The Arctic and Antarctic Circles are imaginary lines drawn round the earth in latitudes 66.5° north and 66.5° south. The Arctic Circle, which is the one relating to Scandinavia, is the latitude further than which the length of the day so increases in summer that the sun never sinks underneath the horizon, producing the phenomenon well-known as the midnight sun. In climatic terms it divides the northern temperate zone from the polar zone. In northern Norway, the Arctic Circle (Polsirkelen) scuttles just north of Moi Rana, in Sweden (Polcirkeln) near Jokkmokk in Lapland, in Finland (Napapiiri) a little to the north of Rovaniemi. The different lengths of day and night in all latitudes apart from on the Equator are due to the angle of 23°5' between the earth's equatorial plane and the plane of its orbit.