Question

Why don't we directly perceive the motion of the earth directly

Answer 1

Earth is moving at a fixed rate, and we all are  moving along with earth and that’s why we don’t feel Earth’s spin. if  the earth slow down or change it's speed we will feel.
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Answer 2

i think that due to the presence of gravity we don't feel the movement of earth and also since we are also moving with the earth in a constant speed we don't feel that we are moving. like for example you are sitting in a bus with uniform motion when you look out of the window you don't feel that you are moving you feel that the trees and all the other things are moving this is what happens with us when we see the night sky . we don't even feel that we are moving we .

i hope my explanation helped u .................