Photos by babaktafreshi / A prehistoric petroglyph appears in moonlight, a hunting scene from about 10,000 years ago in the Teimareh valley of central Iran. With thousands of petroglyphs found in the area it is one of the world’s richest rock art sites, still largely unexplored. The north star Polaris and the rest of the constellation Ursa Minor, the Little Bear, appear in the sky. Polaris is the bright one at the top, the handle of the Little Dipper. Swipe to see the constellation. It’s remarkable that when this rock art was made, Polaris was not a north star at all and nowhere near the north celestial pole, which was almost 45 degrees away across the sky near bright star Vega. This is due to the Earth’s precession, the slow wobble of its rotation axis like a spinning top. But it’s a very slow change, with a cycle of 26,000 years. For a spinning top this happens when it is slowing down. For Earth it is due to the tidal force by the gravity of the moon and sun. For more visual storie...