But a clear, cloudless day-time sky is blue because molecules in the air scatter blue light from the sun more easily than they do red light.

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At sunset, the sun appears red (the blue light has been scattered out of that image, too), so the cells of the eye that detect red are overloaded and incapable of registering weaker red signals.

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Any practiced attendee of the Academy Awards will tell you that the best time to glide across the red carpet is at the end of arrivals time, when the setting sun casts a favorable light on those pesky wrinkles and unsightly bulges.

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Nantucket red, for example, has the look of a red shirt that has been washed countless times and is faded to a light peachy pink from years of sun exposure, he says.

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