You’ve probably heard this fact stated before by your high school science teacher or some killjoy walking out of a movie theater: If movies were trying to be scientifically accurate, there would be absolutely no sound out in space. That means no booster rockets rumbling, no laser blasts during an epic space battle; just pure silence. Space, by it’s very definition, is made up of absolutely nothing. Since sound is caused by vibrations through a medium — air, water, etc. — there’s simply no way for sound to transmit over any distance. Of course, watching almost any action scene from Star Wars with the mute button on would be incredibly boring, so filmmakers usually get a pass for this one.

9. It takes a really loooooong time to get anywhere

In most movies, traveling to another solar system takes about as long as a cross-country road trip. In reality, the distance between planetary bodies is so great that it would take much longer than the average lifespan of a human to reach them. The nearest star to the sun is still 25 trillion miles away from Earth. Even NASA’s fastest rocket would take over 100,000 years to get there.

8. Wormholes would not be useful for space travel

In many movie plots, wormholes are a great means for people to travel large distances almost instantly or even travel through time. But there’s a pretty good reason science fiction writers often pull a wormhole out as an easy plot device though: they’re only theoretical. Scientists have theorized about the existence of wormholes since the 1920’s, but there’s really no evidence that they could be used for space travel, other than mathematical equations. Even if they could act as a portal from one place to another though, they still might not be very useful since some theories say they would be microscopic and only last for a fraction of a second.

7. Traveling at light speed would rip a space craft apart

Several movies use light speed travel as an easy solution to having spaceships travel the enormous distance between galaxies. Traveling faster might seem like the best way to overcome the distance problem, but then it just creates a new problem with all the space debris that would tear the ship apart. For example, the Hubble Telescope has had numerous holes punched in it from meteorites the size of dust particles, and that’s a relatively slow moving vessel. If a ship were to travel at the speed of light, it wouldn’t make it across the Solar System without being reduced to dust itself.

6. We would not be able to communicate with aliens right off the bat

The English language — or any language for that matter — is the product of millions of years of cultural evolution, which means countless coincidences brought us our means of communication for today. With that in mind, just what would be the odds of bumping into an alien species and being able to converse with them at all? Never mind that the chances of finding an intelligent species on another planet are astronomical, just how likely would it be for the Star Trek crew to land on an alien world and instantly start talking with the inhabitants?

5. Asteroids do not clump together

How many movies feature some intrepid space explorer fearlessly diving into an asteroid field to escape an enemy? Unfortunately for those pilots, most asteroids don’t clump together like that. True, our own Solar System has an asteroid belt, but even that is spread out enough for man unmanned spacecraft to pass through. Most asteroids are simply massive chunks of rock floating along their own path, independent of each other.

4. There cannot be fires/large explosions in space

For the same reason that sound cannot exist in space, neither can fires or large explosions. Fire needs oxygen to survive, which definitely doesn’t exist in space. You might get an outburst of energy during an explosion on a spacecraft and maybe even some quick flames burning up leaking oxygen, but it wouldn’t be anything near the spectacle of, say, the Death Star exploding in Star Wars.

3. People do not move in slow-mo in zero gravity

It’s hard to say whether it’s due to some misguided acting or a poor understanding of physics, but astronauts are often depicted moving in slow-motion when they’re in zero gravity. It’s probably because anytime you see a video of real astronauts in space, they’re just floating slowly around the cockpit. What people don’t always seem to notice though is that the rest of their body is still moving normally, and not as if they were underwater.

2. Space exposure is almost instantly fatal

There doesn’t seem to be a single movie out there that accurately depicts what happens to a human body that is exposed directly to the vacuum of space. They either show a person simply suffocating, freezing, or even exploding from the lack of pressure. Unfortunately, the truth is much worse than any of those scenarios. Thanks to Henry’s Law the drastic change in pressure would cause all the liquid in your body to evaporate at once, from your saliva to your blood to your urine. Because of this, your body expands to about twice its size, while you slip into unconsciousness (don’t worry, the whole process takes about fifteen seconds). Within a few minutes all the liquids and vapors remaining in your body will be sucked out into the void, leaving a dried husk of a corpse behind. And no, not all of this is speculation, as a couple of astronauts have actually come close to going through this whole ordeal and were quickly rescued.

1. Not all planets have the exact same gravity as Earth

In every movie where humans travel to different worlds, they might find a different climate or atmosphere, but they almost always encounter gravity similar to Earth’s. This works for a story that revolves around humans exploring a new planet, but the odds of them landing on a planet with tolerable gravity are slim. Even in our own solar system there are planets with enough gravity to crush a person along with planets that would barely hold a person down.