Question

Why polar region receive 6 months day and 6 months night?

Answer 1

For us, the Sun rises in the East and sets in the West.  But at the poles, there are no directions.  From the North Pole, whichever way we look it is South, and from the South Pole, whichever way we look, it is North.  There is no Sunrise or Sunset at the polar regions as we experience at lower latitudes. The Sun appears above the horizon in Summer and makes a 360° circle in the sky - over a period of 187 days at the North Pole 90° North latitude. And in winter, the Sun is below the horizon for 163 days of darkness and  24 days of semi-darkness when the Sun is just below the horizon. It's not exactly six months of darkness/sunlight at the poles.  (In Svalbard, Norway, the northernmost inhabited region of Europe, there is no sunset from approximately 19 April to 23 August, and no sunrise between November 14 and January 29.) Needless to mention, when it is summer in the Northern hemisphere, it is winter in the South.

A solstice happens when the sun's zenith is at its furthest point from the equator.

The December Solstice or Winter Solstice occurring on or about 21st December when the Sun reaches its most southerly declination of -23.5 degrees. In other words, when the North Pole is tilted furthest to 23.5 degrees  away from the Sun. The Sun is directly overhead of the Tropic of Capricorn in the Southern Hemisphere during the December Solstice.