# Why does the air we breath float on Earth?

1. Mar 20, 2014

Why does air on Earth float? Obviously, lighter gases such as Helium and even hot air will float due to having a lowed density than the air around it. Why is it though that the base higher density gases that we breath float rather than sink to the ground? My belief is that gravity is simply too weak to hold the O2 and the other gases completely to the ground.

2. Mar 20, 2014

Air does sink to the ground. Put your head near the ground and breathe in - it still works down there!

Think of a swimming pool. Down at the bottom there's some water, and at the top there's water too. The water at the top of the pool isn't "floating", there's just not enough room for it all to be at the bottom.

On Earth, we're swimming around in a bunch of gases. Some gas at ground level, some is up higher, all in one giant pile. There isn't enough room for it all to be exactly 0 cm from the ground, so it piles up.

Last edited: Mar 20, 2014
3. Mar 20, 2014

### CWatters

Perhaps the question the OP is asking is...

Why doesn't the atmosphere separate out into layers of Oxygen, Nitrogen etc.

4. Mar 20, 2014

Staff Emeritus
Let's let the OP explain what he means rather than start another long thread guessing.

5. Mar 21, 2014

### FactChecker

6. Mar 21, 2014

Staff Emeritus
Please, let's let the OP explain what he means rather than start another long thread guessing.

7. Jan 18, 2015

### Chavers

Air doesn't all sink to the ground for the same reason you don't. Gravity on earth isn't strong enough to compact it that much. The layer of atmosphere we live in is made up of gasses that weigh more than those in higer layers. If earth's gravity was that strong the earth would be a star instead of a planet.

8. Jan 18, 2015

### Staff: Mentor

This thread is 9 months old and the OP never returned to it. Locked.