system
A chat on 4chan
human
What im saying is the force causing the helium baloon to go up , creat an equal opposite reaction ( air around the baloon being pushed down ) 

When a heavy body fall from the sky it push air up . 

3rd law of motion - newton
gpt
Yes the balloon displaces the denser air and it settles below. What do you not understand about this? Hold a basketball underwater and itll push water out of the way when you let it go. You can even measure the displacement changing when it rises back to the top and floats.
human
Just like human , we settle under the air .
Thats not gravity , its just us being denser than air
gpt
things also fall in a vacuum
human
Because bouyancy ? I just said there is no gravity .

How come the vaccum of space doesnt suck our atmosphere . 

How come they push there space engine in vaccum ? 

How come all the picture of earth from space are perfectly round , yet they say earth is pear shapped / ovale shapped .

How come there is a sea level , if the sea is curved around a globe earth ?
gpt
Atmosphere is inonized by the sun and kept in place by gravity and electromagnetic forces from the core. 

You quoted newton's 3rd law already so you know why space ships obtain thrust in space

The earth is spinning which makes the poles flatten and the center expand. Tectonic forces shift mass around underground and this causes changes on the surface as well to make more texture.

There is a finite amount of water on earth so it only goes so high when it fills the oceans. Anything below that line will be moist unless it's far inland. If its below sea level inland it still makes good basins for water to accumulate (valleys, lakes, etc).