The Sky

Astronomers call the sky, as seen from Earth, the "celestial sphere." It can be imagined as an enormas hollow ball with Earth at the centre, and with stars on the inside surface. As the Earth rotate, the stars seem to parade by.

Exactly what section of sky people can see depends partly upon his location. The sky seen from the North  Pole is completely different from the south Pole. Between the poles there is an overlapping. People looking south from New York sees a portion of the Northern part of the sky that is from Rio De Janiero.People from Rio De janiero can only see the southern part of sky area that is seen from New York.Theoretically, a person at the equator cansee the whole sky, but he can see only half of it at once.

At night the sky appears to pass steadily overhead, east to west. This seeming motion is due to Earth's rotation. From the North Pole, the sky appears to turn like an enormous wheel counterclockwise, with its hub directly overhead at the so-called North Star. From the South Pole the sky appears as a wheel turning clockwise.