Why do poles experience about six months day and six months
night? 150 words
Answers
Answer:
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Answer:
That is because the Earth's axis is tilted away from the perpendicular to Earth's orbital plane. The axis always points (more or less) in the same direction in space. However, relative to the Sun, the tilt direction varies, as the Earth orbits the Sun. Each pole tilts towards the Sun for half the year then away from the Sun for the other half of the year. This affects the whole planet, but the effect is most extreme at the poles. At the poles, there are about six months of daylight followed by about six months of night.
An important fact that is sometimes not clearly stated is that, at the poles, the Earth's rotation does not cause the Sun to rise or set. In fact, the Sun's apparent daily motion is (almost exactly) parallel to the horizon all the time.
However, the Sun does rise and set at the poles, at intervals of 6 months. That’s because the distance of the Sun above and below the horizon varies during the year, as the Earth orbits the Sun. Diagrams showing how the Earth’s orbit affects the amount of sunlight at the poles are given in the link below.
Due to refraction by the Earth's atmosphere, the Sun can still be seen for a few days when it's just below the horizon. Also, the Sun moves only very slowly below the horizon as winter approaches, so there is quite a long period of twilight at the poles. It depends on which definition of "twilight" you use, but twilight is usually said to last for about 2 weeks at the poles. The same thing happens as the Sun is ready to rise above the horizon in the springtime. So there is about a month of twilight in total. So really the poles are in proper darkness for a bit less than 5 months of the year. In fact, the length of time when the North pole has no twilight of any kind (strictly defined) is no more than 11 weeks. That’s less than 3 months!