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Astronauts are members of a very elite club: As of 2025, only around 670 people have been to space, and fewer still have spent a significant amount of time beyond Earth’s atmosphere. Those who have had an extended stay in space tend to be crew members of the International Space Station (ISS), which has housed more than 280 individuals representing 26 countries since it became fully operational in 2009. 

The life of an astronaut is full of adventure, drama, and a certain amount of glamour — but life in space still requires many of the same basic chores we have to handle here on Earth. Of course, without gravity’s assistance, even the most mundane tasks can become complex feats of engineering. Here’s how astronauts aboard the ISS adapt to some familiar chores while traveling at a speed of 5 miles per second some 250 miles above Earth.

Bathing

Water has always been problematic on the ISS, for a number of reasons. It’s heavy, so it comes at a premium in terms of shuttle resupplies; it doesn’t behave in microgravity; and it’s potentially dangerous considering all the electronics aboard the station. Bathing, therefore, is a tricky business. 

In the 1970s, when NASA operated its first space station, known as Skylab, astronauts used a collapsible tube shower system. But this system took about two hours per shower, mainly because every water droplet had to be painstakingly collected after bathing. On the ISS, there is no shower — astronauts have instead returned to the old-school way of washing, as used during the Gemini and Apollo missions: a simple sponge bath. 

They squirt small amounts of water and liquid soap onto their skin and use a special rinseless shampoo to wash their hair, then use towels to wipe off any remaining water. An airflow system nearby quickly evaporates excess water, preventing it from floating around the station. 

Housekeeping

Astronauts on the ISS maintain a strict cleaning schedule. The station isn’t a sterile environment, as each astronaut brings microbes from Earth that can potentially flourish on the space station. Cleanliness is therefore a serious priority in the confined environment, both to protect the people living there and the technology and ongoing experiments aboard the orbiting lab. 

Each astronaut is assigned a regular schedule to wipe down surfaces with antimicrobial wipes, including kitchen areas and sweaty exercise gear. Vacuuming — using a surprisingly standard vacuum just like we’d use on Earth — is also important, especially for cleaning the filters and vents where dust accumulates. It’s a noisy process, but at least astronauts don’t have to worry about annoying the neighbors. In space, no one can hear you clean.

Taking Out the Trash

Astronauts generate about 4.4 pounds of trash per person per day, including packaging, paper, tape, filters, food containers, and personal hygiene items. Chucking trash directly into space may seem like the simplest option, but this naturally comes with obvious ethical, practical, and safety concerns. 

Instead, astronauts have relied on a remarkably low-tech method of trash disposal. Crew members compress garbage with duct tape into bundles called “trash footballs,” which they later load onto cargo ships such as the Russian Progress or Northrop Grumman’s Cygnus. These ships then jettison the trash, leaving it to burn up during reentry into Earth’s atmosphere. 

In 2022, the ISS developed a new, more efficient waste disposal method. By connecting a special waste container with a capacity of 600 pounds to an airlock, this system allows astronauts to store and dispose of larger amounts of trash. The whole container is launched from the station directly into Earth’s orbit, where it also burns up on reentry — with no cargo ships needed and no junk left in space.

Window Cleaning

You won’t find many better views than those from the windows of the ISS — but just like here on Earth, those windows need to be wiped down from time to time. Inside the station, astronauts regularly clean windows using alcohol-based wipes to remove fingerprints, condensation, and dust. But that’s the easy part. 

You may think that space, being a near-pristine vacuum, wouldn’t cloud the windows outside the station. And while the windows don’t become murky anywhere near as quickly as they do here on Earth, they do still need an occasional polish. Impacts from micrometeoroids and orbital debris, thruster firings from visiting spacecraft, and outgassing from the ISS can all leave particles that settle on the station’s exterior, including the windows. 

So the ISS windows do need to be cleaned, albeit infrequently. In 2015, for example, Russian cosmonauts took a five-and-a-half-hour spacewalk during which they wiped away grime that had accumulated on the portholes over a period of years — arguably the most extreme window-washing job imaginable.

Exercising

Free from Earth’s gravity, an astronaut’s bones and muscles can atrophy. On Earth, our bones and muscles constantly work against gravity to support our body weight, maintain posture, and help us move around. But in the microgravity of a space station, human bodies no longer need strong bones and muscles to function — so they adapt by breaking them down. 

