earth is a kind of celestial object & a star is a kind of celestial object / celestial body & apparent motion is when an object appears to move relative to another object 's position ->  apparent motion of stars is when stars appear to move relative to earth's position  apparent motion of stars is when stars appear to move relative to earth's position & the earth rotating on its axis causes stars to appear to move across the sky at night ->  the earth rotating on its axis causes apparent motion of stars  the earth rotating on its axis causes apparent motion of stars & stars appear to move relative to the horizon during the night -> the earth rotating on its axis causes stars to move relative to the horizon during the night