1. Introduction
2. Conditions
3. Cause

Introduction

Every once in a while, if the atmospheric conditions are just right, the sun will spark a bright green hue just as it disappears on the horizon.   Called the 'green flash', this phenomena is purported to be caused by the spectral separation of the sun's colors.

Conditions

For the phenomena to occur the atmosphere must be extremely clear.  This particular condition allows the light to be refracted, the colors separated producing the astonishing green flash.

Cause

The individual spectral colors of the sun, with purple located at the top and red located at the bottom, appear one by one as the sun slowly sets producing the notable color changes everyone recognizes as our setting sun.  As the sun sets each individual color is presented one by one until Green, the last color of the spectrum, produces its brief and unexpected flash.