Popular beliefs

Cracking your knuckles has consequences, but not the ones you think

You’ve heard it before: Don’t swim after eating. You’ll lose most of your body heat through your head. Swallow a piece of gum, and it’ll stay in your body for years. Many of these common beliefs that parents or teachers have told you repeatedly over the decades are simply not true. Here are 10 everyday myths that science has set straight, and the real stories behind them.

The myth of carrots providing a better sense of vision in the dark became especially popular during World War II, when the British government promoted this idea to help explain the success of its pilots while keeping its new airborne radar technology a secret. It was just a myth, although there was a scientific explanation to back it up.

Carrots are rich in beta-carotene, which your body converts into vitamin A, an important nutrient for healthy vision. If someone is deficient in vitamin A, eating more of it can improve their eyesight. But for people who already get enough of the vitamin, extra carrots won't suddenly make it easier to see at night.

You hear footsteps in the middle of the night and find a family member quietly wandering through the house while asleep. Your first instinct is to wake them up, but remember you’ve been told it’s dangerous. That’s just a myth, so go ahead and wake them.

The person may be startled, confused, or briefly disoriented, but there’s no evidence that being awakened causes physical injury. The bigger concern is that someone suddenly pulled from sleep may react unpredictably or accidentally lash out because they don’t understand what’s happening. For that reason, sleep specialists usually recommend gently guiding the person back to bed if it’s safe to do so, rather than abruptly shaking them awake, but there’s no intricate danger to waking a sleepwalker.

Almost everyone has heard the sharp popping sound of someone cracking their knuckles, followed by another person saying, "Keep doing that, and you’ll get arthritis."

Researchers have been looking into that claim for decades, and the evidence simply doesn’t support it. The popping sound comes from tiny gas bubbles forming and collapsing inside the fluid that lubricates your joints, not from bones grinding together. Multiple studies comparing habitual knuckle crackers with people who never crack their knuckles have found no higher risk of developing arthritis. Some research has suggested that frequent knuckle cracking may slightly reduce grip strength or cause temporary swelling in a few people, but it has not been shown to damage the joints. So while the sound may bother the people around you, it isn’t likely to lead to arthritis.

Most of us have heard someone say, "Imagine what you could do if you used the other 90 percent of your brain." The truth is that modern brain imaging has shown that virtually every part of the brain has a purpose.

Even when you’re resting, different regions are constantly working together to control movement, memory, breathing, emotions, vision, and countless other functions. While not every area is active at the same moment, there is no large section of the brain sitting permanently unused. Scientists aren’t exactly sure where or how this myth started, but your brain is one of the busiest organs in your body. Even while you’re asleep, it’s hard at work keeping you alive and processing the day’s experiences.

If a child accidentally swallowed a piece of gum, some adult would inevitably claim it would sit in the stomach for the next seven years.

The warning, even if a myth, contains a small grain of truth. The gum base isn’t fully broken down by the digestive system the way other foods are. But that doesn’t mean it stays behind. Instead, it moves through your digestive tract along with everything else you eat and is naturally eliminated within a few days. So while swallowing pieces of gum isn’t something doctors recommend making a habit of, there’s no need to worry if it happens by accident.

After lunch at the lake or a backyard barbecue, the adults would insist everyone, especially the kids, stay out of the water for at least an hour. The idea was that digestion would pull blood away from your arms and legs, causing severe muscle cramps that could make you drown.

Medical research, however, has found no evidence that eating before swimming creates that kind of danger. While vigorous exercise immediately after a very large meal might make some people feel uncomfortable or sluggish, a normal swim after eating is generally considered safe for healthy individuals. The "wait an hour" rule probably prevented plenty of cannonballs during nap time over the years, but it wasn’t based on scientific evidence.

If you ever left the house on a cold winter morning without a hat, chances are someone reminded you to wear one since "most of your body heat escapes through your head." The belief became widespread after military studies conducted in the 1950s observed significant heat loss from uncovered heads. What they didn’t notice was that the subjects were bundled up everywhere else. Naturally, their only exposed body part lost the most heat.

In reality, your head loses heat at about the same rate as any other uncovered area of skin, depending on its size. A warm hat is still a smart idea on a cold day, but only because it covers exposed skin, not because your head has some special ability to leak away most of your body heat.

