Introduction
We all think we have solid general knowledge. Yet some "truths" we have been repeating since childhood are completely false. These myths are so deeply embedded in our daily lives that they pass for established facts. Many false ideas are so deeply rooted that we repeat them without questioning them: the more often we hear a claim, the truer it seems, a phenomenon known as the illusory truth effect. Word of mouth, movies, outdated textbooks, and now social media spread these errors from generation to generation.
Ready to find out if you have been caught out? Here are 15 general knowledge mistakes that almost everyone makes, along with the scientific and historical explanations that set the record straight.
History
1. "The Great Wall of China is visible from space"
The myth: You can see the Great Wall with the naked eye from space, or even from the Moon.
The reality is quite different. The Great Wall averages about 6 meters in width. From low Earth orbit (roughly 350 km), that is like trying to spot a human hair from 3 km away. Several astronauts, including Yang Liwei (the first Chinese person in space), have confirmed it is not visible to the naked eye. This myth dates back to 1932, long before the first space flights. In contrast, motorways and airports, which are much wider, are actually visible from orbit.
2. "Napoleon was short"
The myth: Napoleon Bonaparte was a very short man.
Napoleon was 1.68 m tall, which was perfectly average for the era (the average male height in early 19th-century France was around 1.65 m). The confusion stems from a difference between French and English inches. His height of "5 feet 2 inches" in French measurement actually corresponded to about 5 feet 6 inches in English measurement (~1.68 m). Moreover, British propaganda of the time loved to caricature him as a tiny figure, an image that has survived for two centuries.
3. "Vikings wore horned helmets"
The myth: Viking warriors fought wearing helmets adorned with impressive horns.
No archaeological evidence supports this popular image. Real Viking helmets were simple iron designs, sometimes with a nose guard. The horned image comes from costumes created for a Wagner opera in 1876 and Romantic-era depictions from the 19th century. In battle, horns on a helmet would have been more of a liability than an asset, offering easy grips for the opponent.
4. "Christopher Columbus proved the Earth was round"
The myth: Before Columbus, people thought the Earth was flat, and he proved otherwise in 1492.
The ancient Greeks already knew the Earth was round. Eratosthenes had even calculated its circumference with remarkable accuracy around 240 BC, within less than 2% of modern measurements. During the Middle Ages, European scholars did not believe in a flat Earth. The real debate was about the size of the Earth and the distance to Asia sailing westward. Ironically, Columbus had underestimated this distance and would have perished without the accidental discovery of the Americas.
Science
5. "We only use 10% of our brain"
The myth: Humans only use 10% of their brain capacity, and we could unlock powers if we used the remaining 90%.
Modern brain imaging (functional MRI) clearly shows we use our entire brain, even though not all areas are active simultaneously. Each region has a specific function. Even a minor lesion in any brain area causes measurable consequences. This myth has been popularized by movies like Lucy but has no scientific basis. The brain accounts for only 2% of our body mass but consumes about 20% of our energy, which would be a colossal evolutionary waste if 90% were unused.
6. "Lightning never strikes the same place twice"
The myth: A place struck by lightning will never be struck again.
This is completely false. The Empire State Building in New York is struck by lightning about 25 times per year. Lightning preferentially strikes elevated points and metallic structures, so certain locations are far more likely to be struck than others, repeatedly. American ranger Roy Sullivan was even struck by lightning 7 times during his lifetime and survived each time.
7. "Sunflowers follow the sun all day"
The myth: Sunflowers turn their heads to follow the sun from morning to evening.
Only young, growing sunflowers track the sun (a phenomenon called heliotropism). Once mature and in full bloom, sunflowers remain permanently oriented toward the east. This morning orientation attracts more pollinators because the flower warms up faster with the rising sun, markedly increasing bee visits compared to west-facing flowers.
8. "Glass is a liquid that flows slowly"
The myth: The windows of old cathedrals are thicker at the bottom because the glass has flowed over centuries.
Glass is indeed an amorphous solid, but it does not flow at room temperature. The uneven thickness of ancient stained glass is explained by medieval manufacturing techniques (crown glass blowing) that did not produce uniformly thick panes. Craftsmen often placed the thicker side at the bottom for stability. Physical calculations show that even over billions of years, glass would not flow perceptibly at room temperature.
