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How Do You Calculate the Wind Chill?

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What does it really mean when my weatherman says that it feels like minus-20 in Chicago? Is there a wind chill thermometer somewhere, or is he just using a mathematical formula? Let's answer these and some of the other pressing questions about the ubiquitous winter statistic.

Why does wind make us feel cold?

When the wind blows across the exposed surface of our skin, it draws heat away from our bodies. When the wind picks up speed, it draws more heat away, so if your skin is exposed to the wind, your body will cool more quickly than it would have on a still day.

Who came up with the idea of calculating wind chills?

American explorer and geographer Paul Siple and his fellow explorer Charles Passel made the first breakthroughs in wind chill research while on an expedition in the Antarctic in 1940. Siple and Passel suspended bottles of water outside a hut at their base station and measured how long it took the water to freeze under various wind conditions. After taking hundreds of these readings, the pair had a good idea of how rapidly heat was lost at different wind speeds.

What exactly is a wind chill temperature?

storm-fieldWhen Siple and Passel did their research, they weren't really trying to develop a temperature equivalent that alarmist weathermen could trot out. In fact, their original measure expressed the heat loss in a more esoteric unit: watts per square meter.

The idea of expressing wind chills in terms of an equivalent temperature—the "feels like" language we hear on the news—didn't start until the 1970s. Before the switch, weathermen would report the wind chill in three- or four-digit numbers which were a bit difficult for viewers to wrap their heads around. American weathermen started translating wind chills into temperature equivalents in order to give viewers a more familiar term.

If the air temperature is 40 degrees but the wind chill is 28 degrees, will water freeze?

Nope. Although high winds can make those of us with a pulse feel more miserable than normal, they don't have the same effect on inanimate objects. Lower wind chills mean that inanimate objects cool to the air temperature more quickly, but even high winds can't force the object's temperature below the air temperature. That means that in the above example even though your skin might think it's 28 degrees, your water pipes will still be a balmy 40 degrees.

So is there an actual formula for wind chill?

You bet. Just in case you ever find yourself with a calculator, thermometer, and anemometer but without access to The Weather Channel, the Fahrenheit version of the equation looks like this:

Wind Chill = 35.74 + 0.6215T – 35.75(V^0.16) + 0.4275T(V^0.16)

T is the air temperature in degrees Fahrenheit, and V is the wind speed in miles per hour.

Wait, shouldn't how cold the wind makes you feel depend on all sorts of variables like your body type, and whether you're walking into the wind?

Those things certainly affect how quickly the wind cools a person's skin. The above formula makes some simplifying assumptions to get its numbers. Basically, the wind chill factor you hear reported assumes that your exposed face is roughly five feet off the ground, it's night, and you're walking directly into the wind in an open field at a clip of about 3 mph.

Are those conditions really all that realistic?

If you're in a profession that involves a lot of night-field-walking, sure. Otherwise, maybe not. Critics of wind chill reports note that lots of factors can mitigate the reported wind chill. Your weatherman may tell you that it feels like 50 below outside, but if you're dressed warmly, standing in the sun, or in an area with cover like buildings and trees that block the wind, you will feel significantly warmer.

So if the formula is arguably somewhat dubious, can we just disregard wind chill reports as frivolous statistics?

Not so fast. While the methodology concerning wind chill calculations is still being debated in some quarters, that doesn't mean that the measurements are altogether useless. Remember, the basic concept behind wind chill is that stronger winds will cause exposed skin to cool more quickly. The faster skin cools, the faster frostbite can set it. As wind chills drop south of -50 or so, the onset of frostbite can take as little as five minutes, so it's worth keeping an eye on the wind chill even if the notion of your skin "feeling like" a certain temperature may be a bit misleading.

Has the formula always been the same?

treadmill-coldThe above formula is actually a fairly new development that the National Weather Service introduced in late 2001. During the year 2000, the National Weather Service and its Canadian counterpart had independently started looking for ways to improve the wind chill formula, partially because they had a sneaking suspicion the old formula overstated just how cold it was. This overstatement may sound innocuous, but the weather services worried that it would lull citizens into a false sense of security if it led people to believe they could withstand colder temperatures than they realistically could.

