NATURE

Why Do Leaves Fall Every Autumn?

Credit: Daniel Bernard/Unsplash.com

By October 9, 2026 Updated: October 9, 2026

Every autumn, many deciduous trees perform what looks like an act of botanical self-sabotage: They discard the very leaves they spent all spring growing. This happens year in and year out like clockwork, so much so that English speakers would refer to autumn as “the fall of the leaf,” which eventually was shortened to simply “fall.”

But why would a tree spend so much time developing its leaves only to let them go and start all over again the next year, rather than just keep the foliage it has? In other words, why are some trees evergreen while others are sometimes-green?

Leaves of Burden

Orange leaves — Credit: Allec Gomes/Unsplash.com

As the weather turns cold, the relationship between a deciduous tree (not all, but most) and its leaves has run its course. That once-indispensable foliage becomes more of a liability than an asset, and the tree is better off letting it go. The breakup, however, is a surprisingly orderly affair.

Humans may be embracing solar power more these days, but trees have been using it for 400 million years. Leaves are excellent solar panels. Their broad, thin surfaces capture sunlight, and their chlorophyll-laden cells use that energy to make sugars through photosynthesis.

Chlorophyll absorbs blue light from the sun (as well as other wavelengths) and reflects back the green it doesn’t use. That’s why plants are verdant and lush in the warmer seasons. But a leaf optimized to soak up the sunny days of spring and summer isn’t necessarily built to survive winter.

In colder climates, those thin leaves are vulnerable to freezing and other winter stresses. Cold temperatures and shorter days also slow photosynthesis, while frozen soil can make it difficult for a tree to replace water lost through its exhaling leaves. Plus, leaves are fragile, and by autumn, many are already showing their age after a long growing season — battered by insects, disease, wind, and other hazards.

Keeping thousands of increasingly unproductive leaves attached all winter simply isn’t worth the resources. Leaves can also become a structural liability. A broad canopy catches wind, increasing the strain on branches during storms. Add a load of wet, heavy snow to all that leafy surface area and the risk of broken branches rises. So the tree cuts its losses. Literally.

How a Tree Lets Go

Diagram showing abscission layer — Credit: Leon/stock.adobe.com; Illustration How Everything Works

As autumn days shorten and temperatures fall, leaves are eased into their separation from the tree by a gentle breakup known as abscission. The familiar blaze of fall color that has tourists flocking to New England every year is a sign that this process is underway and that green chlorophyll is beginning to break down. Yellow and orange carotenoid pigments, now free of chlorophyll’s mask, shine through in many species. The leaves of other trees also produce red or purple anthocyanin pigments at this time: One last burst of beauty before the fall.

Meanwhile, the tree begins withdrawing its support. The vessels that carry water into and sugars away from each leaf are closed off. A specialized layer of cells, known as the abscission layer, develops where the leaf stalk meets the twig. This scar-like formation ensures that the tree isn’t left with thousands of tiny open wounds after the separation.

Eventually, there’s little holding leaf and tree together, and gravity or a gust of wind finishes the job, one by one. Free of these burdens, the leafless tree settles into dormancy and conserves its resources through winter, not unlike a hibernating bear.

But the relationship isn’t entirely over. Once on the ground, fallen leaves become leaf litter, an important part of the forest ecosystem. As they decompose, nutrients locked in their tissues are returned to the soil, helping support future plant growth (including that of their ex).

The layer of leaves also shelters insects and other invertebrates and provides cover and insulation for animals such as frogs and salamanders. So while the tree may be ready to move on, its former leaves still have plenty to contribute — not just to its previous partner, but to other nearby life as well.

Short Answer

Deciduous trees shed their leaves before winter because broad, thin leaves are poorly suited to cold conditions and can increase the risk of damage from wind and snow. Darker days also slow photosynthesis, making leaves more of a liability than an asset to the tree. As days shorten and temperatures drop, trees begin abscission, a carefully controlled process that seals off each leaf before letting it go. After they fall, leaves still provide nutrients as they decompose into the surrounding soil.

CULTURE

Why Are Silica Gel Packs In Things You Buy?

Credit: Towfiqu Barbhuiya/stock.adobe.com

By October 9, 2026 Updated: October 9, 2026

When a product you ordered online finally arrives, it might come in a box with Styrofoam peanuts, crinkle-cut paper, or plastic air pillows to protect the items and keep them from jostling too much during transport. But another material that often comes with packages, silica gel packs, serve a different purpose.

These little packets come in different sizes, though usually you’ll find them no larger than a matchbook. Inside are tiny beads and outside is a stern warning not to eat them. Here’s a look at what silica gel packs are for, how they work, and — if you really want to know — why you shouldn’t ingest them.

A Shipping Superstar

Silica gel packs might seem wasteful, but they serve a vital purpose. While other packaging physically protects what’s being shipped, silica gel packs also help keep items in good condition, but chemically. Though called gel, silica packs are filled with solid beads of silica, which is also called silicon dioxide and is one of the most abundant compounds found in Earth’s crust. You’ve definitely seen it before, even if you haven’t torn open a gel pack out of curiosity, because it’s the primary component of sand.

Silica is also a desiccant, meaning it’s a substance that naturally attracts water, including moisture in the air. Standard packets, such as those you find in shoeboxes, contain around 1-5 grams of silica beads, which each absorb around 40% of their weight in water.

Moisture-retaining silica packets help preserve products by keeping them dry. Not only would it be kind of gross to open a new pair of shoes to find them damp, but water also allows bacteria and mold to grow. This means that silica gel also indirectly prevents odors by limiting microorganisms that cause them.

Inorganic materials can be corroded and perishables will perish more quickly when moist. Plus, silica packs help water-soluble items such as vitamins stay intact, which is why you’ll find them in bottles of supplements and medications. Even electronics benefit from a moisture-free environment as they sit on shelves and make their way to your front door.

