So like why does some light (I.e. A lightbulb, the sun, the moon, etc) shine and other forms of light like the light from my face or really everything else not shine?In other words why do you need a form of bright light to see other forms of light that do not shine?
The light-bulb and Sun are primary sources of light. That is, the photons are initially created by these. The electrical current in the bulb creates the photons that you see as light. Nuclear fusion on the Sun creates the photons that you see as light and feel as warmth when it hits your skin. The moon and your face are secondary sources of light in that the photons emanating from them are reflections of light from primary sources. The Moon reflects sunlight, which is the primary light. Your shiny face reflects the desk lamp light which it that primary source. So you have two kinds of light: direct, from primary sources, and reflected, from secondary sources.
Because you face shines with infrared light, which humans eyes cannot see. The is only a very narrow band on the light spectrum that humans can actually see. Known as the visible spectrum typically between 390 to 700 nm.
Your face, technically speaking, actually doesshine but shining is a subjective term. It's in the amount of light coming at you that determines whether or not you perceive it as so. A light bulb produces a large amount of light in a small area; the sun produces copious amount of it, and the moon reflects a sizable amount as well. Your face reflects only a relatively small amount of the ambient light so it doesn't appear as something shining.
