12 Common Things Science Still Hasn't Figured Out

Laughter: Still a scientific mystery
Laughter: Still a scientific mystery

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.

11 Things You Might Not Know About Neil Armstrong

NASA/Hulton Archive/Getty Images
NASA/Hulton Archive/Getty Images

No matter where private or government space travel may take us in the future, NASA astronaut Neil Armstrong (1930-2012) will forever have a place as the first human to ever set foot on solid ground outside of our atmosphere. Taking “one small step” onto the Moon on July 20, 1969, he inspired generations of ambitious people to reach for the stars in their own lives. On the 50th anniversary of Apollo 11, we're taking a look back at the life of this American hero.

1. Neil Armstrong knew how to fly before he got a driver's license.

Neil Armstrong poses for a portrait 10 years before the 1969 Apollo mission
NASA/Hulton Archive/Getty Images

Born August 5, 1930 in Wapakoneta, Ohio, Armstrong became preoccupied with aviation early on. At around age 6, his father took him on a ride in a Ford Trimotor airplane, one of the most popular airplanes in the world. By age 15, he had accumulated enough flying lessons to command a cockpit, reportedly before he ever earned his driver’s license. During the Korean War, Armstrong flew 78 combat missions before moving on to the National Advisory Committee for Aeronautics (NACA), the precursor to NASA.

2. Neil Armstrong's famous quote was misheard back on Earth.

When Armstrong and Buzz Aldrin touched down on the Moon, hundreds of millions of television viewers were riveted. Armstrong could be heard saying, “That’s one small step for man, one giant leap for mankind.” But that’s not exactly what he said. According to the astronaut, he was fairly sure he stated, “That’s one small step for a man, one giant leap for mankind.” The “a” may have broken up on transmission or it may have been obscured as a result of his speaking patterns. (According to First Man: The Life of Neil A. Armstrong, Armstrong said, “I’m not particularly articulate. Perhaps it was a suppressed sound that didn’t get picked up by the voice mike. As I have listened to it, it doesn’t sound like there was time for the word to be there. On the other hand, I think that reasonable people will realize that I didn’t intentionally make an inane statement, and certainly the ‘a’ was intended, because that’s the only way the statement makes any sense. So I would hope that history would grant me leeway for dropping the syllable and understand that it was certainly intended, even if it wasn’t said—although it actually might have been.”) Armstrong claimed the statement was spontaneous, but his brother and others have claimed he had written it down prior to the mission.

3. We don't have a really good picture of Neil Armstrong on the Moon.

Buzz Aldrin is seen walking on the moon
NASA/Hulton Archive/Getty Images

One of the most celebrated human achievements of the 20th century came at a time when video and still cameras were readily available—yet there are precious few images of Armstrong actually walking on the surface of the Moon. (One of the most iconic shots, above, is Aldrin; Armstrong only appears as a reflection in his helmet.) The reason, according to Armstrong, is that he really didn’t care and didn’t think to ask Aldrin to snap some photos. “I don't think Buzz had any reason to take my picture, and it never occurred to me that he should,” Armstrong told his biographer, James R. Hansen. “I have always said that Buzz was the far more photogenic of the crew."

4. A door hinge may have made all the difference to the Apollo 11 mission.

Theories abound as to why it was Armstrong and not Buzz Aldrin who first set foot on the Moon. (On the Gemini missions, the co-pilot did the spacewalks, while the commander stayed in the craft. For Apollo 11, Armstrong was the commander.) The answer may have been the simple logistics of getting out of their lunar module. The exit had a right hinge that opened inwardly, with the man sitting on the left (Armstrong) having the most unobstructed path to the outside. Aldrin would have essentially had to climb over Armstrong to get out first.

5. Neil Armstrong was more concerned about landing on the Moon than he was walking on it.

The lunar module that took NASA astronauts to the moon
NASA/Hulton Archive/Getty Images

The romantic notion of a human stepping foot on space soil captured imaginations, but for Armstrong, it was getting there in one piece that was the real accomplishment. The lunar module Armstrong controlled had to be brought down on the Moon’s surface from 50,000 feet up, avoiding rocks, craters, and other obstacles as it jockeyed into a position for landing. Because there is no air resistance, nothing could slow their descent, and they used thrusters to guide the craft down. That meant there was only enough fuel to attempt it once. The “business” of getting down the ladder was, in Armstrong’s view, less significant.

6. Neil Armstrong was carrying a bag worth $1.8 million.

When Armstrong surveyed the surface of the Moon, he collected a bag of dust for NASA scientists to examine. Apollo moon samples are illegal to buy or sell, but that apparently wasn't the case with the “lunar collection bag” Armstrong used to hold the samples. In 2015, the bag was purchased by Chicago resident Nancy Lee Carlson from a government auction site for $995. But its sale was, apparently, an accident: When Carlson sent the bag to NASA to confirm its authenticity, NASA said it was their property and refused to send it back—so Carlson took the agency to court. A judge ruled it belonged to Carlson, and in 2017, she sold the bag for a whopping $1.8 million at a Sotheby’s auction.

