10 Head-Scratching Facts About Gray Hair

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istock

Whether it’s no big deal or a perplexing affront to your vanity, gray hair is a fact of life—and still a bit of a mystery.

1. How Hair Turns Gray

Hair grows in a follicle, a bulb-like tube on your scalp. The average head has 100,000 to 150,000 follicles, each operating independently from the others. Hair in its basic, unpigmented state is white. It gets its color from melanin, a pigment that also determines skin color. Two types of melanin, eumelanin (dark brown or black) and phaeomelanin (reddish yellow), combine to make all the hair colors. One hypothesis for why hair goes gray is that aging slows or stops the hair from accessing the melanin, so it comes out gray, silver, or white instead.

2. Hair May Bleach Itself From The Inside Out

New research reveals that graying may be from a build-up of hydrogen peroxide in the hair cell, which causes the hair to bleach itself on the inside. Cells naturally have a small amount of hydrogen peroxide in them, but it’s kept in check by an enzyme called catalase, which converts the hydrogen peroxide to oxygen and water. As we age, the body produces less catalase, so the hydrogen peroxide builds up and, according to the New York Times, blocks “the normal synthesis of melanin, the natural pigment in hair.” Thus the hair turns gray, giving new meaning to the phrase “peroxide blonde.”

3. Graying Is Caused By Heredity

When you’re born, your genes are already hardwired for when and how your hair will turn gray. This includes premature graying—people who gray before age 30 usually do so because it runs in the family. For most of us, graying starts in middle age. Dermatologists go by the 50/50/50 rule of thumb: by age 50, half the population will have at least 50 percent gray hair—although a worldwide survey showed that number was much lower, with only 6 to 23 percent of people half gray by age 50.

4. Race Is Also A Factor

In a related matter, race also determines when you’re likely to gray. In general, Caucasians gray in their mid-30s, Asians in their late-30s, and African Americans in their 40s.

5. Plucking One Gray Hair Will Not Cause Three To Grow In Its Place

This old wives’ tale is a myth. Each follicle can contain only one hair, and plucking it won’t make it able to produce multiple hairs. Furthermore, what you do to one follicle has no effect on the ones around it. That said, excessive plucking isn’t a good idea—it can damage the follicles and even stop hair production in that area altogether.

6. Stress Probably Plays A Role In Graying

When President Obama went gray his first term in office, was it stress, age, or a combination of both? Scientists aren’t sure. While some researchers say that your genes alone are responsible for gray hair, others say that there seems to be a connection between graying and stress, just no direct link to prove it. In 2011, a study by Nobel Prize winner Robert Lefkowitz discovered that long-term productions of the body’s fight or flight response—the instinctive ability to mobilize energy in response to a threatening situation—can damage your DNA and cause premature aging, including graying hair.

7. Trauma Won’t Make You Go Gray Overnight

Another myth is that a major shock will cause your hair to suddenly turn gray. This is sometimes called the Marie Antoinette Syndrome because the French queen’s hair supposedly turned white the night before she was beheaded. But hair, once grown, doesn’t change color, so waking up with a head of white hair isn’t going to happen. Although there is a very rare condition where all of the colored hairs can fall out, leaving only white hairs behind, the simpler answer is that Marie Antoinette probably just took off her wig.

8. Smoking May Cause You To Prematurely Gray

Multiple studies have linked smoking with premature aging, which includes early graying. In 2013, a study found that there is a significant relationship between smoking and gray hair in people under 30. In fact, “smokers were two and half times more prone to develop PHG” or premature hair graying.

9. Body Hair Also Turns Gray

All your body hair—chest, nose, pubic, etc.—can turn gray. Body hair tends to gray at a different rate than the hair on your head, which is why some men can have gray beards and brown hair, or visa versa. By the way, dyeing gray pubic hair is a thing. 

10. Someday, Research May Lead To A Gray Hair Cure

Scientists in Europe discovered a breakthrough with vitiligo, a disease where skin loses pigment and develops white patches. Like hair, vitiligo is caused by “massive oxidative stress via accumulation of hydrogen peroxide,” causing the skin to bleach itself from the inside out. Researchers have successfully treated the discolored skin and eyelashes of vitiligo patients, which has led some to predict a potential cure for gray hair. But while the idea sounds promising, history is full of tonics and creams claiming to cure gray hair. As far as we know, none of them have worked yet.