Since the collaborating weather services knew that the old wind chill formula was broken—"feels like -50" actually felt much warmer than standing around on a windless 50-below day—they recruited a group of volunteers to walk on treadmills in a refrigerated wind tunnel. Using sensors on the subjects' skin, scientists calculated a more accurate formula. You can read one of the test subjects' thoughts on the experiments here.

What's the lowest wind chill ever recorded?

With all of the tweaks in the formula over the years, it's tough to say definitively, but how's this for chilly: on July 4, 2003, a remote weather station in east Antarctica picked up a minus-94 degree day. That would be plenty frigid on its own, but the wind was also blowing at 75 miles per hour, which would be good for a wind chill of about minus-150.

This post originally appeared in 2010.

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Big Questions
Why Do Cats 'Blep'?
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As pet owners are well aware, cats are inscrutable creatures. They hiss at bare walls. They invite petting and then answer with scratching ingratitude. Their eyes are wandering globes of murky motivations.

Sometimes, you may catch your cat staring off into the abyss with his or her tongue lolling out of their mouth. This cartoonish expression, which is atypical of a cat’s normally regal air, has been identified as a “blep” by internet cat photo connoisseurs. An example:

Cunning as they are, cats probably don’t have the self-awareness to realize how charming this is. So why do cats really blep?

In a piece for Inverse, cat consultant Amy Shojai expressed the belief that a blep could be associated with the Flehmen response, which describes the act of a cat “smelling” their environment with their tongue. As a cat pants with his or her mouth open, pheromones are collected and passed along to the vomeronasal organ on the roof of their mouth. This typically happens when cats want to learn more about other cats or intriguing scents, like your dirty socks.

While the Flehmen response might precede a blep, it is not precisely a blep. That involves the cat’s mouth being closed while the tongue hangs out listlessly.

Ingrid Johnson, a certified cat behavior consultant through the International Association of Animal Behavior Consultants and the owner of Fundamentally Feline, tells Mental Floss that cat bleps may have several other plausible explanations. “It’s likely they don’t feel it or even realize they’re doing it,” she says. “One reason for that might be that they’re on medication that causes relaxation. Something for anxiety or stress or a muscle relaxer would do it.”

A photo of a cat sticking its tongue out
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If the cat isn’t sedated and unfurling their tongue because they’re high, then it’s possible that an anatomic cause is behind a blep: Johnson says she’s seen several cats display their tongues after having teeth extracted for health reasons. “Canine teeth help keep the tongue in place, so this would be a more common behavior for cats missing teeth, particularly on the bottom.”

A blep might even be breed-specific. Persians, which have been bred to have flat faces, might dangle their tongues because they lack the real estate to store it. “I see it a lot with Persians because there’s just no room to tuck it back in,” Johnson says. A cat may also simply have a Gene Simmons-sized tongue that gets caught on their incisors during a grooming session, leading to repeated bleps.

Whatever the origin, bleps are generally no cause for concern unless they’re doing it on a regular basis. That could be sign of an oral problem with their gums or teeth, prompting an evaluation by a veterinarian. Otherwise, a blep can either be admired—or retracted with a gentle prod of the tongue (provided your cat puts up with that kind of nonsense). “They might put up with touching their tongue, or they may bite or swipe at you,” Johnson says. “It depends on the temperament of the cat.” Considering the possible wrath involved, it may be best to let them blep in peace.

Have you got a Big Question you'd like us to answer? If so, let us know by emailing us at bigquestions@mentalfloss.com.

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Big Questions
What Is Foreign Accent Syndrome?
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One night in 2016, Michelle Myers—an Arizona mom with a history of migraines—went to sleep with a splitting headache. When she awoke, her speech was marked with what sounded like an British accent, despite having never left the U.S. Myers is one of about 100 people worldwide who have been diagnosed with Foreign Accent Syndrome (FAS), a condition in which people spontaneously speak with a non-native accent.

