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10 Things that are Seen as “Common Sense” but are Actually Wrong

6. Common sense: All soaps kill germs.

Fact: Plain (non-antibacterial) hand soaps do not kill germs. Instead, they lift the germs off the surface of your skin, forcing them to be washed down the drain.

Soaps do not kill germs
Soaps do not kill germs. Image Credit: Pexels

Cleaning dirty hands with soap seems to the most common sense thing ever. In the majority of the cases, plain soaps are used for washing hands. But plain soaps have no germ-destroying ability whatsoever. In fact, these soaps just work by removing the germs from one’s hands. The soap particles get attached to the germ molecules in order to move them away with water.


Even the anti-bacterial soaps that claim to destroy 99.9% germs have been proven to be no more effective than plain soaps. In a study carried out in 2015, scientists tested the effectiveness of triclosan, the most common active antiseptic ingredient used in soaps.

The scientists introduced the bacteria in a simulated hand-washing environment. Then they used triclosan for testing. They discovered that there were no significant effects during the short duration of hand washing. The effects can only be seen when the triclosan has been subjected to the bacteria for more than nine hours. (1, 2)

7. Common sense: The darker the coffee, the higher the caffeine content.

Fact: Coffee gets a darker color due to its roast. The caffeine gets cooked out the longer the coffee beans are roasted. So actually, the lighter the roast, the higher the caffeine content.

Darker the coffee, lesser the caffeine content. Image Credit: Wikipedia, Wikipedia

Dark coffee might look stronger than light coffee but it is actually the opposite. There is actually more caffeine in light coffee than the dark ones. The reason behind this is the time for which the coffee beans were roasted.

Coffee gets its light or dark color from roasting. When coffee beans are roasted for longer periods of time, they turn darker in color. Similar to food that loses its flavor if overcooked, coffee beans lose their flavor and caffeine content if roasted for a longer time.

The bitter taste of dark coffee makes people feel that it is stronger than a cup of lighter coffee. People mistake this intense bitter taste for higher caffeine content, which, in reality, is actually the opposite. (1, 2)

8. Common sense: Carrots are good for improving night vision.

Fact: During World War II, the British didn’t want the Germans to know they had secret radar technology. So, they spread propaganda saying that the good eyesight of their pilots was due to carrots. And everyone believed it.

Carrots do not actually improve night vision. Image Credit: Pixabay

As children, we must have heard our parents say a thousand times that carrots are good for our eyesight. Well, that is true considering the fact that carrots are rich in vitamin A, but the fact that carrots have the power to improve night vision or mere eyesight is a complete lie.

John Stolarczyk, the curator of the World Carrot Museum, says, “Somewhere on the journey the message that carrots are good for your eyes became disfigured into improving eyesight.” Although the exact origin of the faulty carrot theory is not known, it was made popular by the Ministry of Information to hide critical information from the enemies.

During World War II, the Germans utilized an attack tactic known as “Blitzkrieg” where they attacked the opposing forces during the dark. The British Government tackled the situation by issuing widespread blackouts so that it became difficult for the Germans to hit targets. Also, the Royal Air Force (RAF) had a secret radar technology that helped them pinpoint German airplane bombers even before they crossed the English Channel. Known as the Airborne Interception Radar (AI), the RAF was able to stop many German bomber planes from causing any harm.

In order to hide this technology, the British issued a response to the newspapers that the reason they were able to do that was that the RAF pilots ate a lot of carrots. This made them able to see better in the dark!

More than the Germans, the common people took it very seriously. There were advertisements and declarations from the Food Ministry to grow and eat more carrots and other vegetables. This fake story caught on fast and became common sense even before people realized. (source)

9. Common sense: You attract more flies with honey than with vinegar.

Fact: Flies actually prefer vinegar over honey.

You attract more flies with vinegar than with honey. Image Credit: Orkin

“You can catch more flies with honey than vinegar” was just supposed to be a life lesson. It translates to that if you just put on a smile every time someone betrays you rather than being bitter, life is just easier. But people have taken this phrase literally and have failed to catch fruit flies with honey.


Fruit flies are attracted to the acetic component in food when they are hungry. Their olfactory senses are advanced enough to even detect the quantity of acetic acid in fruits. In case there is a low content of acetic acid, the flies get the signal that the fruit is not ripe enough and vice-versa. So they just come to fruits that are within this spectrum.

Now vinegar is diluted acetic acid, so it makes sense that fruit flies would be more attracted towards the odor of vinegar rather than honey. (1, 2)

10. Common sense: Water can be used to put out all fires.

Fact: Using water to put out grease fire can be really dumb – and dangerous!

Grease fire
Water cannot be used to put out all fire. Image Credit: Seymour Johnson

According to the National Fire Protection Association (NFPA), 50% of kitchen fires are caused by cooking oils, grease, or fats. And the first rule to put out such fires is to never use water. The reason for this lies in basic chemistry.

Oil and water have different densities because of which they never go together. So, when water is used to put out a grease fire, it just goes and settles at the bottom of the pan on fire. And since the pan is already hot due to the fire, the water molecules instantly turn to vapor in less than a second. The vapor then floats away from the pan taking the grease particles along with it. In the process, the fire on the grease particles is scattered all around.

So, the best way to put out a grease fire is to cover the fire with a lid as soon as possible. This cuts off the oxygen supply and helps to put out the fire fast. (source)


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