Some lies are told deliberately. But the ones that stick around for centuries? Those tend to travel on the back of something more innocent — a misquote passed from teacher to student, a half-truth made catchy enough to survive the morning news cycle, a plausible story that nobody ever bothered to check.

This piece is about those myths. The comfortable, familiar, completely wrong ideas that most of us carry around like loose change we never thought to count. Some will surprise you. A few might even make you a little angry. And one or two will probably make you think twice the next time someone presents a “well-known fact” with absolute confidence.

Let’s get into it.

Neuroscience

The Myth
We only use 10% of our brains

The Truth
Your entire brain is working — all the time.

This one has been cited in self-help books, motivational speeches, and superhero movies for decades. The pitch is appealing: you’re a genius sitting on 90% untapped potential. Unlock it, and sky’s the limit. The problem? It’s not even close to accurate.

Brain imaging technology like fMRI has shown that virtually all regions of the brain are active at one point or another throughout any given day. Even while you sleep, your brain is buzzing. Different regions handle different tasks — your visual cortex lights up when you see, your motor cortex fires when you move — but there’s no dormant 90% gathering dust.

The myth likely evolved from misquotes of psychologists and neuroscientists from the early 20th century, later amplified by the self-improvement industry. It’s a feel-good lie. The brain you have is already fully employed; it’s just a matter of how you use it.

Weather & Physics

The Myth
Lightning never strikes the same place twice

The Truth
Lightning strikes the same spot over and over. Tall structures practically count on it.

The Empire State Building in New York City is struck by lightning roughly 20 to 25 times per year. During electrical storms, it has been recorded taking multiple strikes within a single storm. So much for “never twice.”

Lightning doesn’t have a memory. It follows the path of least resistance between a storm cloud and the ground. Tall, conductive objects — antennas, towers, trees, skyscrapers — get hit repeatedly for precisely this reason. That’s the whole reason lightning rods exist: to be struck, deliberately and repeatedly, so buildings stay safe.

The phrase was originally a metaphor about unlikely misfortune striking again — and somehow it leaked into the public consciousness as a statement of physical fact. It isn’t.

Astronomy

The Myth
The Great Wall of China is visible from space

The Truth
Even astronauts have admitted they couldn’t see it — and they looked.

This claim has appeared in Chinese school textbooks and appears to be one of those “facts” that nobody thought to question because it sounds impressively grand. The Great Wall stretches thousands of miles, after all. Surely something so large must be visible from orbit?

Not quite. Width is the problem, not length. The wall averages about 15 to 30 feet wide. From low Earth orbit — roughly 250 miles up — that’s thinner than a human hair would appear from a meter away. Chinese astronaut Yang Liwei, after completing his first spaceflight in 2003, confirmed he could not spot it. NASA has also repeatedly addressed this: the wall simply isn’t wide enough to distinguish from the terrain around it.

With powerful zoom lenses under ideal conditions, photographs have captured faint traces — but unaided human eyes from space? Not a chance.

Human Biology

The Myth
Blood inside your body is blue

The Truth
Your blood is always red. Every drop of it.

You’ve probably heard this one in a science class: blood in your veins is blue because it’s carrying carbon dioxide rather than oxygen, and only turns red when it hits the air. The veins on your wrist look blue, so it seems to make sense. It doesn’t.

Blood contains hemoglobin, an iron-based protein. When hemoglobin carries oxygen, it turns bright red. When it releases oxygen, it becomes a darker, duller red — not blue. Not ever. If you drew blood directly from a vein into a tube sealed from air, it would be dark red, sometimes almost maroon.

The confusion comes from optics. Skin absorbs different wavelengths of light unevenly, and the way blue and red light penetrate tissue makes deoxygenated veins appear blue or green through your skin. But inside? Your blood has never, not once, been anything other than some shade of red.

History

The Myth
Napoleon Bonaparte was unusually short

The Truth
He was average height for his era — and possibly above it.

Napoleon’s short stature has become one of history’s most persistent jokes. The image of the little emperor with his hand tucked inside his coat, bristling with a short man’s aggression, has become almost cultural shorthand. It’s also largely a fabrication.

Historical records suggest Napoleon stood around 5’7″ — average to slightly above average for a French man in the late 18th and early 19th centuries. The confusion arose partly from a unit conversion error: Napoleon was recorded as 5’2″ in French inches, which were longer than British inches. British propagandists, particularly caricaturist James Gillray, seized on this and depicted him as a tiny tyrant — and the image stuck.

