NATURE

Is Fog Really Just a Cloud?

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By September 16, 2026 Updated: September 16, 2026

Much like alligators and crocodiles or yams and sweet potatoes, it can be hard to discern fog from clouds by appearance alone. Sure, fog hovers close to the ground while clouds soar overhead, but the two look strikingly similar. This raises the question: Is fog just what we call a cloud that’s at a lower elevation, or are they two distinct phenomena?

You might reply that you haven’t the foggiest idea. But unlike the weather in question, the answer is rather clear.

How Do Clouds and Fog Form?

Foggy valley — Credit: Artem Sapegin/Unsplash.com

Clouds and fog form the same way, and it’s connected to something you may find on your weather app: the dew point. You can’t always see it, but the atmosphere holds a lot of invisible moisture — a gas form of water known as vapor. It can only hold so much, though, depending on air pressure and temperature.

When either or both of those change, the air can no longer contain the vapor, and the vapor turns to either liquid or ice crystals. The temperature at which this critical mass is reached is called the dew point.

Also in the atmosphere are countless tiny particles floating in the sky — such as dust, salt, smog, and other biological specks. When vapor turns to liquid — a process called condensation — the droplets form around these particles.

It’s no different from what occurs around a can of soda: The cold metal disrupts the air’s ability to hold its moisture and the vapor condenses into droplets that form on the surface of the can. (When the can is warm, no condensation occurs, since it’s not messing with the air around it.)

As individual droplets or crystals condense around particles in the sky, they clump together. This results in dense visual moisture that takes the form of fog or clouds, which may be thin or as thick as pea soup.

You Must Be This High To Become a Cloud

Diagram illustrating cloud formation — Credit: Encyclopædia Britannica, Inc.

This phenomenon can happen at ground level (fog) or high in the sky (clouds). In fact, the only difference between fog and a cloud is the altitude at which it forms. The National Weather Service defines visible moisture as fog if it starts lower than 50 feet above the ground, while anything at a higher elevation is considered a cloud.

Think of it as the meteorological equivalent of having to be 4 feet tall or above to ride a roller coaster at an amusement park. Anything that doesn’t make the altitude cutoff doesn’t get to be a cloud and is relegated to fog status instead.

Generally, for fog to form the weather needs to be notably humid with lots of water vapor in the air. And just as there are different kinds of clouds, several types of fog can form, depending on weather conditions. Radiation fog, which is not as hazardous as it sounds, occurs when heat radiates off the ground. Radiation fog is common and usually happens overnight, since that’s when the ground is giving off the heat it absorbed during the day.

There’s also valley fog, which forms when cold air settles into a valley while warm air remains overhead. Coastal fog is another type when moist air comes off the water and passes over cooler terrain. As for clouds, they can form as high as 12 miles above sea level and consist of water vapor evaporated from oceans, rivers, lakes, and other water sources.

High Density Means Low Visibility

Clouds and fog can be made of billions of droplets — up to 300 per cubic centimeter. Most of that space is air, though, as one droplet is just 10 microns in diameter. A micron is one-millionth of a meter — in other words, you could line up 1,900 individual droplets across a single penny.

The more droplets per cubic centimeter, the more dense the cloud or fog. The more dense they are, the harder it is for light to pass through them, which is why they reduce visibility. When visibility is under 100 meters (around 328 feet), it’s considered dense fog, and you really want to slow down if you have to drive through it.

Mist, on the other hand, is far less dense than fog or clouds — it can reduce visibility, but only down to 1 kilometer (0.62 miles). For pilots, this can be rough, but it’s generally not a concern for drivers. Since it’s less dense, it also clears up faster than fog. Because of this, mist is considered distinct from fog and clouds.

So the next time you see someone acting dense or with their head in the clouds, consider the altitude. They may really have their head in the fog.

Short Answer

Fog and clouds are both created when water vapor condenses or freezes into tiny droplets or crystals that bind to floating particles such as dust. This forms visible moisture we know as either fog or clouds, and the only difference between the two is altitude. If it’s lower than 50 feet above the ground, it’s fog, while anything formed at a higher elevation is considered to be a cloud.

HEALTH

Why Does Toothpaste Make OJ Taste Awful?

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By September 16, 2026 Updated: September 16, 2026

Two important parts of your morning routine are breakfast and brushing your teeth, but they don’t always play nicely with one another. You roll out of bed, brush your teeth, and pour a glass of orange juice. One sip in, you’re awoken with a rude reminder: Toothpaste and orange juice is an unsavory combination.

