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Most of us don’t think about our ears much until we have trouble hearing. But ears are more important than many of us know. They allow us to balance, and monitor the environment for threats while we’re asleep. Here are six fascinating facts about these indispensable organs on either side of our head.

Ears Provide Our Sense of Balance

Within the ear are three semicircular canals filled with fluid. They lie at different angles, and each one monitors when we move our heads in a specific direction. Together, they send information about body position to the brain, which then sends it on to our eyes and muscles. That’s how we keep our balance. All together, this network is called the vestibular system.

Motion sickness arises from a mismatch in signals coming from our eyes and ears. When you’re in a ship’s cabin, for example, your inner ear picks up on rolling motions and sends one set of signals to your brain. Your eyes see motion, too, but not to the same degree. As a result, you might become dizzy or nauseated.

Ears Are Full of Delicate Hairs

On average, we’re born with about 16,000 tiny sensory receptors, called hair cells, in a hollow spiral-shaped bone located in the inner ear and called the cochlea. These hair cells allow our brains to register sounds. They’re delicate and can be easily damaged to the point where they break and don’t grow back. However, up to half of those cells can be damaged or destroyed before changes in your hearing show up on a hearing test.

Ears Respond to Changes in Air Pressure

The air around us has weight. It presses against everything it touches, as gravity pulls it down. When we go deep into the water, or high up in a plane, or even just into the mountains, that pressure changes dramatically.

Small tubes on each side of our faces, called Eustachian tubes, respond to changes in pressure. They connect our ears to the back of our throats. Normally, they’re closed, but when we yawn, chew, or swallow, they open. They also open when the air pressure in the environment changes. This equalizes the pressure on the two sides of the eardrum, a thin tissue that vibrates in response to sound waves. If the pressure becomes unequal, the drum could tear, causing hearing loss.

Everyday Noise Can Damage Ears

About a quarter of American adults aged 20 to 69 suffer from hearing loss linked to noise. Loud sounds can hurt hair cells, which means the bad effects continue long after the noise stops.

According to the CDC, noise above 70 decibels for a prolonged period can start to damage hearing. That level of noise can be produced by washing machines, dishwashers, city traffic (from inside the car), lawnmowers, and more. Loud clubs or bars can produce noise around 105 to 110 decibels, which can cause hearing loss in less than five minutes. A dog’s loud barking in the ear can cause hearing loss after two minutes.

Ear Wax Is Good

Everybody has earwax, which keeps the ears clean and moisturized. It traps and prevents dust, bacteria, and anything else that gets into your ear from irritating the delicate skin inside. If you try to pry it out with a cotton swab, you’ll just stimulate your ear to make more wax.

However, wax buildups can occur. If you wear hearing aids, they may be stimulating your ears to produce too much wax. Some people just tend to produce too much wax naturally, and it can harden and block sound. Hardened earwax can also give you an earache, aggravate tinnitus, and make your ears feel too full. If you have those symptoms, try using earwax drops available in drugstores, or asking an ear, nose, and throat doctor to clean your ears.

Your Ears Don’t Sleep

When we’re asleep, our ears stay awake. They’re on the job, taking in possible threats while our eyes are shut. Our brains are also on the job, judging which information is important.

It’s work — which is why noisy bedrooms are bad for our health. Noise doesn’t have to wake you up to affect your sleep. It doesn’t even have to be loud. In one study, the murmur of hospital equipment showed a measurable impact in encephalographic measurements of brain activity in sleeping healthy adult volunteers. Their ears heard the noise and their brains measured mild alarm.

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When X-rays were first discovered in 1895, the “X” stood for “unknown.” Today, scientists know a lot more about them. X-rays are a kind of electromagnetic radiation, part of a spectrum of waves of various wavelengths. Longer wavelengths in the spectrum include radio waves, ultraviolet waves, and visible light. X-ray wavelengths are much smaller — between 0.03 and 3 nanometers — and that means they’re also higher in energy than many other waves.

That high-energy attribute, while not exactly healthy for humans, is also what makes X-rays so useful. When X-rays hit an object, their energy is absorbed or scattered at different rates by different components of our bodies. X-rays have a harder time passing through bones, which show up as white on the resulting images, while they more easily penetrate our skin and internal organs, which show up darker.

