Everyone complains about the weather, the old line goes, but nobody ever does anything about it. But it’s not exactly true, is it? People have always done something about the weather—mostly by trying to predict it, then arranging our lives around the forecast.

It makes sense, then, that we’ve picked up a few ideas about outside conditions that don’t quite hold up. From cold weather making you sick to red skies in the morning, here are some common beliefs about the weather that aren’t entirely true. 

Cold weather doesn’t cause colds

You’ve heard someone say it, or maybe you’ve said it yourself: “Put on a jacket—you’ll catch a cold.” The problem is that cold weather doesn’t cause colds—at least, not directly. 

Manal Mohammed, a Senior Lecturer in Medical Microbiology at the University of Westminster, wrote about this for The Conversation. “Cold temperatures do not cause infections by themselves,” she concludes. “Instead, they shape the biological, environmental and social conditions that allow respiratory viruses to thrive.”

For example: People spend more time inside during cold weather, which can help viruses spread. These indoor spaces tend to be heated, meaning the humidity is low, meaning nasal passages are dry. This makes it more likely that you’ll catch a virus. And, according to Johns Hopkins Medicine, the fact that school is in session during the winter is also a factor. 

There are physiological factors as well, according to Mohammed. “Breathing in cold air lowers the temperature inside the nose and airways, which can trigger vasoconstriction,” she writes. She adds that this can weaken the local immune defenses in the lining of your nose and airways. But that’s not the same as a direct causal link. 

So, while it’s true that you’re more likely to catch a cold or the flu during the winter, that isn’t directly caused by your failure to wear a jacket. It’s the viruses, not the temperature, that make you sick. 

Lightning can strike the same place twice

“Lightning hitting the same place twice” is a cultural shorthand for something unlikely happening. But is it accurate? Kind of. It’s true that, all things being equal, it’s unlikely for lightning to strike the same place twice. But all things aren’t equal. 

Lightning tends to hit the highest nearby object, which is why it’s a bad idea to go under a tree during a lightning storm. In big cities this means the largest buildings are hit frequently. New York City’s Empire State Building is hit, on average, 25 times per year, according to New York City Emergency Management. The CN Tower, north of the border in Toronto, is hit three times as often—75 times per year according to the tower’s website. This isn’t to say these buildings are unsafe—both have lightning rods, which give the current a safe path to the ground. It’s just that they’re hit multiple times a year. 

So lightning not only can hit the same place twice, but does so pretty often. Although, according to NOAA, it doesn’t always hit the highest point—so there’s truth to the idea that lightning is hard to predict. 

Red skies really can predict the weather

You’ve heard it: “Red sky at night, sailor’s delight; red sky in the morning, sailors take warning.” The idea that the color of the sky can predict the weather is really old—it’s referred to in the Bible (Matthew 16:2-3, if you want to look it up). But is there any science behind this? 

Yes, it turns out, but it doesn’t work everywhere. To understand why, we need to explain a few things. First: What causes red skies? “A red sky appears when dust and small particles are trapped in the atmosphere by high pressure,” according to the UK Met Office. “This scatters blue light leaving only red light to give the sky its notable appearance.” 

A red sky means there’s high pressure between you and the direction of the sun. The sun sets in the west and rises in the east. So, a red sky at night generally means there’s high pressure to your west; a red sky in the morning means there’s high pressure to the east of you. 

But why does that predict the weather? Because, in the mid-latitudes, the wind generally blows from the west—this is called the prevailing westerlies. High pressure means stable, dry weather. A red sky at night means the high pressure is to your west, which the westerlies will bring to you; a red sky in the morning means the high pressure is to your east, and the wind will blow it away from you. 

But, again, that only works in the mid-latitudes, where the prevailing westerlies are the norm. This region is between 30 and 60 degrees in both the southern and northern hemispheres, a region that includes most of Europe, the continental United States, southern Australia, and Japan, among other places. So, if you’re in one of those places, a red sky in the morning actually does point to a change in the weather. If you’re in the tropics, though, the weather tends to build up locally rather than arriving from somewhere upwind, meaning the colors at sunrise and sunset aren’t as useful for predicting it. 

