around one’s waist, providing easy access to them as currency or for more traditional purposes. According to legend, the practice may have originated when a prince who was running low on currency allowed his soldiers to use knives to barter with villagers. It then became more widespread, until the metal knives were a currency in their own right. Made of bronze, copper, or tin, segments of the knife could be cut off to use as payment, while the knife still retained its usefulness. Eventually the knives shrunk, until they became more like small knife-shaped pieces of metal used for currency than actual knives meant for cutting.

Eastern Grey Squirrel (Sciurus carolinensis) in the nature.
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Squirrels

It may sound gruesome to modern readers, but in Russia and Finland, squirrel pelts were once used as a form of currency. Fur was a valuable commodity in the frozen tundra, providing a source of clothing and blankets. Therefore, the pelts became important in trading. Sometimes those using pelts as currency went even further, using the ears, snouts, and other parts to make change. There was an incredible benefit to this system of currency: Some have speculated that it helped prevent plague. As the Black Death swept through most of Europe, the lack of squirrels to carry infection via fleas meant that people in Russia suffered from the devastating disease less than people in some neighboring countries.

Katanga Cross, archaic money from the Katanga Province of the Democratic Republic of the Congo..
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Katanga Crosses

If you were to see a Katanga Cross in a museum or gallery, you might think it was a piece of art, perhaps religious in nature. In fact, these striking copper crosses were a form of currency in parts of what is now the Democratic Republic of the Congo and Zambia in the 19th and early 20th centuries. The Katanga region is rich in copper, so the metal was frequently used in payment. Coppersmiths made the crosses by pouring molten metal into sand molds. Each one weighed about 2 pounds, and one cross could buy about 22 pounds of flour or six axes. In case of an emergency, the cross could also be melted down to craft into a spear or tool.

Old German notes (Emergency money or notgeld).
Credit: Anton Starikov/ Shutterstock

Notgeld

Currency is usually based on something that has perceived value. But what do you do when you can’t access the material used to make that currency? In the case of Germany and some parts of Europe after World War I, they improvised with notgeld (necessity money). Coins were hard to come by at the time, as they had been melted down for their metal during the war. Postwar financial woes also meant that paper money had little value. And so, localities began to use alternative forms of currency made out of whatever they had access to. Silk, foil, wood, and many other materials were used as notgeld. Although not official currency, their use was widespread within communities as a means to pay for goods and services.

Fiona Young-Brown
Writer

Fiona Young-Brown is a Kentucky-based writer and author. Originally from the U.K., she has written for the BBC, Fodor’s, Atlas Obscura, This England, Culture, and other outlets.

Original photo by Christoph Rueegg/ Alamy Stock Photo

Tunnels are an amazing feat of modern engineering. Since the invention of the tunnel boring machine in 1853, engineers have used advanced technology to drill, blast, and bore into the earth. From carving through mountains at 10,000 feet above sea level to creating underwater railways that connect continents, tunnels are built to make travel more seamless — whether you’re journeying from China to Tibet or hopping on a train from northern to southern Europe. Here’s a peek into the construction of five of the world’s longest tunnels for railways and cars.

A freight train with liquid cargo travels on the Guanjiao Extension Rail of the Qinghai-Tibet Railway.
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China: New Guanjiao Tunnel (20.3 miles)

The New Guanjiao Tunnel sits at 10,800 feet above sea level and comprises part of the highest-altitude railway in the world, the Qinghai-Tibet Railway. It’s also one of the longest tunnels in China, with Dongguan’s Songshan Lake Tunnel beating it by a mere 3.97 feet. As a part of the 1,125-mile railway system connecting China and Tibet, New Guanjiao is one of three high altitude tunnels on the track. Since the railway runs at such a high altitude, the train carries supplemental oxygen for any passengers suffering from altitude sickness. The New Guanjiao Tunnel, which replaced an older tunnel that was only 2.5 miles long, took seven years and a dual boring system to finish. It runs directly through a Tibetan plateau, reducing travel time within the tunnel from 2 hours to a mere 20 minutes.

Trains enter the Channel Tunnel in Folkestone, England.
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England and France: Channel Tunnel (31.3 miles)

Also called the Chunnel or Eurotunnel, the Channel Tunnel connects Folkestone, England, and Sangatte, France, and actually consists of three parallel tunnels — two for railways and one for security cars and emergency services. Named for the body of water that the tunnel bisects, this underwater passageway is considered a feat of engineering and has been named one of the “Seven Wonders of The Modern World." Eleven tunnel boring machines were used to dig the tunnel on either side of the channel. On the British side, the debris was carried out of the tunnel using a railway conveyor belt system; on the French side, it was combined with water and transported through a pipeline.

High speed train station at Pyeongtaek station.
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South Korea: Yulhyeon Tunnel (31.3 miles)

Tied with the Channel Tunnel for the world’s third-longest railway tunnel, South Korea’s Yulhyeon Tunnel is a single-tube, double-track tunnel that is part of the Suseo High Speed Railway, connecting Seoul and Pyeongtaek. The tunnel was primarily built using the New Austrian Tunnel Method (NATM), a construction method that is best employed with variable rock and soil conditions. Although it is the same length as the Channel Tunnel, Yulhyeon took much less time to complete — three years and five months — since it is not underwater, and much of the blasting occurred in a landscape with low mountains and without aboveground urban development to impede progress.

