There are many so called "facts" which simply aren't. You've no doubt heard them at parties, from friends, family or had them forwarded to you via email. Here are a few of the more popular.

Eating carrots improves your night vision:

Carrots do contain Beta-carotene, which is converted to vitamin A in the liver. Vitamin A helps to maintain healthy vision, but the carrots do not improve your vision in the dark. This tale started during WWII when the British spread a rumour that their plane spotters were eating carrots to give them improved vision. This was an attempt to conceal the truth about the invention of radar which provided an obvious tactical advantage for identifying aircraft.

A duck's quack does not echo:

Of course it does. All sounds echo if they are loud enough and if they occur near an area (i.e. a chamber) that provides the right acoustical properties. A duck's quack is relatively short and tends to be quiet, making it hard to hear as an echo; however it does echo and various tests have been conducted by universities to dispel this urban myth.

Mixing Pop Rocks and Soda can be dangerous or even deadly:

It has been claimed that people's stomachs have exploded by mixing these "volatile" substances together. However, both Pop Rocks and soda rely on carbon dioxide gas to produce their fizzing and the very process of drinking Soda actually causes carbonation (release of carbon in the form of fizz and bubbles). This means by the time you drink your Soda and then swallow the pop rocks there's nothing left to react with it, this is also true of mentoes with Soda. The real danger might be to your teeth and long term health if you eat too much sugar on a regular basis.

Chocolate causes acne:

Not so. Chocolate does not cause acne in healthy individuals. Perhaps started to entice children to eat healthy food rather than just confectionaries, this old wives tale associates a negative effect to eating chocolate that is undeserved and has been clinically disproved. Very rarely, some individuals can have a skin reaction (such as a rash) to specific ingredients in chocolate but it is uncommon and of course this isn't acne.

Chewing gum, if swallowed, remains inside your body for seven years:

I guess who ever came up with this one, figured they'd have seven years before anyone caught on. Chewing gum is excreted like any other undigested piece of food or stray object swallowed, generally within a day. However chewing gum does take a long time to break down which may be why this myth was and is so readily accepted by people and why it so often ends up stuck to the bottom of our shoes.

There are many more including old folklore like the existence of vampires and werewolves and newer urban myths such as gangs in cars waiting for people to flash their high beams or that you can catch AIDS from a toilet seat and so on and on. 

I think the success of these and other such myths is rooted in our trusting nature (some might call it naive gullibility). People tend to believe what they see and hear and rarely question information that is provided from a basis of authority. This fact has long been relied upon by many media outlets and publications (take tabloids and popular magazines for example). As long as someone tells us it's that way with conviction then we will tend to believe them unless we already know that the information is wrong.

A game that my family often played actually relied upon misinformation. We'd each select five words we thought the other players wouldn't know and then everyone would create a false definition on a slip of paper and try to make it as convincing as possible.

These new definitions and the original would be drawn from a hat at random and each player would vote on which they believed to be correct. Players were then awarded points corresponding to the number of votes their false definition received.

Here's an example for the word "narcan"

Definition 1: a ruler or member of the royal family in the Incan empire

Definition 2: a potent narcotic drug used with morphine

Definition 3: a space between an arch and the lintel of a portal or window

Definition 4: a state of anxiety or distress, generally associated with infants

So what's your vote?

As you can see it certainly created some convincing false definitions and was a lot of fun to play. Not only did it help to broaden our vocabularies (once we learned the actual definition) but it also honed our misinformation radar and allowed us to develop a healthy dose of scepticism. Something we could all use in this day and age! 
Not completely on topic, but as requested by a reader below, I've written an article on the origins of The Three Wise Monkeys: See No Evil, Hear No Evil, Speak No Evil for those of you who are interested.
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