This movie shows how the stars move with time.
The North Pole is at the center of the circle.
Polaris, the North Star, is close to the North Pole.
Polaris is part of the constellation Ursa Minor.
Another name for Ursa Minor is the Little Dipper.
The handle of the Little Dipper ends at Polaris.
Time is advancing by one hour for each frame.
Notice how the Little Dipper rotates counter-clockwise.
Let's think of the Little Dipper as the hour hand
of a gigantic clock in the sky.
This hour hand circles the clock in about 24 hours.
But the hour hand is going backwards with time.
The stars seem to rotate around the North Pole
because the Earth is rotating around its axis.
Actually, the stars stay in nearly the same place,
but our observing platform is moving with time.
In 24 hours, the Earth completes one rotation.
This accounts for our cycle of nights and days.
During daytime, our position on Earth faces the Sun
and at night, our position points away from the Sun.
The celestial clock doesn't quite match normal clocks.
The Earth rotates in 23 hours, 56 minutes, and 4
seconds (one Sidereal day), relative to the stars.
Astronomers use Sidereal time to track star positions.
After 24 hours, the hour hand completes one cycle. 
Now, time is advancing by one month per frame.
Again, the Little Dipper rotates counter-clockwise.
The hour hand circles the clock in about 12 months.
The hour hand still circles the clock every 24 hours,
but its starting point is changing slightly each day.
The starting point changes because the Earth revolves
around the Sun in about 12 months, or one year.
This accounts for our yearly cycle of seasons.
A Solar day is the length of time for the Sun to appear
at its highest point (meridian) on successive days.
Since the Sidereal day is 4 minutes shorter than the
Solar day, there are about 366 Sidereal days per year.