Construction workers board electric cars in the 33.65 mile Seikan Rail Tunnel.
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Japan: Seikan Tunnel (33.5 miles)

Until recently, the Seikan Tunnel held the record for the world’s longest tunnel. The tunnel travels below the Tsugaru Strait, connecting Honshu Island and Hokkaido Island in Japan. Servicing both passenger bullet trains and freight trains, nearly 15 miles of the man-made tunnel are located underwater. To make this subaquatic section, engineers blasted 2,900 tons of explosives in an area prone to dangerous earthquakes. The land section was created by conventional boring methods. It took 17 years to complete the tunnel, during which time 34 lives were lost due to accidents on the job, including cave-ins and floodings. Still, the underwater train has proved a much safer form of travel than the former inter-island ferry system that was often subject to dangerous weather conditions.

The north entrance of the new Gotthard base tunnel in Erstfeld.
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Switzerland: Gotthard Base Tunnel (35.4 miles)

In 2016, the Gotthard Base Tunnel overtook Seikan for the longest tunnel in the world. To top that, it’s also the deepest tunnel in the world, extending to 8,000 feet underground. The tunnel, which took 17 years to complete, runs a high-speed rail beneath the Swiss Alps, connecting northern and southern Europe. To build the tunnel, engineers faced an immense challenge with the rock’s unpredictability. Some rock was too soft, making it difficult to excavate and slowing down the work. When the conditions were right, however, the workers used a 30-foot tunnel boring machine that was able to dig a record-breaking 131 feet in a single day.

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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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Philosophy can be daunting. Over the past two millennia, there have been dozens of movements, doctrines, and various “isms.” The texts can be excruciatingly dense, cryptic, and dry. Yet some philosophical theories are so powerful, they shape the way you think and act without you even noticing. Here are six major philosophical ideas that still resonate today.

A portrait of Philosopher and mathematician Plato.
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Plato’s Theory of Forms

Close your eyes and imagine a perfect circle. Now open your eyes and try to draw one. That’s Plato’s metaphysics in a nutshell: While most of us can conceive of a perfect circle, none of us can recreate one. According to Plato, every object on Earth is imperfect (like the circle you drew) but possesses an ideal “form” (like the perfect circle in your mind). Forms are unchangeable, pure, and ideal. The objects on Earth are mere “shadows” — blemished imitations — of those forms.

While it may sound uselessly abstract, Plato’s Theory of Forms is actually the bedrock of much Western thought. Early Christian writers, for example, adopted Plato’s theory to build their understanding of God and heaven. It was also a major influence on early scientific thought. And it continues to affect our thinking today.

For example, replace the idea of the perfect circle with the perfect justice system. Many people believe that a truly fair, truly ideal system of justice is “out there.” They also believe that the current system falls short of that vision. Our belief that a standard, fixed, and ideal justice system is “out there” as a goal to aim toward is fundamentally Platonic.

This belief that all things possess inherent, discoverable qualities has a name: “Essentialism.” As we’ll later discover, it can be controversial.

Portrait of Rene Descartes.
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Descartes’ Dualism

“I think, therefore I am.” More than a catchy quote, the famous declaration by René Descartes continues to shape the way people live. And it all started in the 17th century when Descartes was engaged in a tit-for-tat on the topic of “radical doubt.”

At the time, many philosophers believed that we learn about certain truths through senses such as touch and sight. Descartes thought that this was wrong: The senses were deceiving. (A person, after all, could be hallucinating or dreaming.) Descartes’ critics responded by asking: “If the senses can be so deceiving, then what’s stopping us from doubting everything, including our own existence?” Descartes’ response: Cogito, ergo sum — “I think, therefore I am.” The fact that you can doubt your own existence, the philosopher said, is proof that you exist.

Mental phenomena, Descartes declared, are not part of the senses. They are not of the physical world at all. Rather, the mind and body are distinct, separate. Consciousness and the mind are not made of physical matter.

This latter argument, called Cartesian dualism, was widely adopted by thinkers across the West and led to a flourishing of scientific thought, particularly in medicine. Writing for the journal Mens Sana Monograph, psychology professor Mathew Gendle notes, “The formal separation of the ‘mind’ from the ‘body’ allowed for religion to concern itself with the noncorpoeal ‘mind,’ while dominion over the ‘body’ was ceded to medical science.”

This advance contributed to great strides in medicine, but it also created problems. For one thing, it encouraged a view that physical and mental problems are entirely separate, without the ability to influence one another. It also promoted a sense that mental experiences are less legitimate than physical ones, contributing to a culture that often stigmatizes mental health concerns. As it turns out, when an entire society separates mind from body, we risk treating mental health problems as less “real,” even though they can affect us just as much as any broken bone.

The French philosopher Jean Jacques Rousseau.
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Rousseau’s “General Will”

Jean Jacques Rousseau never viewed himself as a mere philosopher — he was also a musician, playwright, and composer. But his political philosophy had a more lasting influence than any aria, shaping governments across the world.

