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Autumn leaves don't turn yellow. The yellow was there all summer
Autumn leaves don't really turn yellow. The yellow carotenoids were in the leaf all summer, hidden under green chlorophyll. In autumn the tree dismantles its…
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…