In most cases, FAS occurs following a head injury or stroke that damages parts of the brain associated with speech. A number of recent incidences of FAS have been well documented: A Tasmanian woman named Leanne Rowe began speaking with a French-sounding accent after recovering from a serious car accident, while Kath Lockett, a British woman, underwent treatment for a brain tumor and ended up speaking with an accent that sounds somewhere between French and Italian.

The first case of the then-unnamed syndrome was reported in 1907 when a Paris-born-and-raised man who suffered a brain hemorrhage woke up speaking with an Alsatian accent. During World War II, neurologist Georg Herman Monrad-Krohn compiled the first comprehensive case study of the syndrome in a Norwegian woman named Astrid L., who had been hit on the head with shrapnel and subsequently spoke with a pronounced German-sounding accent. Monrad-Krohn called her speech disorder dysprosody: her choice of words and sentence construction, and even her singing ability, were all normal, but her intonation, pronunciation, and stress on syllables (known as prosody) had changed.

In a 1982 paper, neurolinguist Harry Whitaker coined the term "foreign accent syndrome" for acquired accent deviation after a brain injury. Based on Monrad-Kohn's and other case studies, Whitaker suggested four criteria for diagnosing FAS [PDF]:

"The accent is considered by the patient, by acquaintances, and by the investigator to sound foreign.
It is unlike the patient’s native dialect before the cerebral insult.
It is clearly related to central nervous system damage (as opposed to a hysteric reaction, if such exist).
There is no evidence in the patient’s background of being a speaker of a foreign language (i.e., this is not like cases of polyglot aphasia)."

Not every person with FAS meets all four criteria. In the last decade, researchers have also found patients with psychogenic FAS, which likely stems from psychological conditions such as schizophrenia rather than a physical brain injury. This form comprises fewer than 10 percent of known FAS cases and is usually temporary, whereas neurogenic FAS is typically permanent.

WHAT’S REALLY HAPPENING?

While scientists are not sure why certain brain injuries or psychiatric problems give rise to FAS, they believe that people with FAS are not actually speaking in a foreign accent. Instead, their neurological damage impairs their ability to make subtle muscle movements in the jaw, tongue, lips, and larynx, which results in pronunciation that mimics the sound of a recognizable accent.

"Vowels are particularly susceptible: Which vowel you say depends on where your tongue is in your mouth," Lyndsey Nickels, a professor of cognitive science at Australia's Macquarie University, wrote in The Conversation. "There may be too much or too little muscle tension and therefore they may 'undershoot' or 'overshoot' their target. This leads to the vowels sounding different, and sometimes they may sound like a different accent."

In Foreign Accent Syndromes: The Stories People Have to Tell, authors Nick Miller and Jack Ryalls suggest that FAS could be one stage in a multi-phase recovery from a more severe speech disorder, such as aphasia—an inability to speak or understand speech that results from brain damage.

People with FAS also show wide variability in their ability to pronounce sounds, choose words, or stress the right syllables. The accent can be strong or mild. Different listeners may hear different accents from the speaker with FAS (Lockett has said people have asked her if she's Polish, Russian, or French).

According to Miller and Ryalls, few studies have been published about speech therapy for treating FAS, and there's no real evidence that speech therapy makes a difference for people with the syndrome. More research is needed to determine if advanced techniques like electromagnetic articulography—visual feedback showing tiny movements of the tongue—could help those with FAS regain their original speaking manner.

Today, one of the pressing questions for neurologists is understanding how the brain recovers after injury. For that purpose, Miller and Ryalls write that "FAS offers a fascinating and potentially fruitful forum for gaining greater insights into understanding the human brain and the speech processes that define our species."

Have you got a Big Question you'd like us to answer? If so, let us know by emailing us at bigquestions@mentalfloss.com.

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