if air is the lightest thing on earth why it won't escape from the earth's gravitational pull?

Answer 1

It does. Well, some of it. But admittedly most of it just sits there. Think of it this way:

The atmosphere is like a bunch of marbles in a bucket. If you just leave the marbles and the bucket alone, not much is going to change. And as long as the bucket isn't too full, you can even kick it around a bit and not loose your marbles (so to speak). Not even if you have really, really, light ones in there (say... ping-pong balls).

That's how we do lose the bits that we do. After all, there are other 'buckets' around - objects like the moon, asteroids, and comets which might attract some of the gases. And the solar wind is constantly exerting a pressure on our upper atmosphere and probably blowing some of it away. It would be hard to draw the line where Earth's really light gases like hydrogen and helium end and the interplanetary gases begin... in a real sense there is no difference between them; they're constantly mixing back and forth.

Hope that helps!

Answer 2

Air is not the lightest thing on Earth - hydrogen is.

This being said, yes air is light. Not that light, though. At sea level, the atmosphere weighs 14.7 pounds on each square inch! That's about the weight of two gallons of water, on each square inch.

Now anything on Earth is submitted to the gravitational pull of it, and this is true of everything, light or not. At sea level, to escape the Earth's gravity for ever, you need to reach a speed of over 26'000 mph. Fat chance that any air at sea level will ever reach that.

Now of course, as you go to higher altitudes, the air pressure dimishes. And the escape velocity also decreases a bit. Though to be fair, you are outside the atmosphere long before the escape velocity has diminished much.

Anyway, at higher altitudes, because of statistical fluctuations in the speed of the atoms of gases that make up the air (Nitrogen mostly, followed by Oxygen), some of them will have enough energy to escape, not for ever but for a bit.

But given the density of the Earth atmosphere, and its strong gravitational field, this is not enough to deplete the atmosphere.

But on a planet that is smaller, and/or has a thinner atmosphere, and/or has a hotter atmosphere (higher speed of atoms in it), the chances become much higher that atoms can escape. And that planet can lose most if not all of its atmosphere.

This is pretty much what happened to Mars (its atmospheric pressure is very small). Or to mercury.

Hope this helps

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Answer 3

Air isn't the lightest thing on earth. If it were helium balloons wouldn't float.

And yet gravity while one of the weakest natural forces ( raise your hand...There you broke the force of gravity) does have a universal effect on all matter. And since Hydrogen (the lightest gas on earth) still has mass and takes up space gravity still reacts to it. Now since the solar wind is the only agitator in our great big solar system, and since the Earth is lucky enough to be far enough away to still have an atmosphere, that atmosphere tends to stay put.

Answer 4

air isn't the lightest thing. there is: 1. hydrogen, 2. helium, 3.oxygen (in that order). Air is made up of all of these and some other molecules. All of these elements have enough mass, however, so that they can't escape the massive force that we call "earth."

Answer 5

A full discussion of this would get us into statistical mechanics, but the short answer is that (almost all) of the molecules of the earth's upper atmosphere are not moving fast enough to escape the earth's gravitational pull. If they were much hotter, they would move faster, and more would escape.

Answer 6

It might be the lightest (or at least close to the lightest) but it still has enough mass that the earth's gravity keeps it near the earth.

Answer 7

Air is not the lightest thing. Hydrogen is, and it is still held in our atmosphere because of gravity. It isn't so light that gravity doesn't have effects on it. I have experience in ballooning and there are 3 ways to fill a balloon and ride with the clouds. One is hydrogen, like the Hindenburg, and risk blowing up and burning. Helium is next in lightness, or in lifting power, will not blow up or burn, but is too expensive. What the rest of us use in ballooning is hot air. Air that is heated enough will lift a balloon. It uses propane gas in its burners to heat the air as needed. That is enough for flight lesson number one.

Answer 8

Air is not the lightest thing and what happens when you put helium in a ballon and let it go???

Answer 9

Hi. Almost all of the hydrogen and helium HAVE escaped. It takes less energy to get them to escape velocity.

Answer 10

still air has mass and it need escape velocity to escape from gravity.