Space, Pressure, and airlocks?

Question

Ok, we've all seen aliens when the queen is sent out the airlock to her death. If an airlock is opened in space, what would happen? Would all the air rush out and why?

Why doesn't the same force cause our atmosphere to do the same?

Answer 1

There is nothing outside the airlock, but there is air inside. When the door opens the air tries to spread out so that there is an equal amount throughout the volume that it is contained in (aka... space). When this happens all the air rushes out of the airlock with explosive force. This wouldn't be like it was in the movies. When an airlock is opened the air would be sucked out so fast that it would take only a second or two for it to be gone because the centrifugal force pushing the water toward the bottom of the bucket is greater than the gravity trying to pull the water out of the bucket.

The reason this doesn't happen on Earth is because the force of gravity is stronger that the atmosphere's urge to spread itself out throughout the universe. It's like when you fill a bucket with water and then spin it in a circle. The water stays in the bucket even when it is upside down.

Answer 2

The air rushes out because the molecules have random velocities. This means that if there is no surface to reverse their velocity, they will continue to move in their initial direction. If you open one side of a container to vacuum, the molecules that would have hit that side (and therefor exerted a pressure on it) will hit nothing and simply continue to move in the direction of the vacuum. In the end there won't be any molecules left in the container.

Our atmosphere is being held back by gravitation. Molecules which do not have escape velocity will simply rise above the surface and slow down. Once they reach their max. height of their trajectory, they will began to fall back until they hit other molecules in the lower, denser atmosphere. Because very few molecules ever reach escape velocity (see velocity distribution as a function of temperature), the atmosphere will be contained for a long time. But not forever. Eventually, if the Earth lived long enough, the atmosphere would disappear.

There is no reason why the alien queen has to die outside of an airlock, by the way. Vacuum is not as deadly an environment as most people believe. We have done experiments with lichen, bacteria etc. and many lower organism which do not need to breath survive just fine. If the alien does not breath oxygen but has an independent way to generate her energy biochemically, she could live easily in space, especially if she has a hard skin like those of some reptiles or if her body is based on an exoskeleton.

And if I remember correctly, Ripley had to blast her with the engines, anyway.

Answer 3

aliens... sheesh... okay, at least we are talking Hollywood.

as i doubt we are talking Toyotas here... you mean, if you opened the airlock in the ISS? definitely a problem, but there are a number of chambers to the space station, so likely not a fatal one.

Hollywood. Remember, when you write something, no matter how stupid it is, that is what happens. As a writer, your job is to convince the audience that, yes, a victorian-age man CAN somehow make a time machine... or ... yes, you COULD get dinosaur DNA from amber and create Jurassic Park.

Then you close the book, or leave the theater and HOPEFULLY get back in touch with reality.

Well, some of us, anyway.

Answer 4

Actually, some of the atmosphere is lost every second to space, but in very small amounts.
Gravity keeps the rest bound to earth.
But if you are in space, vacuum, then when you open an air lock, then the pressure wants equalize to the new area, container. That is the rest of space. The same thing happens in an airplane, if you pop a hole in one of the windows, while the plane is high up then you get the same energetic equalization of pressure.

Answer 5

In the case of the airlock, it is differential pressure that causes the air to move from where it *is* to where it isn't.

In the case of the earth's atmosphere, the force of gravity is more than sufficient to keep it close to earth.

.

Answer 6

Air moves becasue of pressure. Space is a near vacuum so if there is pressure inside the craft then opening the door will release the pressure 9ie out into the vacuum).

Like everything else, gravity holds our atmosphere in place. Even gas has to conform and can only escape IF is it's molecules/atoms/ions are capable of exceeding the earth escape velocity (I believe Hydrogen and Helium are the only gases capable of exceeding escape velocity naturally if they were heated)

Answer 7

The air rushes out because there's high pressure inside the spacecraft, and zero pressure outside.

This doesn't happen on the Earth because Earth's gravity is strong enough to counteract the pressure gradient. If you somehow deactivated Earth's gravity all at once, the atmosphere would explode off the surface of the planet.

Answer 8

yes because i want it to