Toothpaste makes the juice taste bitter, sour, and almost metallic, as if it expired months ago. The culinary arts are all about mixing and matching very different flavors, so why doesn’t mint jibe with OJ?

It turns out that mint isn’t the culprit at all, but rather another common toothpaste ingredient.

A Bittersweet Change

Powdered form of SLES and SLS — Credit: Monika Wisniewska/stock.adobe.com

The reason your morning OJ tastes strange after you brush your teeth? Sodium lauryl sulfate, or SLS. Found in products such as laundry detergent and bubble bath, SLS is commonly used in toothpaste. According to Texas dentist Ben Winters, known online as “The Bentist,” SLS serves multiple purposes when it comes to oral hygiene.

First, SLS is a surfactant, which helps toothpaste spread evenly across your teeth — it’d be a lot trickier brushing them if toothpaste had the consistency of peanut butter. While it does this, SLS loosens oily debris and food particles.

SLS is also a foaming agent (which is why it’s found in many soaps). “The biggest thing people know it for is creating that big foam associated with toothpaste,” Winters said in an interview with How Everything Works. He added, “If you have a natural toothpaste, you’re not going to have that foaming as much.”

That familiar mouthful of suds may make your teeth feel extra clean, but SLS can affect your sense of taste — which continues even after you rinse, spit, and return your toothpaste to the medicine cabinet.

Specifically, it messes with your taste buds, boosting sour and bitter flavors while suppressing the sweet. Taste is a delicate balance of sweet, sour, and bitter, along with salty and savory umami, which combine in certain proportions to provide the flavor you associate with specific foods.

By adjusting how you perceive bitter, sour, and sweet foods, SLS alters the overall taste — think about how off-putting a movie can be if the dialogue volume is turned down too low while the music and sound effects are blasting from the speakers.

Glass with orange juice and straw — Credit: Lala Azizli/Unsplash.com

Orange juice, which includes a fair amount of both acidic (sour) and bitter compounds, is a particularly bad match for SLS. “Normally, sugar balances those flavors,” Winters said. “But if all of a sudden you’re driving down the perceived sweetness, that acidic, bitter side becomes a lot more obvious to you. It’s kind of like removing the sugar out of anything. It’s going to taste weird!”

SLS isn’t necessarily the only reason orange juice might taste strange, either. Mint may pair well with chocolate, but if it’s strong you may not like it with orange juice, and your preferences between peppermint, spearmint, wintergreen, and others can throw off the taste buds too — so switching to SLS-free toothpaste doesn’t guarantee a delicious breakfast drink.

Person applying toothpaste to toothbrush — Credit: A. C./Unsplash.com

Orange juice is the most famous victim of SLS, but it’s far from alone. “Anything that relies on that sweet versus bitter or acidic balance is going to get thrown out of whack,” Winters warned. “Coffee can become super bitter. Chocolate or fruit sodas are going to taste a lot less sweet, so they can taste more bitter, sour, or sharp.”

Fortunately, you don’t have to choose between having clean teeth and indulging in a glass of orange juice. The effect is temporary. Saliva gradually dilutes and washes away SLS, so your taste perception eventually returns to normal — this can be within 30 minutes of brushing, though for some it may take a few hours!

Short Answer

Toothpaste often contains sodium lauryl sulfate (SLS), an ingredient that creates foam, breaks up debris, and helps spread the paste around your mouth. But SLS temporarily interferes with taste perception, dulling your ability to taste sweetness while making bitter and sour flavors more noticeable. Orange juice is especially affected because its natural acidity and bitterness are usually balanced out by sugar. Once that sweetness is muted, the juice’s sharp edge takes over. The effect usually fades within 30 minutes of brushing, as saliva dilutes and washes the SLS away, restoring your taste buds to normal.

SCIENCE

Why Doesn’t a Candle Create Smoke?

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By September 16, 2026 Updated: September 16, 2026

Candles add ambiance with their warm glow, conveying everything from calm and romance to focus and mystery. But they also put on a bit of a magic show. As a candle burns, it seems to pull off a disappearing act, getting smaller and smaller as its flame glows on.

So where does the wax go, and why doesn’t a candle produce any smoke until it’s blown out? If it’s true that where there’s smoke, there’s fire, why doesn’t the reverse apply for candles?

Like any good magic trick, this one depends on some clever transformations behind the scenes.

Burnin’ Up

Three lit candles — Credit: Sixteen Miles Out/Unsplash.com

Have you ever tried lighting the lip of a candle, where there’s no wick? The wax will melt with the heat of a flame, but it won’t catch fire and burn. That’s because wax needs a wick to complete its task. Wax is the fuel of a candle and is used because it burns slowly. However, the wick is what holds the flame.

