photo #7388479

After the Sun sets, the air near the ground can cool and stabilise overnight – particularly, if it’s a starry, clear night that encourages the ground to cool rapidly as it radiates away the day’s warmth. When the air cools enough to reach its saturation temperature, tiny droplets condense and appear as radiation fog. The fog forms in the low air near the surface, and in hilly terrain, it sinks down slopes to gather in valleys, where it’s known also as valley fog. This is what Bob Maysmor spotted glowing in the early-morning light over Pauatahanui Inlet, north of Wellington, New Zealand. Once the Sun rises enough to heat the ground again, these spirits of the valley will slip away. It’ll be as if they’d never been there.