Does Sound Travel Faster or Slower in Space?

iStock/BlackJack3D
iStock/BlackJack3D

Viktor T. Toth:

It is often said that sound doesn’t travel in space. And it is true … in empty space. Sound is pressure waves, that is, propagating changes in pressure. In the absence of pressure, there can be no pressure waves, so there is no sound.

But space is is not completely empty and not completely devoid of pressure. Hence, it carries sound. But not in a manner that would match our everyday experience.

For instance, if you were to put a speaker in interstellar space, its membrane may be moving back and forth, but it would be exceedingly rare for it to hit even a single atom or molecule. Hence, it would fail to transfer any noticeable sound energy to the thin interstellar medium. Even the somewhat denser interplanetary medium is too rarefied for sound to transfer efficiently from human scale objects; this is why astronauts cannot yell to each other during spacewalks. And just as it is impossible to transfer normal sound energy to this medium, it will also not transmit it efficiently, since its atoms and molecules are too far apart, and they just don’t bounce into each other that often. Any “normal” sound is attenuated to nothingness.

However, if you were to make your speaker a million times bigger, and let its membrane move a million times more slowly, it would be able to transfer sound energy more efficiently even to that thin medium. And that energy would propagate in the form of (tiny) changes in the (already very tiny) pressure of the interstellar medium, i.e., it would be sound.

So yes, sound can travel in the intergalactic, interstellar, interplanetary medium, and very, very low frequency sound (many octaves below anything you could possibly hear) plays an important role in the formation of structures (galaxies, solar systems). In fact, this is the mechanism through which a contracting cloud of gas can shed its excess kinetic energy and turn into something compact, such as a star.

How fast do such sounds travel, you ask? Why, there is no set speed. The general rule is that for a so-called perfect fluid (a medium that is characterized by its density and pressure, but has no viscosity or stresses) the square of the speed of sound is the ratio of the medium’s pressure to its energy density. The speed of sound, therefore, can be anything between 0 (for a pressureless medium, which does not carry sound) to the speed of light divided by the square root of three (for a very hot, so-called ultrarelativistic gas).

This post originally appeared on Quora. Click here to view.

How Fossil Fuel Use Is Making Carbon Dating Less Accurate

iStock.com/Harry Wedzinga
iStock.com/Harry Wedzinga

The scientific process of carbon dating has been used to determine the age of Ötzi the Iceman, seeds found in King Tutankhamun’s tomb, and many other archaeological finds under 60,000 years old. However, as SciShow points out in a recent episode, the excessive use of fossil fuels is making that method less reliable.

Carbon dating, also called radiocarbon or C-14 dating, involves analyzing the ratio of two isotopes of carbon: C-14 (a radioactive form of carbon that decays over time) and C-12 (a more stable form). By analyzing that ratio in a given object compared to a living organism, archaeologists, paleontologists, and other scientists can get a pretty clear idea of how old that first object is. However, as more and more fossil fuels are burned, more carbon dioxide is released into the environment. In turn, this releases more of another isotope, called C-12, which changes the ratio of carbon isotopes in the atmosphere and skews the carbon dating analysis. This phenomenon is called the Suess effect, and it’s been well-documented since the ‘70s. SciShow notes that the atmospheric carbon ratio has changed in the past, but it wasn’t anything drastic.

A recent study published in Nature Communications demonstrates the concept. Writing in The Conversation, the study authors suggest that volcanoes “can lie about their age." Ancient volcanic eruptions can be dated by comparing the “wiggly trace” of C-14 found in trees killed in the eruption to the reference "wiggle" of C-14 in the atmosphere. (This process is actually called wiggle-match dating.) But this method “is not valid if carbon dioxide gas from the volcano is affecting a tree’s version of the wiggle,” researchers write.

According to another paper cited by SciShow, we're adding so much C-12 to the atmosphere at the current rate of fossil fuel usage that by 2050 brand-new materials will seem like they're 1000 years old. Some scientists have suggested that levels of C-13 (a more stable isotope) be taken into account while doing carbon dating, but that’s only a stopgap measure. The real challenge will be to reduce our dependence on fossil fuels.

For more on how radiocarbon dating is becoming less predictable, check out SciShow’s video below.

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