Atmosphere is made up of gases that we
collectively call “air”. These are gaseous
molecules that are very loosely bound to anything
or even with each other. Since nothing is pulling
or pushing them, they are free to move. But, of
course there is gravity acting on each of them
pulling them towards earth. Why don’t all of
them get pulled down, crush us and form a layer
near the ground? The reason is that, each
particle has thermal energy (heat) that keeps them
moving in random directions, up or down, left or
right, and forward or backward. These thermal
forces that make them float are stronger than the
effect of gravity.
So, instead of being pulled in one direction
alone by gravity, they float. So all of the
“weight” of our thin atmosphere does not act on us
(thankfully), preventing the collapse of frail
beings likes us.
Here is another way to think about it: if the
weight of the atmosphere did have an effect, we or
a significantly different being would have evolved
to accommodate this (maybe crawling) if life was
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