12 Common Things Science Still Hasn't Figured Out

Laughter: Still a scientific mystery
Laughter: Still a scientific mystery
iStock/pixelfit

We’ve learned enough about physics to send humans to the Moon. We’ve discovered that DNA carries our genetic information. Scientists have even gotten closer to solving the mystery of whether cats can behave as both solids and liquids [PDF].

But there are still some basic questions we haven’t answered, including these frustratingly persistent scientific mysteries.

1. Why We Cry

Some of us tear up watching a sad movie; sometimes, we're so happy that we burst into tears. But according to science, crying in response to intense emotions doesn’t seem to be a useful behavior, and it might not have a biological purpose.

What science does know is that not all tears are created equal. The chemical composition of the tears produced when we cry, which are called psychic tears, is slightly different from the composition of the tears that lubricate and help expel foreign bodies from the eyes. This has led some to theorize that the chemical makeup of psychic tears makes them emotionally healing. But evidence showing that the chemical differences have substantial psychological effects—let alone that such effects explain why crying evolved—is lacking.

And that’s not where the theories end. Some evolutionary psychologists think that crying may have evolved as a distress call that brings help: In a 2009 paper, one researcher suggested that tears may signal submission and helplessness by blurring vision, which prompts others to aid (or at least not harm) the crier. But other researchers have pointed out that we often cry after a stressful situation has resolved, not while it’s in progress and we need to signal for help; it’s also typical for people to avoid crying publicly and to look unfavorably on those who do. In any case, these hypotheses, like most in evolutionary psychology, are difficult to test.

2. How to Cure Hiccups

Maybe you hold your breath. Maybe you chug water. Unfortunately, nothing has been found to reliably eliminate hiccups, despite the overwhelming number of folk remedies on the internet. This sad state of affairs is likely due to insufficient research: Serious cases of the hiccups are rare, and the mild cases are brief and don’t usually cause problems.

Most of the treatments for severe cases of hiccups—doses of sedating antipsychotics like haloperidol, vagus nerve stimulation, digital rectal massage—aren’t exactly things you could try on your own. For now, you’ll have to endure hiccups or stick with unproven, but usually harmless, solutions. At least they give you an excuse to eat peanut butter by the spoonful.

3. How General Anesthesia Works

As you’re rolling into surgery, you probably assume that your doctors not only know how to perform the procedure, but understand how the drugs that knock you out actually do so. But you’d be wrong. Scientists do know that local anesthetics like Novocain block pain signals before they reach the central nervous system by altering the function of specific proteins on nerve cells. But the molecular basis of general anesthesia is more of a mystery. These drugs seem to interfere with the functions of a variety of proteins on nerve cells in the central nervous system, but how they accomplish this is not well understood. General anesthetics come in a variety of types, and they likely don’t all work the same way, so developing models of how the compounds work on the molecular level may continue to be a challenge.

4. How Tylenol Kills Pain

A layperson taking Tylenol to relieve pain might think it works like non-steroidal anti-inflammatory drugs (NSAIDs), such as ibuprofen and aspirin, which block some enzymes and, in turn, the pain- and inflammation-causing chemicals they produce. But that’s not the case—acetaminophen, the active ingredient in Tylenol, seems to need specific chemical conditions to work on those enzymes, and it doesn’t appear to reduce inflammation as the NSAIDs do.

Some researchers think acetaminophen may alter the way pain is perceived by interacting with certain proteins on nerve cells, possibly including serotonin receptors, cannabinoid receptors, opioid receptors, and specific channels on nerves in the spinal cord that transmit pain and itch signals. Acetaminophen byproducts have also been shown to activate these channels rather than shutting them down, further complicating the question.

5. Why We Sleep

Too little sleep impairs thinking in the short term and increases the risk of several serious diseases in the long term, while complete sleep deprivation is fatal. We may have evolved to sleep because it aids healing, memory consolidation, and other important processes, but we still have much to learn about the ways sleeping achieves these ends. Other roles for sleep, like conserving energy during times when it wouldn’t be advantageous to be awake (for example, during scorching-hot days in Death Valley) have been proposed as well.

