The sun is a huge source of light. The most common light sources are thermal: a body at a given temperature emits a characteristic spectrum of black-body radiation. Examples are sunlight, incandescent light bulbs and glowing solid particles in flames.
In Science, the study of light and the interaction of light and matter is termed optics. The observation and study of optical phenomena such as rainbows and the aurora borealis offer many clues as to the nature of light.