The Big Dipper is one of the easiest star patterns to locate in Earth’s sky. It’s visible just about every clear night in the Northern Hemisphere, looking like a big dot-to-dot of a kitchen ladle. As Earth spins, the Big Dipper and its sky neighbor, the Little Dipper, rotate around the North Star, also known as Polaris.

The constellation of Ursa Major completes a full rotation around the North Star every 24 hours, and for that reason, it can never be seen below the horizon. Because of this motion, the constellation has been used as a star clock throughout history.

Because Polaris lies nearly in a direct line with the Earth's rotational axis "above" the North Pole —the north celestial pole—Polaris stands almost motionless in the sky, and all the stars of the northern sky appear to rotate around it.