When a candle’s wick is lit, the flame melts the wax immediately around it, and the wick then draws up the liquid wax. The process of drawing up the liquid wax through the wick is known as capillary action — it’s the same process that allows water (or spilled milk) to climb into a paper towel.

Candle waxes such as paraffin, soy wax, and beeswax are largely made of hydrocarbons — molecules containing hydrogen and carbon (the same elements that make up oil and gasoline). These waxes take a solid form at room temperature, but change their state after the candle is lit and melts them.

Once the liquid wax reaches the top of the wick, the heat of the flame vaporizes it, turning it into a gas. In the flame, the molecules of hydrogen and carbon break apart and react with oxygen in the surrounding air.

That’s where the magic happens. That reaction — known as combustion — converts the wax’s hydrogen and carbon into carbon dioxide and water vapor. You probably remember from chemistry class that hydrogen and oxygen combine to make water, while carbon and oxygen make CO2. That’s precisely what happens during combustion, and this reaction releases energy as heat and light.

Both carbon dioxide and water vapor are invisible, so a steadily burning candle can gradually shrink without producing smoke. Most of the candle hasn’t dripped away or disappeared into another dimension: It has floated into the room as transparent gases.

Smoking candles — Credit: Tony Chen/Unsplash.com

It’s not a total vanishing act, however. Some of the candle’s carbon does form tiny soot particles as it burns. Near the flame’s outer edge, where oxygen is more plentiful, most of the soot burns up before it can escape. A calm candle flame is therefore a remarkably efficient little combustion machine — it creates soot, uses that soot to make light, and then consumes almost all of it.

Smoke becomes visible when something interrupts this process. A draft can push soot particles out of the flame before they have time to burn, while an overly long wick may deliver more fuel than the available oxygen can fully consume. (That’s why occasionally trimming your wicks is recommended.) Drafts and long wicks can cause the candle to flicker, flare, or release wisps of black smoke.

A candle may also smoke briefly when it’s first lit, before the flow of wax and oxygen has a chance to stabilize. And when the flame is blown out, vaporized wax continues rising from the hot wick but no longer has a flame to consume it.

The result is the pale plume we recognize as candle smoke — visible evidence of a combustion process, aka a real-life magic trick, that has suddenly been cut short.

Short Answer

As a candle burns, its vaporized wax reacts with oxygen to become mostly invisible carbon dioxide and water vapor. Tiny soot particles form inside the flame, but most quickly burn up. However, soot can escape and create visible smoke when the flame is disturbed by drafts or when a candle’s wick is too long, as well as when a candle is lit or extinguished.

HEALTH

Why Does Spicy Food Make Your Nose Run?

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By September 16, 2026 Updated: September 16, 2026

When you take a bite of spicy curry, salsa, or hot wings, the heat hits almost immediately. If it’s really got some kick, your eyes may start to water a few seconds later. You may even find yourself suddenly looking around for a napkin because your nose has joined the party, too.

Your sinuses don’t directly play a role when it comes to eating, yet they’ll react to things like wasabi and chili peppers. But that’s exactly what’s supposed to happen. Why? Because your body is treating spicy food less like dinner and more like a threat that needs to be dealt with.

The Nose Doesn’t Know

Chili powder and peppers — Credit: Towfiqu barbhuiya/Unsplash.com

The fiery sensation from spicy foods doesn’t come from temperature. A bowl of chili isn’t physically scorching your tongue and jalapenos will burn even when you eat them straight from the fridge.

Blame capsaicin, the natural compound that gives chili peppers their kick. It doesn’t actually raise the temperature in your mouth. Instead, it sets off the same alarms your nerves use to detect real heat. Your brain takes the hint and reacts as though you’ve bitten into something much hotter than you really have.

Real heat — such as the kind from fire or hot metal — is obviously a threat to your body, which is why it starts trying to defend itself. Your face flushes and you start sweating, which are two ways your nervous system cools you down. (Your adrenaline also spikes — useful in an emergency, but also why some people get a small thrill by eating spicy food.)

Person blowing their nose — Credit: Getty Images/Unsplash.com

Your watery eyes and runny nose represent a different type of response. Instead of trying to cool you down, this is how your body works to physically get rid of the capsaicin, which can waft off spicy food as vapor. Your body may not be smart enough to know the compound isn’t actually fire, but it does know the capsaicin is what’s pulling the alarm.

Inside your nose, glands produce mucus to trap dust, germs, and other particles before they travel deeper into your airways. When capsaicin stimulates those nerves, the glands ramp up mucus production. The extra mucus is your body’s way of trying to wash the irritant away.

