Why does it seem to us as if rocks remain the same and don't change

Most rocks that we encounter in our normal everyday lives are sedimentary rocks.  Sedimentary rocks are rocks that have been worn down gradually over long periods of time.  Because it takes very long periods of time (couple decades) for these rocks to change, it often seems as if they don't change at all, when in reality the change is too small for us to realize it!

Variables,control,conclusion and finally scientific theory