Why is it that we can"t feel how fast the Earth is moving? We are moving like 100,000 mph. And why do we not fall off going that fast
Because the rotation of the earth is very smooth and doesn't change, the centripetal acceleration we feel is very nearly constant. This means that the (small) centrifugal force from the rotation gets added to gravity to make up the "background force" we don't notice.


Taken from Physics SE.