There is no universal rule for how a country determines the citizenship of a newborn. Some countries just follow the jus sanguinis (right of blood) law, which means a baby’s nationality is determined by that of one or both parents. Others observe that rule and jus soli (right of the soil), where a country grants citizenship to a baby that’s simply born on its soil, regardless of the parents’ origin. These countries are mostly in the Americas and include the United States and Canada. And with the expansion of air travel, these laws had to extend to the heavens as well.

If a baby is born over United States airspace, the jus soli rule means the child would be granted U.S. citizenship, according to the Department of State Foreign Affairs Manual. Depending on the circumstances, the child may also be a candidate for dual citizenship if its parents are from a country that grants citizenship based on blood—though that would depend on the countries involved.

This same simplicity doesn’t extend to a jus sanguinis country, though. This means that an American mother can’t attain French citizenship for her baby just because she gave birth over French airspace. The baby would simply revert to the parent’s U.S. citizenship, since the United States also generally follows jus sanguinis when a baby is born to U.S. citizens in a foreign country. Since jus sanguinis is the far more common rule around the globe, most babies born on a flight over international waters or foreign airspace will likely wind up taking the citizenship of its parents.

If there’s a case where the child could potentially be stateless—such as when a mother herself has no official citizenship and the baby is born in international airspace—the baby would likely take the citizenship of whatever country the plane itself is registered in, according to the United Nations’s Convention on the Reduction of Statelessness agreement.

Despite all these complex laws, mid-flight births are exceedingly rare—so rare, in fact, that most airlines don’t even keep track of the number of babies born in the air. An expecting mother likely wouldn’t even be able to get onto a flight in the first place, since many airlines have rules that prohibit women from flying after they’ve reached a certain point in their pregnancy.

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Adam Cheyer:

As a startup, when coming up with Siri’s name, we wanted something that was easy to remember, short to type, comfortable to pronounce, and a not-too-common human name. And we wanted to be able to get the domain name for not too much money.

Once Siri became the leading candidate, everyone on the team had their own favorite explanation of the meaning. Dag Kittlaus, our Norwegian-American CEO, once considered using Siri as the name of his child, and liked the Norse meaning: “beautiful woman who leads you to victory.”

For me, Siri, which means “secret” in Swahili, was a tip of the hat to our pre-named days when we began as stealth-company.com. I also liked the fact that it was the reverse of Iris, a software system I helped build as part of the CALO project, which Siri spun out of. Some liked the resemblance to SRI, which was the research institute that ran the CALO project.

We knew that Siri [meant] “beauty” in Sinhalese, but missed that SHIRI [meant] “butt” in Japanese (they’re not the same word, but the pronunciations are close).

And it was all a big surprise that Apple decided to keep the original Siri name for its launch as part of iOS. There were other candidates that were leading up until the final weeks.

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

Babies, of course, are not big on subtlety. Making silly faces, tickling their feet, or pretending you’ve disappeared in an endless loop of temporal displacement—otherwise known as peek-a-boo—are all ways to get tiny people to laugh. But why exactly are they laughing? Is it because they find their parents funny, or it is a reflex? Are they processing humor, or is it merely a way of socializing? Is baby laughter a way of saying, “Please continue paying attention to me”?

We asked several babies and got no answers. (In many cases, a loaded diaper ended questioning prematurely.) Fortunately, a number of researchers have explored the topic of what infants find funny in depth. “Almost all babies are laughing by the time they’re 4 months old,” Gina Mireault, a professor of psychology in the behavioral sciences department at Northern Vermont University, tells Mental Floss.

But, Mireault adds, in both adults and babies, “one of the biggest misunderstandings about humor is that it doesn’t have to have anything to do with something being funny.”

FROM SMILING TO LAUGHING

Early in their lives, babies are nonverbal—they burble and coo incoherent nonsense. Smiling, laughing, and crying are therefore crucial to interacting with the rest of the world. You probably won’t catch a baby laughing all by herself. “It’s a social response,” Mireault says. “The requisite ingredient is another person.”

