Gas Light Pillar
April 23, 2007
On the evening of January 7 2007, near Benelux, Belgium, I observed a fascinating and alluring light pillar. A few tenuous clouds were visible near the horizon, but what caught my attention was the bright but narrow vertical column of light extending upward toward the faintly visible clouds. The light source responsible for this pillar was neither the Sun nor Moon but rather an enormous flame generated by an oil refinery burning natural gas. Pillars are caused by refraction and reflection of sunlight off of ice crystals (plate shaped hexagonal crystals) in clouds above a strong light source. Light is refracted through the underside of the plate crystal and then reflected off of the upper-side before exiting the way it entered, through the underside. Unlike natural Sun pillars, a slight tilt of the ice crystals isn't necessary to observe artificial light pillars. If the light source is nearby, perfectly aligned crystals will also result in a pillar.