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Why the sky is blue and sunsets are red: it's the same light
The blue sky and the red sunset are the same effect, seen from two angles. Air molecules scatter short, blue wavelengths far more than long, red ones: about…
Why Mars sometimes walks backwards across the sky
Every 26 months or so, Mars slows down, stops, and drifts backwards against the stars for a couple of months before carrying on. Ancient astronomers built…
Why a rainbow is always a circle 42° around your shadow
Every rainbow is part of a circle centred on the shadow of your head, with its red edge about 42° away. That number comes from inside a single raindrop…