Reid: Space is hard to portray in movies. Everything sounds and feels different out there. So it's probably no surprise that space films show a lot of inaccurate stuff. I mean, they're great as creative representations. We're not here to tell you you're favorite sci-fi flick isn't fun, but a few red flags make it clear that these are not factually rigorous documentary films. Here's Caitlin to explain what movies get wrong about space.

Caitlin: Are you regularly told that you're being silly and pedantic when you point out gross violations of the laws of physics in movies because it's "just a movie"? Well, you're about to feel totally validated because we're about to get real silly and pedantic. Hollywood can be pretty negligent about physics and astronomy, even in really good movies. But there are a few specific misconceptions that pop up again and again. So, let's set the record straight on a few of these once and for all. Also, spoilers ahoy! All movies mentioned are listed in the description, so check to make sure you don't want any of these movies spoiled before you keep watching. One of the really common areas where movies take some creative liberties with science is with asteroids and comets, like how the asteroid belt is commonly depicted as a dense minefield of death rocks. Well, the reality of the situation is much less exciting. Asteroids are typically one to three million kilometres apart. For comparison, the Death Star is about 160 kilometres in diameter. So, you're going to be pretty safe. And speaking of safety, if you were to ask a screenwriter how prepared we are to handle any impactor, they would probably say, "Not at all. We are all doomed." In the cinematic masterpiece Armageddon, for instance, NASA detects an asteroid the size of Texas only 18 days before it's going to kill us all. Then, they send out Bruce Willis and his rag-tag team of oil rig roughnecks to blow the thing up. I don't know why Hollywood so vastly underestimates NASA's ability to detect potentially dangerous impactors because NASA would definitely have known about Texas in space way in advance and had everything under control. NASA's Center for near-Earth object studies is constantly scanning the sky for space rocks trying to get too friendly with us, and they're pretty good at it. They keep track of thousands of objects and assess the likelihood of any of them impacting us.

Caitlin: When they find an undiscovered near-Earth object, they calculate its orbit and its potential as a threat. Then, if it could be a problem, they add it to the set of known objects that are tracked and have their orbits periodically reviewed. Orbits are calculated out to 100 years, so we would know way in advance if an extinction-level collision event were going to happen, which would give us enough time to plan to deflect or destroy the thing heading for us. It's true that sometimes we don't detect objects that buzz close to Earth until they're almost here, but the reason it takes us so long to spot them is that they're so small they're hard to detect. And since they're so small, they're not really much of a threat. Definitely not an extinction-level threat. But I could talk about all the good things and the bad things about Armageddon all day, so let's move on to black holes.

In the Star Trek reboot when Spock, Prime, and Nero are consumed by a black hole it sends them back in time whole and alive. But once you enter a black hole you are not getting spat out at any point, you're getting spaghettified. Seriously, that's what astronomers call it. You start to get stretched and extruded like toothpaste through a tube, ripped down to your constituent atoms and subatomic particles. And then the particles that used to be you are stuck in there forever. There are all kinds of other problems with the way black holes are portrayed in that movie, like it should have been impossible for Nero to create a black hole in the center of the planet Vulcan. And even if he had, there's no way it would have been big enough to swallow the planet that quickly. But he shouldn't have lived long enough to try it in the first place.

And finally, on the subject of space deaths, did you know you won't actually explode in space? Not even in the diminished atmospheric pressure of Mars. So as awesome as that scene in the original Total Recall is, where Cohagen is blown out of a building on Mars and balloons up as his eyeballs pop out, it isn't really plausible. Not that much of the movie is. It's a pretty common misconception that the difference in pressures inside your body and outside in space would equalize so quickly that your head would just pop, but actually, your body will keep everything in place. Kind of like a pair of Spanx. Your skin, muscles, and blood vessels have a lot of tension in them and they've got all kinds of nice, springy proteins in them like collagen and fibrillin, and their cumulative tension provides enough force to keep your blood from evaporating and your eyes from popping out. 

