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Days and Nights
The planets spin as they orbit the Sun. A day is the time taken for a planet to make
one complete turn on its axis. Different planets take different amounts of time to do
this. An Earth day is 24 hours - it takes the Earth 24 hours to make one complete turn
on its axis.
It is daytime for us when our part of the planet is facing the Sun, and it is night-time
for us when our part of the planet is facing away from the Sun.
One way to remember which way the Earth turns is to remember "WE spin", which
means the Earth spins from west to east.
During the day, the Sun appears to move through the sky. Remember that this
happens because the Earth is spinning on its axis. If we look south and plot the Sun in
the sky during the day, we find that it appears to move like this:
Sun in the sky
The Sun appears to move from east to west. It 'rises' in the east and 'sets' in the
west. At midday we face south to see it.
During the night, we cannot see the Sun. But the Earth is still spinning on its axis.
This means that the stars appear to move from east to west in the sky, just as the
Sun does in the day.
Star trails made by leaving the camera shutter open during the night