In the 1760s, Rousseau was in his 50s and monarchs were still ruling Europe. The Geneva-born thinker believed that kings and queens had no divine right to legislate the masses, however. He outlined these beliefs in a book called The Social Contract, envisioning a world where free and equal people ruled. When the book was promptly banned in France, it proved Rousseau’s central thesis: Individual freedom was easily hampered by the authority of the state.

In The Social Contract, Rousseau spent a lot of time exploring the contradictions of freedom. Society was expanding at the time, and people were growing more dependent on others for survival. A strong state was necessary to help ensure equality and justice. But how could you build strong political institutions — endowed with power and authority — and still protect individual freedoms?

Rousseau’s solution was his theory of “the general will.” Under a monarchy or a dictatorship, laws routinely impinge on freedoms. Rousseau argued that, to protect those freedoms, laws had to be determined by the collective will (or “general will”) of the citizenry. And the best tool to interpret the general will was via democracy. Only then could the state truly serve the will of the people.

Rousseau’s theory is credited with sparking the French Revolution and possibly inspiring many of the Founding Fathers of the United States. Today, many of our political differences continue to revolve around the fundamental tension Rousseau identified: how best to balance personal freedoms with state power.

Portrait of philosopher Arthur Schopenhauer.
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Schopenhauer’s Theory of Aesthetics

Arthur Schopenhauer was a famous curmudgeon, a wild-haired pessimist who notably helped introduce Western intellectuals to Indian philosophy. His writings, however, would forever change the way we think about art.  

Before Schopenhauer, most artwork — whether music or painting or dance — was considered a frivolous diversion or akin to a decorative craft, not an expression of genius or a person’s innermost feelings. But Schopenhauer helped change those attitudes with his theory about the human will. It’s complicated, but briefly: The philosopher believed we are held captive by our wills — our strivings, our desires, our urges — and are doomed to suffer.

One way to escape this suffering, Schopenhauer argued, was through aesthetic experiences. Art functions as a quasi-religious experience, freeing us from the suffering of our own will. Furthermore, he argued, great art was the product not of mere craftsmen, but of genius.

Naturally, a lot of artists liked Schopenhauer’s thoughts on aesthetics. Richard Wagner, Leo Tolstoy, and reams of other creatives trumpeted his work, which elevated art to a higher plane. Thanks to Schopenhauer’s theories, artists and artwork started being lauded as vital and necessary to the health of society. A canon of famous masterpieces was assembled, with people treating their creators with a growing God-like reverence. Many of these attitudes, which helped define 19th-century Romanticism, still persist today.

Portrait of Friedrich Nietszche.
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Nietzsche’s Übermensch

One of the most misunderstood and misappropriated philosophers, Friedrich Nietszche is often cast as a gloomy nihilist. But that gets it wrong. Nietzsche was staring into the headlights of a crisis and wanted to help humanity before it was too late.

In his 1882 book The Gay Science, Nietzsche famously wrote that “God is dead.” But the philosopher wasn’t advocating for atheism, he was making an observation: Christianity had lost much of its power in Europe.

For centuries, Christian thought was — for better and for worse — the foundation of the continent’s value system. But by the late 19th century, science and scholarship had chipped away at people’s faith. Nietzsche saw two possible outcomes: Either people would despair into nihilism and drift away from any moral principles, convinced life had no meaning, or they would try to find new “religions” elsewhere, namely in mass political movements like fascism or communism.

Nietszche shuddered at the thought of the second option, which would later become frighteningly real in his home country of Germany. He argued that people had no choice but to forge ahead through nihilism instead. But rather than embrace a meaningless life — and fall into corrosive despair — he offered a way to overcome this nihilism: the “Übermensch.”

To Nietszche, the Übermensch is a person who rises above the conventional notions of morality and creates new values that embrace the beauty and suffering of existence. Hardly just the stuff of gloomy teenagers, Nietszche’s philosophy aimed to be life-affirming. (In fact, alternate translations of The Gay Science call it “The Joyful Wisdom.”)  

The philosopher Jean-Paul Sartre.
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Sartre’s Existentialism

Remember Plato’s forms, the idea that everything on Earth is an imitation of an ideal form possessing a distinct essence? Essentialism has helped serve as the foundation of some of humanity’s great ideas. But it’s also been deployed in service of discrimination, suggesting that certain people — based on their race or gender — intrinsically possess specific (often negative) traits.

French philosopher Jean-Paul Sartre thought essentialist thinking was faulty. For Sartre, essences do not pre-exist people. Our world is not an imitation of “forms.” Rather, it’s the reverse: “Existence precedes essence,” Sartre said. Our values, our identity, and our purpose on Earth are not inherent or predetermined. We are not some imperfect manifestation of some perfect cosmic blueprint. Rather, we create our own essence by going out into the word, living, and making choices.

This basic declaration is the very starting point for Sartre’s existentialism, the idea that humans are “condemned to be free” and that “life is nothing until it is lived … the value of it is nothing else but the sense that you choose.”  

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