X-rays revolutionized medicine upon their discovery, but that’s only one aspect of their amazing story. These six facts showcase just how important X-rays are to modern life, and how they’ve made the invisible visible.

The Discovery of X-Rays Was an Accident

Many of the world’s most important discoveries came about by accident, and you can add X-rays to that list. On November 8, 1895, German physicist Wilhelm Conrad Röntgen was experimenting with cathode rays in his laboratory in Würzburg when he noticed that a nearby screen had begun to glow. Not knowing what the mysterious rays causing the effect could be, he eventually called them “X-rays,” with the “X” referring to an unknown item (as in solving for “X” in mathematics). Röntgen noticed that these rays passed through soft tissue, like human skin, but didn’t penetrate harder materials such as metal and bone.

For the next seven weeks, Röntgen continued working in his lab in complete secrecy. When Röntgen’s wife asked what was the matter, he answered that if people knew what he was doing, they would say, “Röntgen must have gone mad.” Finally, on December 28 of that year, he published a paper titled “On a New Kind of Rays.” The world was never the same. Later, when asked what went through his mind when he first discovered X-rays, Röntgen answered: “I didn’t think; I investigated.”

The Discoverer of X-Rays Won the First Nobel Prize in Physics

In December 1896, a year after Röntgen published his groundbreaking paper, Alfred Nobel — famous for inventing dynamite — died in Sanremo, Italy, bequeathing his fortune to the establishment of a prize awarding the greatest advancements in literature, chemistry, physics, medicine, and peace (economics was added in 1969). Following five years of legal wrangling, in 1901 Wilhelm Röntgen became the first recipient of the Nobel Prize for physics, an award that eventually honored such titans of science as Albert Einstein, Marie Curie, and Niels Bohr. Röntgen also received an honorary degree of medicine from the University of Würzburg because of his invention’s immense medical benefits, but he never took out patents related to his invention.

People Used to Take “Bone Portraits” Using X-Rays

Many X-ray entrepreneurs and photo studios began offering “bone portraits” in the early years of the 20th century. The fad didn’t last, though, and that’s probably a good thing, because frequent, intense exposure to X-rays isn’t healthy for you. Those who regularly operated early X-ray machines developed skin lesions and other maladies because of prolonged exposure to ionizing radiation.

However, humans are constantly exposed to what’s called “background radiation.” The American Cancer Society estimates that today’s chest X-ray is the equivalent of 10 days of normal exposure — not terrible, but also not something you want to expose yourself to many times a day. So wearing those heavy X-ray vests probably isn’t a bad idea.

There Are “Hard” and “Soft” X-Rays

Not all X-rays are alike. Medical X-rays, CT scans, airport security scanners, and other devices most commonly associated with X-rays use what are known as “hard X-rays,” because they have smaller wavelengths and can therefore carry more energy. This makes them perfect for penetrating soft tissue to examine the harder structure lying underneath. Soft X-rays, on the other hand, have longer wavelengths, almost approaching the length of UV light. These X-rays can’t carry very much energy at all. However, these X-rays also have their uses in catalysis — the study of chemical reactions caused by catalysts — and biology.

X-Rays Helped Scientists Discover the Structure of DNA

On May 6, 1952, British chemist Rosalind Franklin at King’s College London took her 51st X-ray diffraction pattern of deoxyribonucleic acid, also known as DNA. For the first time in history, the image revealed DNA’s double helix structure. Known simply as Photo 51, the image had been produced by scattering X-rays off a pure fiber of DNA using a process known as X-ray crystallography.

Franklin’s colleague Maurice Wilkins showed the photo to two other scientists without her knowledge, and it was those three men who then won the Nobel Prize for medicine in 1962 — without any mention of Franklin’s contribution. (Sadly, she had passed away four years earlier.) Although she never received recognition from the Nobel Prize committee, scientists and historians now recognize her crucial contributions to molecular biology; the European Space Agency even named its Mars rover the Rosalind Franklin.

X-Rays Revolutionized the Study of Art History

Although X-rays have an obvious application in hospitals, art historians also have a need for technology that can delicately penetrate layers on a canvas to reveal the secrets beneath. X-rays are perfect at surpassing low-density materials to reveal high-density pigments (such as those containing metals like mercury, iron, zinc, and lead) below. This is particularly useful at uncovering underpaintings — the first layer of paint on a painting, often done historically with lead white — and other painted-over areas, which reveal an artist’s step-by-step approach to creating a masterpiece. The technology has been used to examine the works of Leonardo da Vinci, Vincent Van Gogh, and a variety of Dutch masters.

