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Solar and sidereal days

The following diagrams explain the difference between a solar day (based on the Sun) and a sidereal day (based on the stars).

The stars rise 3m 56s earlier each night compared with solar time. This is due to the motion of the Earth in its orbit round the Sun.

Solar day. The Earth makes one rotation compared with the Sun. 3 minutes 56 seconds longer than a sidereal day.

Sidereal day. The Earth makes one rotation compared with the distant stars. 3 minutes 56 seconds shorter than a solar day

schoolphysics solar and sidereal time animation

To see an animation of the motion of solar and sidereal time click on the animation link.
 
 
 
© Keith Gibbs 2013