Unlike the sniffles from a cold or seasonal allergies, this runny nose isn’t caused by a virus or your immune system overreacting. Instead, it’s a reflex triggered by certain foods, especially spicy ones. This reaction even has a name: gustatory rhinitis. For most people, it’s completely harmless and stops once the capsaicin is no longer stimulating those nerve endings.

Spicy meal — Credit: Monika Grabkowska/Unsplash.com

Not everyone experiences the same level of irritation, though. Some people can polish off a plate of extra-hot wings without reaching for a tissue, while others start sniffling after a single bite of medium salsa. Some people simply have more sensitive nerve endings in their nose.

Others may become more tolerant to capsaicin over time if they eat spicy food often, making the reaction less dramatic. This happens because the nerve receptors to the chemical become desensitized when activated frequently.

So if you’re looking for a way to eat spicy food without getting a runny nose, the solution may just be to… eat more spicy food.

Short Answer

Small particles of capsaicin — the chemical that gives spicy food its kick — waft into your nose as you eat. When capsaicin touches certain nerve endings lining your nostrils, it tricks your nervous system into thinking you’re actually encountering intense heat. Your body responds with a series of protective reflexes, including producing extra mucus to help physically clear away the perceived threat. The harmless reaction usually disappears as soon as the spicy sensation fades.

CULTURE

What Makes Gold So Valuable?

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By September 16, 2026 Updated: September 16, 2026

For centuries, gold has been equated with wealth. At times, the precious metal has defined the value of currency. It can be a status symbol for those who can afford to wear it or a display of luxury. Some restaurants even elevate the price of a fancy dish or cocktail by adding actual flakes of gold.

But why gold? There are other shiny metals out there, and plenty of things, such as fresh water, are far more essential to human life. If gold’s worth comes from it being hard to find naturally, why isn’t iridium more valuable? It’s even rarer — but instead of pirate treasure it’s used for spark plugs and TV screens.

Of all the materials in the world, what makes gold so coveted?

Worth Its Weight

Coins — Credit: Scottsdale Mint/Unsplash.com

You’ve heard of noble gases, but what about noble metals? Gold is one of eight noble metals on the periodic table, considered “noble” because it’s highly resistant to corrosion. Unlike more reactive elements, its atoms aren’t constantly trying to bond with other compounds.

This is important when deciding what to use as currency, since no one wants money that rusts, dissolves in water, or worse. For instance, osmium, another noble metal, becomes a toxic gas when it reacts with oxygen.

Gold does not become a gas, toxic or otherwise, at room temperature. That’s another important quality for currency, as gases and liquids are impossible to carry. Radioactive elements are too dangerous to handle, which eliminates some other metals from contention.

In addition to being safe and stable, gold has a low enough melting point that it can be smelted into coins and bars. It’s also rare enough to be considered valuable, but not so rare that it’s nearly impossible to find. That’s why even rarer metals, such as platinum, wouldn’t be a great choice for currency.

Silver is less rare and typically easier to mine than gold, which is mostly why gold is considered even more valuable, despite silver sharing many of the same qualities that make gold ideal for currency. Another advantage gold has over silver is that it doesn’t tarnish.

Both are pretty to look at, though,a which should not be overlooked when it comes to why gold has become so valuable. Ancient civilizations around the world — Mesoamerica, Egypt, China, Greece, India, Rome — all independently developed ways to mine gold into jewelry, decorations, and other objects. It’s the only metal that is naturally yellow in color, adding to its rarity.

Gold is often mixed with other metals, since pure gold can be too malleable, making it easier to bend or break. These alloys are measured by dividing the composition into 24 parts called karats — 1-karat gold means it’s one part gold and 23 parts something else, perhaps copper, zinc, or any number of other metals. Pure gold is 24 karats, because all 24 parts are gold.

Gold’s properties became even more valuable in the 20th century. Because the metal is corrosion-resistant and malleable, as well as highly conductive, it’s often used in electrical components. Even your smartphone probably contains somewhere between 7 and 34 milligrams of gold.

Why Gold Was Standard — And Then Wasn’t

Gold bar on U.S. dollars — Credit: Planet Volumes/Unsplash.com

Gold and silver coins were first produced in 600 BCE by the Lydians, an Iron Age civilization in Asia Minor. In 900 CE, Chinese merchants who were tired of lugging heavy coins around began using paper receipts from banks. These paper notes were proof that the merchants had the gold they wanted to spend and could be traded in lieu of the actual metal.

