The Edge of Space Above the Past

In the foreground, the silent, historic ruins of Össeby church—a medieval parish church built in the 1200s—stand as a monument to passing time in Sweden. Above them, a vibrant display of noctilucent clouds (NLCs) paints the twilight sky in electric blue. These “night-shining” clouds are Earth’s highest, forming roughly 80 km (50 miles) high in the mesosphere, where they catch the sun’s rays long after darkness has settled on the ground.