Kites & Shadow Hiding Glow

Jeff Poplin flew a camera on a kite to image this field of dried corn near Pilot Mountain, North Carolina.

The bright area at left is an Opposition Effect glow directly opposite the sun. A light streak rises from it in the 11 o'clock direction. See below for another view. ©Jeff Poplin, shown with permission


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The ‘glow’ is caused by shadow hiding.   

The dry corn shoots cast shadows on the soil. When looking in the direction exactly opposite the sun these shadows are hidden beneath the bright sunlit corn itself.   As you view further and further from the antisolar point the shadows become more and more visible.    The antisolar point area therefore looks brighter because compared with its surroundings there are fewer shadows.  The 11 o’clock bright streak is the result of shadow asymmetry caused by the tall stems all aligned in more or less the same direction.

Shadow hiding is part of the ‘Opposition effect’.  The name arose from the extra brightness of Mars and the Moon when opposite the sun - at opposition.   Shadow hiding by Martian and Lunar soils does contribute to their brightening but so do retro-reflection by rock minerals and an effect called coherent backscattering.

Shadow hiding is subtle. It is best seen visually when walking or swaying the head.   Small contrast differences are better seen when moving the head from side to side.   Look for it also from an aircraft as a glow drifting across the landscape.