Science Mysteries, Explained

Will too many hot chili peppers kill you? Is the moon on the verge of erupting? PopSci tackles life's whys, hows and who-dunnits in this Q&A-style; feature

The world is full of mysteries, and we at Popular Science strive to
do our part to help you make sense of them. What do animals dream about? Is there any way to ensure a blink-free photo? And what is the worst sound on Earth? We've covered these important bases and more to help you become
the hit of the next cocktail party and your friends' go-to expert on the
most curious parts of life. Launch the photo gallery to learn the answers to questions that have always made you scratch your head. Because sometimes
you just need to know.

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Can I die from eating too many hot chili peppers?

There is no known case of a person dying from eating too many peppers, although several masochists have certainly tested the limits. The reigning king of jalapeño consumption is Nevadan Richard LeFevre, who last October set the International Federation of Competitive Eating record by downing 247 pickled jalapeos in an eight-minute time limit. Looking to top LeFevre and win a place in the Guinness Book of World Records is Anandita Dutta Tamuly, a woman from India who devoured 60 Bhut Jolokia peppers--the hottest pepper in the world--in just two minutes on national television. But she might not have anything on Mexico's Manuel Quiroz, who also wants a shot at the eating record and can squeeze habanero juice into his eyes without blinking. Freakish tolerance levels aside, scientists have found that eating peppers can have medical benefits. Last March, researchers at Cedars-Sinai Medical Center in Los Angeles found that the chemical that makes peppers hot, capsaicin, can kill human prostate-cancer cells grown in mice. The scientists estimated that the dosage was equal to a 200-pound man eating three to eight habanero peppers three times a week. But is there a deadly dose of spicy peppers? Researchers at Niigata University School of Medicine in Japan ran tests on mice to find out. After several hefty doses of pure capsaicin, most of the mice died of lung failure. Don't worry, though--you'd have to eat hundreds of thousands of jalapeños in one sitting to get the equivalent dose, and, the LeFevres of the world notwithstanding, most people beg for mercy after a dozen. --Brandon MillerAntonello Turchetti/Getty Images

I've heard that the moon is moving away from Earth. If we add mass by building a base on the moon, will it speed up that process

Scientists have determined that the moon creeps 1.5 inches farther away from the Earth every year, mostly as a consequence of the tides gradually slowing the Earth's rotation. But could adding mass to the moon's surface alter its orbit even more, just as a glob of mud affects a baseball's spin? NASA's plan to build its first lunar base by 2024 is ambitious, but it won't move the moon. The moon's mass is about 80 billion billion tons, which easily dwarfs the few dozen tons of construction that NASA has proposed. To put this in perspective, imagine a flea sitting on the Great Pyramid and somehow shifting the giant tomb a few inches to the left. Unlikely as it is, though, adding mass to the moon could theoretically change its orbit. Scott A. Hughes, an assistant professor of astrophysics at the Massachusetts Institute of Technology, calculates that we would need to send more than 540 trillion tons to the moon to push it an additional 1.5 inches away. That, however, would require well over a billion flights of NASA's proposed moon transporter, Orion. There's a greater chance of an asteroid hitting the moon and altering its orbit. The Earth-moon separation will ultimately lengthen our days and severely diminish the magnitude of high and low tides, says Jim Bell, an associate professor of astronomy at Cornell University. But this won't happen for a few billion years. And by then, the sun will be burning away the Earth's atmosphere and oceans, so we'll have more pressing things to worry about. --Katherine RyderNASA

How do I take a blink-free group photo?

Sitting for those class pictures in elementary school was always a chore, especially considering that half the kids ended up looking asleep, their faces immortalized mid-blink. It turns out that the seventh grade might have been in better hands with a physicist behind the lens than Bob from Sears. Frustrated with an excess of closed eyes in her photos, Nic Svenson, a communications officer at CSIRO, Australia's national science agency, enlisted the aid of physicist Piers Barnes to develop a mathematical formula for calculating the number of photographs one ought to take to produce a group shot sans blinkers. Barnes's rule--1/(1 - xt)n--takes into account a person's average number of blinks per second (x), the camera's shutter speed plus the duration of an average blink (t), and the number of people in the group (n). Simply plug in your numbers and snap away. Because most photographers can't carry out tricky algebra in their head, Barnes adapted the formula to an easier-to-crunch rule for figuring out the number of photos to take of groups smaller than 20: In good light, divide the number of people by three; in darker conditions, divide by two (with the shutter open longer for a better exposure, there's more time for blinks to creep in). For their efforts, Barnes and Svenson won the 2006 Ig Nobel prize--an annual award that recognizes zany scientific research--for mathematics. Although this bit of math didn't earn a real Nobel, it's an insight you can actually use. No word yet on how to calculate the number of photos needed before everyone in the group looks happy, but we're guessing they don't make memory cards large enough. --Abby SeiffNicholas Prior/Getty Images

I paid an extra $17 to make my cross-country flight "carbon-neutral." Am I saving the planet, or am I a sucker?

