hoiw does the atmosphere around the earth (or any other planet) stay put?

Question

like think about it, its a load of gas right next to a complete vaccum, why doesnt the whole earth depressurise? i dont buy gravity holding it there because the pressure differential between atmosphere and vaccum is huge. (hence space shuttles getting in a bit of a mess if a hole suddenly appears in the hull)

Answer 1

You may buy it. It's gravity.

First, gas has mass. More mass than you probably think. And the only reason pressure exists (or air ressure at least) is becuase of the gravity pulling air. Vacuum has no pressure because there's no air.

Answer 2

gravity is the answer, one thing to remember is that the higher you get the lower pressure gets. if the pressure we have here at the surface of the earth was put right next to a vaccume it absomutely would depressurize. but our atmosphere is touching a slightly lower pressured atmosphere which is touching a slightly lower pressure atmosphere and so on. it slowly disapates intill there is a vaccume.
immagine a free particle in space, gravity will draw it to the nearest body of mass. as it mooves in tward the body (lets say earth) it will experience a gradually increasing frictional force from the atmosphere apposed to the gravitational force. at some point these two forces will be even and the particle will be in equallibrium, and wont want to move.
i get what you're trying to say with the spaceship example but there are two major differences. first off the gravitational force of a space ship is nothing compared to the earth, and second a hole in the ship would create atmospheric pressure in direct contact with a vaccume, different the the gradual pressure differention on earth. also the air would still stay around the ship, but because the gravity isn't strong enough it would be too thin to breath.

Answer 3

Humm... I'm trying to think of a way to convince you that it is gravity but I can understand why your pressure argument is confusing you.

It seems very natural that this big pressure next to a vacuum would just expand into the vacuum. It's even a law of nature that that pressure and volume are inversely related.

The fact is there are two different forces working against each other and when it balances out you end up with the atmosphere we have. If you just had gravity it would pull every ting to the earth, and if you just had the pressure and volume balance all the air molecules would spread out equally.

Remember the density and pressure of air is greatest at the surface and gets smaller and smaller as you go away from the surface, that is as you get farther away from earth's gravitational pull and the molecule spread out.

It's simply a balancing act between the different forces acting on the air particles. I don't know if I answered your question but, I hope it helps.

Answer 4

Firstly: Gravity works I'll sell it to you (for your life), try a 100ft drop. I'll be there at the bottom waiting, if you complain I'll refund you so you keep the purchase cost!

Secondly: What atmosphere vaccum differential (nice word)? The fact is that the atmosphere has a logarithmic differential gradient. Ever heard the expresion its "It must be hard to breath for you, (the air) being so thin up there!"

Thirdly: we are loosing gas, hydrogen as its small atom with high kinetic energy at the cold temperatures in the outer atmosphere escapes the gravitational force of the earth.

Fourth of all: as some one said the earth is spinning, but this actualy gives an outward force as objects always try to maintain their tangental verlocity (verlocity has speed and direction). Gravity again holds it back.

Oh, so you didn't fancy going splat!

Answer 5

gravity is a force. Objects that have mass will exert a gravitational force on other objects. The mass of the earth exerts a very strong gravitational force on the atmosphere keeping it in place. Think on Jupiter and Saturn, the gas giants. These are composed of the lightest elements blown into space when the sun was born, they have formed a planet with immense mass, and being further from the sun are not at as much risk of losing their atmospheres, although they too have magnetic fields. The earths magnetic field protects the atmosphere from being blown away by the solar winds.

Answer 6

At the termination of our atmosphere there is not a 15 lbs presuure differential. The higher your altitude, the lower the pressure gets. It's an even descending gradient until you get to 0... the complete vaccum.

The answer is gravity.

Also, the Earth's Magnetic Field protects the atmosphere from the solar winds.

Answer 7

Well what the hell you asking the question for if you won't accept the correct answer? You think you're right and the rest of science is all wrong, huh? Try writing a paper about all the proofs you have that gravity doesn't hold a planet's atmosphere in place and see how accepted it will be.

Answer 8

Atmosphere is a mass--it's just not solid.

Gravity acts on all masses.

Gravity keeps it here--although how it developed is more complicated, and a planet can lose its atmosphere--or, at least, certain aspects of it.

Think of the vacuum of space as competing with gravity for the air molecules--the atmosphere is the extent to which gravity wins out.

Answer 9

Er, actually its called gravity.
To escape this stuff called gravity each gas atom/molecule would have to travel straight up into space at a speed of about 7 miles per second (I think ... check that bit out). Its called "escape velocity".
All the ones that can, have. And so only the slower ones are left, and they keep falling back to earth (sort of).
PS I am only 11.

Answer 10

The pressure differential at max is one atmosphere, i.e. 760 mm of Mercury. Thus gravity does hold the Earth's atmosphere to itself. But it doesn't really stay put - it swirls and whirls around. Thus you get winds, storms, hurricanes, cyclones etc. Also jet stream.