Why are the poles so cold?
Sunlight hits the poles at a low angle, so the same beam is spread over a much bigger area. There are months of darkness each winter, and snow and ice reflect most of the sunlight that does arrive back to space.
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Slanted sunlight
Shine a flashlight straight down and you get a small, bright spot; tilt it and the same light spreads into a large, dim oval. Near the equator the sun is high and its energy is concentrated. Near the poles it's low in the sky even in summer, and the light also travels through more atmosphere on the way in.
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Months without sun
Earth's tilt means each pole gets months of nearly continuous daylight in summer and months of darkness in winter. During the polar night the surface keeps losing heat to space with nothing to replace it, and temperatures plunge.
Why Antarctica is colder than the Arctic
The Arctic is mostly a frozen ocean, and the water beneath the ice holds some warmth. Antarctica is a continent buried under an ice sheet more than two miles thick in places, so much of it is high, dry and far from any ocean. The lowest temperature ever measured at a weather station, −128.6°F, was recorded at Antarctica's Vostok Station in 1983.
Questions people ask
- Does it snow a lot at the South Pole?
- No. The air is so cold and dry that the interior of Antarctica gets very little snowfall, which makes it a desert.
- Why is it warmer at the equator?
- The sun is high there all year, so sunlight arrives concentrated and the days stay about 12 hours long.