At least for now, we don’t have a single, conclusive answer to the question of why we sleep. But no matter how sleeping arose, we can probably accept that it provided a substantial evolutionary advantage once in place, since sleep is found across much of the animal kingdom.

6. Why Only Some Thunderstorms Produce Tornadoes

A standard explanation of how tornadoes form is that they’re spawned when cold, dry air mingles with warm, humid air—that’s how we justify the fact that Tornado Alley in the central United States, where Arctic air, air from the Southwest, and air from the Gulf of Mexico mix, has so many tornadoes. But that’s not the whole story. These conditions do create more thunderstorms, but not all thunderstorms include tornadoes, and scientists aren’t sure why.

In some cases, tornadoes may form is when there are temperature changes in the air flowing downward around mesocyclones (vortexes within the types of storms tornadoes can come from). This idea has theoretical and experimental support, but even without these temperature variations, tornadoes can still form, demonstrating how much more we have to learn about the phenomenon.

7. Why We Itch

At a basic level, itch is an unpleasant sensation that triggers the urge to scratch. Scratching could end up making an itch worse, but it may also serve a purpose. Mechanical itch—the kind triggered when fine hairs on your body are disturbed—may alert you to the presence of biting insects or parasites, and scratching could brush them away.

This hypothesis is difficult to test, and it doesn’t cover chemical itch caused by histamine and other scratch-provoking substances. Long after you’ve missed your chance to brush a mosquito off your skin, histamine in the itchy bump it has left behind continues to compel you to scratch. Whether this type of itching serves a purpose, or is simply an incidental activation of the itch system, isn’t conclusively known.

8. How We Age

Despite what many beauty experts claim, no one really has aging figured out. Reactive chemicals called free radicals are often blamed, but they’re not the sole cause of aging, and our cells have numerous ways to help keep damage caused by excess free radicals to a minimum. Shortening of the telomeres, the protective caps of DNA at the ends of each chromosome, is another frequently cited cause of aging—but it’s not the only factor. Numerous other contributors to aging have been discovered, but no single factor explains all or even most of the aging process, making this a difficult question to answer.

9. Why We Laugh

Laughter, like crying, may have developed as a social tool. Laughter doesn't appear to be a uniquely human behavior, and it may not even be limited to primates. Rats produce laughter when tickled, for example, and many other social animals, such as dolphins [PDF], make specific sounds associated with play-fighting that have been likened to laughter.

A leading hypothesis for why we laugh is that laughter promotes pro-social behavior by letting playmates know that the fighting is just a game. But even if our interpretations of these behaviors are correct, it’s possible that humans evolved different uses for laughter after our evolutionary splits with other animal species, making the reason for human laughter another open question.

10. How and Why Animals Migrate Back to Their Birthplaces

Some animals migrate to the sites of their birth to mate—a practice known as natal philopatry—with stunning precision. Female Antarctic fur seals, for example, can return to within one body length of their exact birthplaces to breed.

But how do they get there after months or years away? One possibility is that some migratory animals navigate by sensing variations in Earth’s geomagnetic field. While this makes sense given that some migratory animals, such as sea turtles, are known to be highly sensitive to these variations, it has not been conclusively demonstrated that they navigate this way.

Other creatures, such as Pacific salmon, may use smell to direct them toward their breeding grounds. These fish have been shown experimentally to be able to home in on chemical cues from the water in which they developed into adults. But these chemical breadcrumbs wouldn’t be detectable across the vast ocean, meaning that even if the salmon use them to navigate, they must also have a way to direct themselves close enough to the source to smell them. The complete mechanisms behind natal philopatry, even in this well-studied case, are still unknown.