World War I-era gas mask — Credit: Tilcara—iStock/Getty Images

Silica gel beads capture moisture through a process called capillary condensation, which changes vapor into liquid water. Once absorbed, the water gets sealed into silica’s internal structure, which is why we don’t notice a difference in the beads’ texture and they never appear wet.

In addition to moisture, silica gel packs are also a magnet for ammonia, sulfur dioxide, and other gases in the environment. In fact, this ability was why modern silica gel was first used on a large scale, in gas mask canisters during World War I.

Technically, silica is nontoxic (who hasn’t gotten sand in their mouth at the beach?). So why do packets come with a “do not eat” warning? For one thing, the small packets can be a choking hazard for kids, which isn’t something to take lightly. And, while not silica is not poisonous when swallowed, its desiccant properties can irritate your throat and nose, and cause stomach pains, vomiting, constipation, and nausea. Some packets also include harmful chemicals in addition to silica.

You Don’t Have To Throw Them Away

Person looking at family photos — Credit: A. C./Unsplash.com

You might be tempted to throw out these little packs after receiving your shipment, but because they have beneficial moisture absorption properties, they can actually be reused in the home. If you store electronics in a container, toss in a few packets to help keep moisture at bay and protect your tech when not in use.

If they’re explicitly designed as food-safe, you can use packets in spice cabinets to protect freshness and prevent those pesky clumps. Silica gel packs are also a great addition to a gym bag, shoe storage (including shoe boxes), and luggage. You can even toss a couple into your photo boxes or filing cabinets to protect paper goods from mold, discoloration, and warping.

Silica gel packets technically don’t expire, so they can be used over and over again. However, they can reach capacity and lose their ability to take on any more moisture. To test this, place a silica gel packet on a kitchen scale to measure its weight; if it weighs around 40% more than what the packet says, it’s fully saturated.

Fortunately, you can still keep using these resilient packs by evaporating their trapped moisture. Heat them in the oven at around 240 degrees Fahrenheit for up to three hours, depending on how much moisture they’re holding. Once you get in the habit, don’t be surprised if you end up keeping the silica gel packs that came with your package far longer than the items you actually purchased.

Short Answer

The silica gel beads inside packets included in product packaging absorb moisture, ammonia, sulfur dioxide, and other gases. They can hold up to 40% of their weight in water, protecting items from the damaging effects of humidity, odor-causing bacteria, mold, and corrosion while in transit. Silica gel doesn’t expire and can be repurposed at home to keep moisture out of apparel, spice cabinets, and more.

HEALTH

Why Do Placebos Work?

Credit: Roberto Sorin/Unsplash.com

By October 9, 2026 Updated: October 9, 2026

A bad headache can make you really grateful you live in the age of modern medicine. You swallow a pill no bigger than your fingernail, and soon the throbbing begins to fade — thank you, science.

But imagine learning that the pill contained no pain reliever at all: You’d been given a placebo, a treatment without any active ingredients. Yet it’s as plain as day that your headache really did go away.

That doesn’t mean your pain — or your relief — was imaginary, or that you magically willed yourself better. Although scientists are still untangling exactly how placebos work, there is measurable data showing that they can activate real responses in your brain and body. Sometimes they even work when you know you’re taking one. How is this possible?

The Brain’s Medicine Cabinet

Handful of pills — Credit: sourmarb/Unsplash.com

Think “placebo” and you might imagine a sugar pill. Technically, though, a placebo can be any pill, injection, device, or other treatment that has no ingredient or physical action capable of treating a particular condition. Theoretically, a placebo pill could be full of Jell-O, for example.

But think about everything else that happens when you receive medical care. You sit in an exam room, explain what hurts, and interact with someone who tells you that a treatment should help. You may recognize the shape of a pill, the pinch of an injection, or the familiar instructions on a medicine bottle or discharge papers. Your brain draws on previous experiences and interprets those signals, potentially preparing your body for relief.

Researchers are still working out exactly how this response operates. Expectations of relief appear to play a role, but so does conditioning. That is, if swallowing a pill has repeatedly brought relief in the past, your brain may learn to associate the ritual of taking the pill with feeling better — much as your mouth might water when you smell a favorite meal. Strangely enough, that conditioning alone seems to improve how you feel.

Brain scans — Credit: Nomad_Soul/stock.adobe.com

The neuroscience of all this is still being sorted out. The placebo effect has been linked to changes related to how the body uses dopamine, a chemical that regulates learning, pain, and your brain’s reward system. Brain-imaging research suggests that in complex ways, placebos can also alter activity in parts of the brainstem involved in processing painful signals.

That helps explain a crucial distinction: Placebos work best on symptoms the brain helps mediate, such as pain, nausea, fatigue, stress-related insomnia, and emotional distress.

You might think of the brain as controlling a volume knob: A placebo can sometimes turn down the intensity of a symptom, but it can’t necessarily remove its source. It won’t kill the bacteria causing an infection, for example, or lower cholesterol, or cure cancer.

What the Research Says

Doctor and patient — Credit: Getty Images/Unsplash.com

So how effective are placebos? There is no single reliable percentage. A 1955 paper famously claimed that they helped about 35% of patients, but a later analysis heavily criticized that figure. If your headache fades after taking a placebo, the placebo’s actions may have helped — but the headache might also have been about to improve on its own.

That’s what makes the placebo effect difficult to measure. Symptoms naturally fluctuate, and people often seek treatment at the peak of their illness, meaning they can start to feel relief whether they take anything or not.

To objectively study the placebo effect, scientists must compare people receiving a placebo with people receiving no treatment at all. A large review of 202 trials covering 60 health conditions found no major clinical benefits from placebo treatments overall, although placebos had modest effects on some patient-reported outcomes — especially pain and nausea. The results varied considerably depending on the symptom, the type of placebo, and how it was presented.