Bones lose density because the signals telling them to rebuild cells have been removed, and muscles atrophy because they’re no longer working as hard as they do on Earth. To combat that, astronauts must exercise for about two hours per day during a long-duration mission. 

Crew members on the ISS use three exercise machines to stay in shape, which simulate weightlifting, cycling, and running. (NASA astronaut Sunita Williams even used the ISS treadmill to “complete” the Boston marathon from orbit.) 

Despite rigorous exercise programs, some astronauts still experience bone and muscle loss. It remains a critical area of research and technological innovation, especially considering future long-duration missions planned for the moon and Mars.

Maintenance and Repairs

Some of the most demanding chores on the ISS involve maintenance and repairs. Unlike space shuttles that return to Earth for servicing, the ISS never comes home, so astronauts must handle both preventive maintenance (inspection and replacement) and corrective maintenance (fixing broken equipment), which they train for on Earth before heading into orbit. 

Inside the station, astronauts repair everything from oxygen generators to water pumps and computer systems. They replace air filters, fix toilets, troubleshoot ventilation systems, and swap out failing components using spare parts stored aboard the ISS. 

The most dramatic and dangerous repairs are those that must be done outside the station. In 2007, for example, astronaut Scott Parazynski performed one of the most dangerous spacewalks in ISS history, riding on the end of a robotic arm to repair a torn solar panel. Any major repair, especially one outside the station, requires careful planning — and, sometimes, nerves of steel.

Some Chores Are Best Left on Earth

Some common chores aren’t done at all in space, either because they’re not required or because they’re simply too tricky to carry out. Doing laundry, for example, is a nonissue on the ISS. There’s no washing machine on the space station, primarily due to water constraints, so astronauts simply have a limited number of garments they wear again and again until they’re too smelly or dirty for further use (at which point they’re tossed in the trash). 

Cooking is another task that requires very little effort. There’s a permanent eight-day menu aboard the ISS, consisting of three meals and one snack a day — but it’s all prepackaged and preprepared, ready to be reheated or rehydrated in seconds (which also means there are no dishes to wash).

Aspiring astronauts in their teenage years can also breathe a sigh of relief, as there’s no need to make beds on the ISS. Sleeping in microgravity is a challenge, and there’s no real way to lie down, so astronauts instead tuck themselves into secured sleeping bags when it’s time to rest. 

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The human body is constantly working to maintain a healthy internal temperature, roughly 97 to 99 degrees Fahrenheit. When you get hot, regulating body temperature is a relatively simple fix: You sweat, the sweat evaporates, and your body cools down. But the opposite problem, holding onto heat when it’s cold out, isn’t as straightforward.

Humans lose body heat in several ways. The majority is lost through radiation as heat naturally escapes into the surrounding air. Conduction and convection — when skin comes in contact with a cold surface or when wind moves warmth away from the body — can speed the process up as well. 

Even evaporation plays a role: Sweat or damp clothing can cause heat loss surprisingly quickly. When all this adds up, your body temperature can start to fall, and when it does, a series of wondrous physical responses kick into gear to keep you warm. Here are a few surprising ways cold can affect your body.

Involuntary Muscle Contractions

We all know the feeling: You’re cold, your teeth start chattering, and your whole body seems to shake in mini convulsions. But shivering isn’t just a side effect of being cold — it’s actually the body going on high alert. 

Shivering is a controlled energy-burning response. Small muscle contractions, an action that burns chemical energy, occur quickly and automatically. While some of that energy is channeled into movement, most of it is released as heat, warming the body from the inside out in an attempt to keep that core temperature where it should be.

The body’s brown fat kicks into gear when you get cold, too. Also known as brown adipose tissue, this special fat stores and burns small amounts of energy to help maintain body temperature, a process that ramps up when body temperature drops.

Though present in the largest amounts in babies — up to 5% of their body weight can be brown fat — adults also retain small amounts throughout the body, including in the neck, chest cavity, and along the spine. Brown fat activation and shivering are part of the body’s thermogenic response — basically an internal thermostat that kicks in when the temp drops.

Weakened Immune System

Though frigid temperatures themselves aren’t a cause of illness, being cold can make you more susceptible to getting sick. 

According to the Mayo Clinic, cold weather forces the body to work harder to maintain core temperature, which can cause your immune defenses to temporarily weaken. And a weakened immune system, of course, means viruses and bacteria have an easier time taking hold, resulting in a bit of a snowball effect — pun intended.

