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.
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This direct angle heats the surface more than slanted light does elsewhere.
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Places farther north or south get sunlight at a lower angle in winter.
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That spreading effect makes each ray deliver less warmth per square meter.
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The equator also has nearly equal day and night lengths every day.
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No long winters mean no time for heat to escape into space.
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Warm air rises there and moves toward the poles slowly over weeks.
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Ocean currents near the equator also hold and move huge amounts of heat.
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That’s why tropical countries rarely see frost or snow even at night.
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You can feel this difference just by comparing Singapore and London in January.