Another problem with quantifying the effects of placebos is that there’s no official bar a treatment must clear to be considered effective. Its effects are instead judged by whether it is statistically significant and large enough to matter to patients — standards that vary by symptom, condition, and the individual patient.

Interestingly, placebos might not always require deception. In open-label studies, where patients are explicitly told that they’re receiving an inactive treatment, some still experience relief from taking the inert medicine.

Even when you know nothing of note is in the pill, the familiar ritual of treatment — combined with conditioning, supportive care, and the possibility of improvement — may be enough to set your brain’s response in motion.

Short Answer

Placebos can work because your brain is able to adjust how we perceive pain and react to certain stimuli based on expectations, previous experiences, and the ritual of treatment. This can allow medical care that doesn’t directly treat an ailment to improve how you feel, whether the placebo is a device, drugs for a different affliction, or even just a sugar pill. Because the placebo effect is related to signals from your brain, it’s most apparent in symptoms the brain has some control over, rather than underlying causes of diseases or bacterial infections.

TECHNOLOGY

Do Lie Detectors Actually Work?

Credit: Getty Images/Unsplash.com

By October 9, 2026 Updated: October 9, 2026

Gritty police procedurals would have you believe lie detector tests take place in dark rooms where a guilty perp breaks only after the clever detective asks the right “gotcha” question, sending the machine’s needles skittering across the page. In reality, that machine isn’t called a lie detector — it’s called a polygraph, and that’s because instead of lies, it’s actually designed to detect something else: stress.

For most people, lying is stressful: We’re uncomfortable bluffing during a poker game or concealing a surprise party from a prying friend. But how does a polygraph detect stress, and how can the results tell an investigator if someone is telling the truth or not?

More importantly, does a polygraph even work — or is it TV-friendly pseudoscience?

Stress Test

Diagram of how lie detectors work — Credit: How Everything Works

When you’re stressed or afraid, your body shifts into fight-or-flight mode. Your brain signals your heart and lungs to work harder to more effectively move oxygen and blood throughout the body, better preparing you for either action.

A polygraph is designed to detect this shift. It’s equipped with devices that measure the subject’s heart rate, pulse, respiration rate, movement, and the changes in the skin’s electrical conductivity that occur when someone begins to sweat — all in an effort to determine if, and when, stress occurs. The word “polygraph” actually translates to “many writings,” a reference to the several biomarkers it measures.

Before the test, an interviewer explains the test and observes the subject’s baseline behavior — how they talk, move, and express themselves when they’re not stressed. They’ll also build rapport so that the subject feels comfortable with the interviewer — unnecessary anxiety could throw off the results.

They’ll discuss the case, including the questions they’ll ask. The intent isn’t to catch the subject off guard, but to measure the response to the same questions over time.

Then, the interviewer connects the subject to the machine and asks a series of simple yes-or-no questions. The comparison-question technique (CQT) is the most common interrogation method. It uses three types of questions.

The first type is relevant questions that pertain to the case: “On September 14, did you steal a Pontiac Grand Am?”

The second type is irrelevant questions that are benign, such as “Do you have a pet cat?” These questions give the interviewer a feel for the subject when they’re relaxed.

The third type is control questions that don’t relate to the case, but are meant to elicit a stress response. For example, “Have you ever hurt someone you loved?” “Have you ever stolen from your job?”

The concealed-information technique, though less common, adds information only a guilty person would know. For example, “Was a knife used in John Doe’s murder?” The idea is that a guilty person’s stress response will increase when actual truthful information is presented that an innocent person wouldn’t know or have an emotional response to.

But Is It Accurate?

A 2003 National Academy of Sciences report found that CQT testing could identify a lie better than detecting it by chance, but the study couldn’t determine how often a truthful statement was misinterpreted as a lie.

While it’s true that people often exhibit signs of stress while lying, some people don’t or are able to willfully suppress their own stress response. Others can be anxious just because they’re being tested, even when telling the truth.

There are several recorded cases of inaccurate results, including those with serious consequences. For instance, Floyd Fay spent over two years in prison for a murder he didn’t commit after he “failed” a polygraph test. Meanwhile, the infamous Green River Killer, Gary Ridgway, remained calm enough to pass a polygraph in the 1980s, despite later confessing to murder.

In the U.S., individual states can decide if polygraph results are admissible as evidence. Due to its unreliable results, about half have banned polygraph evidence, while the other half allow it only if both the prosecutor and defense have agreed to it.

Most private sector employers are banned from using polygraphs in employee screenings, though some U.S. government agencies, including the FBI and the Department of Defense, still use them for background checks, clearance, and internal investigations, including into information leaks. That said, Aldrich Ames, a CIA operative who spied on behalf of the Soviet Union and Russia for several years, passed multiple polygraph tests while acting as a mole.

So, while a polygraph can accurately detect the stress of someone lying, it’s not foolproof. If only the “pants on fire” test were more definitive.

Short Answer

Despite being commonly known as lie detectors, polygraphs actually measure stress, using blood pressure, heart rate, respiration, sweat, and other indicators. Because lying is stressful for many people, the idea is that a polygraph, used in conjunction with a series of specific types of questions, can help determine if the subject is being truthful or not. While this can work, polygraphs have proven to be wrong before, which is why several U.S. states have banned their results as evidence in legal proceedings.

HEALTH

Why Are Some Belly Buttons Outies?

Credit: María Juárez—iStock/Getty Images

By October 9, 2026 Updated: October 9, 2026

Your belly button is basically a souvenir from before you were born — and it comes in two main styles: innie and outie. An innie navel is a recessed dip in the middle of the abdomen. Conversely, an outie sticks out from the same spot and is far less common. Only about 10% of people normally have an outie as opposed to an innie, so it’s roughly as rare as being left-handed.