11. What Dreams are For

If the question of why we sleep is complicated, the question of why we dream is even more so. Dreaming—especially with vivid, fanciful dreams—is most correlated with rapid eye movement (REM) sleep, which itself is poorly understood. One thought is that dreaming evolved to help us sort out or rehearse solutions to problems in our waking lives, but there is no hard evidence that this is the case.

Although our dreams may feel significant to us, it’s also possible that they serve no purpose—they may simply be a byproduct of other processes that occur during REM sleep. Studying the neurological basis of the strange and highly subjective experience of dreaming is complicated, which is why understanding the origin of dreaming is still beyond our grasp.

12. How Turbulence Happens

Understanding how turbulence works is incredibly important from an engineering perspective, since it affects everything from how internal combustion engines work to how far golf balls can travel. And now that most of classical physics (encompassing the laws of mechanics, thermodynamics, and so on) has long been established, turbulence is considered one of the biggest remaining problems in the field. No one has figured out a way to perfectly model turbulent flow.

Modeling turbulence requires the Navier–Stokes equations, which describe the motion of fluids (liquids, gases, and plasmas). And that’s the main problem: These equations themselves are poorly understood—so much so that producing a proof about one of their basic properties is one of the seven Millennium Prize Problems. It’s considered one of the most important open classic questions in math—and there's a million dollars waiting for anyone who can figure it out.

9 Facial Reconstructions of Famous Historical Figures

A facial reconstruction of King Richard III unveiled by the Richard III Society in 2013
A facial reconstruction of King Richard III unveiled by the Richard III Society in 2013
Dan Kitwood/Getty Images

Why look at a painting of a historical figure when you can come face to face with one? Forensic facial reconstruction using scans of skeletal remains allows researchers to create 3D models of the face through a combination of science, history, and artistic interpretation. The results may be somewhat subjective, but they’re fascinating anyway. Here are nine facial reconstructions of famous people.

1. Richard III

In 2012, King Richard III’s skeleton was found below a parking lot in Leicester, England, where in 1485 he was hurriedly buried after dying in battle. A reconstruction (above) shows a young man, only 32 years old, with a gentle, approachable face. It’s a far cry from the child-murdering villain portrayed by Shakespeare and other writers. One thing they said does seem accurate, however: The skeleton had a curved spine from scoliosis, suggesting that Richard’s humpback may have been real.

2. Bach

J.S. Bach’s bust has sat on innumerable pianos for centuries, but he only posed for one portrait in his lifetime. So this reconstruction of his face—which was taken from a bronze cast of his skull—offers an interesting glimpse into the man beneath the 18th century wig. You get the same thick neck, underbite, and stern brow you see in the painting, but the reconstruction’s friendly, confused stare lacks the soul of the real man … and his music, for that matter.

3. Shakespeare

Apparently, no one knows anything about Shakespeare for sure—his hair color, his sexual orientation, how he spelled his name, whether he liked his wife, etc. Some people aren’t even sure whether he wrote his plays or not. So this rendering, taken from a death mask found in Germany, is bound to be controversial. But if it is Shakespeare, it’s pretty intriguing. It shows a man who suffered from cancer and had a sad, soulful face.

4. Dante

Maybe it’s because The Divine Comedy dealt with the ugliness of sin that Dante Alighieri is usually depicted as unattractive, with a pointy chin, buggy eyes, and enormous hooked nose. But a reconstruction done from measurements of the skull taken in 1921—the only time the remains have been out of the crypt—reveals a much more attractive Dante. The face has a rounder chin, pleasant eyes, and smaller nose than previously thought. It’s a face with character.

5. King Henri IV

The mummified head of France’s King Henri IV was lost after the French Revolution until a few years ago, when it showed up in a tax collector’s attic. In his day, Henri was beloved by everyone except the Catholic fundamentalists who murdered him in 1610. The hard-living king looks a bit old for his 56 years, but there’s a twinkle in his eyes. What the model cannot show, however, was how much the king stank—apparently he smelled of ”garlic, feet and armpits.”

