This article originally appeared on grandparents.com. To learn more click here.

You may think of your body as just skin and bones, a vehicle that gets you where you want to go, but it’’s also capable of jaw-dropping feats and mysteries.

When someone told us that the length of your foot matches the length of your forearm, we had to check it out. (It’’s true!) That made us wonder what other amazing (or amusing) things we might not know.  Turns out, a lot!

Read on for ten little-known fun facts about the human body.

Your body measurements equal each other

You’re probably familiar with Leonardo da Vinci’s famous sketch, The Vetruvian Man. It’s one of the earliest and best explorations of anthropometry, or the scientific study of the measurements and proportions of the human body.

As we mentioned, your foot will fit neatly into your forearm, from elbow to wrist. But did you know:

  • Your height basically equals to the span of your arms when you stretch them out to the sides.
  • You height is also roughly 10 times the length from your wrist to the tip of your middle finger, and about seven times the length of your foot.

This kind of anthropometric correlation isn’t just fun to know. An anthropologist might use it to determine how tall the owner of a particular bone was, and a forensic scientist might use a footprint or handprint to estimate the height of a criminal.

You’re tallest in the morning

Did you know that you’re at your tallest first thing in the morning?  It took NASA to make believers of us!

NASA reports that astronauts are as much as two inches taller in space than they are on Earth. The absence of gravity prevents compression of the discs in the spine, so while they’re in space, astronauts not only weigh less, they get to be taller, too!

While the effect is not nearly so pronounced here as it is in zero gravity, we gain about two centimeters each night. When we’re lying down, our joints decompress because gravity isn’t literally pulling us down, and we can start each day standing tall.

Your body can boil water

In just half an hour, your body gives off enough combined heat to bring a half gallon of water to a boil.

That’s 212 degrees!

Of course, your body thermo-regulates to keep you at a comfortable 98.6, on average. But all the biochemical reactions of your cells—especially those in your liver—create a lot of heat, and your body lets most of it go unused.

Those same processes make you electric, too!  At rest, the average human gives off about 100 watts of electrical energy, which is enough to (you guessed it) power a 100 watt light bulb. And a sprinting athlete might produce as much as 2000 watts of energy!

Your bones are stronger than steel

We may not be faster than a speeding bullet or more powerful than a locomotive, (or be able to rock a cape and tights with a straight face), but we share something in common with Superman just the same.

Inch for inch, our bones are stronger than steel.

A cubic inch of bone is strong enough to bear 19,000 pounds. That’s pretty impressive for a material that’s more than 30% water!  For an idea of just how strong that is, consider that helicopters, small jets and semis weigh in at about 14,000, and a large male elephant tops out at about 15,000.

Another way bone is better than steel? If it does happen to break, it will immediately begin to repair itself.

Hair is durable as rope

Remember the story of Rapunzel and the prince that climbed her tresses to join her in the tower where she was imprisoned? As it happens, a rope of hair would be strong enough to bear the weight of several men. 

One strand of healthy human hair can bear about 3 ounces, which may not sound like much, but it means that, combined, the hairs on the average woman’s head would be capable of bearing 12 tons!

Aside from being flammable, hair is virtually indestructible. Even most acids can’t destroy it, a fact which anyone who has tried to clear it from their plumbing knows all too well.

Your heart can regulate to music

Your favorite music really can make your heart beat faster! In fact, the connection between music and the heart is so powerful, that medical schools—including Harvard— are studying its use in helping to heal heart disease. Your heart’s response to music can actually strengthen the heart and help you recover from any kind of trauma more quickly.

Basically, your heart “mirrors” the beat of whatever music it hears, so a Mozart concerto may slow it down a bit, while a Rolling Stones concert will speed it up.   And you’ll respond most strongly to the music that appeals most to you, so experiment.

When you find something that makes you feel happy, there’s a good chance that it will be good for your heart literally and figuratively!

You can smell and see more than you think

For decades, the common belief was that the human nose could identify roughly 10,000 smells. But earlier this year, a team at Rockefeller University proved otherwise. In fact, they say, you can smell at least one trillion scents!

It was “eye envy” that drove the team to the lab to disprove the previously held assumption. The human eye has only three color receptors, yet can see up to 10 million colors. By contrast, the nose has 400 olfactory receptors, and the team reasoned that it must be capable of smelling more than 10,000 scents.

Turns out, our noses deserve much more credit than we’ve given them.

You see with your brain not your eyes

Your brain is responsible for seeing, not your eyes. Your eyes collect information, which is then transferred to your brain for processing. But other sensory systems, such as the tongue, can be used to relay that sensory information as reliably.

The process is called sensory substitution, and was pioneered by Dr. Paul Bach-y-Rita. In the 1960s, Dr. Bach-y-Rita invented a machine that enabled people who had been blind since birth to see well enough to recognize photos of then-supermodel Twiggy and other images.

In more recent years, his research has been used to help Navy SEALS orient their bodies when they are underwater, where the senses work differently.

Your mouth has literally millions of bacteria

The average mouth contains more bacteria than there are people on the planet, which means your mouth is teeming with more than six billion bacteria. And – we’re not making this up – they form colonies and communities in there.

Bacteria that live at the roof of your mouth are distinct from those that hang out under your tongue. Those on the top of your tongue and different from those on the inside of your cheeks. Every strain, it seems, has its favorite real estate.

10-second kiss can transfer as many as 80 million bacteria from one person’s mouth to another. But don’t worry! Saliva actually contains powerful antibacterial and antimicrobial compounds that help to kill off any bad guys.

Your body is a lot like the solar system

In the early 1980s, the astronomer Carl Sagan narrated a 13 part series for PBS called Cosmos and famously said, “… the cosmos are within us. We are made of star stuff.

It may sound like a fanciful, New Age notion, but it’s literal truth and is widely supported by scientific research and quantum physics. The iron in your blood, the calcium in your teeth, even the oxygen that fills your lungs, all were created when novas and supernovas exploded and began to make their way through interstellar space.

Some of the stuff in your cells may be more than four billion years old.  And if knowing you’re made of stardust doesn’t make your eyes sparkle, we don’t know what will!

{{slideNumber(index)}}

{{slide.title}}

{{slide.title}}

{{slide.caption}}
{{slide.credit}}

Watch this

How to care for loved ones from a distance