Some myths die hard. They travel from generation to generation, get repeated in school hallways and family dinners, and eventually take on the feel of settled fact. The trouble is, settled doesn’t mean accurate. A surprisingly large number of things most people accept without question have been quietly dismantled by researchers, physicians, historians, and scientists.
What makes these myths so persistent isn’t stupidity. It’s familiarity. Once an idea gets embedded in culture – in movies, parenting advice, or casual conversation – it tends to stick around regardless of what the evidence says. Here are fifteen of the most widely believed myths that experts say have no real basis in fact.
1. We Only Use 10 Percent of Our Brains
The ten-percent-of-the-brain myth states that humans generally use only one-tenth of their brains, a claim that has been misattributed to many famous scientists and historical figures, notably Albert Einstein. Neuroscientific research utilizing methods such as functional magnetic resonance imaging (fMRI) and positron emission tomography (PET) has demonstrated that many areas of the brain remain active even during simple tasks.
Researchers note that all of the brain is constantly in use and consumes a tremendous amount of energy. Despite making up only about two percent of body weight, it devours roughly twenty percent of the calories a person consumes. If we needed only ten percent of our brain, the majority of brain injuries would have no discernible consequences, since the damage would affect parts of the brain that weren’t doing anything to begin with. That alone makes the myth implausible on its face.
2. Cracking Your Knuckles Causes Arthritis
While cracking your knuckles may be annoying for those around you, it has no correlation to arthritis in those joints. Several studies that aimed to find a link between the two found no substantial evidence of any correlation. Knuckle cracking is simply a bubble being formed and popped by the liquid that surrounds the knuckle joints, and it causes no trauma to these areas that would accelerate the onset of inflammation, which is what arthritis actually is.
However, those who excessively cracked their knuckles did have slightly weaker grip strength later in life. So while it won’t give you arthritis, that doesn’t mean it’s entirely consequence-free. Still, for decades parents have been warning children about a joint disease that knuckle cracking simply cannot cause.
3. You Need to Drink Eight Glasses of Water Every Day
The idea that people need to drink eight cups of water every day was derived from a 1940s article in which the specifics of the recommendation were lost in the article’s summary. The article actually stated that fluid ingested through food counts toward that amount. How much a person should hydrate depends on the humidity and average temperature of their climate, as well as their activity level and genetics.
This doesn’t mean hydration doesn’t matter – it absolutely does. It means the famous “eight glasses” rule was never a hard scientific prescription. Individual needs vary considerably, and people get meaningful fluid intake from the foods they eat every day, not just from water poured into a glass.
4. Eating Carrots Dramatically Improves Your Eyesight
This notion dates back to World War II and a British propaganda campaign claiming that carrots can help you see in the dark. Ultimately it is a myth, but it is based on a sliver of truth. The real reason RAF pilots were able to locate and shoot down German planes was an improvement in radar technology. The British government simply needed a cover story – and a vegetable surplus to move.
Studies show that taking vitamin A can reverse poor vision caused by a deficiency, but it will not strengthen eyesight or slow decline in people who are already healthy. Binging on carrots would not improve most people’s eyesight. If your diet is reasonably balanced, loading up on carrots won’t sharpen your vision at all.
5. Sugar Makes Children Hyperactive
The claim that sugar causes hyperactivity in children has been debunked by numerous studies. Sugar does not cause hyperactivity in children. One study reported that children who were given sugar had higher levels of adrenaline, which is a possible explanation for this misconception because higher adrenaline levels lead to symptoms similar to those of hyperactivity. The association isn’t with the sugar itself.
Part of what sustains this belief is expectation. When parents believe their child has consumed sugar, they tend to rate that child’s behavior as more hyperactive – even if the child was given a placebo. Context and anticipation do much of the work that people attribute to the sugar itself.
6. The Five-Second Rule Keeps Food Safe to Eat
Otherwise known as “the five-second rule,” this myth contends that if food falls on the floor and you scoop it up within five seconds, it’s safe to eat because it’s not enough time for germs to transfer. Scientists tested this theory and found that bacteria can hop aboard dropped food almost immediately upon contact. Whether or not you get sick depends on what type of bacteria happens to catch a ride into your digestive tract.
The type of floor surface and the moisture content of the food actually matter more than time. Wet or sticky foods pick up bacteria faster than dry ones, and a highly contaminated surface transfers pathogens almost instantly. The five-second window is essentially a cultural comfort, not a biological fact.
7. You Can’t Teach an Old Dog New Tricks – and Adults Can’t Learn New Skills
There’s a common belief that learning is primarily for children and young adults. In reality, learning is a lifelong process. Adults can continue to grow intellectually and develop new skills at any stage of life. The brain retains a degree of plasticity throughout adulthood that scientists once thought was reserved for childhood.
Many people pursue new hobbies, careers, or areas of study well into their later years, proving that education has no age limit. Neuroplasticity – the brain’s ability to form new connections – doesn’t simply switch off at a certain birthday. It slows, but it never fully stops. Adults who engage in regular mental challenges continue to build new neural pathways.
8. Lightning Never Strikes the Same Place Twice
The idea that lightning doesn’t strike the same place twice is a popular misconception. Lightning strikes are far too frequent to avoid hitting the same place on earth multiple times. Studies show that around five hundred to a thousand lightning strikes happen globally every second.