The Western world was slower to adopt paper money. The Massachusetts Bay Colony issued the first American paper currency in 1690. The gold standard was first adopted by England in 1821, with most major countries following suit over the next century.

The monetary system specifically ties a unit of currency to a fixed weight of gold. For example, when the U.S. adopted it, $1 was worth about one-twentieth of an ounce of gold. People could exchange gold for cash, or vice versa, using that rate.

There were several benefits to the gold standard, making it as valuable to modern society as the metal itself. It allowed fixed exchange rates between nations that used it. It also prevented governments from overprinting money, as they could only issue more money if there was actually physical gold to back it. Gold supplies changed slowly (since it’s hard to mine and nobody is throwing out the gold they have), meaning prices remained relatively stable.

But gold mining can’t always keep pace with the economic growth of a nation, and the same rigidity that offered predictability also prevented governments from responding to crises. For example, needing a sudden influx of money during a recession, war, or pandemic.

In 1971, President Richard Nixon suspended the ability to convert dollars to gold, and by 1973, most countries had abandoned the gold standard. Today, the U.S. dollar, the euro, the Japanese yen, and other units operate as fiat currency. They aren’t backed by any tangible goods, and are instead based on a complex relationship between prices, supply, and demand. That’s why the value of a U.S. dollar can be more or less than it was yesterday, and why the government can print more money without having to add more gold to its reserves.

Just as it did before it became the standard currency, gold still has value. Investors purchase physical gold or gold funds in the hopes that its value will increase, just as with stocks or commodities such as oil.

These days, you don’t need a pickaxe and a dream if you want to acquire gold. You can even buy both bars and coins from Costco!

Short Answer

Gold has a combination of characteristics that have made it valuable since ancient times, including its appearance, resistance to corrosion, and ability to be smelted into coins and bars. These properties also make gold useful for electronics, as does its electrical conductivity. Importantly, gold also has a level of rarity that makes the precious metal hard to find naturally but still practical enough for mainstream use. Up until the 1970s, many nations backed their currency with gold, though that’s no longer the case.

HEALTH

Why Do You Get Charley Horses?

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By September 15, 2026 Updated: September 16, 2026

The origin of the phrase “charley horse” is a bit of a mystery, but it’s a fitting name: The leg cramp comes on fast, hard, and without warning, like a startled horse that starts to bolt.

You could be walking across the kitchen or drifting off to sleep when suddenly your calf muscle locks up into a tight, stubborn knot. Here’s what causes this notorious muscle cramp, how you can stop it, and why it has such a deceptively friendly name.

A Pain in the Calf

Person stretching calf — Credit: Getty Images/Unsplash.com

Electrical signals from your brain tell your muscles to contract and relax, and when these signals misfire, your muscle fibers cinch together like the reins on a horse being yanked too tightly (though that’s not where the name comes from).

A hard knot forms under your skin because those muscle fibers are unable to relax after tightly contracting, and the knot can be very uncomfortable. The pain usually goes away in a few minutes once your muscle stops spasming, but it may be sore for a while.

You can get cramps in any muscle, but they’re most common in your limbs and abdomen. A charley horse is the name typically associated with a cramp occurring in the leg — usually the calf or thigh, but also the foot.

The origins of this strange name can be traced back to several different legends tied to American baseball slang in the 1880s. Most have to do with players with a leg injury or cramp resembling an old or injured horse as they walked or ran the bases. The exact horse varies depending on the legend, but the animal was named Charley. Other possible origins include a limping baseball player named Charley Hoss or afflicted players resembling children riding hobby and rocking horses.

Person tying shoe during workout — Credit: Aedrian Salazar/Unsplash.com

Just as its name has several possible sources, a charley horse can happen for lots of reasons. Exercise is one of the most common triggers, especially if you overdo one particular muscle. Not staying hydrated, especially while you work out, can also set one off.

Low levels of electrolytes such as sodium and potassium, which help regulate electrical signals in your nervous system and which you lose through sweat, are also a common culprit.

But you also can get a charley horse from just sitting or standing still in one position for a long time, because that can reduce blood flow to your leg muscles. (This is also why you can get them while you sleep.) Injuries, certain diseases or medications, and even stress can also cause cramping.

How To Rein in a Charley Horse

Person stretching their legs and feet — Credit: A. C./Unsplash.com

Age also matters. As you get older, your tendons become shorter and you become less flexible, which makes getting muscle cramps such as charley horses more likely. That’s because a relaxed muscle has less electrical activity, which means less chance of a nerve misfire.

