十万个为什么·科学启蒙30篇（3）
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The Sun Hits the Equator Straight On
阳光直射赤道，所以更热
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Near the equator, sunlight strikes Earth almost straight down all year.赤道附近全年阳光几乎垂直照射地球。
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This direct angle heats the surface more than slanted light does elsewhere.这种直射角度比其他地区斜射的阳光更能加热地表。
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Places farther north or south get sunlight at a lower angle in winter.纬度更高的南北地区冬季阳光入射角更低。
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That spreading effect makes each ray deliver less warmth per square meter.这种散射效应使每束阳光单位面积传递的热量减少。
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The equator also has nearly equal day and night lengths every day.赤道地区每天昼夜长度几乎相等。
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No long winters mean no time for heat to escape into space.没有漫长的冬季，热量便无从大量散逸到太空。
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Warm air rises there and moves toward the poles slowly over weeks.暖空气在此上升，并在数周内缓慢向两极移动。
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Ocean currents near the equator also hold and move huge amounts of heat.赤道附近的洋流也储存并输送巨量热量。
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That’s why tropical countries rarely see frost or snow even at night.因此热带国家即使夜间也极少出现霜或雪。
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You can feel this difference just by comparing Singapore and London in January.仅对比一月的新加坡与伦敦，你就能感受到这种差异。