So why do some people have outies? For generations, folks have blamed the medical professionals in the delivery room for the difference, imagining that a doctor or nurse somehow snipped or tied the umbilical cord in a particular way and voila: an outie.

But that’s not how it works. In fact, your body has much more to do with how your belly button looks than anything anybody did the day you were born.

Scarred for Life

Newborn in nursery — Credit: Jimmy Conover/Unsplash.com

While “navel” is considered a more mature (and less fun) way of describing your belly button, the actual medical name is “umbilicus,” which makes sense since the feature is a direct result of humans having an umbilical cord in the womb. Before we’re born, the umbilical cord is our connection to the placenta and our supply of oxygen and nutrients.

Blood vessels inside the cord carry these nourishments to us while also removing carbon dioxide and other waste products. After we’re born, we don’t need that connection anymore. So, the doctor clamps and cuts the cord, leaving a small stump attached to the abdomen. Over the next few weeks, the stump dries out, shrivels, and eventually drops off.

What remains becomes your belly button, a scar marking the spot where the umbilical cord once entered your body. Because the healing was more than skin deep, it’s a permanent scar.

Close-up of stomach — Credit: chanerin/stock.adobe.com

After the umbilical cord falls away, the body repairs and closes the area. Scar tissue forms as the opening heals, and how that tissue settles against your abdominal wall determines your belly button’s shape. That shape naturally varies from person to person and can be round, oval, horizontal, vertical, bulb-shaped, or even T-shaped.

Your belly button is almost certainly unique thanks to subtleties in its shape, but it’s fairly easy to classify whether you have an innie or an outie. Generally, an innie belly button looks like a little dimple while an outie looks more like a knot protruding out.

Whether you have an innie or an outie and the precise shape of your navel comes down to how it heals. There’s no “outie” gene you can be born with — it’s essentially random.

Side view of a navel — Credit: HENADZY/stock.adobe.com

There are a few exceptions, though. Babies with certain medical conditions that affect the navel are more likely to have outies. For instance, the healing process can leave an extra bit of tissue called an umbilical granuloma. It can look like a tiny red or pink bump and may bulge from the belly button. It’s usually harmless and can be treated if it doesn’t heal on its own.

Another reason for an outie is an umbilical hernia at birth. This happens when the umbilical cord pushes through an opening in the abdominal muscles. Normally, the opening closes after birth. But if it doesn’t close completely, a small amount of tissue can push through, creating a bulge near the belly button.

Even if you grow up with an innie, it’s possible for your navel to change to an outie later in life. This can happen for a number of reasons, including fluid buildup from a liver or kidney disorder, or even the swelling of the liver itself, or the spleen. A more benign change can occur for pregnant women as the uterus pops the belly button outward as it grows larger.

But, just as with the navel shape you’re born with, none of these are because a doctor botched cutting the umbilical cord.

Short Answer

Your belly button is scar tissue formed when the remaining umbilical cord falls off after you’re born. This scarring naturally develops differently in everyone and results in various shapes and sizes, including determining whether the navel recesses inward (an innie) or protrudes outward (an outie). Outies are far less common but are determined randomly, not by genetics or the actions of the staff in the delivery room. However, some outies can be related to minor medical issues or even form later in life from an innie.

SCIENCE

Why Is Gas Unleaded?

Credit: Ali Mkumbwa/Unsplash.com

By October 9, 2026 Updated: October 9, 2026

Pull into any gas station today and you’ll likely see the word “unleaded” all over price signs and pumps. Is that adjective really necessary, though? It’s not like you’re going to use the rival station across the street because you were actually looking to put “leaded” gas in your tank.

As a matter of fact, today all gasoline available for passenger cars is unleaded — calling it “unleaded” is like selling “frozen” ice. Gas used to have lead in it, though. In fact, the world used to run on leaded gas.

Why Lead Is Good for Gas

In 1921, as automobiles were beginning to transform modern society, a General Motors engineer discovered that adding lead, specifically tetraethyl lead (TEL), raises gasoline’s octane rating. Octane (another word you’ll find at the gas pump) refers to a fuel’s stability — the less chemically stable fuel is, the more likely it is to prematurely combust before your engine needs it. This ill-timed combustion causes engine knock and can damage a vehicle (and endanger the humans inside).

Fuel with a higher octane rating is more stable. Lead raises that rating because it bonds with the combustible hydrocarbon free radicals that make gas unstable, neutralizing them. The innovation of leaded gasoline made cars easier, safer, and more efficient to drive.

Although cars ran on leaded gas for decades, experts were — even in the 1920s — aware of lead’s adverse health effects. Some public health officials were staunchly against the idea of leaded gasoline from the start. Although other chemicals, including benzene and ethanol, also increase octane, the oil and gas industry largely ignored them in part because they cost more to produce.

Lead is so toxic that its widespread use is believed to have resulted in the premature deaths of millions worldwide. Lead exposure came from many sources in the 19th and 20th centuries, including lead pipes and lead paint, but leaded gas was a significant contributor. You don’t need to drink gasoline for lead to make its way into your body — people were inhaling it, bit by bit, from the ubiquitous exhaust fumes produced by vehicles.

Ironically, though, the downfall of leaded gas came from the U.S. government regulating other pollutants. The passage of the Clean Air Act in 1970 didn’t ban lead from gas, but it did require that car manufacturers install catalytic converters to reduce smog and carbon monoxide. Because lead damages catalytic converters, gas providers needed to let drivers know which fuel was okay to use if they had a newer vehicle equipped with one — and so the word “unleaded” started gracing gas station signs more and more.

Is ‘Leaded’ Gas Still Used Today?

Plane being fueled — Credit: Getty Images/Unsplash.com

Eventually, leaded gas for passenger cars was banned completely in 1996 as part of amendments to the Clean Air Act, and fuel manufacturers switched to benzene- and ethanol-based additives to increase octane ratings instead. (Benzene itself was later restricted for also being toxic to humans, but that’s a story for another day.)

