<|im_start|>user
Why is the sky blue?<|im_end|>
<|im_start|>assistant
Earth's atmosphere scatters short-wavelength light more efficiently than that of longer wavelengths. Because its wavelengths are shorter, blue light is more strongly scattered than the longer-wavelength lights, red or green. Hence, the result is that when looking at the sky away from the direct incident sunlight, the human eye perceives the sky to be blue.<|im_end|>
