The North Star sits nearly above Earth's axis, making it a reliable navigation marker.

The longer version

Earth's rotation axis points almost directly at Polaris, so as the planet turns, the star stays in nearly the same spot above the northern horizon while the rest of the sky wheels around it. Its height above the horizon roughly matches the observer's latitude. Navigators have long used it to find direction at night.

The match is temporary on cosmic timescales because the axis slowly wobbles like a spinning top, a motion called precession. Thousands of years ago a different star held that role, and thousands of years hence another will. Polaris is also slightly variable in brightness, and it is not especially bright, but its fixed position makes it easy to identify.

Where this entry sits

The night sky looks calm, yet almost everything up there is moving, burning, or slowly changing. These facts cover planets, stars, the Moon, gravity, black holes, comets, and the story of how people began exploring beyond Earth. The full list sits on the Space and Sky page, where every entry is listed in order.