A vocabulary of landscape — a landscape of words
1469 entries
false dawn
A false dawn is a cone of faint light standing up from the horizon before true daybreak, or after dusk in the west, and it is not sunlight scattered by air at all. It is sunlight reflecting off dust spread through the plane of the solar system. It needs a moonless night, no artificial light, and clear air, and it is easiest to see from low latitudes where the ecliptic stands up steeply from the horizon.
Etymology
The English term translates the Arabic, where the distinction is a practical one rather than a poetic one. Islamic prayer times depend on first light, and the vertical glow of the false dawn had to be told apart from the true dawn, which is a horizontal brightening spread along the horizon. Arabic names the two separately: the lying dawn and the true dawn. The word for the deceptive one is also used for the tail of a wolf, from its shape.
Notes
The astronomical name for the same light is zodiacal light and the dust producing it is now thought to come largely from comets and from collisions in the asteroid belt. On very dark nights, the band can be traced all the way across the sky, with a faint brightening directly opposite the sun called the gegenschein.