A170: The Earth spins on its "axis". This axis is an imaginary line running through the Earth. If you were to be high above the Earth, looking straight down along the axis, all the points on Earth would appear to move in circles around the axis. If you followed this axis out into space from the northern hemisphere on Earth, it would point toward a particular star in the sky. We call that star the "North Star" since it sits in the direction that the spin axis from the northern hemisphere of Earth points.