That means stretching and massaging a cramp helps rein in a charley horse, as you’re helping the muscle relax again. If it’s your calf that is cramping, you can also try pulling your toes upward to relieve the cramp. Some people find relief by walking slowly until it relaxes. You can also apply ice or heat to see if either releases the spasm.

The best way to deal with a charley horse is to prevent one in the first place. Stretching and staying hydrated are a must when exercising, but also good practice in general. Comfy shoes can also make a difference. Why rein in a charley horse when you can keep it locked in the stable?

Short Answer

A charley horse is a painful muscle cramp in the leg or foot that often comes on without warning. It happens when electrical signals in your muscles misfire, which can occur when you’re dehydrated, among other reasons. You can normally get relief by stretching or massaging the muscle. Relaxed muscles cramp less, so you can help prevent a charley horse by staying hydrated and stretching properly.

NATURE

How Do Birds Know Where to Migrate?

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By September 15, 2026 Updated: September 15, 2026

Humans get around using road signs and GPS, yet we still regularly get lost just trying to find our cars in the parking lot. Meanwhile, birds travel for thousands of miles across continents and oceans and return to where they came from, all without writing down any directions. Many young birds even make their first migration without a parent showing them the route. How do they do it?

Well, bird brains have evolved several different methods to traverse the skies — adding up to a navigational toolkit that the GPS on your phone can only dream of.

Finding Their Way

Close-up of bird eye — Credit: Zdeněk Macháček/Unsplash.com

Migration is no easy feat — it takes days or weeks, can cover vast portions of the globe, and continues through darkness, clouds, storms, and shifting winds. No one sense or source of information is reliable under all those conditions.

That’s why birds have figured out an eclectic collection of navigational tools. Some appear to be instinctive, while others are learned through experience or picked up from fellow travelers. While scientists are still sorting out how all the parts work, together these abilities provide something like a map, as well as a sophisticated compass to follow.

In some cases, birds seem to be born with inherited instructions. According to the “clock-and-compass” theory that scientists have developed, a first-time migrating bird instinctively knows what direction and approximate length of time to fly.

In effect, the bird is running an internal program — call it “Tweet-PS” — telling it something like, “Head southwest for seven days.” This can guide a juvenile bird even if it has never been outside its neighborhood and has no parent leading the way — the unaccompanied minors of the avian kingdom.

As they make their journey, birds also likely consult several natural compasses. This is similar to how (human) sailors navigated for thousands of years. During the day, they can use the sun’s position, adjusting for its movement across the sky in combination with their own circadian rhythms.

At night, they can orient themselves with the stars. Rather than memorizing a celestial map, young birds seem to observe how the stars rotate, which teaches them which way is north and which is south.

Amazingly enough, birds can also detect Earth’s magnetic field, though scientists aren’t entirely sure how they do it. One long-standing theory that a naturally magnetic mineral found in their beaks does the job has been debunked, although the mineral, which is present, may play a role elsewhere in their bodies and is still being studied.

Another major theory suggests that light-sensitive proteins in bird eyes allow them to perceive the direction of the magnetic field as a visual cue. Scientists are still working out exactly how these mechanisms work, but experiments clearly show that altering the magnetic field around a bird can send it flying in the wrong direction.

Illustration of birds and navigational methods — Credit: Gary Bendig/Unsplash.com; Illustration How Everything Works

Once birds have reached familiar territory, landmarks may also help guide them. Remember a time before GPS when you’d find your in-laws by counting traffic lights and making a left at the 7-Eleven? Birds may do the same, but with rivers, coastlines, mountain ridges, and valleys, which can all serve as markers.

Smell may provide another kind of navigation tool: Seabirds can use odor to find breeding colonies on the open ocean, while other species learn how characteristic scents (from a particular field or forest, say) become stronger or weaker in different directions.

In effect, the birds seem to travel using a kind of odor-based map. It would be like you trying to find that new Italian restaurant everyone’s been talking about by rolling down your window and following the smell of lasagna.

Experience makes this whole system more effective. Adult birds can recognize when they’re off course and adjust their route accordingly, suggesting that they gradually develop a more detailed mental map. Some species also learn through social cues from their flock.

Exactly how birds combine and prioritize all these cues as they travel remains something of a mystery. Different species may favor different systems, and an individual bird may switch methods as conditions dictate. (Using the sun won’t do much good on a cloudy day.)

Rather than possessing one flawless internal GPS, migrating birds navigate by constantly comparing a suite of senses — and learning a little more with every journey.

