Name a man-made object you can see from space. If you answered the Great Wall of China, I'm afraid you're wrong. But don't feel too bad about it.
Just like the above mentioned piece of trivia, there are many widely held 'facts' present in our collective knowledge which are actually completely wrong. Some of them are based on old ideas, some are simply inaccurate, and some are downright lies. Despite often having been debunked years and years ago, these 'facts' still persist and are often brought out in various social gatherings. Next time that happens, simply become the pedant you were born to be and deliver one of the following corrections.
1. Columbus Did Not Discover 'America' or Prove the Earth Was Round
The famous Genovese explorer Christopher Columbus is a veritable hive of inaccuracies. Firstly, he never set foot on any land which would later become the United States of America. In fact, he never arrived on either the continents of North or South America. Instead all four of his expeditions landed on various Caribbean islands. Secondly, he was unlikely to be the first European to have discovered America - Norse explorer Leif Erikson reached Canada perhaps 500 years before. Thirdly, Columbus did not prove the Earth was round. Few learned people actually held that view in the 15th century, and the ancient Greeks and Romans already knew the Earth was spherical.
2. Romans Did Not Like to Vomit Between Meals
You may have heard wealthy Romans retired to the 'vomitorium' to throw up their food before returning for another helping. Although purging is recorded, it is almost always seen as uncouth and undesirable. Furthermore, there were no rooms dedicated to it. The vomitorium is in fact the entrance to an amphitheater or stadium. Its name comes from the Latin to 'disgorge' or 'spew forth.'
3. Roman Gladiatorial Combat Did Not Always Involve Death
Let's keep it in Rome for the time being. Gladiatorial combat is usually seen as a fight to the death, however in reality gladiators were often too expensive to kill off. Slaves and criminals were usually thrown into deadly battles, but seasoned gladiators would often avoid delivering a death blow - especially if their master (known as lanistae) wanted to stay in business. Sponsors could demand deathly combat, but it would cost them extra. Instead bouts were often ended when one combatant was exhausted, wounded or simply gave up. According to some historians, around 80-90% of fights did not end in death. Oh, one more thing, they also did not say, "Those who are about to die, salute you!" There is only one unique reference to this quote being said and it was not widespread. Check out Russell Crowe skewing the survival statistics in the Gladiator clip below:
4. Bulls Do Not Charge at the Color Red
In reality bulls have dichromatic vision - which means they can only see green and blue. The bull charges because it feels threatened by the movement of the matador's cape. In fact, a red cape would appear green to a bull.
5. Chewing Gum Doesn't Take 7 Years to Digest
Chewing gum is actually impossible to digest. Don't worry though, your stomach isn't slowly filling with accidentally swallow gum. It merely passes through digestive system until it is 'expelled' in the usual fashion.
6. A Black-Belt Owner Is Not a Martial Arts Expert
In most martial arts which use a belt system, the black belt is not automatically the highest grade. Instead it merely demonstrates that the wearer is competent in the style's basic techniques and principles, although they have yet to perfect them. The myth of the 'black belt' has been perpetuated by various movies and some martial arts schools which use them as a marketing 'gimmick.' Such schools are often contemptuously called 'McDojos.'
7. Cracking Your Knuckles Does Not Give You Arthritis
Despite the longstanding belief that crackling your knuckles is bad for you, there is no scientific evidence to back it up. In one study, Doctor Donald Unger cracked the knuckles on his left hand every day for sixty years, and left his right hand 'uncracked.' After 60 years, no arthritis formed in either hand. So just enjoy cracking your knuckles!
8. Mount Everest Is Not the Tallest Mountain in the World
At 8,848 meters (29,029 ft) Mount Everest is the highest mountain in the world, but it is not the tallest. Height is judged as anything above sea-level, while a mountain's tallness is the distance between its base and its summit. With this in mind, Mauna Kea in Hawaii is actually the tallest. Much of the mountain is under the sea, although if the sea is discounted Mauna Kea measures 33,465 feet - 4,000 feet taller than Everest.
9. Humans Did Not Evolve from Modern Apes
No, I'm not a creationist, but humans did not evolve from chimpanzees or gorillas. We simply share an ape-like ancestor further down our evolutionary past. One evolutionary offshoot of this ancestor would later evolve into chimps, gorillas and other apes, while another would become homo sapiens (i.e. us). We are also not 'more evolved,' simply 'differently evolved.'
10. Fishes Do Not Have 3 Second Memories
Studies have actually shown fish can remember information for up to 5 months. Young fish were conditioned to associate a sound with feeding before being released into the sea. Four to five months later, the sound was played again and the fish returned. Furthermore, some fish such as minnows, sticklebacks, and guppies can navigate mazes and recognize other fish. Goldfish in particular can be tamed and may even recognize the face of their feeder.
11. Vikings Did Not Have Horned Helmets
Horned helmets did exist during the Dark Ages and earlier, although almost always for ceremonial purposes. There is, however, no evidence to suggest they were particularly prevalent with the vikings. Instead, the modern myth has been attributed to an 1878 performance of Wagner's Der Ring des Nibelungen which featured horned helmets.
12. Sugar Does Not Make Kids Hyperactive
Studies as early as 1995 have shown that sugar does not affect the behavior or cognitive performance of children or adults. Instead, one study suggested the sugar actually changed the parents' behavior. Those who believed their kid had drunk a sugary drink often reported they were more hyperactive, despite the fact they had really had a placebo. The same is true for the 'sugar rush.' It is in fact self-induced and is not related to the properties of sugar.
13. We Know How Bees Fly
One myth suggests that bees - due to their shape and weight - should not be able to fly. Some have even suggested the bumblebee can only fly because it thinks it can - which is a bizarre, if slightly adorable, explanation. However, the means by which they achieve flight is actually well-known. Using high-speed photography and mechanical models, researchers discovered an extremely high wing beat rate (230 a second) combined with a special movement keeps the bee in the air.
14. You Cannot See the Great Wall of China from Space
As the introduction suggests, the Great Wall of China is not visible from space. In fact, it is barely visible from the edge of our atmosphere and with the assistance of telephoto lenses. The Great Wall is hard to spot for various reasons. Firstly, despite being very long, it is not that wide. Secondly, is it of the same color as the surrounding terrain, and thirdly, it follows the natural contours of the geography. The photo below (taken from the ISS with a telephoto lens) claims to show it, but even this is debatable:
Although individual buildings cannot be seen, city lights do become visible at night.
15. You Cannot 'Swallow Your Tongue'
First aid courses often stress the importance of ensuring an unconscious individual hasn't blocked their airways by 'swallowing their tongue.' In reality, the lingual frenulum, which attaches your tongue to the floor of the mouth, means it is impossible for it to get stuck at the back of the throat.
16. Vaccines Are Not Linked to Autism
Despite widespread belief that the MMR vaccine is connected to autism, there is zero scientific evidence to back this up. According to the CDC, studies in 2004, 2011 and 2013 have categorically rejected claims vaccines can cause autism. The controversy stems from one study conducted by the now widely discredited Andrew Wakefield. The paper has since been withdrawn from the medical journal it was published in, and Wakefield was struck off as doctor due to misconduct. The paper has since been described by the journal's former editor as "utterly false." Wakefield's fraudulent theories were allowed to spread due to naive and sensationalist media reporting.
17. Humans Have More Than Five Senses
Although we commonly think humans only have five senses - taste, touch, smell, sight and hearing - we actually have a lot more. Additional senses include, equilibrioception (balance), thermoception (detecting temperature), kinesthetic sense (knowing where our body parts are), pain and introception (internal senses such as hunger).