Babies typically start smiling at 6 to 12 weeks old. At 3 to 4 months, babies will laugh at actions involving physical stimulation, like tickling, raspberries, or being bounced on their caregiver’s knee. (In a 2014 study conducted by developmental psychologist Caspar Addyman at the Goldsmiths InfantLab at the University of London, parents reported that tickling was the top way of getting their child to laugh.) At 5 to 6 months, they’ve learned enough about the world around them to comprehend the basic tenet of humor—a distortion of reality. Once they’ve grasped the appearance of normal human behavior, they’ll giggle at big eyes, blown-out cheeks, and high-pitched voices.

“It tends to involve behavior my colleagues have described as ‘clowning,’” Mireault says. “It could be a giant hat, a big bow tie, unusual voices, or walking in a funny way.” In observing these social rule violations, babies are amused because they have expectations about how people normally behave. You pretending to be a kangaroo is not what they anticipate.

“Surprise is one of the key elements of humor,” Mireault says. “There are two theories. One is called the Arousal-Safety hypothesis, and another is called the Benign Violation Theory. They’re the same thing. The idea is that humor that involves a surprise is perceived as non-threatening.”

If you hand your child a stuffed animal, they will expect the stuffed animal. If you suddenly toss it on the floor, this new development will probably cause them to laugh. The key is familiarity and a sense of playfulness. A smiling adult tossing it aside will be funny. A stranger angrily throwing it against a wall will not. Even Charles Darwin made note of this, writing in his 1872 work, The Expression of the Emotions in Man and Animals, that being tickled by a stranger would prompt a child to “scream in fear.”

There are exceptions. In London, children’s theater producers Sarah Argent and Kevin Lewis have staged several plays aimed at a baby demographic aged 6 months and older with assistance from Caspar Addyman and research from the InfantLab. Plays like Out of the Blue and Shake, Rattle, and Roll anticipated a baby’s natural wariness of strangers. Performer Maisie Whitehead “met” the babies at the start of Shake, Rattle, and Roll, singing to them to get them accustomed to her presence. During the show, Whitehead pretending to “wobble,” losing and regaining her balance, entranced the babies.

What stood out for Lewis was the idea that a baby’s laugh can be a method of control. “There is a sense that laughter is a tool of power,” Lewis tells Mental Floss. “’If I laugh, the big person does this thing or action again. I can keep making them do it again and again and again and again and keep having pleasure and I am in control!’” In laughing, babies are utilizing a form of manipulation.

WHY BABIES LOVE PEEK-A-BOO

Babies can also pick up on intention. If you pretend to drop something and say “ha, ha,” the baby will probably laugh. But if you say “uh-oh” and seem concerned, the baby will treat it like a serious event. Dropping objects with an exaggerated response was, in fact, a highlight of Argent’s productions, sending babies into giggle fits.

There’s an expiration date on such actions, since babies will quickly learn the unexpected action—tossing the stuffed animal—can now be expected. Or, as Mireault puts it: “Babies aren’t stupid. They won’t find it infinitely funny.”

The more babies learn about the world, the more caregivers are able to subvert their expectations. But one misunderstanding is what leads to the closest thing to a guaranteed laugh parents can perform without resorting to the cheap trick of tickling: peek-a-boo.

There are a couple of reasons why it works. One relates to a construct identified by Swiss psychologist Jean Piaget called object permanence, or the idea something that’s out of sight still exists.

To a baby, the existence of a physical object depends on whether it’s visible. “If you hide something from a 6-month-old baby, like car keys, by covering them up, the baby won’t look for them,” Mireault says. The idea the keys have been obscured is not a concept they can grasp.

