Here are ten very common beliefs that are often accepted as fact which are actually untrue:

1. We only use 10% of our brain. This is completely false.  There is no underutilized part of our brains. People seem to like this myth because it suggests that there is some untapped potential we can access. Read more: https://www.scientificamerican.com/article/do-people-only-use-10-percent-of-their-brains/
2. Most heat escapes from our head.  Wrong.  This myth likely comes from a poorly done experiment by the army in the 1950s and reprinted in the 1970 Army Field Manual.  Actually, what the experiment found was that in arctic conditions if you are wearing a survival parka without a hat most of your heat escapes from your head. However, if you were naked or wearing thin clothes most of your heat loss would come from elsewhere. Read more: https://www.theguardian.com/science/2008/dec/17/medicalresearch-humanbehaviour
3. Swallowed Gum Stays in your Stomach for Seven Years. Nope – its pretty harmless. If gum did hang around for seven years Sean Spicer would have a gargantuan stomach because he swallows about 35 pieces of gum each day before noon: https://motherboard.vice.com/en_us/article/science-of-sean-spicer-gum-swallowing
4. Lightning Doesn’t Strike the Same Place Twice. Actually, it is common for lightning to strike the same place over and over.  The Empire State Bldg gets struck by lightning about 100 times per year. Some areas of ground have characteristics that make them more likely to be struck multiple times such as salt, moisture, metal content or the terrain.
5. A Penny Dropped from the Empire State Building Would Kill Someone if it Hit Them on the Head. Nope.  It wouldn’t bore into your skull.  It would likely feel like you were flicked in the forehead – in other words it would sting a bit, but not injure you. Read more: https://www.scientificamerican.com/article/could-a-penny-dropped-off/
6. The Hair and Nails Continue to Grow for Months After Death. We’ve seen it in movies and of course the Thriller music video – corpses with gnarly long hair and nails.  Not true though.  Hair and nails need glucose to grow and glucose is no longer produced after death.  The reason for this myth likely is that other tissues retract due to dehydration and may make the nails and hair appear as if they’ve growth. Source: http://www.bbc.com/future/story/20130526-do-your-nails-grow-after-death
7. Alcohol Kills Brain Cells. Fortunately, this is not true.  Alcohol doesn’t kill brain cells – it can, however, interfere with communication between cells and also damage the cells – but it does not kill them. Read more: http://mentalfloss.com/article/49024/does-drinking-alcohol-kill-brain-cells
8. Cracking Your Knuckles Causes Arthritis.  The “pop” of a cracked knuckle is caused by bubbles bursting in the fluid that helps lubricate joints. The bubbles pop when you pull the bones apart. While there are studies on this, the best evidence comes from Donald Unger, a doctor who cracked the knuckles on his left hand periodically for 60 years but never cracked the knuckles on his right hand.  Neither hand developed arthritis and he won an Ig Noble award for his efforts. Source: http://www.health.harvard.edu/pain/does-knuckle-cracking-cause-arthritis
9. If you Swim Soon After You Eat You’ll Get a Cramp and Drown. Not true. There is no evidence of even one case of drowning due to post meal cramping. Overexertion can cause cramping, but having eaten recently is not a cramping factor.  Read more: http://www.snopes.com/oldwives/hourwait.asp
10. The Great Wall Of China is the ONLY Man Made Object Visible From Space. Actually, it’s really hard or impossible to see the Great Wall from even low orbit. Things that are visible from space: the pyramids, large bridges, cities at night, Donald Trump’s ego.  Here’s a picture of the Great Wall from orbit: