The Earth spins around from west to east. If you were hovering above the north pole, you would see the Earth turn beneath you in a counterclockwise direction, whereas, if you were above the south pole, it would be seen to spin in a clockwise fashion. An observer on the rotating Earth is rather like an observer on a roundabout. Looking outward from a spinning roundabout it appears as if the rest of the world is spinning around you; you know that it is not, but that is the way it looks and feels. Likewise, to an observer on the rotating Earth, it seems as if the Sun, Moon, stars, and planets are revolving round our planet from east to west. The ancient Greek astronomers believed that the stars were fixed to a huge sphere that rotated round the Earth once a day. Although we now know that the stars are all remote suns lying at vast and very different distances from us, when we try to describe their positions and apparent motions, it is convenient to imagine that they are indeed attached to the inside of a sphere – the celestial sphere – that rotates around our planet.

CELESTIAL POLES AND EQUATOR

By analogy with the Earth, we can define the equator and poles of the celestial sphere. The Earth's axis – extended into space – meets the imaginary sphere at two points, the north and south celestial poles.