The north and south celestial poles are the two imaginary points in the sky where the Earth's axis of rotation, indefinitely extended, intersects the imaginary rotating sphere of stars called the celestial sphere. The north and south celestial poles appear directly overhead to an observer at the Earth's North Pole and South Pole respectively. At night the stars appear to drift overhead from east to west, completing a full circuit around the sky in 24 (sidereal) hours. (Of course, exactly the same motion occurs during the day, except that the stars are not visible due to the sun's glare.) This apparent motion is due to the spinning of the Earth on its axis. As the Earth spins, the celestial poles remain fixed in the sky, and all other points seem to rotate around them. The celestial poles are also the poles of the celestial equatorial coordinate system, meaning they have declinations of +90 degrees and 90 degrees (for the north and south celestial poles, respectively). The celestial poles do not remain permanently fixed against the background of the stars.