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  Day and Night
  Planets spin. The spinning causes one part of a planet to face toward the Sun for a while. This is day. Soon that same part turns away from the Sun. This is night.
  Look at the picture of the spinning
top. You see how it tilts. A top
spins around an imaginary center
line called an axis. Earth also
spins, or rotates, on an axis. One
whole spin of an object on its axis
is called a rotation. The Earth
completes one rotation, or one
day, in about 24 hours.
  The diagram shows the Earth’s tilt  
 
  and spin. The northern end of Earth’s axis is called the North Pole. The southern end is the
South Pole. During its orbit around the sun,
Earth’s axis always points in the same direction
in space. Where is Earth’s axis in the diagram?
  Locate the North and South Poles. Which pole
is tilted toward the Sun? How can you tell?
   
 
  As Earth spins, the
Sun, Moon, stars, and
planets only seem to
rise in the east and set
in the west. When you
see a sunset, remember
that it is you who are
moving. You are riding
on the spinning Earth.