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Long, beautiful hair
Shining, gleaming
Streaming, flaxen, waxen

Give me down to there (hair)
Shoulder length or longer (hair)

No, these aren’t the words of a shampoo commercial. When American men were drafted to fight in Vietnam, their hair was cut short. Long locks on men became a sign of defiance, and such hairdos seemed thrillingly shocking to theatergoers, who flocked to the rock musical Hair (which featured the song above) when it opened on Broadway in 1968.

Hair has sent cultural messages for millennia. It also sends signals about our body chemistry, including our age and health (which may be the unconscious reason some of us get so upset about “bad hair” days). Let these six facts about hair show you a whole new side of your crowning glory.

Human Hair Contains Silicon and Gold

Although each person’s hair is a bit different, one strand usually contains 45% carbon, 28% oxygen, and 15% nitrogen. Hair also contains up to 12% to 15% water and traces of mineral elements, including copper, zinc, iron, and silicon. Our hair even contains gold, which is excreted from our bodies through both hair and skin. Babies have more gold in their hair than adults, because gold is passed along in breast milk. Overall, the average human body is said to contain around .2 milligrams (less than the weight of a poppy seed) of gold.

Some Hair Loss Is Normal

During your life, your hair grows, falls out, and regrows around 20 times. In fact, it’s normal to lose 100 hairs a day, and even more during the fall and spring. The reason may be that in areas with four seasons, the sun damages the hair bulbs during the summer, leading to hair loss in the fall. Winter cold restricts blood flow to the scalp, causing the spring shedding. The solution: Cover your head!

However, if you’re suddenly noticing much more hair in your brush or in your shower drain, you may be suffering from low iron, or anemia. This is more likely in people who menstruate if they have heavy periods. People also can experience temporary shedding after a sickness like COVID-19, with a change in estrogen levels after pregnancy or stopping birth control pills, or during menopause.

Hair Reveals Stress

It’s true: Stress can make hair go gray or white faster. But there’s good news, too. Gray or white strands can sometimes turn back to their previous color, according to a large international study in 2021. “Just like tree rings hold information about past decades, and rocks hold information about past centuries, hairs hold information about past months and years,” the researchers wrote.

These transformations can happen on hair anywhere on the body — sometimes quickly. One person in the study regained five hairs with color after they took a two-week holiday.

We Can Go White Overnight

Extreme stress can even turn hair white overnight (or at least very quickly). This may have happened to Queen of France Marie Antoinette before the morning she walked to the guillotine. Sir Thomas More’s hair is also said to have turned white overnight in the Tower of London before his execution. Dermatologists now call this rare phenomenon “Marie Antoinette syndrome.”

Wigs and Hair Dye Are Nothing New

Because hair reflects our mental and physical health, people have gone to great lengths throughout history to change its appearance. We dye away gray, use chemical products to fight hair loss, or wear wigs.

Dye to camouflage gray dates back at least to the ancient Egyptians, who used henna. The ancient Greeks used henna too (and even colored their horses’ tails with it).

In the Roman Empire, blond was a popular hair color. It had an exotic allure, and was associated with people from Gaul (modern France and Germany). Roman prostitutes were also required by law to have yellow hair to signal their status. Some very wealthy Romans even powdered their hair with gold dust. That was a more pleasant option than one dye that was used to turn hair black: fermented leeches.

The first commercial hair dye was created in 1907 by a French chemist, Eugene Schueller. He initially called his creation Aureole, but later renamed it L’Oréal, which was also the name of the company he founded two years later.

People Save Their Cut Hair

Among the sentimental Victorians, it was common to give locks of your hair to friends, family members, or lovers. The New York Public Library’s archives contain, for example, an auburn lock from Mary Shelley, the author of Frankenstein; a lock from Walt Whitman, author of Leaves of Grass; and a lock from Charlotte Bronte, who wrote Jane Eyre.

To this day, we continue to value hair as a memento. In 2009, a bidder paid $15,000 for a lock of Elvis Presley’s hair at an auction. That’s actually cheap: In 2021, a jar of the rock icon’s hair sold for $72,500.