The Empire State Building was once used as a lightning laboratory because the building is struck with lightning around one hundred times a year. Tall structures, isolated trees, and metal objects are actually more likely to attract repeated strikes precisely because they offer a reliable path of least resistance. The saying is poetic – it just isn’t physics.
9. The Great Wall of China Is Visible from Space
The Great Wall of China is certainly large, at 13,171 miles long. But it is unable to be seen from space with just the unaided eye. In November 2004, an astronaut named Leroy Chiao was determined to get a picture of the wall from space, and with the aid of his camera’s lenses, he was able to capture the first photograph of the Great Wall from space. Note: he needed a camera with a lens, not just his eyes.
The Great Wall of China is nearly the same color as the area surrounding it, so it’s difficult to distinguish the wall from its surroundings. From low Earth orbit, astronauts have said they can see cities, major roadways, dams, and even airports – but those are wide and visually distinct. A wall that blends with its landscape simply doesn’t register at that distance.
10. Ostriches Bury Their Heads in the Sand When Frightened
Contrary to the popular myth, ostriches don’t stick their heads in the ground when they feel threatened. Their first instinct is to run, and they are fast – their top speeds reach 43 miles per hour. If they can’t run, they aren’t afraid to fight. An ostrich can kick with such force that it can easily take out a full-grown lion.
The myth did have an origin in ostrich behavior. Ostriches will lay down flat to play dead if they feel they can’t win a fight, and this combined with their lightly colored head and neck makes it look as if the ostrich has buried its head into the earth. So the behavior is real – the interpretation of it just got mangled over centuries of retelling.
11. Bulls Are Enraged by the Color Red
The popular myth that bulls become angry when they see red comes from the tradition of bullfighting, where a matador waves a red cape. However, it’s not the color of the cape that angers the bull – it’s the movement of the cape. Many experiments with different colored capes being stationary and being moved showed the bull favored movement over color every time.
Bulls are actually red-green colorblind and would have a hard time distinguishing red from green, orange, and brown. The red color of a traditional bullfighting cape is a theatrical tradition, not a functional one. It may help conceal bloodstains and create visual drama for the crowd, but for the bull, the color is essentially irrelevant.
12. Putting a Wet Phone in Rice Will Save It
Submerging a water-damaged cell phone in a bag of rice has been the quick go-to rescue remedy for years, but tech experts now warn against it. Originally, it was thought that sticking a wet cell phone into uncooked rice would absorb all the phone’s moisture. But the small particles of rice are incapable of sucking out the water and can introduce dust and other particles into the phone, causing internal damage.
In addition, mushy and sticky pieces of rice can get stuck inside certain essential parts of the phone, such as its speaker cavities and ports. Experts now recommend gently drying a wet device, leaving it powered off in a dry environment, or contacting the manufacturer for guidance. Rice is better left for dinner.
13. Listening to Mozart Makes Babies Smarter
The belief that listening to Mozart or other classical music makes people smarter is widespread. While music can be relaxing or enjoyable, there’s no solid evidence that it significantly enhances cognitive abilities. The original “Mozart effect” came from a single, limited 1993 study on college students completing spatial reasoning tasks – not babies, and not long-term intelligence.
Subsequent research has largely failed to replicate meaningful cognitive gains from passive music listening. The study’s findings were modest, temporary, and specific to one narrow type of task. The leap from that to “play Mozart to your infant for lasting brain benefits” was made by marketers and popular media, not scientists.
14. Eating Smaller, More Frequent Meals Boosts Your Metabolism
The idea behind this myth is that eating small, frequent meals could boost your metabolism so you burn more calories. However, studies show that splitting the same number of calories into six meals rather than three does not help with daily energy expenditure or fat loss. Researchers at the University of Colorado found that those who ate smaller, more frequent meals actually ended up feeling hungrier than their counterparts who ate less often.
Total caloric intake and the overall quality of what you eat still matter far more than meal timing or frequency. There’s no metabolic magic in grazing throughout the day. For some people, eating more frequently may actually make portion control harder, not easier.
15. You Shouldn’t Wake Someone with a Concussion
Back in the day, the only way to test brain function in a concussed person was to wake them every hour and gauge their level of responsiveness. Now, CT, MRI and PET scans can tell us how alert and oriented a patient is. We now know that the brain recovers more quickly when it gets lots of rest. Keeping a concussed person awake through the night was a precaution rooted in the limitations of older medicine, not in neuroscience.
Today, medical professionals advise rest and monitoring rather than sleep deprivation. If there are serious warning signs – such as unequal pupils, repeated vomiting, or severe headache – those require urgent medical attention regardless of wakefulness. The old practice of hourly wake-ups, while well-intentioned, turns out to have been counterproductive to actual recovery.
What’s striking about so many of these myths is that most of them contain a tiny seed of something plausible. Carrots do have vitamin A. The brain does have resting states. Knuckle cracking isn’t good for you. That partial truth is often exactly what keeps a myth alive – it gives people just enough reason not to question the rest of it. The real takeaway isn’t that common knowledge is always wrong. It’s that familiarity is not the same as evidence, and it’s always worth pausing to ask who actually checked.