The same holds true for faces. If a parent covers their face with their hands, its sudden reappearance is a delightful surprise. Adds Mireault, “When you pop up again, it’s like, ‘Holy smokes, where did you come from?’”

Peek-a-boo is also a baby pleaser because it involves that distortion of reality—big eyes and silly faces. By 8 or 9 months, however, babies have caught on to object permanence. Now, when a parent leaves the room, the baby might get upset. They know the adult is in another room, as opposed to just having briefly blipped out of existence.

That doesn’t mean peek-a-boo will no longer be effective. They can be amused by the fulfillment of the expectation—that their parent resurfaces—or by hiding themselves. Alternately, a baby may laugh, but as they get older, it may become less sincere. “Babies can fake laugh at 6 months,” Mireault says. “They can laugh to get attention. They start to babble and get vocal control and use voluntary laughter. Like when someone says, ‘Ha, ha, ha,’ and it doesn’t sound super genuine. It’s just a nice social gesture.”

It is disturbing to think that an adult considered a comic genius by a baby at 4 months may be a Vegas hack by 6 months, deserving only sympathy chuckles. By laughing, Mireault says, “The infant is saying, ‘Look, this is not that funny anymore, but I don’t want to stop playing, so come up with something else.’”

BABIES’ SENSE OF HUMOR

As babies age into toddlerhood, other kinds of humor begin to make sense. At 7 to 9 months, they find humor in contradictions. Put a hat on a dog and watch them crack up. At 12 months, they may see a cup and call it a spoon or laugh at an adult who does the same thing.

But the real landmark in a baby’s sense of humor may come when they make an attempt to make others laugh. At 5 months, enough motor control has been established so that babies can begin to hold up their own smelly feet rather than wait for a parent to do it. At 8 months, they’ll tease others. “It shows they understand other people can be tricked,” Mireault says. “They’ll offer something like car keys and when you reach for them, they’ll pull them away.”

This is more than just humor. It shows a theory of mind, or the idea that other people have different thoughts, beliefs, and expectations. Funny faces may seem simple, but humor is a cognitive puzzle that helps babies grow up—and eventually keep the car keys.

Our home planet may be the most precious place we know, but it isn’t priceless. The Earth’s resources and the value it offers to humans add up to some unknown, tangible cost. The species may never have to worry about buying or selling the world, but thinking of it in terms of concrete numbers can help us better understand its value. Now, as Treehugger reports, one scientist has developed a special formula that allows us to do just that.

According to the calculations of Greg Laughlin, an assistant astronomy and astrophysics professor from the University of California, Santa Cruz, the Earth is worth roughly $5 quadrillion (or $5,000,000,000,000,000). He came up with that price after gauging the planet’s mass, temperature, age, and other factors that directly correlate to its ability to sustain life.

To emphasize just how valuable the Earth is, Laughlin also estimated the worth of other planets in our solar system. Our nearest neighbor Mars costs about the same as a used car at $16,000. That’s a fortune compared to Venus, which he appraised at the meager value of one cent.

Laughlin doesn’t expect these numbers to have applications in the real world. Rather, he hopes they will inspire people to better appreciate the only home they know. He’s not the first person to put a massive, hypothetical price tag on something just for fun. The cost of the Death Star from Star Wars has been calculated at $852 quadrillion—many times Laughlin’s estimate for Earth.

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But white jackets weren’t always the norm. If you’ve seen a few period dramas set in the 19th century or earlier, you might recall the family physician showing up in a smart black suit. According to Medelita, black made the most sense for figurative and literal reasons alike. Black apparel was considered formal and sober, so it matched the general tone of medical visits. It was also much easier to conceal splotches and stains on a dark garment than a light one.

By the late 19th century, however, doctors and scientists had begun to realize the importance of keeping facilities as clean as possible to prevent bacteria from growing and infectious diseases from spreading. The color white connoted cleanliness, and hospitals started transitioning to white sheets and white garb to reflect their crusade against germs.

