Question

Why north pole and south pole have sunlight and darkness for concqutive

Answer 1

Daylight, Darkness and Changing of the Seasons at the North Pole
Illustrated with images from the North Pole Web Cam

Winter

 · Diagram showing locations of the North Pole and sunlight for the four seasons
· Equinoxes & Solstices
· Arctic Sunrise & Sunset times
· Definition of Sunrise, Sunset, Equinox, Solstice, and Twilight 
· What causes Seasons? 
* from athropolis.com

The darkest time of year at the North Pole is the Winter Solstice, approximately December 21. There has been no sunlight or even twilight since early October. The darkness lasts until the beginning of dawn in early March.

Spring

The sun rises at the North Pole on the Spring Equinox, approximately March 21, and the sun rises higher in the sky with each advancing day, reaching a maximum height at the Summer Solstice, approximately June 21.

Shadows cast in May are long, because the sun is low in the sky.In June, near the Summer Solstice, the shadows are short, because the sun is higher in the sky.

Summer

 In summertime, the sun is always above the horizon at the North Pole, circling the Pole once every day. It is highest in the sky at the Summer Solstice, after which it moves closer to the horizon, until it sinks below the horizon, at the Fall Equinox.

The North Pole stays in full sunlight all day long throughout the entire summer (unless there are clouds), and this is the reason that the Arctic is called the land of the "Midnight Sun"*. After the Summer Solstice, the sun starts to sink towards the horizon.

Autumn

At the Autumn Equinox, approximately September 21, the sun sinks below the horizon, and the North Pole is in twilight until early October, after which it is in full darkness for the Winter.

Answer 2

This phenomenon occurs because the Earth is tilted on its axis by approximately 23 degrees. At the poles (both north and south), this means that the sun only rises and sets once each year. Of course, these phenomena aren't limited to only northern areas. They also occur in southern regions near the Antarctic Circle.