7. Neil Armstrong and his fellow Apollo 11 astronauts had to spend three weeks in quarantine.

Richard Nixon greets the returning Apollo 11 astronauts
NASA/Hulton Archive/Getty Images

When Armstrong, Aldrin, and Michael Collins (who remained behind in the command module while the other two touched down on the Moon) returned to Earth and were fetched by the USS Hornet, they got a king’s welcome. The only asterisk: They had to bask in their newfound fame from inside a sealed chamber. All three men were quarantined for three weeks in the event they had picked up any strange space virus. When President Richard Nixon visited, he greeted them through the chamber’s glass window.

8. Neil Armstrong's space suit was made by Playtex.

Yes, the undergarment people. In the early 1960s, NASA doled out contract work for their space suits to government suppliers, but it was Playtex (or more properly the International Latex Corporation) and their understanding of fabrics and seams that led to NASA awarding them responsibility for the Apollo mission suits. Their A7L suit was what Armstrong wore to insulate himself against the harsh void of space when he made his famous touchdown. The astronaut called it “reliable” and even “cuddly.”

9. Neil Armstrong became a university professor.

Newil Armstrong sits behind a desk in 1970
AFP/Getty Images

Following his retirement from NASA in 1971, Armstrong was reticent to remain in the public eye. Demands for his time were everywhere, and he had little ambition to become a walking oral history of his singular achievement. Instead, he accepted a job as a professor of engineering at the University of Cincinnati and remained on the faculty for eight years.

10. Neil Armstrong once sued Hallmark.

Hallmark was forced to defend itself when Armstrong took issue with the company using his name and likeness without permission for a 1994 Christmas ornament. The bulb depicted Armstrong and came with a sound chip that said phrases like, “The Eagle has landed.” The two parties came to an undisclosed but “substantial” settlement in 1995, which was, according to First Man, donated to Purdue University (minus legal fees).

11. Neil Armstrong was a Chrysler pitchman.

Armstrong’s preference to lead a private life continued over the decades, but he did make one notable exception. For a 1979 Super Bowl commercial spot, Armstrong agreed to appear on camera endorsing Chrysler automobiles. Armstrong said he did it because he wanted the struggling U.S. car maker to improve their sales and continue contributing to the domestic economy. The ads never mentioned Armstrong was an astronaut.

Pioneering Heart Surgeon René Favaloro Is Being Honored With a Google Doodle

Dr. René Favaloro (left) pictured with colleague Dr. Mason Sones.
Dr. René Favaloro (left) pictured with colleague Dr. Mason Sones.
The Cleveland Clinic Center for Medical Art & Photography, Wikimedia Commons // CC BY 4.0

Argentinian heart surgeon René Favaloro is the subject of today’s Google Doodle, which features a sketched portrait of the doctor along with an anatomical heart and several medical tools, The Independent reports.

The renowned doctor was born on this day in 1923 in La Plata, the capital of Argentina’s Buenos Aires province, and pursued a degree in medicine at La Plata University. After 12 years as a doctor in La Pampa, where he established the area’s first mobile blood bank, trained nurses, and built his own operating room, Favaloro relocated to the U.S. to specialize in thoracic surgery at the Cleveland Clinic.

In 1967, Favaloro performed coronary bypass surgery on a 51-year-old woman whose right coronary artery was blocked, restricting blood flow to her heart. Coronary bypass surgery involves taking a healthy vein from elsewhere in the body (in this case, Favaloro borrowed from the patient’s leg, but you can also use a vein from the arm or chest), and using it to channel the blood from the artery to the heart, bypassing the blockage. According to the Mayo Clinic, it doesn’t cure whatever heart disease that caused the blocked artery, but it can relieve symptoms like chest pain and shortness of breath, and it gives patients time to make other lifestyle changes to further manage their disease.

Favaloro wasn’t keen on being called the “father” of coronary bypass surgery, but his work brought the procedure to the forefront of the clinical field. He moved back to Argentina in 1971 and launched the Favaloro Foundation to train surgeons and treat a variety of patients from diverse economic backgrounds.

Favaloro died by suicide on July 29, 2000, at the age of 77, by a gunshot wound to the chest. His wife had died several years prior, and his foundation had fallen deeply into debt, which Argentinian hospitals and medical centers declined to help pay, The New York Times reported at the time.

“As a surgeon, Dr. Favaloro will be remembered for his ingenuity and imagination,” his colleague Dr. Denton A. Cooley wrote in a tribute shortly after Favaloro’s death. “But as a man ... he will be remembered for his compassion and selflessness.” Today would have been his 96th birthday.

[h/t The Independent]