As Dr. Mark S. Hochberg explained in a 2007 article for the American Medical Association Journal of Ethics [PDF], the color white stood for something else, too: truth and transparency. The word candor, meaning “frankness” and “freedom from mental bias,” derives from the Latin verb candere, which translates as “to be white and shining.”

Doctors’s sartorial shift from black to white took place pretty quickly, as evidenced by two paintings by American artist Thomas Eakins. In his 1875 work The Gross Clinic, Dr. Samuel Gross and his fellow physicians, all clad in black suits, perform surgery on a man’s leg. Less than 15 years later, Eakins painted The Agnew Clinic, which depicts a different group of doctors—this time, in white shirts and smocks—operating on another patient.

Though white coats help doctors stand out in crowded hospitals, they’ve also been known to negatively affect patients. “White coat syndrome” or “white coat hypertension” describes the rise in blood pressure that some people experience when they step foot inside a doctor’s office or other clinical atmosphere. Some doctors, especially pediatricians, skip the coat at times to help put their patients at ease.

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According to the American Kennel Club, dogs sometimes yawn as a way to calm down. Next time you see your dog yawning excessively, assess the situation they’re in. Maybe your dog is frustrated trying to learn a new trick, or anxious about a visitor in your home. They can also become overstimulated by things they enjoy, such as playtime or the prospect of a walk. A good yawn, canine behaviorists say, may help dogs regulate their mood.

Yawns can be a form of communication in times of stress as well. If your dog is struggling with a game or training session, a yawn may be their way of telling you they need a break. In some scenarios, dogs may yawn as a way to diffuse conflict. If your pet yawns in the presence of a new dog or person, they may be signaling that they’re not a threat.

Of course, not every canine yawn is connected to uncomfortable interactions or feelings. Dogs that yawn around bedtime or when waking up from a nap probably are just sleepy. An isolated yawn during the day is also nothing to worry about. But if you see your dog yawning multiple times in a short period, pay attention: They may be trying to tell you something. Here are more common dog behaviors and the meanings behind them.

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In addition to being a handy heads-up, kneeling to propose presumably has roots in some age-old historical practice—or a combination of several. As MarthaStewart.com points out, people have been genuflecting (derived from Latin for “bending the knee”) to show respect or reverence for thousands of years. It may have originated in the Persian Empire, when proper salutations depended on societal rank. “In the case where one is a little inferior to the other, the kiss is given on the cheek,” Greek historian Herodotus observed in Persia around 430 BCE. “Where the difference of rank is great, the inferior prostrates himself upon the ground.”

This greeting system, known as proskynesis, was adopted by Alexander the Great when he took over the empire a century later, and some historians believe that genuflection was part of it. Many of Alexander’s existing Greek and Macedonian subjects disapproved of the new ritual, thinking such gestures should be reserved for gods, so not everybody acquiesced.

But the idea of genuflection as a sign of deference would prove popular in both religious and secular spheres in the future. Catholics, for example, drop to one knee when facing a tabernacle that contains the Eucharist (wafers blessed to be the body of Jesus). And European warriors knighted after battle often knelt in front of their commander, who dubbed them with a sword. In fact, citizens knighted by Queen Elizabeth II are still usually expected to kneel when dubbed.

According to Bustle, it’s possible that bending the knee first took on a romantic significance during knights’ heyday. In the 11th century, knights started to form close bonds with ladies of the court—a custom later christened “courtly love.” Since the woman was often already married, the nature of the relationship wasn’t often sexual, but it was always a serious commitment. Knights pledged themselves to serve and honor their lovers with the same fervor applied to their lords and kings. Guinevere’s romance with Sir Lancelot is a good example of courtly love, as is the tale of Tristan and Isolde (though both of those cases did involve adultery). There’s no explicit link between that medieval trend and today’s proposal tradition, but a lot of the artwork depicting courtly love features the man kneeling before the woman—a scene that mirrors many modern-day engagement photos (sans all the armor).

