This episode is sponsored by 80,000 Hours. 80,000 Hours is a nonprofit that aims to help people have a positive impact with their career.

Head to 80000hours.org/scishowspace to start planning a career that can help solve one of the world’s most pressing problems. [♪ INTRO] As exciting as space is, it’s also a famously hostile environment. Between the temperature, the vacuum, and the radiation, it’s a dangerous place for us earthlings.

But as we’ve started exploring the final frontier, astronauts have discovered another way space poses a danger: sleep. It’s really hard to sleep well in space. And while space agencies have done a lot to make it easier, there’s still plenty keeping astronauts up at night.

Lack of sleep is a problem for a bunch of reasons. It can hurt people’s ability to think, stay alert, and make good judgments. It also makes them less efficient and more likely to make mistakes.

As a result, poor sleep can be deadly, especially in space. In fact, it’s enough of an issue that NASA requires astronauts on the International Space Station dedicate at least 8.5 hours a day to sleep time. The ISS is even outfitted with a dedicated sleeping area.

It’s got small compartments with a pillow, lamp, laptop, and a sleeping bag that can be strapped to the wall. Despite these accommodations, astronauts only actually sleep about six hours a day. That’s partly for logistical reasons.

While astronauts do their best to have a set sleep schedule, they don’t have control over the timing of things like dockings, space walks, and experiments, and sometimes, those things just have to happen “at night”. One study showed 13% of days on the International Space Station have something scheduled that keeps astronauts from their normal routine. Those days make it even harder for an astronaut to establish a regular sleep schedule, which disrupts their sleep for way longer than just the single day.

But on top of these logistical difficulties, astronauts are often experiencing a perfect storm of physical and psychological stressors that keep people awake. For one thing, the world outside the space station goes from one sunrise to the next in about 90 minutes. That’s a whopping 16 transitions from day to night to day in 24 hours.

That would screw up anyone’s circadian rhythm. Our internal clocks have been trained to reflect the cycle of light and dark in a 24-hour day on Earth. But the artificial light that the space station uses to mimic an Earth day isn’t bright enough to retrain astronauts’ circadian rhythms, so their sleep-wake cycles go haywire.

And while we tend to talk about our circadian rhythm as what makes us sleepy at night and alert in the morning, it’s really much more than that. Circadian rhythms control a whole slew of physical and mental processes that operate on a 24-hour pattern. For instance, they’re also responsible for lowering your body temperature at night, which is important for getting a good night’s sleep.

So if your circadian rhythm is off, your body temperature may not drop at bedtime, leading to hot and restless sleep. That’s not the only thing keeping astronauts warm and awake, though. The temperature in the space station stays at a comfortable room temperature, around 22 degrees Celsius.

Now, for most people, the optimal temperature for sleep, under blankets, is around 30 degrees. But remember that astronauts are zipped into sleeping bags. For the inside of their sleeping bags to be 30 degrees, the temperature of the air would have to be way lower, more like 13 to 19 degrees.

So astronauts are often a little too toasty to sleep well. But if they decide to sleep outside their compartment to stay cooler, they can run into a different problem. On Earth, warm air rises, which means that the warm carbon dioxide we breathe out floats away from our mouth and nose, allowing us to breathe in fresh oxygen.

But on a space station, that carbon dioxide doesn’t go anywhere. It just stays where it’s breathed out, creating a bubble of CO2 around your head. That means that if an astronaut isn’t sleeping next to an air vent, they may wake up gasping for breath with a nasty headache.

On top of all this, there’s noise, other people moving around, having to get up and pee, and all the things that make it harder to sleep on Earth, too. And even if an astronaut can get physically comfortable, they still have to contend with psychological sleep disruptions, like being overworked. The space station has a small crew, so everyone has to work a lot just to get everything done.

Sometimes work shifts get extended, which cuts into sleep time. Plus, the pressures of the work day don’t just disappear as soon as you go to bed. If you’ve had a job, chances are you’ve seen firsthand how job-related stress can lead to you thinking about work outside of work.

Like… when you’re supposed to be sleeping. But it’s not just the bad stuff that keeps astronauts from sleeping soundly. Being in space is exciting!

If you’ve ever had trouble falling asleep the night before your birthday or a big vacation, you know that excitement can make it harder to sleep. Astronauts are especially prone to bad sleep at the beginning and end of a spaceflight. But even when they’ve gotten used to being in space, individual exciting events can still disrupt sleep.

Like, the night before an astronaut has a space walk scheduled, they get even less sleep than normal. So unfortunately, astronauts live at the perfect intersection of physical and psychological factors that make sleep tough. But space agencies have already taken huge steps to facilitate better sleep in space, with things like air vents in the sleep compartments, reduced noise levels, separate sleep and work areas, and recommendations for how long people should work.

So, while it may never be the most ideal place to get some shut-eye, future astronauts will have a better chance at getting the rest they need. And there’s no reason they won’t continue to make improvements, allowing them to boldly go where no one has slept before. Astronauts have one of the few careers where people want them to sleep on the job.

But every career is different. Some can be more rewarding than others, and 80,000 Hours is a nonprofit that helps you find one that’s fulfilling. This SciShow Space video is supported by 80,000 Hours.

They aim to help people have a positive impact with their career and find one that really does some good in the world. All of their curated high impact career postings are free to access through their job board. And if you’re still early on in your career search, you can check out their blog posts and podcast that explore different global problems and careers that help solve them.

One blog post in particular might be interesting to you and these astronauts. It’s called “All the evidence-based advice we found on how to be more successful in any job” and it walks through topics like self-care and health. Click our link in the description or go to 80000hours.org/scishowspace to be sent a free copy of their in-depth career guide.

That’s also where you can go to sign up for their newsletter full of updates on their research and job opportunities. [♪ OUTRO]