In the past couple years, the quest for what's known as carbon neutrality--essentially, canceling out the greenhouse-gas emissions caused by your activities by supporting clean-air projects--has become a multimillion-dollar industry. Corporations, big-budget movies, rock bands like the Rolling Stones and Coldplay, and even the Super Bowl are now making carbon neutrality part of their brand identity, offsetting their emissions by funding such projects as building wind farms in Nebraska, providing solar panels to Africa, and planting mango trees in India. Dozens of companies will gladly take your money to help assuage your global-warming guilt. According to the Environmental Protection Agency, the average American generates 10 tons of carbon dioxide annually, which most companies estimate can be offset for $100 to $200. Last August, the online travel services Expedia and Travelocity began offering customers the option of canceling out the CO2 resulting from their purchased travel ($17 for a round-trip coast-to-coast flight on Expedia; $10 on Travelocity). But is it all a scam? Not necessarily. The key is to make sure your money is funding projects that actually do prevent emissions and that reduce them beyond what would be achieved by business as usual, a concept known in the industry as "additionality." One organization that educates consumers on which programs measure up is the nonprofit Clean Air-Cool Planet ( ). Last December, it released a comprehensive evaluation of offset providers, rating each on a scale of 1 to 10. Of 30 companies evaluated, only eight earned a 5 or higher. Meanwhile, the European watchdog group Gold Standard Foundation ( ) certifies well-run, legitimate carbon-offsetting projects using a system that works much like the "fair trade" coffee and "100% organic" labels. "Beware of any old company claiming to be carbon-neutral," says marketing director Jasmine Hyman. "It's the wild, wild West." Bottom line: Instead of paying an intermediary to offset your emissions, make a contribution directly to a well-reviewed organization (Atmosfair and NativeEnergy are two good bets). And remember, the best way to guarantee that your personal emissions will be reduced is to reduce them yourself. Money's not enough, something Coldplay found out the hard way. The mango trees in India that they funded died due to a lack of maintenance. --Kalee ThompsonErik Simonsen/Getty Images

Why do cats hate getting wet?

A misbehaving cat caught in the sights of a spray bottle doesn't necessarily run away because it hates getting soaked. It's probably afraid of water. Scientists believe that house cats' limited experience with water-mostly leaky faucets and water dishes-makes them fearful of wet stuff. The domestic cat's desert-dwelling ancestors also had limited experience with water. Genetic studies conducted at the National Cancer Institute show that the house cat's closest relatives are wild cats from Africa and Europe and the Chinese desert cat. And ever since humans first domesticated cats-the earliest evidence dates to Cyprus 9,500 years ago-cat owners have protected their pets from the elements. "Cats have not evolved to do much with water," says animal-behavior specialist Katherine Houpt of Cornell University's College of Veterinary Medicine. Whether a cat enjoys water depends not only on where it lives but on its interactions with predators and prey, says Jack Grisham, the St. Louis Zoo's director of animal collections. Lions stay on dry land to avoid bathing in rivers patrolled by crocodiles, and leopards live in trees, away from water and predators below. In contrast, some domesticated farm cats prowl ponds for frogs. And the fishing cat, native to wetlands from India to Indonesia, taps the water's surface with its paw and then snatches its prey with webbed claws. Owners can also train the fear of water out of cats by bathing them as kittens. Most vets don't recommend this, however, because it can dry out a cat's skin and wash away pheromones essential for communicating with other felines. Besides, a cat already has all the supplies it needs to keep itself clean: Its saliva contains a natural detergent to reduce grease, and its barbed tongue combs out dirt. Still, some cats enjoy getting wet so much, Houpt says, "they actually play with water." Even the threat of the spray bottle, she admits, stops only 70 percent of cats from scratching the sofa. -Corey BinnsMike Powell/ Getty Images

What's the worst sound in the world?

The grinding whine of a dentist's drill? A beginning violin student? Not even close, according to researchers in England who set out to determine the world's most repulsive sound. The group, led by acoustic engineer Trevor Cox of the University of Salford, uploaded a selection of 34 sounds on and asked users to rate each sound on a scale of one (not bad) to six (plug-your-ears-and-cry horrible). More than 1.6 million votes later, the answer was clear across all age groups and cultures: There's nothing worse than the sound of someone else vomiting. To create what Cox calls the proper "slopping sound," the team had an actor make yacking noises while he dumped baked beans into a bucket. That vile audio snippet beat out strong contenders such as squealing microphone feedback and an electronic version of fingernails clawing a blackboard. "We're looking at what psychologists call a disgust reaction, which is a survival mechanism," Cox says. "If someone's coughing or vomiting, they're carrying disease, and thus we avoid it." Although Cox believes that culture plays a role in what sounds we find repulsive, the instinct to be repulsed by the sounds of disease probably evolved as a mechanism to avoid catching an illness from a neighbor. In 2004, Val Curtis at the London School of Hygiene and Tropical Medicine ran a study using disgusting photos rather than sounds and also concluded that disease is universally the most revolting characterististic. For the record, the blue ribbon went to a photo of a person's gums infested with parasite eggs--which might even be gross enough to elicit genuine vomiting. --Fred KoschmannAndy Reynolds/Getty Images