So while leaded gas still works exactly as it did 100 years ago (and, for engines at least, provides material benefit), you cannot buy it at a gas station. Even if you don’t see the word “unleaded” anywhere, you can rest assured that’s exactly what the gas you’re pumping is.

That said, some other industries still use leaded gas. The biggest one is aviation, because the piston engines of aircraft require higher-octane fuels that are difficult to produce without lead. To clean up its act a little, the airline industry switched to 100 Low Lead (100LL) fuel in the 1970s. Today, most commercial airliners’ jet engines burn unleaded kerosene fuel, but the Federal Aviation Administration reports roughly 220,000 piston aircraft still use 100LL. Thankfully, the agency hopes to phase out the fuel by 2030.

Other than these airplanes (and a few specialty and off-road vehicles), the era of leaded gasoline is over — the signage at your local gas station remains mainly out of habit. Consumers have come to expect to see “unleaded” and managers don’t want to make their paying customers think twice about stopping at their pumps.

Because of this and its historical context, “unleaded” has become synonymous with fuel that’s compliant with current regulations.

Short Answer

Until the 1970s, lead was added to most automobile gas as an octane booster to increase the fuel’s stability. Lead neutralizes reactive free radicals that can cause fuel to combust prematurely, leading to serious mechanical failures such as engine knock. In the 1970s, catalytic converters, which are damaged by leaded gas, became mandatory for new cars, so gas stations began selling unleaded fuel. Leaded gas was banned for car use in 1996 as it’s highly toxic to humans, but the “unleaded” label persists today.

HEALTH

8 Ways Your Body Changes at Night

Credit: Pablo Merchán Montes/Unsplash.com

By October 9, 2026 Updated: October 9, 2026

Sleeping isn’t usually considered a productive activity. You’re lying still, your eyes are closed, and (hopefully) you’re blissfully unaware of the world around you. It can feel as though you’re simply pressing pause until morning.

But beneath the covers, your body is anything but idle. As darkness falls, your internal clock flips a remarkable series of biological switches. Billions of cells begin a carefully choreographed overnight routine.

Nearly every organ in your body behaves differently at night than it does during the day, and all in service of helping you wake up healthier, sharper, and ready for whatever tomorrow brings. Here’s a look at how your body works the night shift.

Your Body Cools Down

Person sleeping in sunlight — Credit: Mina Rad/Unsplash.com

One of the first signs that bedtime is approaching isn’t something you consciously notice: Your core body temperature begins to fall. As your circadian rhythm (a natural cycle guided by your internal clock) signals that night has arrived, your temperature drops by about 1 to 2 degrees Fahrenheit. Blood vessels near your skin widen, allowing heat to escape, which helps make you feel sleepy and stay asleep.

By morning, your temperature gradually climbs again, helping prepare you to wake up and become more alert. This is why it’s often recommended to keep your bedroom cool for a good night’s sleep, as warmer temps can throw your body off.

Your Hormones Change

Person looking at screen at night — Credit: Yuliya Matuzava/Unsplash.com

As daylight fades, your brain releases melatonin, often called the “sleep hormone.” Rather than knocking you unconscious, melatonin acts more like a signal that tells the rest of your body it’s time to transition into its nighttime routine. Bright light — such as the glare that comes from phones, tablets, and computer screens — can interfere with this signal by convincing your brain that it’s still daytime.

Meanwhile, levels of cortisol, often nicknamed the “stress hormone,” do almost exactly the opposite. Cortisol falls after you drift off to sleep, then begins rising again in the early morning hours, helping prepare your body to wake up. Growth hormone also surges during the night, supporting tissue repair, muscle maintenance, and healthy metabolism.

Your Heart Takes It Easier

Person checking their heart rate on smartwatch — Credit: Káplár Bálint Áron/Unsplash.com

Your cardiovascular system finally gets a chance to slow down at night. During non-REM (rapid eye movement) sleep, your heart rate decreases and your blood pressure drops, giving your heart and blood vessels a chance to recover from the demands of the day. (They are more varied during REM sleep, when you’re likely to have your most intense dreams.) As morning approaches, both gradually rise again, preparing your body for more rigorous activity.

Doctors see the overnight decrease in blood pressure as a normal and healthy dip. People whose blood pressure doesn’t decline at night may have a higher risk of cardiovascular problems, demonstrating the relationship between good sleep and a healthy heart.

Your Brain Files Memories — and Takes Out the Trash

Neurons in brain — Credit: Getty Images/Unsplash.com

Although your body is lying still (more or less), your brain remains remarkably active while you sleep. As you cycle through different sleep stages, your brain consolidates important memories and organizes information gathered throughout the day. It’s one reason cramming all night before a test is often less effective than getting a good night’s sleep.

Researchers also think that sleep gives the brain time to carry out essential maintenance. During non-REM sleep, overall brain activity slows, while REM sleep sees activity surge again — almost to daytime levels — supporting cognitive processes that happen even while you’re awake. Ironically, though, your brain struggles to make memories while you dream, which is why you often can’t remember your dreams when you wake up.

Your Muscles Relax

Human muscles of left shoulder, forearm, chest, and neck — Credit: Planet Volumes/Unsplash.com

Sleep isn’t just for resting tired muscles; it’s also when much of the body’s repair work actually happens. As you move into deeper stages of non-REM sleep, your muscles gradually relax as your body’s overall energy demands fall. Behind the scenes, cells repair everyday wear and tear and tissues recover from the stresses of daily life.

During REM sleep, most of your voluntary muscles also become paralyzed (don’t worry, it’s just temporary). This prevents you from physically acting out your dreams while your brain is highly active. Fortunately, the muscles responsible for breathing and eye movement don’t take the night off and continue to work normally.