Cold, dry air can also strip moisture from the mucous membranes lining the nose, mouth, and throat, weakening your first line of defense against germs. At the same time, the tiny, hair-like structures known as cilia in the upper respiratory tract don’t move as efficiently in the cold, allowing viruses to inhabit the nose and throat for longer. 

Another surprising culprit? Spending more time indoors. Respiratory droplets from talking, coughing, or sneezing are smaller and lighter without humidity, which is often sapped out of indoor spaces during furnace season. This means those pesky droplets overstay their welcome, lingering in the air longer and allowing viruses to travel farther and find more unsuspecting victims.

Blood Moving to Your Core

One of the first parts of your body to get cold in chilly weather is your hands — and that’s no coincidence. As the body cools down, blood vessels near the skin’s surface constrict, pulling blood away from extremities such as the fingers, toes, ears, or nose. A lack of blood flow can even make your lips turn blue when you’re cold.

This is the body’s way of redirecting blood flow to the core and the vital organs in your core. But that protective response also forces the heart to pump against more resistance, raising blood pressure and heart rate. If you’re vulnerable to heart problems, it’s advised not to shovel or perform strenuous activities in cold weather.

A Purposefully Runny Nose

Having a runny nose when it’s cold outside isn’t exactly a surprise, but the reason it happens might be. Known as cold-induced rhinorrhea, a sudden surge of nasal fluid when body temperature drops is actually a sign of your body working to protect your lungs. 

The cold, dry air you breathe in needs to be warmed and humidified before it reaches the lungs, so the nose’s blood vessels and glands ramp up blood flow and fluid production to help make that happen. The nasal glands also produce excess mucus to keep the inside of the noise moist and reduce irritation. 

When you exhale, the warm, moist air from your lungs meets the cold air outside. As the condensation of that breath hits the cold tip of your nose, more moisture forms, causing additional cold-weather drippage.  

Sneaky Hypothermia

It’s common knowledge that cold can induce hypothermia, but it doesn’t only happen when temperatures plunge. Hypothermia can also strike in the spring and fall, when temps are relatively mild. A combination of factors can contribute to the body cooling down too quickly even when it’s not freezing out, including: wind, damp clothing, and rain, which can all draw heat away from the body faster than it can be regenerated.

Hypothermia begins when the body’s core temperature drops below 95 degrees Fahrenheit, and it can wreak quite a bit of havoc. Mild symptoms include shivering and chattering teeth, poor coordination, and sleepiness. 

As the body’s temperature falls and hypothermia progresses, more severe — and surprising — symptoms set in, including hallucinations, slurred speech, and, oddly enough, a decrease in shivering. Without treatment, hypothermia can slow vital organ function to a life-threatening point.

To stay as warm and safe as possible, whether it’s cold or just wet and windy outside, it’s best to dress in layers that balance insulation and ventilation and to keep your head, hands, and feet covered. On the days you happen to forget your gloves at home, take comfort in the fact that, luckily, your body has a few surprising ways to help pick up the slack.

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We often think about our physical peak — the years when we can run fastest, stay up late without consequence, or bounce back from a pulled muscle overnight. But the brain’s peak isn’t quite so easy to pin down. 

Mental performance involves many abilities, including how quickly we process information, how well we remember facts, how creatively we solve problems, and how deeply we draw on experience and judgment. The question of when the brain is at its best depends on which ability we’re talking about — and how we define “best.”

For decades, scientists assumed that mental capacity increased through adolescence, hit a high point in the 20s, and then declined steadily. But more recent research has overturned that long-held view. Our brains develop, plateau, and adapt in complex ways over their lifespans, with different skills rising and falling on their own schedules. Processing speed, memory, vocabulary, reasoning, and emotional intelligence all follow distinct arcs — and can peak at different times in our lives

The brain is far more dynamic than we once believed. It remodels itself constantly, responding to how we live, what we learn, and how we connect. Some kinds of quick thinking may slow with time, but deeper forms of intelligence — such as judgment, emotional regulation, and creativity — continue to grow as the decades stretch on.

The Long Climb to Maturity

When we talk about mental agility — how quickly we can reason, adapt, or learn new information — we’re referring to fluid intelligence. This ability underpins problem-solving, pattern recognition, and the capacity to think on our feet. Research suggests that fluid intelligence peaks relatively early, often in the late teens to early 20s for processing speed, while some aspects of fluid reasoning and short-term memory may continue to improve into the late 20s or early 30s. 