6. Cleopatra’s Sister

Cleopatra hated her half-sister Arsinoe IV so much she had her dragged out of the temple of Artemis and murdered. In 2013, researchers said they had discovered what may be Arisone’s body, based on the shape of the tomb, carbon dating, and other factors. The resulting facial reconstruction shows a petite teenager of European and African blood. And yeah, maybe this is closer to what Arsinoe would look like if she were trapped in The Sims, but since Cleopatra’s remains are long gone, this may be the closest we get to knowing what she looked like.

7. King Tut

King Tutankhamun, whose famous sarcophagus has traveled far more than the “boy king” did in his 19-year lifetime, had buckteeth, a receding chin, and a slim nose, according to 3D renderings of his mummy. His weird skull shape is just within range of normal and was probably genetic—his father, Akhenaten, had a similarly shaped head. Tut’s body also had a broken leg, indicating he may have died from falling off a horse or chariot.

8. Copernicus

Nicolaus Copernicus, who challenged the belief that the sun revolved around the earth, died in 1543 at age 70. When his body was found in 2006 in a Polish church and confirmed by matching DNA to strands of his hair left in a book, the Polish police used their forensic laboratory to make this portrait. They made sure to include Copernicus’s broken nose and the scar above his left eye. Who knew that the Father of Astronomy looked so much like the actor James Cromwell?

9. Santa Claus

The remains of St. Nicholas, i.e. Santa Claus, have been in a church in Bari, Italy, since they were stolen from Turkey in 1087. This reproduction, taken from measurements of his skull, reveal that St. Nicholas had a small body—he was only 5’6”—and a huge, masculine head, with a square jaw and strong muscles in the neck. He also had a broken nose, like someone had beaten him up. This is consistent with accounts of St. Nicholas from the time: It turns out that Santa Claus had quite a temper.

A version of this list was first published in 2013.

Bombshell, Victoria’s Secret’s Bestselling Fragrance, Also Happens to Repel Mosquitoes

Dids, Pexels
Dids, Pexels

People love Bombshell, the best-selling fragrance at Victoria’s Secret, for its summery blend of fruity and floral notes. Not everyone is a huge fan, though: As Quartz reports, the perfume is surprisingly good at warding off mosquitoes. In fact, it’s almost as effective as DEET insect repellent, according to the results of a 2014 experiment by researchers at New Mexico State University.

Researchers took 10 products that are commercially available and tested their ability to repel two different species of mosquitoes: the yellow fever mosquito (Aedes aegypti) and the Asian tiger mosquito (Aedes albopictus), both of which are known to transmit diseases like dengue fever, chikungunya, and yellow fever. In doing so, volunteers subjected their own flesh to the test by placing their hands on either side of a Y-shaped tube containing the blood-sucking critters. One hand was covered in a synthetic rubber glove, while the other hand was sprayed with one of the products but otherwise left bare. Researchers recorded which tunnel the mosquitoes flew to, and how long they avoided the other end.

Three of the products contained DEET, while four products didn’t. In addition, there were two fragrances (including Bombshell) and one vitamin B1 skin patch. The DEET products were the most effective, but Bombshell proved to be nearly as good, keeping mosquitoes at bay for roughly two hours.

“There was some previous literature that said fruity, floral scents attracted mosquitoes, and to not wear those,” Stacy Rodriquez, one of the study’s authors, said in a statement. “It was interesting to see that the mosquitoes weren’t actually attracted to the person that was wearing the Victoria’s Secret perfume—they were repelled by it.”

This isn’t the first time a perfume has had an unintended effect on the natural world. It turns out that tigers are obsessed with Calvin Klein’s Obsession for Men cologne, partly because it contains a synthetic version of civetone, a pheromone that's secreted by glands located near a civet’s anus. This substance was once used to create musky fragrances, but nowadays the scent is mostly reproduced in a lab. Still, the fake stuff must be pretty convincing, because big cats go crazy when they catch a whiff of it.

[h/t Quartz]

SECTIONS

arrow
LIVE SMARTER