So this isn’t entirely a myth—there’s truth to the saying. It just doesn’t work everywhere on Earth. 

The post 3 myths about the weather appeared first on Popular Science.

Between 20 and 30 percent of Americans bite their nails, according to The Cleveland Clinic. Why? Among other reasons, nail biting “often has a self-soothing quality—in fact, it provides a sense of calm—so people may use it as a coping mechanism.” It’s also common to bite nails while bored or stressed. 

Whatever the reason, you may be wondering if biting your nails is scientifically gross, so let’s explore its health impacts. (Short answer: 1000xYes, it’s gross.)

Turns out your hands are dirty

You know how you’re supposed to wash your hands before eating? There’s a reason for that: hands are filthy, mostly because they’re always touching everything. Biting your fingernails is worse than eating without washing your hands—you’re sticking your fingers directly into your mouth. 

And fingernails themselves are uniquely gross. A widely cited 1988 study in the Journal of Clinical Microbiology by researchers from the University of Pennsylvania and Johns Hopkins University found that under the fingernails is the region of the hand with the most bacteria, by a long shot. “The subungual spaces had an average log10 CFU of 5.39, compared with a range from 2.55 to 3.53 for other hand sites.” Those numbers might not sound that different, but we’re talking about a logarithmic scale of 10, where 5.39 is 10 to the power of 5.39, which works out to around 245,000. And 2.55 works out to about 355, which is far smaller. So, mathematically, it’s pretty nasty under your fingernails.

Research also suggests that biting your nails means more bacteria in your mouth. A widely cited 2007 study published in Oral Microbiology and Immunology by researchers at Atatürk University in Turkey tested the saliva of 25 nail biters and 34 non-nail biters. 76 percent of nail biters tested had some kind of Enterobacteriaceae in their sample, compared to just 26.5 percent of non-biters. A 2017 study published in the Annals of International Medical and Dental Research by researchers tested 200 saliva samples—half from chronic nail biters and half from non-nail biters. The results were similar: 58 percent of chronic nail biters tested positive for Enterobacteriaceae, compared to just 16 percent of non-nail biters.

Basically, there’s a lot of bacteria, dirt, and fungus under your nails, and biting your nails means putting those things directly into your mouth. Decide for yourself whether that’s gross. 

You’re damaging your fingers and teeth

But this isn’t just about bacteria getting in your mouth—the habit is gross in other ways. A 2022 paper published in the International Journal of Environmental Research and Public Health outlines a number of negative impacts of nail biting. 

First, there’s the damage to your fingers: “Patients typically present with abnormally short and uneven nails, absent or ragged cuticles, and nail folds in different stages of healing,” the paper states. “Other visible changes in the nail and periungual regions include linear and pinpoint hemorrhages, longitudinal melanonychia, transverse grooves, brittleness, macrolunula, and pterygium, a scar in the nail matrix.” Basically, biting your nails causes a lot of visible problems, and it’s probably not just your doctor who notices them.

The damage isn’t limited to your hand. The paper mentions damage to your teeth, worn down by chewing, and to your gum tissue. 

I could keep going. UCLA Health summarizes these problems quite well, while also mentioning the delightful potential for fungal and skin infections. 

You can stop, with the right tools

If all of this has you questioning your fingernail biting habit, you’re not alone—I grossed myself out while writing this. But quitting fingernail biting isn’t easy. People bite their nails for a variety of reasons, many of them psychological. For this reason, the Cleveland Clinic recommends behavioral therapy as one way to stop biting your fingernails. Self-care and finding other ways to relax are another option. 

The American Academy of Dermatology recommends regularly trimming your nails to reduce temptation—you’re less likely to bite if your nails are already short. They also recommend applying nail polish, the idea being you’ll be less likely to bite your fingers if you put work into making them look nice. There’s also bitter nail polish specifically designed to help break the habit of nail biting. At the very least, clean underneath your nails regularly.

The post How gross is biting your fingernails? appeared first on Popular Science.

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