And your head definitely won't explode, so that scene in 2001: a Space Odyssey where Dave has to break in his own spaceship from outside is actually pretty accurate. His head doesn't blow up or anything, it's just really windy for a second as the air rushes out of the escape hatch. As long as you keep your exposure to a vacuum under 10-15 seconds, you'll be fine! You probably won't even lose consciousness. so that's just a tiny sampling of some of the terrible science we see in movies, but that doesn't mean you shouldn't watch them, bad movies can still be super fun, just don't believe everything you see.

But these aren't the only things movies get wrong about space, you've probably seen at least one spaceship dogfight in a Star Wars film, complete with "pew! pew!" blaster noises. But even given the existence of blasters. a space dogfight wouldn't sound like that because there's no sound in space! At least none that our ears could pick up, here's why:

If you're hearing me talking right now, congratulations! That means you are not adrift in the cold, near-vacuum of space. Sound waves can't travel through space, so if you were floating around out there, they'd never reach your ears, no matter what those sci-fi make it sound like, you'd never hear any ships exploding. But audible or not the universe is making noise and scientists have developed ways of eavesdropping on it. When we say "sound" we're referring to particles that vibrate in a particular pattern.

Those vibrations create a longitudinal wave, which just means that they move back and forth, or oscillate, in the same direction they're travelling. The wave continues when the moving particles knock into the ones next to them, which is why sound waves have to travel through a medium, like air or water. Basically, there needs to be particles nearby to keep the vibrations, and therefore the sound, going.

In space, things are a little different. It's not completely empty out there, even in interstellar space. But it's so close to a vacuum that there aren't enough particles to pass along the vibrations of sound waves. But there are other types of waves moving through the universe, and all it takes to listen in is the right equipment. 

Electromagnetic waves are like longitudinal waves in the sense that they oscillate in a predictable pattern. But since they're travelling as changes in electric and magnetic fields instead of as moving particles, electromagnetic waves don't need a medium to travel through. Still, just like sound, electromagnetic waves have a frequency, which is the measure of how often they oscillate over time.

And when they travel through plasma, the ionized gas and dusts that spread through space, they affect its electric and magnetic fields.

All this makes electromagnetic waves extremely useful because we can pick up on the changes in those fields, and in a way, scientists can use them to actually listen to space. In 2013, a NASA probe was able to interpret waves in interstellar plasma as sound that humans could hear.

In March of 2012, the sun had a tantrum in the form of a massive solar flare. This produced a kind of electromagnetic shock wave and about a year later it hit the plasma surrounding Voyager 1, the space probe that spent nearly 40 years leaving the solar system. As the electromagnetic waves resonated through the plasma they were picked up by the Voyager sensors.

No human could hear these plasma waves themselves but they did vibrate at frequencies that fall within the range of human hearing which is between 20 - 20,000 hertz, or oscillations per second. Voyager 1 recorded the vibrations and sent them back to Earth where physicists used the data to figure out the density of plasma the probe was traveling through. Turns out the density matched what was expected for inter-stellar space.

Voyager 1 had officially left the solar system. And when they reproduced the frequency of the plasma out there as if it had travelled through the air, it sounded like this. Another famous addition to our universe's soundtrack came from our old friend, the comet 67P/Churyumov-Gerasimenko.

In November of 2014, the European Space Agency's Rosetta Spacecraft detected some strange vibrations. Like the interstellar activity Voyager 1 observed, these sounds wouldn't have been audible without a bit of tweaking since at 40 to 50 millihertz they fell far below the range of human hearing. Scientists still aren't sure what exactly caused those vibrations but they think it was the comet releasing particles into its coma, the plasma atmosphere that surrounds it.

By increasing the frequencies of the plasma waves by 10,000 times, we're able to listen to the a scaled-up version of Comet 67P belting them out. So those wooshing sounds spaceships make in movies are just dramatic sound effects for the entertainment value of us earthlings. Because no medium in space means no sound.

