Why doesn't Earth's atmosphere get sucked away into space?

There’s sort of a part two to this as well.

The Earth’s magnetic field prevents the atmosphere from being blown off into space by solar winds.

Yeah, the big misconception is imagining that vacuums suck. Actually, it is the atmosphere that blows. If you were in the space shuttle and opened the door, you wouldn’t be sucked out by the vacuum…you’d be blown out by the air the space shuttle deciding to leave the shuttle.

Or…remember Alien Ressurection? In one scene someone gets sucked into space through a tiny hole in the hull of a spaceship and turned into spaghetti. Completely impossible. The force to push you out the hole would come only from the air inside the ship. There’s a bit of energy potential there, but how much? How much pressure is the air inside the ship exerting on the hull of the ship? One atmosphere, likely. Can one atmoshere of pressure pull you into spaghetti? No, you’d need vastly greater pressure. That’s why your eyes can’t get sucked out of their sockets by a vacuum…there would have to be air behind your eyes blowing your eyes out that’s only counterbalanced by 1 atmosphere of pressure pushing your eyes in. There might be small amounts of air behind your eyeballs, but very very little, and once that air escaped into the vacuum there’d be nothing left to push your eyeballs out.

So, there is a certain atmospheric pressure on earth caused by the earth’s gravity pulling all that air in. The atmosphere wants to blow away into space, but gravity won’t let it. The amount of atmospheric pressure is determined by the weight of the column of air above a certain spot. If there were more air on earth but the same gravity, we’d have higher atmospheric pressure, like on Venus, with less air we’d get the opposite. If gravity were lower, atmospheric pressure would be lower, and if gravity were higher pressure would be higher. The total amount of atmosphere is determined by how much gasses are generated over time balanced by how much atmosphere manages to reach escape velocity over time. Oxygen and Nitrogen molecules in the air on average are moving much slower than escape velocity. However, some are moving slower than average, some are moving faster. A few are moving much slower, a few much faster. A very very very few are moving at escape velocity. Since the rate of loss of atmosphere is constant, and the rate of production of atmosphere is roughly constant, the earth’s air pressure has reached an equilibrium. Venus is in equilibrium too, but has much higher air pressure, Mars is in equilibrium but has much lower air pressure.

Yes, they do. A vacuum cleaner equipped with a centrifugal fan will easily maintain a pressure differential of 100cm H[sub]2[/sub]O between the input and output ends. ShopVacs typically use this type of blade, while many uprights use a less efficient straight impeller design, but they all work by creating a vacuum.

Would the air be sucked out if you would install a theoretical vacuum resistant tube / hose with one end near the earths surface and the other end in deep space away from any atmosphere so full vacuum? This would create a differential pressure of 1 bar causing the air to flow through the tube into space? And since all the air from the top will be sucked out no air column would prevent the air from flowing towards space.

Friction losses should be possible to reduce by increasing tube diameter.

Also with regard to the vacuum cleaner. The goal of the vacuum cleaner is to maintain a vacuum for a certain loss rate. If the flow would stop the vacuum cleaner would reach a lower absolute pressure limited by how much resistance the fan will be able to overcome!

This is a zombie thread, but no, that wouldn’t work.
Think about it - what’s magical about a tube? The upper part of the atmosphere is already touching a vacuum…

In answer to the first part (and please note this thread hasn’t been posted to in 7 years, and some of those who did post to it have been banned, while others may not be posting any longer for reasons of their own), no. You can see this on a smaller scale using a vacuum tube filled with a denser fluid than air - a mercury barometer. There’s a very good vacuum above the mercury, not an absolute one but close enough for present purposes such that the pressure differential is one bar to within a small rounding error, and it won’t support a mercury column of infinite height but only one of about 30" depending on local atmospheric pressure. That models what you’d get with your vacuum-proof tube into deep space - when the weight of the air in the column matches the push of the atmospheric pressure from below, you have equilibrium, and no irresistible force sucking your atmosphere into space. :slight_smile:

Vacuum sucks.
But gravity (on Earth at least) sucks even more.
YMMV (like, if you’re on Mars or the moon).

Ha! I knew that the tube-to-space question had been asked relatively recently.

During my freshman orientation at UVM, a LONG time ago, I attended “Uncle Donny’s Traveling Magic Show”, an entertaining lecture hosted by Dr. Donald Gregg, retired professor (emeritus) of chemistry.

At one point, he had a long-necked flask filled with ammonia gas, sealed at one end. He put the end in a tank of water and removed the stopper. The gas instantly dissolved into the water, and the water fountained up into the flask. He had added phenolphthalein to the water, so also turned pink as it rushed up the neck of the bottle.

He then said, “Now all of you are thinking that the water was just sucked up into the flask. That is WRONG. I know some people say UVM sucks, but this is not an example of that! What actually just happened is that after the gas dissolved into the water, the water was PUSHED into the now-empty space by the weight of the air surrounding it.”

Made the point very effectively, and I have never forgotten it.

Interesting zombie. I too had the misconception that vacuum somehow sucked.

Nature abhors a vacuum, but not Zombies.

BTW, Mars did lose its atmosphere long ago. But then, Maris has only 1/10 the mass of Earth, and so proportionately less gravitational pull.

“why is the hatrack moving?”

“That’s not a hatrack, that’s Maris!”

And as said above it also lacks a magnetic field, which makes things worse since the solar wind strips away much of what atmosphere its gravity lets it hold on to.

Hi, what I think is happening is that the cold and coagulated gases at the top of our atmosphere is the one being pulled so hard to keep the whole atmosphere in place. But the mystery is that the magnitude of low pressure or vacuum in space is so great, the gravity should not be able to hold it up. Let use an analogy (it’s the best thing to explain),: so let look at a jar made of a thin glass material; the region in it is kept at absolute Zero pressure or vacuum. If this jar is placed in space, nothing happens, but if placed in within earth’s atmosphere, the jar burst inward due to the difference in pressure OR if the same jar is filled tightly with a gas, in space it burst-outward. So if the jar is our coagulated-gas at the top of our atmosphere and the internal region of the jar is our much more lower-gaseous region of our atmosphere. The stronger the jar, the harder it is to burst. So it could be possible that it’s our gravity which is keeping our atmosphere in place but the void out there is stronger and beyond the critical-threshold of this gravitational pull-strenght.

Unlike this ramble, the previous, decade-old, answers in this thread explain the OP’s question adequately.

As it slowly approaches a vacuum the atmosphere “closest to empty space” is hotter and less dense than that down here, making your “cold coagulated-gas” explanation terribly, terribly wrong.

Since the OP was answered 10 years ago, let’s close this Zombie.

samclem, moderator