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25 Weird But True Facts About The Human Body

For something that is literally a part of us, there's a lot about our bodies that we don't know. Check out these surprising facts about our strange and awesome bodies:

1. The sound you hear when you "crack your knuckles" is actually gas popping. Small bubbles form in your joints and pop when you torque them, and no this doesn't cause arthritis.

Actor Tom Selleck.Tracy Burnette

2. What's the weird way to spot an intelligent man? Look for body hair. A study of men in MENSA (a club for people with high IQs) found that hairier men were also smarter, and men with back and chest hair were the smartest of all.

From left to right: a test subject, a photo measuring light taken in a dark room, and a heat scan of the subject.Kyoto University

3. Ever notice someone with a "natural glow?" in fact we all have one. Human bodies really glow, even in the dark. And your face is the brightest spot of all.

4. There are some proportions that all human bodies seem to share. Here's one: take the height of your head and multiply it by 7. That's about the size of your body (most people are somewhere between 7 and 7.5 heads tall).

5. Know anyone who never seems to blush? It's a physical reaction caused by your emotions, so some people never seem too. In fact babies, who have no sense of adult emotions and feelings, actually can't blush.

Some NBA players have wingspans taller than their heights.WSJ

6. Here's another weird proportion: stretch your arms to the side. This measurement (called the wingspan) is usually very close to your height.

High speed photography of a sneeze.Quiz Club

7. When you sneeze, air is pushed out of your nose and mouth at 100 miles per hour, shooting mucus as far as 30 feet. For comparison, wind only needs to blow at 74 miles per hour to qualify as a hurricane.

Pop quiz: how many bones are in your body? Actually, it depends on your age...

8. When you're born, your body has 350 bones, but by the time you reach adulthood there are just 206. So what happened? As you grow up, smaller bones fuse together into bigger ones.

A baby's skeleton and an adult's compared at the same height.Daniel Maidman

9. Our bodies create a shocking amount of energy. While you're resting, you create enough power to light a 100 watt light bulb. Meanwhile, when Usain Bolt is sprinting down the track his body generates 20 times that much electric power.

10. If you plan on robbing a bank, don't stick your tongue out at the security camera. Like fingerprints, every person's tongue has a unique pattern that can be traced back to them.

11. Hair is tougher than we give it credit for. If Rapunzel really made a rope out of her hair, it could support the weight of several people (but that would probably give her a headache).

Take the hair on an average woman's head and weave it tight enough, and the rope you make could lift 12 tons.

12. What's that smell? Your brain can identify a trillion individual scents, from burnt popcorn to fresh daisies. Your nose is much more sensitive than your eyes, which can only see 10 million different colors.

13. The average brain weighs just under 3 pounds, but size doesn't matter when it comes to intelligence. And no, we don't use just 10% of our brains, we use every part of it for something different.

14. Women often complain they feel colder than men, and it's true. Women's bodies concentrate fat around their midsection instead of their extremities, which warms their organs but leaves them feeling chilly.

Plus, women have smaller blood vessels, which shrink faster in the cold giving their bodies that chilly feeling.

15. If you let your fingernails grow for a year, they would be 4 inches longer. On average nails grow by 1/8 of an inch each month, and they'll keep growing after you die.

Shridhar Chillal has been growing his fingernails since 1952.Guinness World Records

16. All the cells in your body are replaced by new ones every so often. Your stomach lining changes the fastest (once every 3-4 days) because of the strong stomach acid it's exposed to.

Cells replace each other over time.I Am Not The Body

You can say that you become a whole new person every 7-10 years, because that's how long it takes for your body to replace every single cell.

17. Beards grow faster or slower based on the time of year. In the winter beards grow slower than usual, because men's bodies contain less of a hormone called androgen. Beards grow fastest in spring, when men have the most androgen.

18. Humans shed skin just like animals, in fact most of the dust in your house is made of flakes of skin. By the time they turn 70, the average person sheds 105 pounds of skin. Ick!

Okay, losing dry skin doesn't normally feel this glamorous.Bloody Loud

Which part of your body generates the most heat? The answer will surprise you.

19. In an hour, your body generates enough heat (212 degrees) to boil 5 liters of water in the same amount of time. The natural actions of your body generate heat, and your liver creates more heat than any other organ.

Steam rises from a football team's breath before a game.Pro Football Weekly

20. Your eyes are a lot more complicated than you think. First of all, they actually take in images upside down, then your brain flips the image the right side up.

Who knew our eyes were doing so much extra work?Quora

Your eyes also swap sides when they send these images to be corrected: things you see on the left side of your vision are processed on the right side, and vice versa.

21. Doctors know that hiccups are caused by spasms in your diaphragm, but we're still not sure what causes those spasms. One theory is that mankind's ancestors from more than 350 million years ago had lungs and gills, and hiccups are a leftover habit from that weird arrangement.

22. Your heartbeat will actually slow down or speed up to match the music you're listening to. Doctors are trying to use this trick to treat patients with dangerously irregular heartbeats.

23. The length of your foot is the same as the length of your forearm, and the width of your hand is also the width of your foot between your ankle and toes.

24. Your bones are actually tougher than steel. A cubic inch of human bone can hold 19,000 pounds of weight, which is heavier than an adult elephant. Plus, bones are self-repairing.

25. You're taller in the morning than at night - a difference of as much as 2 centimeters - because at night gravity pushes down on your body while it's horizontal.

Scott Kelly (right) returned from space taller than his identical twin Mark.NASA

Throughout the day, we sit and stand upright as gravity pushes down on us and shrinks us. In space, where astronauts aren't weighed down by gravity, humans stretch out by up to 2 inches.

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