Short Answer

Birds are born with some navigational instincts that they then combine with cues from the sun, stars, Earth’s magnetic field, physical landmarks, and smells. Some species also learn routes by following other birds in their flock. Scientists are still unclear on how birds mix and match all these tools, though. As birds gain experience, they develop more detailed mental maps that help them correct mistakes and refine their routes.

HEALTH

Why Does Pepper Make You Sneeze?

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By September 11, 2026 Updated: September 14, 2026

Sprinkling a dash of pepper onto your food doesn’t just tease the taste buds — it also affects your nose. Just as the spice can add flavor, it can make a meal smell tastier. But it can also create an unpleasant feeling in your nostrils and even result in a big sneeze. This can happen whether you love the taste of pepper or not.

Your body isn’t being a fussy food critic. Instead, it’s acting more like a bouncer and being overprotective when it comes to what you’re breathing in as you cook and eat. Here’s why your brain mistakes pepper for something more sinister.

Pepper Gets on Your Nerves

Nose and mouth — Credit: Pham Nhat/Unsplash.com

The nostrils are highly sensitive, with many nerve endings that help warn your body when germs, pollen, and dust try to sneak their way in. Unlike many other foods, finely ground pepper has a similar size and shape to these irritants.

When you shake pepper onto your meal, some of the teeny-tiny particles become airborne and find a cozy spot to rest inside your nose. This can tickle the nerve endings, which alert the brain and result in an instant sneeze — your body’s attempt to get the dust out of your nose. The nerves are like a smoke detector, with the sneeze acting as the automatic sprinkler that deals with the problem when the alarm goes off.

These nerves aren’t just attuned to physical intruders, but chemical ones as well. Pepper contains a chemical compound called piperine, which also irritates these sensitive nerve endings and can even trigger a pain response.

Chili peppers — Credit: Curated Lifestyle/Unsplash.com

Even if the nose doesn’t come in direct contact with physical pepper dust, inhaling the chemical compound can cause irritation that’s similar to (but usually not as painful as) the spicy oils that waft through the air when cutting or cooking fleshy chili peppers such as jalapenos.

In some cases, the irritation can linger. Whether from the dust or the piperine, pepper in your nose can also feel like a tickle or an itch that you must immediately scratch — once you let that sneeze out, of course. You may find yourself compulsively reaching for and rubbing your nose to gently scratch the itch away.

This automatic response is just another way your body is trying to expel the pepper as quickly as possible, without stopping and asking your permission if it’s a good time for you to sneeze or rub your nose.

Obviously, sneezing while cooking food isn’t exactly ideal. If it happens often, consider opting for a small spoon or finger pinch to disperse ground pepper, rather than sprinkling it on with a shaker or mill. Keeping the lid on dishes and turning your range hood fan on can also help keep pepper from floating up toward your nose, while still allowing you to spice up your meal.

After all, you’re supposed to be chewing your food — not achooing it.

Short Answer

When nerve endings in your nostrils sense irritants (such as pollen and germs) trying to enter your body, they alert your brain, which triggers actions to quickly expel the irritants. These include sneezing and compulsively rubbing your nose. Ground pepper is small and light enough to easily float into your nose when you sprinkle it from a shaker. Since it physically resembles dust, it activates a sneeze. Pepper also contains a chemical compound called piperine, which similarly prompts the brain to get rid of the irritation. Your nostrils’ nerves can sense this chemical and trigger a sneeze even if pepper doesn’t physically make its way into your nose.

SCIENCE

Why Do Fans Make You Feel Cooler?

Credit: Feng Yu/stock.adobe.com

By September 11, 2026 Updated: September 11, 2026

If you’ve ever sat on your front porch fanning your face with a magazine, you know just how effective a gust of air can be at offering respite from a sweltering summer day.

Whether generated by yourself or by an electric fan, this breeze doesn’t actually lower the temperature. When it’s hot enough, a fan may even be just blowing warm air toward you.

It may seem counterintuitive, but fans still help keep you cool by doing this. Unlike air conditioners, they’re not designed to chill the air — instead, they help your body regulate its own temperature. Here’s how.

Taking the Heat

Person dealing with heat — Credit: Nathan Dumlao/Unsplash.com

Let’s clear the air: A fan has no significant effect on the temperature in a room. In fact, fans can add heat given off by their motors. But this doesn’t mean they don’t work — you haven’t been ripped off by the Big Fan industry.

What a fan does is move the air around, which has a cooling effect on people. When it gets hot, we sweat. Our bodies need to maintain a relatively constant internal temperature (around 98 degrees Fahrenheit) to function properly, and sweating is how we help keep that temperature steady. When the small beads of water and salt that appear on our skin evaporate, they take heat away with them, allowing our skin temperature to cool.

