At the North Pole the Sun rises once a year and circles overhead for months
At the poles the Sun rises and sets just once a year, at the equinoxes. For six months it circles the sky, spiralling higher until the summer solstice and then sinking again. Moving away from the pole, the midnight sun shrinks to weeks, then days, then a single night.
The effect comes from Earth's axial tilt of about 23 degrees 26 minutes. Right on the Arctic Circle the centre of the Sun stays up for only one night, yet just 100 km nearer the pole it stays up for weeks. Because the atmosphere bends light over the horizon and the Sun is a disc rather than a point, the midnight sun can appear up to about 90 km outside the polar circles, which is why Iceland, lying mostly just south of the Arctic Circle, is famous for it.
The two ends of the planet are not treated equally. Earth is closest to the Sun in early January and farthest in early July, so northern summer lasts longer: the North Pole gets 186 days of polar day and 179 of polar night, while the South Pole gets the reverse. At Utqiagvik, Alaska, polar day runs 84 days against 68 of darkness. Murmansk, the largest city north of the Arctic Circle, keeps the Sun up from 22 May to 22 July, and Svalbard goes without a sunset from roughly April to August.
Farther south, people get white nights instead. Where the Sun dips less than about 6 degrees below the horizon, a clear night stays bright enough to read by. Saint Petersburg marks the season with a White Nights Festival across the last 10 days of June, and Fairbanks, Alaska, has staged a Midnight Sun Game of baseball around midnight on 21 June since 1906.
Clocks muddy the picture. Fairbanks sits south of the Arctic Circle, but thanks to its time zone and daylight saving the Sun there sets at 12:47 a.m. at the solstice, and solar midnight falls at 1:51 a.m. Even at North Cape in Norway, the Sun hits its lowest point at about 00:19 Central European Summer Time, because each degree of longitude east of Greenwich moves the moment 4 minutes earlier and each hour of time zone moves it an hour later.
Source: Midnight sun