Your Breathing Changes With Your Dreams

Person with eyemask sleeping — Credit: Pablo Merchán Montes/Unsplash.com

Your breathing also follows a different rhythm at night. During non-REM sleep, breathing becomes slower, steadier, and more regular than it is during the day. But once REM sleep begins, things become much more variable.

Your breathing speeds up, becomes shallower, and can even become irregular — one reason sleep specialists often pay close attention to breathing patterns when evaluating sleep disorders. Your cough reflex is also dialed down during sleep, helping prevent small irritations from waking you (and perhaps your partner) unnecessarily.

Your Kidneys Slow Down

Dimly lit bathroom — Credit: Mesut çiçen/Unsplash.com

If your kidneys worked exactly the same way overnight as they do during the day, most of us would spend far more time making nocturnal trips to the bathroom. Instead, they deliberately reduce urine production while you sleep, helping you stay asleep longer without interruption. That’s why sleeping through the night without needing the bathroom is perfectly normal for many healthy adults.

Your Internal Clock Keeps Everything on Schedule

Nocturnal dreamscape — Credit: Behnam Mohsenzadeh/Unsplash.com

The remarkable thing about these changes is that they aren’t happening independently. They’re coordinated by your circadian rhythm — your body’s built-in 24-hour timing system.

A tiny region of the brain acts as a master clock, taking cues from light entering your eyes and coordinating countless biological processes throughout the body. In response, your organs, hormones, metabolism, body temperature, mood, digestion, and even your immune system all shift into different operating modes depending on the time of day.

Scientists now know that nearly every part of the body keeps time. Rather than simply turning off each night, your body follows an intricate schedule that has evolved to balance activity with repair. So, from the outside, it may look like nothing much is happening after your head hits the pillow, but your night shift is only just getting started.

SCIENCE

Are You Really Made of Stardust?

Credit: How Everything Works

By October 9, 2026 Updated: October 9, 2026

Astronomer Carl Sagan once said, “The cosmos is also within us. We’re made of star stuff. We are a way for the cosmos to know itself.” It’s a beautiful idea connecting humanity and the universe across time, but is it scientifically true, or just poetry?

It’s poetic and it’s true. Nearly everything in your body — along with every other object on Earth — was created inside a long-dead star before even the sun came into being.

Where Do Atoms Come From?

Diagram showing the elements that make up the human body — Credit: How Everything Works

Humans are primarily made of six elements, including oxygen, carbon, and hydrogen. So what did Sagan mean when he said we’re made of “star stuff”? How can we get water (hydrogen and oxygen), or other elements from a big ball of gas that’s millions of miles — or light-years — away? To answer that, we first have to look at the most basic ingredients that make up both stars and humans: atoms.

The big-bang theory (the theory, not the sitcom) suggests that about 13.8 billion years ago, a dense, hot dot tinier than the head of a pin rapidly expanded and stretched like a balloon to an unfathomable size. As it cooled, that energy turned into atoms, the smallest building blocks of matter. Everything that has mass and takes up space, including you, is matter, and all the matter and energy that exists was created simultaneously from the big bang, meaning it’s a fixed amount that can’t be increased or decreased.

The human body contains about 7 octillion atoms — that’s a 7 followed by 27 zeroes. Every one of those atoms has a nucleus that houses positively charged protons as well as neutrons, which have no charge at all. Zooming around the nucleus are negatively charged particles called electrons.

An element is a pure substance in which every atom has the same number of protons. For example, hydrogen atoms are the simplest, as they each have just one proton. Sodium atoms have 11. Iron atoms have 26. The atoms of plutonium, the heaviest naturally occurring element, have 94 protons — every element heavier than that has been made in a lab within the past 90 years or so.

The number of protons is known as an element’s atomic number, and it’s how elements are ordered on the periodic table, from 1 to 118. (The heaviest element, oganesson, atomic number 118, was first created in 2002, meaning any periodic tables from before then are out of date).

Atoms are the basic building blocks of chemistry — they can’t be broken down into simpler substances. There are subatomic particles out there, including incredibly tiny ones smaller than even an electron, but that’s getting into much more advanced physics — when it comes to everyday, tangible chemistry, the buck basically stops with atoms.

“Building blocks” is a surprisingly apt term, as atoms can bond with other atoms during chemical reactions, or when they share electrons, coming together to make increasingly larger structures. You’re basically made of atomic Legos.

A molecule forms when two or more atoms bond together. These atoms can either be the same element, such as two oxygen atoms, or different elements, such as water, which consists of two hydrogen atoms and one oxygen atom (H2O).

Elements have different properties from one another — they have different boiling points and melting points, for example, which is why iron is solid at room temperature while mercury is liquid. For complex life to exist, several elements must come together (hence why you won’t find a solid gold animal that isn’t jewelry).

The reason life — and nearly all matter, really, including asteroids and planets — exists is because nearly all of the elements on the periodic table are forged by stars.

Stars Are Element Factories

Supernova in outer space — Credit: NASA Hubble Space Telescope

Without stars, the periodic table would be much smaller (and easier to memorize), as the entire universe would consist of just hydrogen and helium. There’d be no oxygen or carbon, which means there’d be no you.

Stars create elements, but they can’t create matter out of thin air (or whatever was around before oxygen existed), because the amount of matter and energy in the universe is fixed. So instead of making elements from scratch, they change one element into a different one by changing its atomic structure.

While atoms frequently bond and swap electrons, they rarely change the number of protons they contain. If an atom did give away one or more protons, it would mean becoming an atom of another element, as its atomic number would literally change.

Such a change requires a tremendous amount of energy, which is why nuclear fusion (fusing atoms together) and nuclear fission (breaking atoms apart) are very difficult for humans to do — and extremely explosive when we do it. However, stars have a lot of energy, and elements changing into other elements is exactly what’s going on inside a star.