That early advantage has biological roots. During adolescence and young adulthood, the brain undergoes synaptic pruning and increased myelination, refining connections and optimizing speed. 

Importantly, the prefrontal cortex — responsible for planning, impulse control, and decision‑making — continues to mature into the mid‑20s and early 30s. As a result, adults entering their 30s are often better equipped to manage complex tasks, set long‑term goals, and regulate emotions than they were just a decade earlier. In other words, younger brains may process information faster, but older brains often make better choices.

So if “peak” brain function means raw speed, that typically occurs in our youth. But if it means the integration of knowledge, empathy, and problem-solving — the ability to balance logic with perspective — the real peak likely comes later, in our 50s, 60s, or beyond.

The Rise of Knowledge and Judgment

If fluid intelligence gives us speed, crystallized intelligence provides depth. This form of intelligence reflects our accumulated knowledge, vocabulary, and experience-based understanding — and it tends to increase for decades.

Studies have shown that adults in their 40s, 50s, and 60s continue to expand their vocabularies and refine their decision-making skills. In fact, when researchers combined reasoning, verbal ability, emotional understanding, and moral insight into a composite measure of cognition, they found that the average mental “peak” occurred between ages 55 and 60.

Experience strengthens connections between brain regions, allowing older adults to integrate information more effectively. Tasks that rely on judgment and perspective — managing a team, interpreting social cues, or solving nuanced problems — often favor those with years of lived experience. Research has also found that older adults are less likely to make impulsive decisions or fall prey to cognitive biases such as overconfidence thanks to a lifetime of trial and reflection.

Different Peaks for Different Skills

A 2015 study based on data from about 48,000 participants found that different mental abilities peak at different ages, rather than all at once. Processing speed tends to reach its height in the late teens or early 20s, while short-term and working memory often top out in the late 20s to early 30s. Vocabulary and other knowledge-based skills, however, continue to improve well into middle age, with some measures peaking in the late 60s or even early 70s.

This variation reflects the brain’s adaptability. Younger adults excel at rapidly learning new skills, while older adults draw on broader context and emotional insight. For example, a 25-year-old may be able to master a new app more quickly, but a 60-year-old may approach a difficult decision with deeper understanding and better judgment.

Brain imaging studies have shown that as people age, the two hemispheres of the brain tend to work together more frequently — a phenomenon captured by the HAROLD model (hemispheric asymmetry reduction in older adults). Younger adults usually rely more on one hemisphere for specific tasks (for example, left for language and right for spatial reasoning), while older adults often use both sides. Researchers believe that this shift helps compensate for slower processing speed and declining neural efficiency, allowing older adults to maintain cognitive performance.

Emotionally, the brain often gains ground as it matures. Research shows that the amygdala — which helps process fear and negative emotions — tends to respond less strongly to negative stimuli in older adults, while the prefrontal cortex engages more strategically to regulate emotions. The result is often a calmer, more balanced emotional state. 

Many adults in midlife report experiencing fewer negative emotional swings and the ability to focus more on meaningful goals, which can support clearer thinking and more thoughtful decision-making.

Keeping the Brain at Its Best

While some cognitive changes are inevitable with age, lifestyle plays a major role in maintaining brain health. Physical activity is one of the strongest predictors of long‑term cognitive function: Regular aerobic exercise, even brisk walking, boosts blood flow to the brain, stimulates the growth of new neurons, and supports the hippocampus, a key region for memory.

Nutrition and mental engagement also matter. Diets rich in fruits, vegetables, fish, and healthy fats are linked to slower cognitive decline, with omega‑3 fatty acids in particular supporting neuron health and reducing inflammation. Learning new skills, tackling puzzles, exploring hobbies, or practicing music and languages stimulates neuroplasticity — the brain’s ability to form and strengthen connections — and is linked with reduced risk of cognitive decline.

Social and emotional factors further protect cognition. Maintaining strong relationships and a high level of community involvement counteracts loneliness, which is associated with faster cognitive decline and higher dementia risk. Adequate sleep allows the brain to clear waste proteins that can impair cognition, while managing stress through meditation, yoga, or quiet reflection helps preserve neurons and supports long‑term mental resilience.

At the end of the day, rather than asking when the brain peaks, it may be more accurate to ask which kind of intelligence we’re measuring and how we’re nurturing it. After all, the brain’s greatest strength may not be its speed but rather its remarkable ability to evolve throughout our lifetimes.