In short, bending the knee has long conveyed devotion and humility, which you might want to embody when asking someone to spend eternity with you. But popping the question on two feet doesn’t violate any written-in-stone code of conduct for proposals.

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You were wide awake mere minutes ago, and the protagonist just uncovered a promising new lead in the case. So, what gives?

As the BBC’s Science Focus explains, the coziness of your covers could be working against you. People usually try to read in a quiet, comfortable atmosphere, and those conditions happen to be ideal for sleep. Reading also eases your mind and draws its focus away from whatever preoccupations might otherwise keep you awake.

“For many [people], reading can be relaxing and enjoyable, which can put your mind and body in the appropriate mindset or mood to go to sleep,” Dr. Raman Malhotra, a neurologist and member of the American Academy of Sleep Medicine’s board of directors, told Refinery29. “The main reason reading may help some fall asleep is that it allows your mind some time to rest and relax before turning out the lights to fall asleep.”

The concentration required to process every word can be pretty exhausting, too, especially if your chosen tome is dense. And reading line after line of anything can make you feel like giving your eyes a break.

These factors all make reading a great activity to add to your pre-sleep routine if you’re looking for ways to fall asleep faster. But if your body’s snoozing impulse is continually keeping you from enjoying a good book, there are some tricks to thwart it. Book Riot suggests reading in the morning, or trying an audiobook instead. Reading in a spot that isn’t your bed—preferably one where you’re sitting up, rather than lying down—can help, too. Reading in a public place like a coffee shop or park can also discourage dozing.

[h/t Refinery29] Can You Catch Up On Sleep?

We recommend you read our article on How To Study For Long Hours At Night Without Sleeping Off

The internet’s infatuation with Gökçe’s stylish seasoning technique suggests that there’s something inherently satisfying about watching salt and other spices rain down on food from a distance. It does add a certain elegance to the process, and it also gives you an extra moment to appreciate the art of cooking. But chefs don’t only season food from on high when there’s an audience to impress—so it seems like the method must serve another purpose.

As The Kitchn explains, they do it because the height makes it easier to sprinkle herbs and spices more evenly over a dish. If you’re cooking something that requires lots of stirring, you can reallocate a clump of ground cumin without too much trouble. But if whatever’s in your pan is supposed to be mostly stationary, like meat or fragile vegetables, you want seasonings to land as evenly as possible from the get-go.

While the hack makes sense in theory, you may be wondering how well it actually works in real-life kitchens. Researchers at Cook’s Illustrated conducted an experiment where they sprinkled ground black pepper on chicken breasts from three heights: 4 inches, 8 inches, and 12 inches. The 12-inch one was the most evenly seasoned by far. And a foot is probably all the distance you need—if you go much higher than that, there’s a good chance some seasoning will end up landing outside your plate or pan.

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The lack of windows is a component of retail shopping psychology, where retailers try to create an environment where people feel comfortable to spend both time and money. It’s why many stores have tile floors, which cause carts to make a lot of noise—forcing shoppers to instinctively slow down and browse more, or why stores may play up-tempo music when a store is busy to speed shoppers up.

In the case of windows, stores are after a sense of suspended time, where shoppers won’t notice inclement weather or encroaching darkness. The longer they shop, the more they spend.

There are practical considerations, too. Large windows letting in sunlight might cause fading on packages, making them seem worn to consumers. Swapping out valuable wall space for windows would also reduce the number of displays—and products—available to shoppers.

It’s possible this retail theory could eventually go out of fashion. Discount supermarket chain Aldi has experimented with stores in Germany that let in more natural light, though UV coatings are needed to prevent sunlight from affecting fresh food quality or product label fading.

Whether that will become more common in the grocery industry at large remains to be seen. If you’re feeling stifled by the lack of light, there’s always a farmer’s market.

[h/t Business Insider]