Stars are balls of hot gas, made when gravity pulls dust and hydrogen gas together into clumps. As gravity squeezes the growing clumps tighter and tighter, the material inside gathers pressure and heat. Once hot enough, nuclear fusion occurs.

Hydrogen atoms — which each have one proton, remember — collide to create helium, which has two protons. This nuclear reaction releases a burst of energy that we can see from all the way down here on Earth as a tiny prick of starlight (or, if it’s from our own sun, as much brighter sunlight).

The very first stars in the universe began as just hydrogen and helium because these two simplest elements were all that existed after the big bang. But as stars age, helium atoms fuse into larger carbon atoms, carbon can become oxygen, and so on, all the way up the periodic table until iron, which has an atomic number of 26.

Why does it stop there, if at least 118 elements exist? Because iron doesn’t release energy when it fuses. So when a star becomes so massive that its core becomes iron, that core collapses, creating a huge explosion known as a supernova. This is considered the death of a star.

Spiral galaxy — Credit: NASA Hubble Space Telescope

A supernova is so powerful that it can create heavier elements, such as gold, silver, and uranium. (Note that atoms with an atomic number of 104 or higher are known as superheavy elements, and they’re all synthetic. They never occur in nature, not even in a supernova.)

A supernova explosion sends all these newly made atoms careening into space. The drifting atoms, countless little specks, are not unlike dust, and some of this stardust clumps into balls to become asteroids, moons, and planets. New stars also form, but this time with sprinklings of heavy elements as opposed to just light elements. This is how astronomers can figure out how old a star is: A star with almost no heavy elements at all is ancient, but a star with more must have formed later.

Our sun is the latter kind of star, forming relatively recently — about 4.5 billion years ago. It amassed when the solar nebula — a spinning cloud of gas and dust containing hydrogen and helium left over from the big bang, along with material scattered by generations of dead stars — collapsed and flattened.

Earth and all the planets in our solar system formed at the same time, as smaller clumps from this same cosmic sandbox. The iron in your cookware, the salt you use to season food, and the oxygen and other heavy elements that make up your body all originated this way. So Carl Sagan was 100% accurate when he observed that “we’re made of star stuff.”

HEALTH

How a Cut Heals Itself, Step by Step

Credit: Road Red Runner/stock.adobe.com

By October 9, 2026 Updated: October 9, 2026

Whether it’s the sharp sting of a papercut or a deeper slice from a knife slip while chopping veggies, you’ve undoubtedly had a few cuts in your lifetime. But unless a wound is serious enough to require stitches or a trip to the doctor, we rarely stop to consider how a cut goes from bleeding to healed, almost like magic. So how does the body pull off this impressive repair?

The process is actually quite complicated, biologically speaking. For a wound to heal, it goes through four distinct phases, including hemostasis, inflammation, growth and rebuilding, and strengthening. These steps require cells, proteins, and other nutrients to work together to keep out infection, rebuild the site of the wound, and repair tissue until it’s fully healed.

Here’s what’s happening behind the scenes after you reach for the Band-Aid.

Step 1: Hemostasis

Diagram of bleeding cut — Credit: 100% HAND-CRAFTED/stock.adobe.com; Illustration How Everything Works

When a cut on your skin occurs, it will likely start bleeding, even if it’s just a shallow papercut. Almost immediately, your body springs into action. When blood begins to flow, blood cells called platelets gather right away, forming a clump to clot your blood and stop additional bleeding. Eventually, when the clots dry and harden, they will turn into scabs.

Scabs contain fibrin — a protein created from fibrinogen that flows in plasma (the liquid part of your blood) — which weaves a sticky mesh that stops the flow of blood. Together with the platelets, fibrin covers the wound and helps hold the scab in place.

Step 2: Inflammation

Diagram of inflammation as a cut heals — Credit: 100% HAND-CRAFTED/stock.adobe.com; Illustration How Everything Works

After the blood has clotted and a scab is formed, your blood vessels expand so that oxygen and other nutrients can easily flow to the area. Getting just the right amount of blood-borne oxygen to the site of the wound is a critical part of the process, and it can be disrupted if there’s too much or too little.

At the same time, macrophages (immune cells) act like a microscopic cleanup crew. They trigger inflammation to fight off germs or any infections from the wound while controlling the response so that the healthy tissue isn’t damaged. Macrophages also work to get rid of any dead cells from the wound site, and then repair the tissue.

Step 3: Growth and Rebuilding, aka Proliferation

Diagram of new tissue growing as a cut heals — Credit: 100% HAND-CRAFTED/stock.adobe.com; Illustration How Everything Works

The next step involves rebuilding the wound and is often referred to as the proliferation phase. Here, new tissue begins to form as your skin knits itself back together, beginning at the edges of the cut. New blood vessels are also formed during this phase, and fibroblasts (another type of cell) create collagen and proteins to support newly formed tissue. Additionally, other types of cells will move across the surface of the wound and cover it to form a protective layer. Finally, the edges of the cut will contract to begin closing the wound.

Step 4: Strengthening, aka Remodeling

Diagram of scarring as a cut heals — Credit: 100% HAND-CRAFTED/stock.adobe.com; Illustration How Everything Works

The last phase of wound healing is strengthening, or remodeling, and it’s how your body builds the skin back up to face whatever slipping kitchen knife comes its way in the future. At this point, collagen and proteins are still working to strengthen the injured tissue. The proteins also support the structure of the wound and will continuously remodel as it changes throughout the healing process. The wound will continue to contract until the tissue is fully closed, and as the tissue matures, it will gain elasticity and strength.

Scars may also form after a wound has completed healing, even if it went through all four phases without interruption. (Healing can sometimes be slowed or stopped by issues such as a lack of blood supply to the wound or infection.) A wound’s size, location, and your own genetic factors can affect the size and appearance of the resulting scar. But no matter how large or noticeable it is, the scar tissue that’s formed will feel less flexible and slightly firmer than the surrounding skin.