Is it true that I use only 10 percent of my brain?

Historians have traced the earliest reference of this rumor back to the beginning of the 20th century, when it was perpetuated by self-help gurus promising to expand people's mental abilities. But just as a few sips of a tonic made from herbs and roots will fail to improve one's physique, the brain claim is resoundingly false. "There's no question," says Marcus Raichle, a neurologist and professor of radiology at Washington University in St. Louis, "you're using every little bit of this thing." Even when you're sleeping or just sitting around watching TV, your brain is burning a disproportionate amount of energy for its size. At 2 percent of an individual's body weight, the brain accounts for 20 percent of the total energy the body consumes. Most of that energy, however, is used for tasks other than thinking. Scientists know that the remaining energy is largely used for the organ's regular upkeep and communication among neurons. The rest, they speculate, might go toward preparing the brain to receive information by making predictions based on past experiences. For example, instead of scanning your entire fridge each time you go to grab some milk, you reach directly for the shelf where you last left it. This preprocessing strategy helps us deal with the enormous amount of detail we encounter on a regular basis. Regardless, you can be certain that all of your brain is working hard, even when you're not thinking hard. "One needs to back away from the notion that the only thing the brain is doing is sitting around waiting for something to happen," Raichle says. "Every piece of it is running full-tilt all the time." -Todd NealeNew Line/Neal Peters Collection

Why do boys and girls fight differently?

Science is still some way from explaining why boys throw punches and girls pull hair on the playground. In the boxing ring, though, it's making progress--at least when the combatants are fruit flies. Edward Kravitz, a professor of neurobiology at Harvard Medical School and the Don King of fly fights, has identified a gene that controls the fighting tactics of male and female fruit flies. To instigate the same-sex battles, Kravitz offers lavish prizes: yeast for the females and, for the males, the privilege of courting a headless female. "We won't get into social commentary with that fact," he jokes. As you might expect, the males fight fiercely. They lunge and then rear up to drop blows with their forelegs. "If you watch in slow motion, they just flatten their opponent," Kravitz says. Females choose to shove and head-butt, a daintier but equally effective approach. But are the different fighting styles learned behavior, or are they hardwired in the flies' DNA? To find out, Kravitz transplanted the male version of a gene previously associated with gender-specific behaviors, such as male courtship, into females and put the female version in males. After the gene swapping, the males fought like females and the females adopted male techniques, providing the first evidence of gene-controlled gender-specific aggression in fruit flies. Kravitz's research doesn't translate smoothly to humans, however, because we don't have a gene corresponding to the one he swapped in flies. Also, scientists generally agree that different levels of testosterone exposure early in life are probably responsible for the aggression-related gender variation in humans. But Kravitz thinks his finding will help neurobiologists understand how complex behaviors like aggression get wired into the nervous system--without anyone getting pummeled in the ring. --Michael RosenwaldHerman Eisenbeiss/ Lew Robertson/ S. Meltzer

What do animals dream about?

When Spot pedals his legs in a futile sprint to nowhere during a nap, he's probably reliving the morning's game of fetch or his latest attempt to catch a squirrel. Scientists have found that, as with humans, what goes on in animals' brains while they're sleeping is influenced by what they did that day. In his lab at the Massachusetts Institute of Technology, neuroscientist Matthew Wilson and his colleagues implanted electrodes in rats' brains to record just what goes on in there while the critters are catching some shut-eye. Wilson observed the rodents' brain activity first as they ran through a maze and then when they were sleeping afterward. The activity in the sleeping rats' hippocampus--the area most responsible for forming autobiographical memories--matched patterns detected while they had been in the maze. At the same time, the visual cortex replayed corresponding sequences too, suggesting that the sleeping rats were not only remembering how they scurried through the maze but also what they had seen--all in the order that it had actually occurred. But mazes aren't the only thing rats dream about. Wilson's team has recorded many unidentified brain-activity patterns, which they hypothesize are memories of the rodents' "free time" spent sitting in their cages or hanging out with other rats. The relatively simple daily life of rats and other animals makes for what appear to be unimaginative dreams. "People's dreams tend to be more complicated, with bizarre content," Wilson says, "because our life experience is more complex than many animals'." Replaying the day's events, he says, might be a way for animals and humans to learn from the past in order to make better choices in the future. For example, dreaming about the maze might help a rat take a more direct route to the cheese on its next attempt. "That," Wilson says, "is the kind of learning you don't have time for when you're awake." --Corey BinnsGary Randall/Getty Images

If a pair of female identical twins mates with a pair of male identical twins, will their kids also be identical?

