"God beams" are the result of clouds blocking sunlight just so. More scientifically, they're called crepuscular rays. Either way, they add incredible drama to a landscape photo at sunrise or sunset.
Wikipedia explains them: "These rays, which stream through gaps in clouds (particularly stratocumulus) or between other objects, are columns of sunlit air separated by darker cloud-shadowed regions...The name comes from their frequent occurrences during crepuscular hours (those around dawn and dusk), when the contrasts between light and dark are the most obvious. Crepuscular comes from the Latin word "crepusculum", meaning twilight."
Now you can go impress your friends with your new knowledge of crepuscular rays, or simply go enjoy a gorgeous twilight hour!
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