Whether a cut leaves a faint mark or fades away completely, that new layer of tissue is proof of a quiet biological marvel.

ENGINEERING

What Is the Strongest Shape?

Credit: Vimal S/Unsplash.com

By October 9, 2026 Updated: October 9, 2026

If The Three Little Pigs taught us anything, it’s that in construction, materials and methods matter if you don’t want your house to collapse under a strong wind. But shapes do, too, which is why certain ones are frequently used when building buildings, bridges, tunnels, and other structures.

Some shapes are ideal for distributing weight evenly, while others are better able to withstand external or internal pressures. Some get used in more than one form, such as how you can find circle architecture in domes, spheres, and cylinders. Here are some of the best shapes employed by engineers and what makes them so great for construction.

Triangle

It’s not a coincidence that the pyramids have been around for thousands of years. Triangles are commonly considered the strongest shape, making them a mainstay of supporting structures in architecture and engineering. So what’s a triangle have that a square or rectangle doesn’t?

Imagine a square or rectangular box. Now, imagine pushing on one of its sides. With enough force, the corners will give and the box will flatten. A triangle, however, is structurally rigid, meaning its shape is determined by the length of its sides and can’t change unless one of those sides bends or breaks first.

So when force is applied to a triangle’s joint, the weight, or load, can only be distributed down either side, causing compression (the force is squeezing them together) in the sides and tension in the bottom (the force is pulling it apart).

Because of this, triangles are frequently used in supports. For example, bridges, which have to bear the weight of many vehicles, often rely on triangular trusses. The Eiffel Tower’s legs are built from iron lattices, forming triangles throughout that allow the famous landmark to withstand wind.

However, a triangle is less efficient at enclosing or spanning a large space, since the shape comes to a narrow point — hence why we don’t all live in triangular houses.

Arch

Arches are capable of holding weight through compression, making them one of the strongest (and utilized) shapes in engineering. In an arch, the load pushes down on its highest point, which is the keystone in the middle.

The keystone distributes weight along each side of the arch and down to the ground. Much like the two sides of a triangle squeezing together, the wedge-shaped pieces of the arch, called voussoirs, squeeze into one another, creating a stable structure — sometimes even without glue or anything else holding them together.

For the best support, arches do need supporting walls, buttresses, or a series of connected arches. Without them, an arch will exhibit thrust. This means it pushes outward, eventually spreading its feet and causing the arch to collapse. (Imagine pushing down on two books leaning against one another in an inverted “V” shape.)

In ancient Rome, arches were commonly used in bridges, aqueducts, and even the Colosseum — and some survive to this day. They were often made of stone or brick, a material that resists compression well. Today, you’ll still find them in bridges and architecture, often made of steel and concrete.

Domes, Spheres, and Cylinders

Diagram of how a dome distributes weight — Credit: How Everything Works

Domes are often used to form ceilings or, in some cases, complete structures. Whether a dome can stand on its own with thin walls or needs support depends on how weight is distributed across its surface. A dome ceiling or roof can spread weight evenly, but because it will exert thrust all around its perimeter, it requires strong supporting walls, much like an arch.

An exception is the geodesic dome, which is made up of triangular or polygonal facets that allow the structure to distribute stress within itself and therefore requires light or no walls.

Like a dome, a sphere has no corners or flat surfaces, meaning it evenly distributes stress across its entire surface. Cylinders have two flat end caps, but no corners. Their curved walls can spread stress evenly around their sides. This makes both shapes especially handy as vessels in high-pressure environments or as containers for high-pressure gases or liquids.

Diagram of how a sphere distributes weight — Credit: How Everything Works

For example, you’ll notice that fire extinguishers and diving tanks, which must hold pressurized air, are cylindrical — not rectangular or triangular. So are propane tanks, in which propane gas is heavily pressurized to the point where it becomes a liquid. Soda cans are another example, holding carbonated beverages under pressure.

In nature, eggs present a similar benefit, but in reverse: Though delicate by our standards, their curved shape allows a mother hen to sit on them without them breaking, as her weight is distributed around the shell instead of concentrated at any point.

What spheres don’t do is stack or pack efficiently, which is why rectangular and square boxes are far more practical as containers for storing everyday items. The shape also makes it harder to use land efficiently (or furnish in the case of circular-shaped rooms), which is partly why most homes and buildings have boxier shapes than round ones.

Hexagon

By itself, an equilateral hexagon (a shape with six equal sides), isn’t the strongest shape. It’s not rigid like a triangle, and, unlike a circle, its six corners can still collect pressure.

But what a hexagon does have going for it is the ability to tessellate (arrange together in a repeating pattern) with no gaps in between, while using less material than a square or triangle would when accounting for the same area. If you were laying down new tile over your bathroom floor, you’d need about 7% less grout to connect hexagon tiles than you would for square ones, because the shape has a shorter perimeter (edge) overall.

When tiled hexagons face pressure, they’re able to split that load evenly along all six sides, in every direction. You can see this in nature in a honeycomb. Each hexagon in a honeycomb fits perfectly with its neighbors, creating several equally sized pockets for bees to store honey.

Do bees inherently know hexagons are more compact and require less wax to build, at scale, than any other shape? Probably not. Current theories suggest bees may have evolved to build honeycombs or that it’s a matter of physics. Bees start by building circular cells, which flatten into hexagons as their body heat warms the wax.

Because less material means less weight, we’ve borrowed the bees’ design for lightweight honeycomb composite panels. These get sandwiched between outer panels in spacecraft, aircraft, or other applications where maintaining a low weight is critical, and some geodesic domes employ a mix of hexagonal and triangular panels.

This goes to show that engineers don’t always reach for whichever shape is strongest. Other qualities — including weight, stackability, and practicality — also play important roles in the structures we build.