Five hazards of human spaceflight

Protecting astronauts against space radiation

Outside the protective atmosphere of Earth, astronauts are constantly bombarded by radiation, which, among other dangers, increases the risk cancer. While those of us on Earth can mitigate the effects of similar radiation by limiting exposure,...

Prolonged space travel significantly impacts multiple human body systems

Astronauts can lose 20% of their muscle mass after two weeks and 10% of their bone mass after six months in space. Decreased sharpness of eyesight and changes in neural connectivity, brain structure and gut bacteria have also been observed.

There are no established minimum fitness standards for spaceflight

Microgravity is known to cause arterial hardening, bone weakening, and other health issues, but the novelty of space tourism and the minimal exposure time for suborbital trips have limited the number of research studies. Many companies have participants sign extensive waivers to bypass the requirement of specific medical standards.

How do astronauts battle loneliness and depression?

You’re stranded hundreds of miles away from your friends and family, constantly surrounded by coworkers who also are your roommates, and you’re only allowed the shortest of walks outside. There’s also no takeout, and gravity has essentially broken up with you. You might need a little help adjusting mentally. That’s where space psychologists and psychiatrists step in, according to this article.

Watch how dozens of everyday human tasks are performed in space

This playlist features clips of astronauts aboard the International Space Station explaining how they cook, eat, sleep, and conduct research in microgravity. Other activities to pass the time, including watering plants and playing soccer, are also shown.

Research suggests the cleanliness of the ISS may make astronauts unhealthy

The International Space Station's sterile conditions deprive astronauts of the opportunity to strengthen their immune systems through microbial exposure. To address this problem, future missions may use probiotic-based cleaners and foster diverse microbes in space habitats.

Listen to the five-part podcast series that reconstructs how Challenger failed

The "American Scandal" podcast devotes a five-part series to Challenger, tracing the engineering warnings, internal pressure to launch, the moment of the explosion, and the long aftermath that reshaped NASA's safety culture.

Has anyone had sex in space?

Reproduction is a basic human function, and while we've spent decades in space, no research has been done into the process. With many discussing the possibility of human-occupied bases on the moon, Mars, and more, understanding how sex works outside...

Stephen Hawking on the need to explore space

Should we be content with being cosmic couch potatoes? In this interview, the late Professor Stephen Hawking lays out the case for continued and increased human space exploration, despite its cost and challenges.

Why haven’t humans reached Mars?

Mars remains the most viable interplanetary destination due to its relatively habitable orbit. There are many challenges, however, including the huge distance to Mars, the need for advanced propulsion systems, uncertainty over the impacts of long-duration space travel on astronauts, and the need for safe landing techniques and equipment to handle Martian conditions. Human-manned missions to Mars are not likely to occur until the 2030s at the earliest.

What is space sickness?

Mix motion sickness minus gravity with a host of other variables, and you’ve got a recipe for space adaptation syndrome. It can hit anyone, even astronauts who escaped the issue previously. This article details the history and science behind space sickness.

Who owns outer space?

More and more material ends up in Earth's orbit, posing threats to orbiting space stations and satellites. A 1960s treaty technically made space the common property of humankind, but with increasing chances of conflict in space, things can seem anarchic. This video breaks down the brewing tensions in space.

In 2013, an astronaut's helmet began filling with water during a spacewalk

A leak in the cooling system of Luca Parmitano's spacesuit caused water to obscure his vision and silence his radio as the International Space Station entered Earth's shadow, forcing him to feel his way back to the airlock in darkness.

Increasing space tourism may require changing the definition of astronaut

Though astronaut has been used to describe any crew member in space, civilian explorers who lack formal training have instead been dubbed "space travelers" by some. The term astronaut may one day fall out of use or be modified by ongoing media and social perceptions as the space tourism industry continues to evolve.

Eleven deaf men played a pivotal role in America's human spaceflight program

In the mid-20th century, 11 deaf men volunteered for a series of experiments that offered unprecedented insights into the effects of weightlessness on the human body. Most of the men had become deaf in early childhood as a result of spinal meningitis, a condition known to damage the vestibular system and make them less susceptible to motion sickness. For a decade, these men participated in extreme motion sickness situations, including living in a slowly spinning room, spending time in centrifuge pods designed to simulate hypergravity, and flying in parabolic flights sometimes referred to as the "Vomit Comet." (Some users may experience a paywall.)

Space tourism rockets emit up to 100 times more CO₂ per passenger than airplanes

Rocket launches release significant amounts of water vapor, nitrous oxide, and rocket propellants, which generate greenhouse gases and air pollutants. High-altitude emissions can persist for years, affecting the ozone layer.

As an experiment, the first B2 mission highlighted the challenges of isolated systems

Some argue that isolation from the outside world was compromised—making the experiment a failure—when a crew member was taken from Biosphere 2 for surgery and returned hours later. This position was strengthened when it was revealed that oxygen had been pumped into the facility.

An unedited interview with the first person to float freely in space

Astronaut Bruce McCandless was the first person to ever float freely in space, completely untethered from a shuttle. How did he enter the field? What are his thoughts on current space travel? Listen to his experience and opinion firsthand in this 19-minute video.