Many tongue illustrations show the tongue divided into neat sections, with one area for sweet foods, another for salty flavors, and others for sour and bitter. The famous "taste map" came from a misunderstanding of research published in the early 1900s.

While some parts of the tongue may be slightly more sensitive to certain flavors than others, taste buds across nearly the entire tongue can detect sweet, salty, sour, bitter, and umami, the savory taste found in foods like mushrooms, cheese, and broth. The old diagram appeared in textbooks for decades, making it one of the most successful scientific misconceptions ever taught in classrooms. Today, we know the tongue is much more versatile than that simple map suggested.

If you grew up in the age of bulky television sets, you may remember a parent telling you to back away from the screen before you damaged your eyes. That warning became especially common in the 1960s when early television models were found to emit unusually high levels of radiation because of a manufacturing defect. Those sets were quickly recalled, but the myth lingered long after the problem disappeared.

Modern televisions don’t pose that risk. Sitting very close to the screen may leave your eyes feeling tired or dry after a while, but it doesn’t cause permanent damage to your vision. Even if screen time is not recommended for children up until 7 years old, the screen itself isn’t likely to be the cause of poor eyesight.

Everyone learned about the five senses at some point: sight, hearing, smell, taste, and touch. That lesson dates back more than 2,000 years to the ancient Greek philosopher Aristotle.

However, modern science paints a much more intricate picture. In addition to the five traditional senses, your body constantly relies on other senses that work without you even noticing them. These include your sense of balance, your awareness of where your arms and legs are without looking, your ability to feel pain, temperature, and more. Depending on how they’re classified, scientists recognize anywhere between 10 and 20 different senses.

Deathbed statements

Beyond the grave: Take a look at the last words of 12 famous people

Image: Daderot, CC0, via Wikimedia Commons

Throughout history, hundreds of historical figures have left their mark on the world through their marvelous achievements. When their lives came to an end, their last words were often a reflection of their lives and ideals. From George Washington and Mark Twain to Frank Sinatra and Leonardo Da Vinci, in this article, we will reveal 12 final words of memorable personalities.

Image: The New York Public Library

After serving two terms as the United State's first president, George Washington retired to his Virginia plantation. In mid-December 1799, he developed a cold and a severe sore throat. Despite doctors' efforts to cure him, the end was imminent.

His long-time secretary, Tobias Lear, was at his side during his last days and documented all the events that transpired, including the former president's last words. According to his account, shortly before he took his last breath George Washington said "Tis well" —an old-fashioned way of saying "everything is okay."

Image: Signal Corps Archive from United States, Public domain, via Wikimedia Commons

Noir icon of perpetual elegance and rebellious charisma, Humphrey Bogart is an undisputed legend in cinema history. A Hollywood Golden Age star, Bogart is still remembered today for his scar on his upper lip, his everlasting cigarette, and his perfect portrayal of gangsters and detectives.

At the age of 57 Bogart was diagnosed with esophageal cancer, for which he was hospitalized for several months. According to lore, the legendary star's last words were "I should never have switched from scotch to martinis." However, his wife Lauren Bacall confirmed that the last thing he actually said was "Goodbye Kid. Hurry back," before she left his bedside to get their children.

Image: Miscellaneous Items in High Demand, PPOC, Library of Congress, Public domain, via Wikimedia Commons

As one of the greatest American writers of all time, Mark Twain is usually credited with all sorts of great quotes that he often didn't say. For that reason, there are different versions of what his last words were before he died in 1910 at the age of 74.

The most plausible theory can be found in an article published one day after his death. According to this chronicle, Samuel Langhorne Clemens' last words were not spoken aloud but written. The famous humorist and essayist reportedly wrote to his daughter Clara, who accompanied him on his bedside, "Give me my glasses."

Image: MGM, Public domain, via Wikimedia Commons

Joan Crawford, the Oscar winner for Mildred Pierce and one of the greatest stars of Hollywood's golden age, died in 1977 of a heart attack.

The actress, who had a complicated personality, was true to her nature until her last breath. She was so ill that her doctor felt it wasn’t worth taking her to the hospital. One of her nurses began to pray aloud in desperation. Losing her patience, Crawford snapped for the last time and said, "Damn it... Don't you dare ask God to help me."

