Why does the sun set only ones a year in anterctica?

Answer 1

Setting 'once a year; is not quite right as there are significant periods in Spring and Autumn (Fall) where it does set, depending on how near you are to the South Pole. However, there are also significant periods of time where it never rises (in the Southern Winter) or never sets (in the Southern Summer).

This also happens in the North Pole region, but here the seasons are reversed from the South Pole so that when the North has its summer, the South has its Winter.

It all happens because the earth is tilted on its axis by 23.5 degrees. This means that during the Northern Summer, the north pole points a little towards the sun and continues to point to the sun during the summer months. Therefore, no matter how much the earth turns on its axis, the north pole is always in sunshine. This means that the sun never sets at the north pole in the northern summer. However, at the same time at the south pole Antarctica is pointing away from the sun and is continually in darkness no matter how much the earth turns. This is the southern Winter and is continually dark for a few months depending upon how near you are to the pole. In the northern Winter and southern Summer things reverse, and the sun never rises in the north and never sets in the south.

Even for people who live away from the poles (say, in the USA, Canada, UK, Australia, S Africa and New Zealand) this can be seen to a lesser extent. In the northern hemisphere in summer the days are longer, and in winter the days are shorter. The further you go north the more difference there is until you pass the Arctic Circle. On the Arctic Circle there will be one day in winter where the sun never rises, and one day in summer where it never sets, with the number of days where this happens increasing as you go further north beyong the Arctic Circle. In the Antarctic the same happens only the seasons are reversed with respect to the north.

I experienced this for myself in 2006 when I took a trip to Northern Norway in the summer. Thre, the sun never sets in the height of summer and never rises in the sepths of winter. It was very strange walking around at midnight until 1.00am in the bright sunshine - but we were thankful of heavy curtains in the hotel that shaed this out when we needed sleep!

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