But we don't need air, we've got science. So we've crossed

So we've crossed Armageddon, Star Trek, Total Recall, 2001: A Space Odyssey, and Star Wars off the list of potential documentary films. But wait, there's more! You've probably seen movies that explored the idea of generating artificial gravity by spinning, like Ender's Game, or the Disney Channel original movie, Zenon: Girl of the 21st Century. But spacecraft or space stations would have to be spinning really fast or be really big to generate gravity that way. Here's one from me about why it's so hard to spin artificial gravity into existence.

You see it in, like, all the movies, either there's a space station that's a big spinning wheel, or there are spaceships that use some invisible technology so that somehow even though the character should be floating around, because they're in space, they're sticking firmly to the floor. Artificial gravity is more than just convenient. Weightlessness is bad for humans. It makes bones and muscles degrade; causes heart and vision problems; the list goes on. So you'd think after more than 50 years of space flight we'd have come up with a way to make artificial gravity. But, we haven't 'cause it's hard.

The only practical way to make you feel like you're experiencing the full effects of gravity is by spinning. You've probably seen this effect at an amusement park. A ride spins really fast like a centrifuge making you stick to the walls. That's because, as the ride spins, centripetal forces are constantly pushing the wall towards you. They're making you turn, instead of just zoom off in a straight line. So, if you sent a disk into space, and set it up carefully enough, you could make it so that the centripetal acceleration was 9.8 meters per second squared, the same as Earth's gravity. That might sound pretty simple, but it's really not. For one thing, the smaller your disk is, the faster you have to make it spin to achieve the same centripetal force. But, as you can probably imagine, living in a disk, whirling around like a spinning top is not super comfortable. If you want a useful artificial gravity habitat that spins slowly enough to be habitable, scientists estimate that it would have to be around 100 meters in radius.

I'm talking about a structure that would be twice as big across as the International Space Station is long, which would be incredibly expensive and time-consuming to build. Even if you could build it, there would still be problems, because standing inside a spinning disk isn't exactly like standing on the ground.

For one thing, your head would be closer to the centre of the disk, so it would feel less of those centripetal forces. It would be like your head was experiencing less gravity than your feet, and the human body didn't evolve to handle that kind of thing. Your heart, for instance, would have to work harder to make sure that all of your blood was distributed properly and not spending extra time drifting around in your head. And if you bent down, or even tilted your head to the side, you'd get super disoriented. Because the fluids that fill the internal gyroscope of your inner ear would suddenly be swirling in a different direction, which makes me nauseous just thinking about it.

Still, figuring out a way to safely simulate gravity would be useful, especially if we want to send humans on long-distance trips to places like Mars. So, researchers have been working on it. For a long time!

In 1966, astronauts on the Gemini XI capsule actually tethered their craft to another ship called the Agena target vehicle and set them spinning very slowly, like, one rotation every seven minutes, to see what would happen. Turns out, it was enough to simulate only 5 ten-thousandths of Earth's gravity, too small for the astronauts to even feel.

Much more recently, a mission concept was proposed in 2011 called Nautilus X, a spacecraft that included a spinning disk designed to simulate gravity for astronauts on board. But, the mission was cancelled because of its costs before the team could develop an effective centrifuge. And, in July 2015, engineers at MIT built a very small centrifuge meant to fit inside the ISS and be used mainly for exercise. The researchers tested it on 12 people on Earth who used an exercise bike while being spun around at up to 32 revolutions per minute. They did experience motion sickness, as you might imagine, but it was mostly while the centrifuge was speeding up or slowing down.

With so many complications and so much research left to do, it'll probably be a while before we see spinning spaceships that can produce artificial gravity. But when we do, astronauts will be in for a wild ride!
So none of those movies with sounds or spinning gravity could've been documentaries. It's a good thing none of them claim to be. They're just good old-fashioned popcorn fun. It's still fun to spend your time watching them and hopefully watching videos like this one too.
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