十万个为什么·科学启蒙30篇（4）
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Why the Sky Looks Bluer at High Altitudes
为什么天空在高海拔更蓝
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Sunlight contains all colors, but blue light scatters more easily than red in Earth’s atmosphere.
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At sea level, thick air scatters blue light multiple times, mixing it with other colors slightly.
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Higher up, there is less atmosphere above you, so scattering happens less frequently.
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That means more pure blue light reaches your eyes without being diluted by scattered white light.
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Also, fewer dust particles and water vapor exist at altitude to diffuse the light further.
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Mountaineers often notice the sky appears deeper and richer in blue near mountain peaks.
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Polarized sunglasses enhance this effect by reducing glare from scattered light.
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This bluer hue confirms that Rayleigh scattering depends strongly on air density.
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Airplanes flying at cruising altitude see an even more intense azure sky.
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The change reminds us how much our view depends on the invisible layer surrounding Earth.