His nickname among his own soldiers was “le petit caporal” — “the little corporal” — which was a term of affection, not a jab at his height. History, it turns out, has short-changed him in more ways than one.

Sleep & Insects

The Myth
You swallow 8 spiders in your sleep every year

The Truth
Spiders have very little reason to wander into your mouth — and they usually don’t.

Few myths are as viscerally upsetting as this one, which is perhaps why it spreads so effectively. The specific number — always 8, always per year, always “on average” — lends it a scientific authority it doesn’t deserve.

Spider researchers and entomologists have addressed this repeatedly. A sleeping human is essentially a terrifying landscape for a spider. The vibrations from breathing, the rumble of snoring, the warmth and movement — all of these are predator signals to a small arachnid. Spiders don’t seek warmth inside mouths, and they have no food-related reason to go there.

The myth was actually used as an example of how easily false information spreads, in a 1993 magazine column by columnist Lisa Holst, who made it up to illustrate that people believe anything stated with enough confidence. It worked so well that the myth outlived the joke.

Nutrition

The Myth
Carrots improve your eyesight

The Truth
Carrots prevent a deficiency — but they won’t give you eagle eyes.

This one has a surprisingly traceable origin. During World War II, British RAF pilots with powerful new radar technology were shooting down German planes in the dark. To conceal the secret weapon, British intelligence put out propaganda claiming their pilots had exceptional night vision from eating carrots. The story caught on, and was even promoted to the British public as a reason to eat more of the vegetable during rationing.

Carrots contain beta-carotene, which the body converts to Vitamin A. Vitamin A deficiency can cause night blindness and vision deterioration — and in that case, getting more carrots (or any Vitamin A source) genuinely helps restore normal vision. But if your Vitamin A levels are already fine, eating more carrots does precisely nothing for your eyesight.

You can’t improve a system that’s already running at full capacity by throwing extra fuel at it. The orange vegetable is healthy — just not magic.

Human Body

The Myth
Hair and nails keep growing after death

The Truth
Growth requires living cells. The dead don’t grow — but they do shrink.

This one has fueled countless horror stories and gothic literature, lending the recently deceased an eerie quasi-life that makes them feel not quite finished. As atmospheric as it is, the biology doesn’t support it.

Hair and nail growth both require glucose and cellular activity driven by living tissue. Once the heart stops and circulation ends, that cellular activity ceases. What actually happens is that the skin dehydrates and retracts after death, pulling back from the hair follicles and nail beds. The hair and nails appear longer because the surrounding skin has shrunk, not because the keratin itself has extended.

It’s an optical illusion produced by biology — an illusion so convincing that it became part of our folklore about death. Not the last time that the living have badly misread what the dead are doing.

Animal Intelligence

The Myth
Goldfish have a 3-second memory

The Truth
Goldfish can remember things for months — and can even be trained.

Poor goldfish. They’ve been reduced in the cultural imagination to the world’s most forgetful animal — swimming in an eternal present, always discovering their bowl for the first time. It makes the small plastic tank seem more acceptable, perhaps.

In reality, goldfish have demonstrated memory spans of at least three months in controlled research settings. They can be trained to press levers for food, navigate mazes, and even distinguish between different music pieces. Studies have shown that goldfish learn to associate specific times with feeding and will congregate near feeding spots in anticipation.

The origin of the “3-second memory” claim is unclear — no scientific study appears to have originated it. It may simply have stuck because it was funny and convenient. The fish, for their part, are probably less forgiving of us than we are of them.

Health & Exercise

The Myth
Swimming right after eating causes dangerous cramps

The Truth
It might cause mild discomfort, but the drowning risk is essentially fiction.

Generations of parents have issued this warning with total conviction. Wait 30 minutes. Wait an hour. Wait two hours. The numbers vary depending on the parent, but the core threat remains constant: swim too soon after eating and you will cramp up and drown.

The concern isn’t entirely without basis — digestion does redirect blood flow toward the gut, and intense physical exertion with a very full stomach can cause discomfort or side stitches. But the claim that this leads to incapacitating cramps severe enough to cause drowning has no medical basis. No credible study has documented this as a cause of drowning. The American Red Cross no longer includes it in swimming safety guidelines.

