Glory Over Johannesburg, South Africa
April 05, 2010
This picture of a colorful glory was taken from the window seat of a commercial jet while on approach to Johannesburg, South Africa. Glories are caused by diffraction of sunlight in cloud water droplets. They’re similar to coronae but are centered about the antisolar point rather than on the Sun. In order to detect this phenomenon, the observer must be directly between the Sun and the cloud – your view out the window faces away from the Sun. However, you don’t have to be onboard a plane to see a glory. When sunlight enters minute water droplets (approximately 0.0010 – 0.0050 mm in diameter), the droplets deflect light more readily than they refract or reflect it. Though, at least one reflection is involved in a glory. Water droplets are many times smaller than the raindrops or ice crystals that compose most clouds. In essence, sunlight interacting with the tiny droplets produce rings of interference (overlapping colors), like a wavelet from a thrown stone deflecting off a piling and interfering with the next approaching wavelet. Note the dimmer outermost ring. Photo taken on the morning of March 14, 2010.