Rising satellite numbers pose increased risks of planes being hit by falling debris

Projections of more than 100,000 satellites in space by the 2030s—eight times the number in 2025—highlight a growing threat to aviation. Experts suggest the odds could reach seven in 10,000 annually by 2035, alongside higher risks to people on the ground.

The science of fear

The Hidden Brain podcast team explores the science of fear by traveling to a haunted house curated by a scientist to investigate what scares us, and why some people enjoy this sensation more than others.

Astronauts have repaired genetic damage in space using CRISPR—a molecular tool that can make precise changes to DNA and is used in single-celled organisms to attack invasive viruses.

Depending on environment, aliens' bodies would have wide-ranging possibilities

Humans tend to imagine aliens as humanlike, but that's probably unlikely. From small space spiders to metallic carnivores, life on other planets—and how we could interact with it—is difficult to imagine.

Five potential ways to achieve time travel

While the author discounts the possibility of traveling to the past, it lays out five hypothetical modes of catapulting into the future: speed, gravity, suspended animation, wormholes, and light. Each has some scientific basis, but none are realistic for humans. Read the article to learn where they offer promise and where they fall short.

Are smart cities a dumb idea?

Smart cities require vast troves of data to run, making their systems attractive to hackers. Listen to this one hour podcast to learn about the risks and what is being done to mitigate them.

Before humans, the Soviet Union and the United States sent animals—including apes, dogs, and cats—to space during the Space Race.

Listen to why extensive ear rinsing can create problems

The clinician who hosts this podcast discusses how his patient developed swimmer's ear after he flooded his ears with water during his daily showers, ostensibly to clean them. The resulting itchy, painful ears were the result of removing protective earwax in the ear and also altering the typical pH of the ear.

Watch an expert's take on the rare disease hantavirus—and why it's not of great concern to the general population

This rare zoonotic disease, transmitted to humans primarily through infected rodent droppings, urine, or saliva, is rarely spread between people. The disease was of particular concern in spring 2026, when an outbreak occurred on a 150-person cruise ship, prompting a flurry of action, including contact tracing for passengers in their home countries. The disease can be fatal. But early care—primarily oxygen support—can help patients survive.

Human-to-human transmission of hantavirus remains extremely rare, so the 2026 hantavirus cruise ship outbreak doesn't mean we're facing a COVID-style pandemic risk.

Apollo astronauts left items in the moon's 'toss zone,' including golf balls, family photos, and bags of human waste, to make room for lunar rocks.

Radioactive elements can introduce software errors because the ionizing radiation they produce can detach electrons from atoms, and computer code relies on the distribution of electrons.

About 12.5% of US adults experience a phobia in their lifetime, a diagnosis that hinges on the intense fear interfering with daily life and persisting for at least six months.

Listen to an in-depth conversation on the links between Parkinson's disease and herbicide exposure and the challenging pace of scientific investigation.

An investigation suggests a Scottish island became awash in forever chemicals via seafoam and seaspray—raising questions about what that means for the safety of other coastal areas.

Explore our favorite visualization of the immense scale of space, from an astronaut to the size of the observable universe

SpaceX's S-1 or 'prospectus' revealed many previously unknown details about the company, including its unprofitability despite doing $18.7B in revenue in 2025, exactly how many voting shares Elon Musk will have in the company (roughly 85%), and more.

Firework or sparkler burns, even if they cover a relatively small area of skin, can significantly affect our range of motion.

Explore what it's like inside a patient isolation unit, used in situations such as treating a patient or suspected patient with Ebola.

After 25 people used virtual reality headsets to practice flying with virtual wings—flapping their arms—their visual cortex responded to the wings almost as if they were real arms, treating them as body parts.

The United States has had a tumultuous relationship with Cuba since its 1959 revolution, highlighted by a nuclear crisis and a decades-long trade embargo.

Discover the catastrophic consequences of a failure of the US electrical grid—something that is more likely than many Americans think.

How fusion—which releases energy when two lighter atoms combine to form a heavier atom—differs from fission

While the sun's gravity keeps the planets in orbit, their gravity also pulls on the sun, causing it and everything else in the solar system to orbit around a mutual balance point called the barycenter—the true center of the solar system.

Take a 3D tour of the Hajj, Islam's annual pilgrimage to Mecca, undertaken by over 1.5 million Muslims.

Children are now three times more likely to say they want to be a YouTuber when they grow up than an astronaut, with some even attending 'YouTube camps' that teach kids how to create content for the platform.

Shooting stars, or meteors, are fragments of asteroids and comets that burn up as they enter Earth's atmosphere, creating streaks in the sky called meteor showers.

Massive 3D printers have been used to build homes by stacking layers of 'concrete toothpaste,' a fire-resistant material that effectively insulates against outside noise.

Existentialist writer Jean-Paul Sartre coined the famous phrase 'Hell is—other people' in his play 'No Exit'

Studies suggest when you sleep is as important as how much you get, and syncing with your circadian rhythms may lead to less fatigue and improved long-term health outcomes

Volcanoes 'die' when their supply of magma runs out, if they are shifted away from their underlying magma reservoir, or if they get clogged by collapsing or their magma cooling back into rock.

The Russia-Ukraine conflict is the largest ground war in Europe since World War II in casualties, forces mobilized, and displacement of civilians.