Elite swimmers train and compete after eating. Olympic athletes don’t sit on the pool deck watching the clock after their pre-race meal. A bit of discomfort, yes. A genuine drowning risk? No.

Animal Behavior

The Myth
Bulls are enraged by the color red

The Truth
Bulls are colorblind to red. It’s the movement that makes them charge.

The image is iconic: a matador flourishes a red cape, the bull snorts and charges. The red must be driving it wild, right? As it turns out, bulls are dichromats — their color vision is similar to a human who is red-green colorblind. Red, as a color, means nothing to them.

What actually triggers the charge is movement. The waving, flapping motion of the cape — not its color — is what provokes the animal. In bullfighting demonstrations, bulls have been shown to charge capes of other colors with equal intensity when moved the same way. The red cape is a tradition that may also serve to disguise bloodstains — practical theater, not psychology.

This myth persists largely because it makes a satisfying visual story, and because we tend to assume animals experience the world as we do. They don’t.

Human Perception

The Myth
Humans have only five senses

The Truth
Depending on how you count, humans have anywhere from 9 to 21 senses.

Sight, hearing, touch, taste, smell. This Aristotelian shortlist has sat at the center of science education for centuries, and it’s a significant undercount of what our bodies actually do.

Consider proprioception — your sense of where your body parts are in space, even without looking. Or vestibular sense, which tells you whether you’re upright or tilting. Thermoception detects temperature. Nociception registers pain. You also have interoception, which monitors internal body states like hunger, thirst, bladder fullness, and heartbeat. Some researchers include senses that detect time, balance, and even blood chemistry changes.

The traditional five are real, but they represent the most obvious — the ones visible from the outside. The nervous system’s full sensory vocabulary is far richer and far stranger. You’re more perceptive than you’ve been told.

Evolution

The Myth
Humans evolved from chimpanzees

The Truth
Humans and chimps share a common ancestor — we didn’t descend from them.

This misstatement is one of the most common misconceptions about evolutionary theory, and it’s one that even people who broadly accept evolution often carry around. “If we evolved from monkeys,” the argument goes, “why are there still monkeys?” The question misunderstands what evolution actually claims.

Modern humans and chimpanzees did not emerge from each other. Both species share a common ancestor that lived roughly 6 to 8 million years ago — a creature that was neither a modern human nor a modern chimpanzee, but something distinct that gave rise to both lineages over deep time.

Think of it as two branches growing from the same point on a tree, rather than one branch growing from another. Chimps continued evolving along their own path while the hominin lineage that would eventually produce Homo sapiens developed along a separate trajectory. We are cousins, not descendants.

Ophthalmology

The Myth
Reading in dim light ruins your eyes

The Truth
It causes eye strain. It does not cause lasting damage.

This is one that parents have deployed for generations to get children to turn the lights on and stop reading under the covers. It’s genuinely well-intentioned — and genuinely wrong, at least in the most alarming version of the claim.

Reading in low light makes your eyes work harder. The muscles controlling your pupil dilation strain to pull in maximum light, and sustained effort can lead to eye fatigue, headaches, and temporary difficulty focusing. That discomfort is real. But ophthalmologists are clear: it does not cause permanent damage to vision, alter the structure of the eye, or increase myopia.

The concern about myopia — nearsightedness — is legitimate, but it’s correlated with reading up close in general, not specifically with low light. The dim light connection appears to be an extrapolation that hardened into received wisdom. Your childhood reading by flashlight under the blanket? Probably fine.

Biology & Taste

The Myth
Different areas of the tongue taste different flavors

The Truth
Taste buds detecting all flavors are distributed across the entire tongue.

The tongue map. You may remember it from a school science textbook — a diagram of a tongue color-coded into zones: sweet at the tip, bitter at the back, salty and sour along the sides. It was taught as established fact in classrooms across the world for most of the 20th century.

The diagram was based on a mistranslation of a 19th-century German paper by D.P. Hanig, which described subtle differences in sensitivity — not exclusive zones. Modern research using taste receptors at the cellular level has confirmed that taste-sensing cells detecting sweet, salty, sour, bitter, and umami are present throughout the tongue, with no meaningful regional specialization.

The myth was so thoroughly embedded in educational materials that it persisted long after scientists had moved on. It’s a reminder that textbook diagrams aren’t immune to error — and that sometimes the most confidently taught things are the most worth questioning.