This is why humidity makes the weather feel so much worse — if sweat can’t evaporate into air that’s already saturated with moisture, our bodies can’t shed excess heat. When we’re standing in front of a fan (or enjoying a nice breeze while outside), the moving air helps sweat (which is trapping excess heat within each droplet) evaporate faster, so we feel cooler.

Our bodies also radiate heat, creating a layer of warm air around our skin (similar to how air over a charging phone may feel warm). Wind strips that layer away, making room for more heat to leave the body.

Using Fans as Heaters

Ceiling fan in a bedroom — Credit: Hans/Unsplash.com

This is great when it’s a refreshing breeze on a hot day, but dangerous when it’s a frigid gust on a cold day. In that case, you want your body enveloped in a layer of warm air, and having it blow away will make you feel much colder. That’s why weather reports include the wind chill effect, letting us know how much wind will affect how we perceive the actual temperature.

If you do find yourself cold in the winter, a ceiling fan can be used to warm you up. This only works if the direction of its blades can be reversed. That’s because warm air rises toward a room’s ceiling while cooler air remains toward the floor.

A ceiling fan rotating clockwise at a low speed pulls colder air up and pushes warmer air back down toward you. The fan will continue to circulate the warm air, even as it drifts back up, preventing cold spots. So, really, it’s a good thing fans just move air and don’t actively cool you down — otherwise you definitely wouldn’t want to turn one on in the winter.

Short Answer

Fans create moving air, which doesn’t reduce the temperature in the room but instead whisks away the warm layer of air that radiates naturally from your body. Fans also help sweat evaporate faster, creating a cooling effect. That’s because your body regulates its internal temperature by releasing heat through sweat – you can’t release additional heat until the sweat on your skin evaporates and dissipates that heat into the air.

TECHNOLOGY

How Do Traffic Lights Know When To Change?

Credit: Carter Saunders/Unsplash.com

By September 11, 2026 Updated: September 11, 2026

Nobody likes pulling up to an intersection where it seems as if the light stays red forever. Maybe the cross traffic is heavy, or — even worse — you’re the only car waiting. Whatever the situation, the light just refuses to turn green.

Of course, it’s just a machine — it doesn’t know any better. It doesn’t know anything. Or does it? Do traffic lights just rotate on timers or are they “smart” enough to know when they should change?

Red Light, Green Light

Traffic Controller Box — Credit: Rosemarie Mosteller/stock.adobe.com

The brains of the device are the traffic signal controllers. They’re those large metal boxes you see near the intersection, and they control how the traffic lights work based on how traffic engineers program them. But, how these controllers decide when to change the light can vary, as different traffic lights use different methods.

At some intersections, traffic signals use fixed schedules. These lights phase through green, yellow, and red using a strict order, rather than any sensors. The schedules can be adjusted by the traffic engineer for specific times of the day. For instance, when traffic is heavier, such as during rush hour, the light can be programmed to remain green longer before changing.

But sometimes you may pull up to a red light and see it change to green almost immediately. That’s because it sensed your car, most likely with something called an inductive loop detector — those grooves carved into the asphalt at a stop light.

Buried underneath are wire loops that create an invisible electromagnetic field. When you drive over them, your car disrupts that field, which sends a signal to the traffic light.

If no passing cars are disrupting the other fields underneath the intersecting road, this signal tells the light, “Hey, we’ve got someone waiting here! Let’s go already!” You then get the green light (literally) to go.

Traffic light hanging above city street — Credit: Raphael Lopes/Unsplash.com

Other intersections may rely on cameras, radar, or other sensors to detect traffic and change signals. Video cameras analyze the roads and determine if cars waiting for the light to change are beginning to back up. Radar uses radio waves to sense cars and can work even when cameras can’t.

And sometimes it’s triggered by people. By pressing the crosswalk button, a pedestrian lets the traffic signal controller know they’re waiting to cross the street. The light might not change immediately, but the controller factors in their request when changing during the next light cycle.

If you’re the pedestrian, it might feel like you’re being ignored and pressing the button has no effect, but it does. Similarly, if you’re a driver sitting at a red light, you may feel unseen, but the light has nothing against you.

It’s more likely following a carefully programmed schedule and has to consider every car and pedestrian that wants to cross and from where. Just as we have to share the road, we also have to share the traffic lights.

Short Answer

Not all traffic lights change the same way. They can be based on fixed schedules or use cameras, radar, or sensors underneath the road to recognize traffic and decide when to change. Pedestrians pushing the crosswalk button can also affect when a light changes.