Light

"light is one of the five fundamental "subtle" elements (tanmatra) out of which emerge the gross elements" (philosophical schools of Samkhya and Vaisheshika,around the 6th–5th century BC, Ancient India)

Light Sources:
Sunlight (Solar radiation)
Stars
Bioluminescence
Lightning
Chemoluminescence (Lightsticks)
Fluorescence
Phosphorescence
Candles
Fire
Gas lighting
Kerosene lamps
Lanterns
Incandescent lamps
Electroluminescent (EL) lamps
Arc lamps
LED / semiconductor
Gas discharge lamps
High-intensity discharge lamps


Shadow - A shadow is a region of darkness where light is blocked. It occupies all of the space behind an opaque object with light in front of it. The cross section of a shadow is a two-dimensional silhouette, or reverse projection of the object blocking the light. It begins as the light moving through but is blocked depending on the density. (Wikipedia.org)

Shadow people (also known as shadow men, shadow folk, or shadow beings) are supernatural shadow-like creatures of both modern folklore and traditional native American beliefs. According to folklore, they appear as dark forms in the peripheries of people's vision and disintegrate, or move between walls, when noticed
Reports of shadow people occupy a similar position in the popular consciousness to ghost sightings, but differ in that shadow people are not reported as having human features, wearing modern/period clothing, or attempting to communicate. Witnesses also do not report the same feelings of being in the presence of something that 'was once human'. Some individuals have described being menaced, chased, or in some rare instance, attacked by shadow people. There have also been reports of shadow people appearing in front of witnesses, of which they stay there or lingering for several seconds before disappearing. Witnesses report that encounters are typically accompanied by a feeling of dread (Wikipedia.org)

Shadow play (Chinese: 皮影戏, pi ying xi) or shadow puppetry is an ancient form of storytelling and entertainment using opaque, often articulated figures in front of an illuminated backdrop to create the illusion of moving images. It is popular in various cultures. At present, more than 20 countries are known to have shadow show troupes. (Wikipedia.org)