why does the earth have an atmosphere and why isn't it escaping towards space?

Question

im not asking for its composition and its uses. please stick to the question.

pardon me if i don't think that gravity holds our atmosphere down. it is because that i've noticed in the movies that when space ships had an opening, everything gets sucked outside towards space, despite the fact that they have artificial gravity there.

another thing, if i went to the moon(where there is also gravity) , and i released some air that i brought, will it stick to the moon floor because of the moon's gravity?

Answer 1

Atmosphere is the general name for a layer of gases that may surround a material body of sufficient mass. The gases are attracted by the gravity of the body, and held fast if gravity is sufficient and the atmosphere's temperature is low. Some planets consist mainly of various gases, and thus have very deep atmospheres

Surface gravity, the force that holds down an atmosphere, differs significantly among the planets. For example, the large gravitational force of the giant planet Jupiter is able to retain light gases such as hydrogen and helium that escape from lower gravity objects.

Answer 2

The concept of escape velocity applies here. We can talk about pressure and temperature when many molecules are colliding. At the top of our atmosphere the molecules have a velocity and do not collide so often. Once in a while an air molecule will achieve escape velocity and leave the earth.

Some of the gas that escapes a space ship will head toward the earth and join our atmosphere.
There is in reality(sorry movies) no artificial gravity. If a container spins its contents will be thrown to the sides. Like an amusement park ride.
Spinning cannot contain a gas. Only real gravity can.

Answer 3

It all has to do with temperature and gravity. Some chemicals such as hydrogen and helium have the particles moving past the escape velocity at earth temperatures. This means that our atmosphere can't retain there elements and they float off into space. Where nitrogen and oxygen (the primary components of our atmosphere) don't move as fast and can be held onto by the gravity of the earth.

Answer 4

There are two issues here. Let's deal with the atmospheric loss first. Yes, the earth does lose atmosphere at the top. Over the last few billion years there has been oxygen loss. Here is a reference for you to read:

http://thayer.dartmouth.edu/spacescience/wl/misc/Outflow/Seki%2001.pdf

When the atmosphere was young, and dominated by carbon compounds like methane, there was significant hydrogen loss; it is lost now but at a much lower rate:

http://thayer.dartmouth.edu/spacescience/wl/misc/Outflow/Seki%2001.pdf

The primary component of the atmosphere is nitrogen. Estimating iits loss is tricky, very tricky. It moves into and out of the mantle, but here is a resource on its loss:

http://geosci.uchicago.edu/~dauphas/RefereedArticles/dauphas_marty_EPSL04.pdf

Finally, overall the atmosphere maybe be growing and not shrinking do to out-gassing from the earth's crust:

http://www.huxley.ic.ac.uk/Local/EarthSciUG/ESFirstYr/EarthMaterials/mrpalmer/EarthMaterials/earth/earth1/l1.html

The other issue is your not believing that gravity dominates the dynamics of the atmosphere. I don't know what to say there, except that a little research leads one to concluded that the average escape velocity for molecules in the atmosphere is very, very much less than the 7 miles/sec needed to escape the earth.

HTH

Charles

Answer 5

In the same way a rock falls, a molecule or atom of gas falls too, towards the centre of mass of the planet. Small amounts are constantly escaping into space, but the escape velocity (or speed) of Earth is around 25,000 mph, so the heavier molecules, when they collide, high in the atmosphere, rarely attain that speed. Lighter molecules and atoms, like hydrogen & helium, can reach that speed much more easily, so we now have very little left. You are wrong about the rest, but the explanation is long, so study physics and ask your teacher.

Answer 6

Like everyone else said Gravity. But also think, the space has none and also nothing moves there because of lack of gravity and oxygen (no life form found until now), its all mostly carbon dioxide!

Answer 7

Gravity is holding it down

Answer 8

"pardon me if i don't think that gravity holds our atmosphere down."

You're wrong. The Earths gravity is what retains the atmosphere.

Answer 9

we have an atmosphere so that we are all capable to live basically. gravity is what keeps it in place. theres really no other way of answering that!

Answer 10

the atmosphere stays where it is because of gravity... not sure about the first q