Sets of identical twins actually pair up more often than you might guess, forming what are known as "quaternary" marriages. Fortunately for the rest of us, the result is not an army of clones. In fact, the chance of the kids of two pairs of twins being identical is zero, says geneticist Rob Martienssen of Cold Spring Harbor Laboratory in New York. The only way to produce identical people is to have a single fertilized egg split into two identical embryos in the womb. But, because the children of a quaternary marriage are born of separate wombs, they can't undergo this twinning process. Instead, as with any child with non-identical parents, each embryo receives a random assortment of genes from mom and dad. And even though in a quaternary marriage the respective moms and dads are genetically identical, there is no chance that these gene selections-for characteristics such as eye color and height-would be the same for each child. Thus, the offspring would be no more likely to look alike than a pair of siblings produced by a non-twin couple. All this assumes, of course, that twins are identical in the first place. As people age, small chemical groups are added to 1 percent of their genome, a process called methylation. These groups don't rewrite your genetic code, but they can affect how genes make proteins. Although scientists have yet to observe the inheritance of methylation patterns in humans, studies have revealed that this can happen in mice. So by the time twins have their own children, their DNA blueprint is probably no longer identical anyway. In other words, even identical twins aren't really identical. -Christopher MimsSuperstock

Is the moon volcanically active?

Claims that the moon was anything other than a cold, dead rock used to be the domain of crackpots. As far as scientists can tell, the last volcanic eruptions on the surface of our steady companion occurred anywhere from one billion to three billion years ago, when the basaltic plains of the lunar seas were formed. Since then, the only changes to the surface were thought to have resulted from a constant bombardment of meteorites. Last November, however, geologist Peter Schultz of Brown University and his colleagues published a fresh examination of photos from the Apollo missions and data from recent satellite observations of the lunar surface. It revealed a hill on the moon that looked fresher than it should, with an age of no more than 10 million years. The researchers hypothesize that occasional bursts of gas from surface fissures blow as much as 30 feet of dust off the mile-wide formation, called Ina, hinting at ongoing internal processes not previously suspected. The eruptions, which could have occurred any time in the past 10 million years, could be the product of a still-cooling magma core or pockets of trapped gas rupturing from the moon's crust, but Schultz stops short of crediting volcanic activity for the burps. "These are not explosions of lava coming out, and since we haven't seen [the gas bursts], we don't know if they're hot or not," he says. "But my guess is that this is very likely cold gas that may have been hot deep in the interior." Schultz's team hasn't yet determined exactly what gases are spewing from the fissures--although NASA's Lunar Prospector satellite detected radon, polonium and carbon dioxide near the surface--but he doesn't expect the eruptions to hinder future lunar missions or bases. "In fact," Schultz says, "it might be a good place to go and explore." --Todd Neale

Can the food I eat affect my descendants' genes?

Maybe. A recent study suggests that the same vitamins in spinach that perform instant wonders for Popeye's biceps might pack longer-lasting effects, such as dictating the hair color and health of future generations. Last November, a study led by David Martin, an oncologist at the Children's Hospital Oakland Research Institute in California, tested whether a mouse's diet alone can affect its descendants. The researchers fed meals high in minerals and vitamins--such as B12, which fortifies leafy greens--to pregnant mice that have a gene that makes their fur blonde and also increases the likelihood that they will grow obese and develop diabetes and cancer. On the new diet, the mice produced brown-haired offspring that were also less vulnerable to disease. Even when those mice were denied the supplements, their offspring retained the improved health and still grew dark fur coats. Martin's study isn't the first to note this type of generation-spanning phenomenon. In 2002, Swedish researchers dug through century-old records and determined that a man's diet at the onset of puberty affected his grandson's vulnerability to diabetes. The study tracked 303 men, and those with an abundant supply of food were four times as likely to have grandchildren die of diabetes. Though far from exhaustive, the study indicates that genes are more susceptible to outside forces than has been commonly believed. But don't start choking down spinach or putting your teenager on a diet just yet--scientists caution that the influence of specific foods and diets on human gene expression are not fully understood. Nevertheless, Martin says, "the general implication for human health is an obvious one: An external agent can have an effect for a very long time. Given how long human generations last, the environmental exposures experienced by a pregnant mother can still have an effect 100 years later." --Abby SeiffNewmann/Zefa/Corbis