Why doesn’t the atmosphere (air we breathe) just float off into space?
Some objects in space have atmospheres like Earth and Jupiter. Others like asteroids and the moon don’t have an atmosphere.
Why doesn’t earth atmosphere just drift away into space?
What am I missing about the concept of atmosphere?
In: Planetary Science
Gravity.
No, really, even though it seems like air is massless, it isn’t. In fact, in relatively small volumes it is more massive than you are expecting it to be. We are just used to 1 G of atmospheric pressure so it seems like nothing to us.
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The same reason you don’t float off into space. Gravity is holding it down.
Most of the things that don’t have an atmosphere are smaller, and therefore exert lower gravity than the Earth. There are some other factors as well – like a magnetosphere providing “shielding” against solar wind – but gravity is by far the most important one.
Quite possibly that atmospheres are made up of particles that have mass, and thus are subject to the gravity of the planets they cover?
Gravity. Air has weight.
Molecules of atmosphere need the same velocity anything else would to escape a gravity well. For Earth this is about 11km/s. It’s rare for Nitrogen or Oxygen to be moving that fast at the temperatures you see in the upper atmosphere, so it just falls back down.
Lighter gases have higher velocity at the same temperature,(higher velocity at the same kinetic energy), so it’s easier for those to reach escape velocity. Gas giants have much higher gravity, so they can hold on to things like Helium and elemental Hydrogen.
Air is affected by gravity, so bigger objects with more gravity tend to have atmospheres, while smaller ones do indeed tend to lose any.
It’s not quite black and white, though. Our Moon, for example, does have a tiny bit of ‘atmosphere’ but it’s just so thin that everyone says there isn’t one. I don’t think there’s an agreed on definition of how thick an atmosphere needs to be before you call it one
What makes you think it doesn’t?
Gravity is a weak force, strong enough to hold on to some gas particles, see our atmosphere. Many more escape our pull and slowly drift away day by day.
Google magnetosphere.
Long short, our molten core generates a charge that keeps our atmosphere even safer.
Gravity though they are gases they still have mass and are pulled in toward the centre of the Earth. The other element is the Earth has a liquid metal core which creates a magnetic field around the Earth which stops the Solar wind from ripping the atmosphere away. https://youtu.be/HUm3aN6X04s
Gravity holds our atmosphere in place. Gases, like anything else, have mass and are affected by gravity. The lighter gases, like H and He, do indeed drift off.
This does happen for some of the lighter gases. Even though the Universe is 75% hydrogen, we don’t have any substantial amount in our atmosphere. Why could that be? It turns out that you can do rough relation between the velocity of a particle and its temperature. At Earth temperatures, light elements like hydrogen move faster than Earth’s escape velocity (how fast you have to go to overcome gravity and leave the Earth) for no other reason than their temperature. So we lose them. However, this like nitrogen, O2, whatever, do not exceed the escape velocity with their thermal speed, so they stick around due to gravity.
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