Image: Municipal Library of Trento, CC0, via Wikimedia Commons

The year 2024 marked the 700th anniversary of the death of the man who better described remote lands. Marco Polo was a merchant who spent more than 20 years of his life traveling through the Orient and wrote about his adventures in a book that became a bestseller when the printing press wasn’t even invented.

Marco Polo was, and still is, a legend. When, on his deathbed, his wife and friends begged the brave explorer to confess if what he had told in the book was true, he barely whispered: "I have not told the half of what I saw and did."

Image: MGM, Public domain, via Wikimedia Commons

Julius Henry Marx, better known as Groucho Marx, is considered one of the most influential comedians of all time. The man with the bushy black mustache was one of the Marx Brothers. Together they made 13 films, including the classic Duck Soup. After a long and prominent career, Groucho passed away in Los Angeles in 1977 at the age of 86.

His brilliant one-liners are still remembered and replayed to this day, so it is not surprising that not one but several final words are attributed to him. A few close friends have suggested that his last line was "This is no way to live!", while most suggest that his last words were in fact dedicated to his wife: "Die, my dear? Why, that's the last thing I'll do!"

Image: Nicolas de Largillière, Public domain, via Wikimedia Commons

Voltaire, the French writer, philosopher, historian, and lawyer, one of the major figures of the Enlightenment, died in 1778 at the age of 83. Different accounts of his deathbed make it impossible to determine exactly what his last days were like.

One of these stories, however, is consistent with his ideas about God and his well-known criticism of the Church. According to this version, when the priest asked him if he wanted to renounce Satan before he died, Voltaire replied, "This is no time to make new enemies."

Image: William Wallace Denslow, Public domain, via Wikimedia Commons

L. Frank Baum was a prolific American author. He wrote 55 novels, 82 short stories, and more than 200 poems. However, his most memorable work is his series of children's fantasy books The Wonderful Wizard of Oz.

On May 5, 1919, Baum suffered a heart attack. He died the next day, shortly before his 63rd birthday. Disturbed by the imminence of death, he whispered to his wife: "Now we can cross the Shifting Sands," a clear reference to the Land of Oz.

Image: National Archaeological Museum of Athens, CC0, via Wikimedia Commons

Augustus, the first Roman emperor, is often attributed with the phrase: "Behold, I found Rome of clay, and leave her to you of marble," alluding to the great infrastructural works carried out during his prosperous 40 years of rule.

However, according to other historical accounts, his last words were addressed to the friends who stayed with him on his deathbed: "Have I played the part well? Then applaud, as I exit."

Image: English: Distributed by NBC. Photographer unknown., Public domain, via Wikimedia Commons

"Darling, you've gone through worse and you can beat this too. You have to fight," implored Barbara Marx, Frank Sinatra's fourth wife, to her beloved on his deathbed. "I'm losing," The Voice whispered through teary eyes.

Barbara recounted the last hours of the singer of such hits as My Way and New York, New York in her memoir Lady Blue Eyes: My Life With Frank. Frank Sinatra, one of the most popular entertainers of the mid-20th century, pronounced his last words in 1998 at the age of 82.

Image: Jean-Auguste-Dominique Ingres, CC0, via Wikimedia Commons

Despite being one of the most famous artists of the Renaissance, Leonardo da Vinci was very hard on himself. All his life he challenged his own limits, evident in his paintings and sculptures as well as in his inventions, some of which were truly revolutionary.

Even after a lifetime of success, he wasn’t quite satisfied. When he suffered a stroke at the age of 67, he sent for a priest to receive the Holy Sacrament and, according to historians, his greatest regret was that he hadn’t achieved excellence with his work. In that sense, it is said that his last words were: "I have offended God and mankind because my work did not reach the quality it should have."

Image: National Museum of Health and Medicine, Public domain, via Wikimedia Commons

The Yankee Clipper was one of the greatest baseball players of all time but he is also known for having been married to the iconic American actress Marilyn Monroe. Joe and Marilyn were together for less than three years. In 1955 the actress left him for American playwright Arthur Miller.

DiMaggio was devastated. He never married again, and never got over his one true love. His last words before he died in 1999 at the age of 84 were: "I'll finally get to see Marilyn."