Roseberry was looking its usual self this morning as we trudged up Aireyholme Lane, the sun just beginning its obligatory climb over the Cleveland Hills. From this angle, Roseberry‘s distinctive shape is rather less obvious. High above, a waning gibbous moon lingered sulkily in the sky, and the early morning sunlight—in what us self-important photographers refer to as the “golden hour”—painted everything with a reddish tint. Magical. Meanwhile, the sheep grazed nonchalantly.
This reddish tint, for those who care, is thanks to something called Rayleigh scattering. Do not get excited; it has nothing to do with Sir Walter dabbling with his potatoes. It is simply what happens when sunlight meets the Earth’s atmosphere. The longer wavelengths of light, being less bothered by air molecules, saunter through to our eyes when the sun is low, while the shorter ones scatter like startled pigeons.
For those who like their science watered down, here is a basic explanation dredged up from the days of prisms in school physics. Sunlight is made up of all the colours of the rainbow, each with its own wavelength. Blue light, having shorter wavelengths, is scattered more vigorously than red light, which has the good sense to be longer and more resistant. This is why the sky is blue, though I will leave that tangent for another time.
At sunrise, the sun loiters near the horizon, forcing its light to slog through a thicker slice of the atmosphere. As it does so, the shorter wavelengths—blue and violet—are scattered out of sight, leaving only the lazier, longer wavelengths—red, orange, and yellow—to greet us. In winter, when the sun can barely be bothered to climb above the horizon at all, the light has even more atmosphere to navigate, enhancing the scattering effect and making the reddish hues of sunrise and sunset even more pronounced.
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